Differential Diagnosis in Neurology

10.18. Traumatic and Compressive Neuropathy

• General features:
  • Peripheral nerve injury occurs in 2–3% of patients admitted to level I trauma centers; addition of root and plexus injuries increases this figure to 5%
  • Seldom used classification of peripheral nerve injury:
    • Neurapraxia-axons are intact, but fail to conduct action potentials due to focal demyelination
    • Axonotmesis-transection of axons, but the nerve trunk is intact
    • Neurotmesis-transected nerve trunk
• Sunderland classification of peripheral nerve injury:
  • First degree injury:
    • Disruption of myelin sheath with intact axons and stroma
  • Second degree injury:
    • Transection of axons with intact stroma
  • Third degree injury:
    • Transection of axons and endoneural tubes; perineurium is intact
  • Fourth degree injury:
    • Transection of axons, endoneural tubes and the perineurium; fascicular transection occurs; epineurium is intact
  • Fifth degree injury:
    • Transection of the nerve trunk

Prognosis for Peripheral Nerve Injury

• Degree of injury
• Damage to the nerve
• Distance from the muscle that is innervated
• Gradual or higher injuries cause Wallerians degeneration

Long Thoracic Nerve

• General features:
  • Derived from C5, C6, C7 roots prior to origin of the brachial plexus
  • Innervates the serratus anterior muscle
  • Pathogenesis of injury:
    • Lesions affecting the component roots
    • Associated with neuralgia amyotrophica
    • External compression and stretch
• Clinical presentation:
  • Paralysis of the serrates anterior with scapula winging
  • Shoulder stabilization is decreased
  • No cutaneous innervation
  • Inferior scapular border is rotated medially; vertebral border is more prominent when arm pushes against resistance
• Differential diagnosis:
  • Intercosticobrachial nerve from the medial cord of the brachial plexus:
    • Purely a sensory nerve that innervates the lateral and upper anterior chest wall and radiates under the breast to the midline
  • Neuralgia amyotrophica:
    • May be damaged in isolation (the long thoracic nerve)
    • Severe shoulder pain for days to weeks
    • Difficulty with shoulder movement
  • Scapular winging occurs with:
    • Rhomboid weakness:
      • Moves away from the back midline when the arm is pushed forward
    • Trapezius weakness:
      • Dropped shoulder
      • Poor shrug
  • Limb girdle muscular dystrophia

Suprascapular Nerve

• General features:
  • C5–C6 roots; arise from the upper trunk of the brachial plexus
  • Passes through the suprascapular notch
  • Anomalous fibers may supply the distribution of the axillary nerve distribution
• Pathogenesis of injury:
  • Entrapment usually occurs at the suprascapular notch; may be compressed at the spinoglenoid notch
  • Repetitive movements
  • Ganglion cysts, sarcoma, metastatic disease
  • Positioning during surgical procedure (knee, chest position)
  • Weight lifting (shoulder abduction and protraction)
  • Volleyball, dancing, baseball pitchers (injury distally at the spinoglenoid notch)
  • Neuralgia amyotrophic (with other shoulder girdle nerves)
• Clinical presentation:
  • Impingement at the suprascapular notch causes shoulder pain
  • No cutaneous innervation; sensory innervation to deep tissues (muscles of the capsule of the glenohumeral joint)
  • Deep seated throbbing pain along the superior border of the scapular toward the shoulder (exacerbates by stretching the adducted arms across the chest)
  • Entrapment in the suprascapular notch both supra and infraspinati weakness; at the lateral border of the spine involves the infraspinatus muscle alone
  • Weakness of shoulder abduction and external rotation of the arms; atrophy of the infraspinatus may be prominent
  • Infraspinatus injury at the spinoglenoid notch is painless and only involves this muscle
  • Pain may be prominent at the suprascapular notch
• EMG:
  • No sensory nerves to test; lateral antebrachial cutaneous median, radial sensory involvement rule it out.
  • NCV with stimulation at Erb's point and recording over corresponding muscle denervation
  • Needle EMG demonstrate denervation in infra and suprascapular muscles (infraspinatus alone if the lesion is at the spinoglenoid notch)

Differential Diagnosis of Supra and Infrascapular Nerve Lesions

• Musculoskeletal pains around the shoulder; subacromial bursitis, bicipital tendonitis, acromioclavicular arthritis or separation; pericapsular fibrosis
• Rotator cuff injury (no weakness)
• C5, C6 radiculopathy; often referred pain to the deltoid cap (C5); C6 (thumb and lateral forearm); often pain radiates to the upper arm; weakness of biceps; depressed biceps and brachial radialis reflexes
• Brachial neuritis; neurologic amyotrophy; abrupt onset of pain and weakness of other muscles innervated by the plexus; may be bilateral
• Brachial plexus traction injury (neuropraxic): Tinel's sign throughout the arm (supra and infraclavicular fossa, neurovascular bundle; Arcade of Frohse, pronator canal); positive Roo's abduction stress maneuver; trunk and cord sensory loss and weakness.

Axillary Nerve

• General features:
  • Originates from the posterior cord of the brachial plexus; derived primarily from C5, C6, C7 roots (upper trunk/posterior cord)
  • Passes through the quadrangular space
  • Innervates the teres minor and deltoid (external rotation and abduction of the shoulder)
  • Lateral shoulder sensory innervation (at the caps of the shoulder)
• Pathogenesis of the injury:
  • Dislocation and fracture of the shoulder
  • Fracture of the humerus
  • Surgical positioning
  • Entrapment in the quadrilateral space
• Clinical presentation:
  • Sensory loss over the lateral shoulder
  • Weakness of shoulder abduction and external rotation
• EMG:
  • Denervation of the deltoid and the teres minor
• Differential diagnosis:
  • Orthopedic shoulder conditions
  • C5–C6 radiculopathy
  • Brachial plexus traction injury
  • Neuralgia amyotrophica
  • Suprascapular neuropathy

Spinal Accessory Nerve

• General features:
  • Pure motor nerve; C1–C4 ventral root denervation; ascends through the foramen magnum and exits through the jugular foramen (pars venosum)
  • Supplies sternocleidomastoid muscle and then runs in posterior cervical triangle to innervate the trapezius muscle
• Pathogenesis of the injury:
  • Stretch or compression of the posterior cervical triangle
  • Carotid endarterectomy
  • Lymph node biopsy
  • Compression from tumor (lymphoma)
• Clinical presentation:
  • Distal lesions cause:
    • Atrophy and weakness of the trapezius muscle resulting in a dropped shoulder; mild scapular winging in abduction, weakness of shoulder abduction and external rotation (due to lack of fixation)
    • Traction of the brachial plexus with pain due to stretch of the cords and trunks
    • Proximal lesions causes weakness of the sternocleidomastoid muscle with weakness of neck flexion and contralateral head turning
• EMG:
  • Decreased CMAP of the upper trapezius muscle
  • Denervation of upper, middle and lower fibers of the trapezius
• Differential Diagnosis:
  • Brachial plexus traction injury
  • Skull based tumors
  • Surgical damage to the posterior cervical triangle
  • Jugular foramen tumors (glomus jugulare)
  • Compression injuries

Musculocutaneous Neuropathy

• General features:
  • Arise from the lateral cord of the brachial plexus; innervates the coracobrachials, biceps brachialis; after the elbow it is the lateral antebrachial cutaneous nerve (does not innervate the thumb); lateral and slight component of the posterior forearm innervation; posterior sensory branch may anastomose with the radial sensory nerve or the posterior cutaneous nerve of the forearm; rare anastomosis of the anterior branch with median nerve sensory fibers.
• Clinical presentation:
  • Weakness of elbow flexions
  • Decreased or absent biceps reflex
  • Sensory loss in lateral forearm
  • Lateral antebrachial cutaneous neuropathy sensory loss is increased with pronation and extension (entrapped between the biceps tendon, and fascia and the brachialis muscles)
• Pathogenesis of the injury:
  • Trauma of upper arms and shoulder
  • Fracture of the proximal humerus
  • Positioning during surgery
  • Upper extremity strenuous repetitive injury
  • Benign humeral exostoses
• EMG:
  • Denervation of biceps and brachioradialis
  • Sensory conduction deficits of the lateral antebrachial cutaneous nerve
  • Decreased SNAPs of this nerve with proximal and distal lesions
• Differential diagnosis:
  • C5–C6 radiculopathy
  • Brachial plexus pathologies (upper trunk)

High Median Nerve Compression in the Region of the Shoulder or Proximal Humerus

• General features:
  • Uncommon; most often traumatic
  • Anterior dislocation of the shoulder
  • Axillary compression from long arm crutches
  • Hanging the arm over chairs
  • Aneurysm of the brachial or axillary artery
• Clinical presentation:
  • Forearm pronation deficit: paralysis of the pronator teres and pronator quadratus
  • Weak wrist flexion with ulnar deviation due to weakness of the flexor carpi radiales
  • Paralysis of: flexor pollicis longus, flexor digitorum superficiale of the digits (therefore absence of flexion of the distal inter phalanges joint and proximal interphalangeal joint of the index finger). The weakness of grasp of the fourth and fifth digits (flexor digitorum superficialis); Slight weakness of the flexor digitorum profundus with consequent weakness of distal interphalangeal flexion. Paralysis of thenar muscles (motor branch of the median nerve) and decreased sensory supply to median nerve innervates digits.

Median Nerve Compression at the Elbow

• General features:
  • Five centimeters above the medial epicondyle of the humerus there is a supracondylar process (occurs in approximately 0.7–2.7% of the population. The median nerve and brachial artery and vein course under this ligament of struthers
  • In the antecubital fossa the median nerve courses adjacent to the brachial artery
  • In the forearm it courses below the thick fibrous band known as the lacertus fibrosus (originates from the medial biceps tendon and attaches to the forearm flexor musculature)
  • Between the two heads of the pronator teres; after it passes this area the anterior interosseous nerve is given off posteriorly.
  • Passes deep to the flexor digitorum sublimes muscle and its aponeurotic tendinous edge the sublimus bridge
• Pathogenesis of nerve injury:
  • Trauma; casting, direct injury, venipuncture, tumor or hematoma
  • Neuralgia amyotrophia can involve the anterior inter osseous nerve
  • Chromosome 17; CMT1a; hereditary neuropathy with sensitivity to pressure (HNPP)
  • Elbow dislocation
  • Persistent median artery

Ligament of Struthers Compression

• Clinical presentation:
  • Pain in the volar forearm
  • Paresthesias in the median nerve innervated digits
  • Sensory symptoms exacerbated by forearm supination and extension at the elbow
  • Palpation of the distal spur on the medial humerus
  • Weakness of the pronator teres > other median innervated muscles

Pronator Syndrome

• Clinical features (evocative maneuvers):
  • Lacertus fibrosis site:
    • Forced supination and elbow flexion
    • Pronator teres:
      • Forced pronation and elbow extension
    • Sublimus bridge:
      • Flexion of the proximal interphalangeal joint of the middle finger
    • All three sites of entrapment:
      • Weakness of the FPL and APB; rarely FDP
      • Paresthesias of median nerve innervated digits
      • Aching of the proximal forearm; may radiate to the elbow or shoulder
      • Tenderness of the proximal forearm over the pronator teres
      • Clumsiness and weakness of the hand
• EMG:
  • Abnormal in a minority of patients; acute and chronic denervation of median nerve innervated muscles
  • Focal slowing of the median nerve at the elbow
  • Denervation of median forearm and hand muscles

Differential Diagnosis of Pronator Teres Syndrome

• Carpal tunnel syndrome: pronator teres is associated with weakness of the forearm flexor muscles; palmar cutaneous nerve numbness (includes the thenar eminence absent in CTS) Tinel's signs at the wrist rather than the elbow (pronator canal)
• Cervical radiculopathy; C6 or C7 root may cause forearm pain; vague sensory loss into the thumb index and third finger. Positive Spurling's sign at the nerve root exit foramina in the neck; lateral rotation of the neck causes paresthesias in the thumb and index finger; pain down the spinous processes of the neck; weakness of the biceps (C6); triceps (C7); decreased biceps reflex for C5, C6 and triceps reflex for C7.
• Brachial plexus traction injury (upper trunk and lateral cord)
• Musculoskeletal disease at the elbow:
  • Sprains of the flexor pronator muscle
  • Vascular anomaly; aneurysms of the median artery; A-V shunts for dialysis; fistulas due to traumas (knife > bullet)
  • Minimums or no sensory loss

Anterior Interosseous Nerve

• General features:
  • Nerve arises from the median nerve 5 to 8 cm distal to the lateral epicondyle
  • Innervates flexor pollicis longus, flexor digitorum profundus to index and long finger and pronator quadratus
  • No cutaneous sensation; proprioception and pain afferents to the wrist joint
  • Anomalous innervations:
    • Anterior interossei may supply all of the flexor digitorum profundi (patient is unable to flex any distal digital joints); all median hand.
    • Flexor digitorum profundus to index or long finger spared (innervated by the ulnar nerve)
    • 50% of Martin–Gruber anastomosis arise from the anterior interosseous nerve
• Pathogenesis of nerve injury:
  • Repetitive elbow flexion and pronation
  • Trauma with casting
  • Open reduction of forearm fractures
  • Anatomic anomalies: tendinous origin of the deep head of the pronator teres; tendinous compression of the flexor digitorum superficialis of the third finger
• Clinical presentation:
  • Inability to flex the distal phalanx of the thumb and index finger; weak pronation (pronator quadratus)
• EMG:
  • Decreased distal motor latencies from the elbow to the pronator quadratus
  • Denervation of the flexor digitorum profundus (I–II); FPL, pronator quadratus
• Differential diagnosis of anterior interosseous injury:
  • Paralytic brachial neuritis with concomitant anterior interosseous involvement (pain that lasts for days to weeks)
  • Vascular anomaly of the lateral cord of the brachial plexus (no motor involvement)
  • Rheumatoid arthritis; rupture of the FPL and FDP to the tendons index finger on the tubercle of the scaphoid bone
  • Cervical radiculopathy (sensory loss with biceps, triceps or brachialis reflex loss)

Carpal Tunnel Syndrome

• General features:
  • Proximal to the wrist and carpal tunnel, the palmar cutaneous sensory branch arises and innervates the thenar eminence
  • Carpal bones make up the floor and sides of the carpal tunnel; transverse carpal ligament forms the roof.
  • In the palm the motor branch arises to innervate the first and second digits and the thumb, the recurrent thenar motor branch supplies the opponens pollicis, APB, superficial head of the flexor pollicis brevis; sensory branch supplies the medial thumb, index, long finger and radial side of the 4th finger.
• Pathogenesis of median nerve neuropathy at the wrist:
  • Narrow carpal tunnel (congenital)
  • Most common in middle aged women 3:1 female to male; often bilateral; dominate hand most severely involved
  • Edema, vascular sclerosis and fibrosis of transverse carpal ligament
  • Repetitive hand use
  • Hypothyroidism, diabetes mellitus, scleroderma, rheumatoid arthritis, amyloidosis
  • Lyme disease
  • Sarcoid
  • Colles fracture
  • Pregnancy
  • Hemodialysis
  • Anomalous flexors tendons
  • Flexor tenosynovitis (rare)
  • Gout
  • Secondary to brachial plexus fixation with compromised movement through the carpal tunnel (often bilateral)
• Clinical presentation:
  • Numbness; index, middle finger and radial 1/2 of the fourth finger; larger percentage of patients complain of paresthesia of all fingers
  • Nocturnal paresthesias; awaken patients from sleep; hand held off the bed as a position of comfort
  • Activities that elicit pain or paresthesias; driving, writing, holding a phone or book, typing on a computer
  • Pain: hand, forearm, rarely the shoulder; wrist flexion exacerbates distal and proximal pain radiations (Phalen's sign; usually flexion needs to be held 1–2 minutes to elicit pain); Tinel's sign over the carpal tunnel (not specific as it may occur in normal people).
  • Weakness or tiredness during writing; dropping objects
  • Raynaud's phenomenon and autonomic dysregulation of the hand (median nerve supplies bulk of the sympathetic fiber to the hand)
  • Hypesthesia in the median nerve distribution in 70% of patients. The thenar eminence is spared (palmar branch of the median nerve) leaves the nerve 3 cm prior to the carpal tunnel). The tip of the index finger is the earliest and most severe area of sensory loss. Two-point discrimination is affected prior to pin prick and temperature loss. The radial split of the 4th finger is characteristic. Tinel's sign is positive at the wrist.
• EMG:
  • Decreased sensory conduction at the wrist is most sensitive
  • Prolongation of the distal motor latency
  • Reduction of median motor and sensory amplitudes.
• Differential diagnosis:
  • Brachial plexopathy (lateral cord; upper trunk)
  • Cervical radiculopathy (C6; C7)
  • Median neuropathy at the elbow (sensory loss of the thenar eminence; weakness of distal thumb flexion, arm pronation, and wrist flexion)
  • Lacunar infarction of the motor knuckle or lateral thalamus
  • Rarely TIA
  • Seizure
  • Migraine

Ulnar Entrapment at the Elbow

• General features:
  • Second most common nerve entrapment of the upper arm (<CTS)
  • Derived from C8, T1 roots; lower trunk of the brachial plexus; some fibers through the medial cord
  • Rarely a small component of C7
  • Antebrachial and medial brachial cutaneous nerve and median nerve derive from the medial cord
  • Anatomical variant:
    • Dense fibrous band at the cubital tunnel
    • Epitrochleoanconeus may occur between the medial epicondyle and the olecranon process in the ulnar groove.
  • In the proximal forearm the nerve passes under the humeral-ulnar aponeurosis between the heads of the flexor carpal ulnars which makes up the cubital tunnel
  • Dorsal ulnar cutaneous sensory branch supplies the dorsal medial hand the dorsal 5th and medial 4th digit
  • Palmar cutaneous sensory branch (medial palm territory)
  • Muscular innervation of dorsal and volar interossei, 4th and 5th lumbricales, hypothenar, muscles (palmaris brevis, abductor, flexor and opponens digiti minimi); adductor pollicis (1/2) and the deep head of the flexor pollicis brevis.
• Pathogenesis of ulnar neuropathy at the elbow:
  • Cubitus valgus deformity with elbow instability;
  • Flexion contraction
  • Ten centimeters proximal to the medial condyle compression of the nerve at the arcade of Struthers or the intermuscular septum
  • Occupational trauma
  • Bedridden patients and following anesthesia due to compression and incorrect positioning at the ulnar groove
  • Tardy ulnar palsy: trauma and arthritic changes at the joint years before the neuropathy
• Clinical presentation:
  • Initially, intermittent hyperesthesia in the ulnar distribution exacerbated by elbow flexion; symptoms abate with elbow extension; rarely symptoms are restricted to the hand
  • Rarely initial complaints hand weakness; lateral displacement of the fifth finger; loss of control of the fifth digit
  • May initially present with intrinsic hand muscle atrophy
  • Decreased sensation of the ulnar aspect of the palm. The volar surface of the fifth digit and the ulnar side of the fourth digit. The dorsal sensory branch supplies the dorsal 1/2 fourth finger and the entire fifth digit.
  • Tactile greater than pin prick loss; pure loss over the distal two phalanges of the fifth digit
  • Ulnar nerve innervation stops at the skin crease of the wrist (small triangular area); proximally the innervation of the forearm is from the antebrachial cutaneous nerve of the forearm)
  • Decreased coordination of digital flexion and extension. Weakness of the interossei and flexor digitorum profundus to the fourth and fifth digits.
  • Weakness of the flexor carpi ulnaris; may be spared with elbow lesions as it is lateral and posteriorly placed.

Bone or Scar Impingement at the Elbow

• Spur at the distal end of the humerus
• Fracture of the humerus
• Malalignment after supracondylar fracture of the humerus with valgus deformity
• Lesions within the cubital tunnel:
  • Osteophytes from a fracture or arthritis
  • Synovitis from rheumatoid arthritis
  • Tumors of the elbow joint
  • Epitrochleoanconeus ligament
  • Chondromatosis
  • Ganglion of the ulnar nerve sulcus

Recurrent Subluxation of the Ulnar Nerve

• 10–20% occur in asymptomatic patients
• Congenital laxity of the aponeurosis
• Direct trauma
• Repetitive flexion and extension of the elbow
• Controversial:
  • Repeated subluxation may cause a clinically significant ulnar palsy

Cubital Tunnel Syndrome

• An aponeurotic band from the medial epicondyle of the humerus to the medial border of the olecranon at the entrance of the cubital tunnel; the nerve then passes between the two heads of its flexor carpi ulnaris muscle
• The cubital tunnel narrows with elbow flexion; medial collateral ligament further compromises the tunnel in flexion
• EMG:
  • Focal slowing of the ulnar nerve across the elbow
  • Denervation of ulnar forearm and intrinsic hand muscles

Compression of the Ulnar Nerve in Guyon's Hand/Wrist

• General features:
  • Proximal border is the pisiform bone; distally the hook of the hamate
  • Floor: transverse carpal ligament; hamate triquetrum bones
  • Roof: pisohamate ligament that extends from the hook of the hamate to the pisiform bone
  • Prior to exit from the canal (motor fibers to the ADM, palmaris brevis, opponens digiti minimi, FDM)
  • In the hand:
    • Superficial sensory branch and deep palmar motor branch
  • Deep motor branch (3rd/4th lumbricales; 4 dorsal interossei; 3 palmar interossei; adductor pollicis; deep head of FPB (flexor pollicis brevis)
• Pathogenesis:
  • Ganglion
  • Occupational; long distance bicycle racers (deep palmar motor branch)
  • Fracture of the carpal bones
  • Aberrant muscles
  • Fracture of the radius
  • Dislocation of the pisiform bone
  • Accessory ossicles
  • Fracture of the metacarpal bones
  • Lipoma
  • Pisohamate arthritis
  • Ganglion of the triquetral hamate joint
• Clinical presentation:
  • Pure motor (deep palmar brevis); weakness of 3, 4th lumbricals, interossei
  • Pure sensory (digital sensory fiber (1/2 4 and 5th digit)
  • Motor and sensory (proximal; hypothenar and deep palmar motor and digital sensory branch)
  • Pure motor branch of the deep palm involves hypothenar muscles
  • Midpalmar branch: spares the 4th interosseous muscles
• EMG:
  • Deep branch compression often compromises the branch to the abductor digiti minimi, prolonged distal latency to the first dorsal interossei
  • Ulnar nerve damage at the wrist demonstrates a 20% slowing of motor NCV
  • Denervation of all hand muscles except these of the thenar eminence.
  • Deep branch including branch to the ADM (abductor digiti minimi)
    • Denervation of all ulnar innervated hand muscles
  • Proximal lesion (to the wrist):
    • Involvement of the superficial and deep branches of the ulnar nerves cause decreased SNAP from the Vth finger
  • Volar sensory branch:
    • Sensory abnormality to digits IV and V; with decreased sensory nerve action potentials

Differential Diagnosis of Compression at the Elbow vs the Wrist

• Flexor carpi ulnaris and flexor digitorum profundus muscles are spared (if at the wrist)
• Intact dorsal sensory branch innervation

Differential Diagnosis of Ulnar Entrapment at the Elbow

• Entrapment at Guyon's canal at the wrist (no weakness of the flexor carpi ulnaris; or the ulnar flexor digitorum profundus); isolated sensory loss; decreased volar 4th and 5th digit loss with retained dorsal sensation and sensory branch of the ulnar nerve
• ALS:
  • Usual concomitant involvement of radial nerve innervated muscles
  • Monomelic ALS (involvement of only one extremity)
• Multifocal motor neuropathy with conduction block (usually bilateral, but often starts asymmetrically); high titers of anti GM1 antibodies
• Spinal cord disease:
  • Metastatic intramedullary lesions
  • Infarction of the cord
  • Glioma (rare; associated with long tract findings)
  • Syringomyelia (benediction sign)
  • Lower trunk brachial plexus lesion (positive Tinel's sign at the infraclavicular Gossa; sensory loss in the medial forearm)
• Cervical radiculopathy (disk, spondylosis):
  • C8 lesions are rare (not a motion segment)
  • Pain usually located in the neck and shoulder with disc disease and spondylosis
  • Spondylosis most common at C5–C6; pain affects more than one root; often bilateral
• Thoracic outlet syndrome:
  • Rib band syndrome with lower trunk involvement (C8–T1)
• Brachial Plexus traction injury:
  • Sensory loss in upper trunk, medial and lateral cord territories
  • Positive Roo's sign (abduction stress maneuver)
  • Frequent concomitant sympathetic signs (coldness, hyperhidrosis)

Compression of the Ulnar Nerve in the Forearm

• Pathogenesis:
  • Compartment syndrome (Volkmann's contracture)
  • Cast immobilization
  • Fracture
  • Nerve compression (coma)
  • Hypertrophy of the flexor carpi ulnaris
• Clinical presentation
  • Both motor and sensory involvement
  • Proximal lesion; dorsal sensory branch to the hand is involved

Dorsal Sensory Branch Compression

• Splits from the parent trunk 6–8 cm proximal to the wrist
• Supplies the dorsum of the hand; 1/4 IV and Vth finger; the dorsal middle and distal phalanges are from the volar digital nerves
• Pathogenesis is blunt trauma or laceration
• Variation of dorsal hand innervation due to different radial sensory nerve innervation patterns

Clinical Presentation of Ulnar Neuropathy

• General features:
  • Motor symptoms greater than sensory particularly with mechanical compression
  • Decreased hand dexterity and strength
  • Inability to flex the distal interphalangeal joints of the 4th and 5th fingers
  • Benediction hand posture:
    • Clawed 4th/5th digits
    • Hyperextension of the MP joints, with flexion of the proximal and distal IP joints (weakness of 3rd and 4th lumbricals)
    • Abduction of fingers and thumb (weakness of interossei and adductor pollicis)
  • Wartenberg's sign:
    • Abducted little finger due to weakness of the 3rd palmar interosseous muscle
  • Froment's sign-long flexors of the thumb and index finger are used to pinch
  • Pain may radiate to the elbow, medial forearm and wrist

Radial Nerve Entrapment

• General features:
  • Most often damaged in the upper arm and axilla, least involved of the arm nerves
  • Innervation forum C5 to T1; contribution from all trunks of the plexus
  • Posterior divisions of all three trunks divide to make the posterior cord (axillary, thoracodorsal and subscapular nerves leave the posterior cord).
  • Upper arms posterior brachial nerve of the arm, posterior ante brachial nerve of the forearm
  • Upper arm motor (triceps, anconeus) at the elbow (brachioradialis, extensor carpi radialis longus and brevis)
  • Four centimeters proximal to the lateral epicondyle the nerve bifurcates into the superficial sensory nerve and the posterior interosseous nerve.
  • Superficial radial sensory nerve: dorsal lateral hand; lateral part of the thumb and the proximal phalanges of the index, middle and ring fingers.
  • Posterior interosseous innervates nerve extensor carpi radialis extensor carpi ulnaris extensor commons is abductor pollicis longus; extensor digiti communis (EDC), APL, EIP (extensor indicis proprius); EPL/EPB (extensor pollicis longus and brevis)
    • Innervates the interosseous membrane and joints between radius and ulna

Radial Entrapment at the Spiral Groove

• General features:
  • Abuts the humerus
• Clinical presentation:
  • Wrist and finger drop
  • Mild weakness of supination (supinator muscle)
  • Weakness of elbow flexion (brachioradialis)
  • Spared elbow extension (C7 comes off more proximally)
  • Decreased sensation lateral dorsal hand and dorsal first through fourth fingers (superficial radial sensory)
• Pathogenesis:
  • Fracture of the humerus (2–16% injured in spiral groove)
  • Compression (Saturday night palsy)
  • Vasculitic infarction
  • Strenuous exercise
  • Multifocal motor neuropathy with conduction block
  • Compressions by lateral head of the triceps or fibrous band

Radial Nerve Injury in the Axilla

• Similar to spiral groove lesions except weakness of arm extension and sensory loss of lateral dorsal hand (superficial radial sensory) posterior and lateral arm and forearm (posterior cutaneous nerve of arm; lower lateral cutaneous nerve of the arm; post cutaneous nerve of the forearm:
  • Normal deltoid and thoracic dorsal nerve function which rules out posterior cord lesion of the brachial plexus
• Pathogenesis:
  • Crutch injury
  • Axillary surgery (hyperabduction; direct injury)
  • Lymphoma or tumor extension
  • Transaxillary first rib resection
• EMG:
  • Focal slowing of the radial nerve in the upper arm
  • Denervation of radial innervated muscles in the forearm
  • May spare triceps when lesion is beyond the axilla

Posterior Interosseous Nerve Injury

• General features:
  • Deep muscular branch of the radial nerve
  • No cutaneous sensory loss; pain emanates from innervation of the interosseous ligament
  • Enters the supinator muscle in the Arcade of Frohse
• Clinical presentation:
  • Pain in the elbow and proximal forearm for a few days
  • Pain can be elicited by compression of the nerve distal to the radial head (extensor carpi radialis brevis)
  • Wrist extension weakness with radial deviation; extensor carpi ulnaris weaker than extensor carpi radialis
  • No extension of the fingers at the MCP joint
  • No thumb extension at the MCP joint; no radial thumb abduction
  • Weak extension of the thumb
  • IP joints of the intrinsic hand muscles are innervated by the median and ulnar nerves
  • Partial paralysis of the nerve; decreased extension at MCP joint of IV, V: extension of proximal interphalangeal digits (PID) and distal interphalangeal digits (DIP) because they are innervated by the median/ulnar nerves
  • Rare patterns of partial involvement:
    • Weakness of MCP extension of the thumb
    • Weakness of extension of V
• Pathogenesis:
  • Ganglion cysts
  • Nerve sheath tumors
  • Entrapment under the Arcade of Frohse of the supinator muscle (brachial tunnel)
  • Lipoma
  • Rheumatoid elbow synovitis
  • Ganglia of the elbow joint
  • Bursae
  • Dislocations of the elbow
  • Fracture of the ulna
  • Open reduction of fracture of the proximal radius with plating
  • Tendinous band in the supinator muscle
  • Sensitization from brachial plexus traction injuries
• EMG:
  • Focal slowing across the Arcade of Frohse
  • Prolonged distal latency from the elbow to the EDC
  • Denervation in all muscles supplied by the nerve
  • Supinator and ECR are normal (supplied by more proximal part of the nerve)
  • Cutaneous branches of the superficial radial nerve are normal.

Radial Tunnel Syndrome

• General features:
  • True neurogenic syndrome requires weakness of posterior interosseous innervated muscles.
• Clinical presentation:
  • Lateral elbow pain
  • Dull ache deep on extension the muscle mass of the forearm; night pain; distal and proximal radiations
  • Increased pain on resisted active supination of the forearm
  • Weakness of posterior interosseous innervated muscles
• EMG:
  • Denervation of EDC
  • ECR should be spared
• Pathogenesis:
  • Fibrous band
  • Recurrent fan of aberrant vessels
  • Tendon of the extensor carpi radialis
  • Tendinous band at Arcade of Frohse (most common)

Superficial Radial Nerve Injury

• General features:
  • Derived from the radial nerve at the elbow; extends subcutaneously adjacent to the radius in the distal 1/3 of the forearm
• Clinical presentation:
  • Deficits depend on the overlap with the lateral antebrachial cutaneous nerve
  • Superficial radial nerve sensory territory extends to PIP joints of the II, III, IV digits; lateral dorsum of the hand
• Pathogenesis:
  • Compression by handcuffs; straps; bandage; watch
  • Surgical procedures for de Quervain's disease; joint degenerative arthritis, scaphoid fracture, tight casts; accessory brachioradialis muscle; IV cannulation
• EMG:
  • Decreased SNAP of the nerve
  • Amplitude is decreased in lesions of the radial nerve middle trunk or posterior cord of the brachial plexus
  • Lesions of the spiral groove
  • No abnormality with posterior interosseous nerve or C6 root.

Digital Nerve Entrapment in the Hand

• General features:
  • Compression neuropathy in the palm and digits less frequent than proximal compression
• Clinical presentation:
  • Hypesthesia in the fingers is the most common symptom from chronic extrinsic trauma or compression
  • Compression from expansion of the digit often affects one proper digital nerve causing pain and paresthesia
  • Injury to digital artery causes Raynaud's phenomenon
  • Digital nerve involvement in the palm causes numbness in adjacent sides of the digit
  • Positive Tinel's sign or mass over the affected nerve
• Pathogenesis:
  • Acute external blunt trauma to the palm or digit
  • Dislocation or fracture
  • Bowler's thumb; pain on the ulnar side of the base of the thumb
  • Neuroma in continuity associated with perineural and intraneural fibrosis; severe Tinel's sign with lancinating digital pain
  • Cysts of the flexor tendon sheath (proximal flexion crease); volar and lateral extension is painful
  • Degenerative arthritis of the digit
  • Tumors:
    • Giant cell tumor of the flexor tendon
    • Schwannomas of the digital nerve
    • Fibrosarcoma
    • All cause digital numbness
  • Rheumatoid flexor tenosynovitis (may compress the common or proper digital nerve within the lumbrical canal).
  • Dupuytren's contracture

Differential Diagnosis of Digital Nerve Injury

• Glomus tumor of the pulp; a painful digit; exquisite tenderness; cold sensitivity; bone erosion of the phalanx; shooting pain with palpation. There is no bone erosion with a neuroma
• Isolated herpetic infection (herpes simplex) of one digit (usually the index finger); recurrent vesicles and rash (usually out of the nerve distribution)
• Lipoma of the thenar palm (blocks adductor muscle contraction)

Differential Diagnosis of Radial Neuropathy

• Most patients present with a wrist drop
• Radiculopathy at C7 (the root that innervates most muscles that extend the wrist and fingers)
• Radial neuropathy at the spiral groove or axilla involves the brachioradialis muscle (C5–C6 roots) which is not affected by a C7 root lesion; triceps is spared but would not be in C7 root injury
• If C7 root is damaged the pronator teres, flexor carpi radialis would also be affected
• A brachial plexus posterior cord lesions would involve the thoracodorsal (latissimus dorsi) and the axillary nerve (deltoid) as well as other radial nerve innervated muscles
• Motor knuckle stroke (central sulcal branch of the superior division of the middle cerebral artery) may present with a wrist drop.

Entrapment Neuropathy of the Lower Extremity

Sciatic Nerve

• General features:
  • Originate from L4–S2 roots
• Formed after the merger of the superior and inferior gluteal nerves, lateral division is the peroneal nerve and the medial division is the tibial nerve
• Sciatic notch:
  • Pyriformis muscle (originates from the front of the ramus, the gluteal surface of the ilium, and the anterior capsule of the sacroiliac joint; inserts on the greater trochanter:
    • The sciatic nerve passes under the muscle in approximately 70% of patients
    • Variation in whether the peroneal nerve passes alone through or above the muscles
    • Rarely the entire nerve passes through the muscle
  • Tibial component innervates the semitendinosus, semimembranosus and the long head of the biceps femoris; branch to the adductor magnus muscle
  • Common peroneal innervates; the short head of the biceps femoris
  • Common peroneal and tibial nerve separate most often in the mid-thigh or upper popliteal fossa

Sciatic Injury at the Hip or Thigh

• General features:
  • Lateral greater than medial division affected; difference of fascicular pattern and the course of the nerve in the epineurium
• Clinical presentation:
  • Foot drop; peroneal component more affected than the tibial; slight weakness of hamstrings, gastrocnemius and posterior tibial muscles
  • Rarely a high sciatic lesion may manifest as a pure peroneal palsy
  • Depressed or absent ankle jerk
  • Decreased sensation on the side and lateral foot; spared area around the medial malleolus (saphenous nerve)
  • Instability of the foot
  • Impairment of gait due to knee and ankle instability
• Pathogenesis:
  • Sciatic mononeuropathy is uncommon; most diseases affect the L4–S2 nerve roots; this compromises one or two roots from disc disease, lumbar spondylosis, spondylolisthesis, intervertebral osteophytes or metastatic disease
  • Hip replacement surgery:
    • 1–3% of patients after hip joint replacement surgery have clinical evidence of sciatic nerve damage (much higher by EMG criteria)
    • Higher incidence in total hip revisions; surgery requiring limb lengthening, and with congenital dysplasia or dislocation:
      • Noted following surgery
      • Neuropraxic (stretch) injury
  • Rarer causes of surgical injury:
    • Methyl methacrylate leakage
    • Traction dislocation
    • Migrating traction wires
    • Hemorrhage
    • Prosthetic dislocation
  • Hip fracture; femur fracture (injuring occurs during internal fixation or closed reduction)
  • External compression of the nerve:
    • Coma
    • Poor positioning during anesthesia:
      • Gluteal or posterior thigh compartment syndrome
    • "Toilet seat", lotus position; operative sitting procedures
  • Malignant or benign tumors
  • Enlargement of the lesser trochanter
  • Persistent sciatic artery
  • Severe direct trauma: gun shot or stab wounds
  • Improper injections (often only the peroneal component):
    • Maybe delayed due to fibrosis
  • Hemorrhage within the gluteal compartment:
    • Anticoagulants
    • Hemophilia
    • Hip surgery
    • Rupture of an iliac artery aneurysm
  • Endometriosis:
    • Catamenial sciatica
    • Starts prior to menstruation and ceases with its end
  • Ischemic nerve injury:
    • Inflammation of the vaso vasorum (vasculitis)
    • Iliac or femoral artery occlusion
    • Catheter in the femoral artery
  • Congenital lesions

Pyriformis Syndrome

• General features:
  • Controversial: suggested that the sciatic nerve can be compressed at the pelvic outlet by the pyriforms muscle
  • Anomalous relationships between the sciatic nerve and the pyriformis muscle often do not correlate clinically
  • Some patients (women > men) demonstrate an anomalous band or vessel in the sciatic notch in proximity to the sciatic nerve
  • Muscle spasm with pyriformis compressions of the nerve induced by rheumatic disease, bursitis or trochanteric disease at its insertion
  • Muscle tendon or fascial inflammation
  • History of minimal trauma to the buttock
• Clinical presentation:
  • Buttock pain and tenderness without sciatic radiation; sciatic notch point tenderness
  • Pain exacerbated by sitting, bending at the waist
  • Maneuvers requiring hip adduction and internal rotation
  • Relieved with standing and walking
  • Dyspareunia in women
  • Paresthesia in sciatic distribution that is patchy
  • No weakness, reflex change or hard sensory loss
  • Positive Trendelenburg sign
  • Leg externally rotated with walking
  • Rarely mild wasting of the glutens maximus
  • Positive Freiberg, Pace Beaty tests, pain on adduction, internal rotation and flexion
  • Myofascia band between the biceps femoris and abductor magnus:
    • Distal thigh pain above the posterior popliteal fossa
  • Baker's cyst in posterior distal thigh of either the peroneal or posterior division of the nerve
  • Sciatic compression from muscle fibrosis (pentazocine)
• EMG:
  • NCV and muscle studies are negative
  • Denervation in both peroneal and tibial division
  • Peroneal more affected
  • Short head of biceps less affected than other hamstring muscles
  • Flexor digitorum longus and medial and lateral gastrocnemius reveal fibrillation potentials.

Differential Diagnosis of Sciatic Nerve Injury

• Peroneal nerve lesion at the fibular neck:
  • Tinel's sign at the fibula neck
  • Foot pain is rare
  • No back pain or L5–S1 radiations
  • Negative stretch maneuvers (SLR test)
  • Normal ankle jerk, inversion, toe flexion and plantar flexion
  • Sensory loss at an area between great toe and first digit
• Herniated lumbar disc:
  • Long standing back pain
  • Position of comfort (flexed knees in recumbency)
  • Cough, sneezing, laughing are painful as are all Valsalva maneuvers
  • Monoradicular symptoms S1 > L5 > L4
  • Proximal pain primarily in the buttocks or posterior thigh
  • Often bilateral asymmetric symptoms (loss of foraminal exit maintenance as the uninvolved as well as the involved side)
• Spinal stenosis:
  • L4–L5 > L5–S1 levels; mid lumbar to midsacral levels; epidural compression
  • Progressive calf and foot pain induced by walking and relieved by rest; frequent calf neurogenic cramps.
  • Simian posture (forward flexed back)
• Vascular monomeric neuropathy:
  • Primarily in diabetic patients
  • Acute onset (several days)
  • Wasting is prominent
  • No back pain
  • Sciatic symptoms are mixed with those of the femoral or saphenous nerves
  • Prior history of leg ischemia
  • Sensory loss is stocking and glove; sciatic lesions the saphenous territory is spared
• Malignancy of the spinal cord:
  • Intraspinal tumor
    • Gastrocnemius more severely involved than anterior tibialis or extensor hallucis longus
  • Lymphoma
    • Wraps around the lumbosacral cord on MRI; often involves lower sacral roots
  • Myeloma
    • Root compression by fracture and displacement of bone; marrow signal lost at multiple spinal levels on MRI

Peroneal Nerve

• General features:
  • Branch exits near gluteal fold to innervate the short head of the biceps femoris
  • In the popliteal fossa:
    • Exit of the lateral cutaneous nerve of the calf (upper 1/3 of lateral leg)
    • Sural communicating nerve (joins the sural nerve)
  • Common peroneal nerve passes through the fibular tunnel (tendon of the peroneus longus muscle and fibula); divides into deep and superficial branches
  • Anterior peroneal nerve (deep peroneal branch):
    • Motor; course in the anterior compartment
    • Innervates: tibialis anterior; EHL; peroneus tertius; EDL
    • Under the extensor retinaculum (proximal to the ankle joint the nerve divides into):
      • Lateral motor branch innervating the EDB
      • Medial sensory branch-webspace between the great and second toe
  • Superficial peroneal nerve
• Clinical presentation:
  • Innervate the peroneus longus and brevis (lateral compartment)
  • In the distal leg it becomes the superficial peroneal sensory nerve:
    • Becomes subcutaneous 10 cm proximal to the lateral malleolus; intermediate and medial cutaneous branches innervate the skin of the lower 2/3 of the leg and the dorsum of the foot except for the webspace between the first and second toe.
  • Accessory or deep peroneal nerve:
    • Anomaly in approximately 20% of people; arises as a continuation of the muscular branch of the superficial peroneal nerve and innervates peroneus brevis muscle; distally innervates part of EDB, ankle joint and ligament
• Clinical manifestation:
  • Sensory loss lower lateral leg and dorsum of the foot; exacerbated with walking or running
  • Tinel's sign at 10 cm (fascia)
  • Pain in distal anterolateral leg
  • Ankle pain with or without numbness over the dorsum of the foot if affected at the ankle; increased pain with plantar flexion or inversion
• Pathogenesis:
  • Blunt trauma, boots, lipoma neuromas
• EMG:
  • Absent or low amplitude superficial peroneal SNAPs

Common Peroneal Mononeuropathy at the Fibular Neck

• Men > women, 3:1; R = L; bilateral in 10%
• Weakness of the ankle and toe dorsiflexion is predominate; process many develop gradually
• Weakness of eversion
• Invertors of the foot, toe and plantar flexion are spared
• Sensory abnormalities are noted in the lower 2/3 of the lateral leg
• Rarely Tinel's sign is positive at the fibular neck
• Intact ankle jerk

Deep Peroneal Nerve Mononeuropathy

• General features:
  • Anterior tibialis muscle and extensors of all toes are affected
  • Sensory loss between the first and second toes; webspace
  • Extensor digitorum brevis is supplied by either the superficial or deep branch
  • Distal peroneal lesion (traction injury from ankle sprain) there is selective weakness of the toe extensors with normal ankle dorsiflexion
• EMG:
  • Peroneal CMAPs, EDB and TA are low in amplitude
  • Normal superficial peroneal SNAP

Acute Peroneal Palsy at the Fibular Neck

• General features:
  • Few or no sensory symptoms
  • Loss of motor function; deep peroneal nerve more affected than the superficial nerve
  • Entrapment or a progressive lesion due to tumor, cyst; radiating pain with slowly progressive motor or sensory symptoms
• Pathogenesis: common peroneal palsy at the fibular neck:
  • Compression:
    • Poor positioning during anesthesia
    • Coma (diabetic, drug overdose)
    • Habitual leg crossing
    • Weight loss (HIV, anorexia nervosa)
    • Positional; Yoga, childbirth
    • Casts
    • Lithotomy position with stirrups
    • Pneumatic compression devices
  • Trauma:
    • Blunt and direct trauma
    • Tibial plateau fracture
    • Dislocation of the knee
    • Knee joint ligament rupture
    • Superior tibia-fibular joint dislocation
    • Arthroscopic knee surgery
    • Knee replacement (joint)
    • Knee surgery

Differential Diagnosis of Deep Peroneal Neuropathy at the Fibular Neck

• L5 radiculopathy:
  • Normal ankle inversion and toe flexion in peroneal palsy, but weak in L5 radiculopathy
• Anterior compartment syndrome:
  • Follows contusion or fracture, snake envenomation (hematoxin with DIC)
  • Strenuous exercise
  • Anterior compartment contains AT (anterior tibialis), EDL (extensor digitorum longus), EDB is outside of the compartment
  • All muscles of the compartment are weak; EDB may be denervated when peroneal nerve is involved
  • Differential points of anterior compartment syndrome from deep peroneal nerve involvement:
    • Severe pain (peaks 1–3 days in anterior compartment)
    • Pain on toe and plantar flexion of the ankle
    • Swelling and heat over the compartment
    • Tissue pressure above 60 mmHg is diagnostic at the ankle
• Forcible inversion of the foot (hemorrhage into the nerve trunk); inversion/plantar flexion ankle sprain; childbirth
• Prolonged squatting position (tendon of the posterior border of the peroneus longus at the fibular head versus tendon of the biceps femoris of the distal thigh as cause of compression)
• Rarely: compression between fibula and tendinous edge of peroneus longus (nerve passes between two levels of the muscle)
• Mass lesions:
  • Ganglia from the superior tibia-fibular joint (originate from the synovial membrane)
  • Bakers' cyst
  • Osteochondroma
  • Giant cell tumor
  • Pseudoaneurysm
  • Schwannoma
  • Sarcoma
  • Neurofibroma
  • Intraneural ganglion cyst
• Infections:
  • Leprosy
  • HIV
• Vasculitis
• Entrapment (fibular turmoil syndrome)
• EMG:
  • Denervation of anterior tibialis, EHL or EDB (Deep peroneal innervated muscles); peroneus longus (superficial peroneal muscle)
  • Need to r/o proximal common peroneal mono-neuropathy by demonstrating no denervation of the short head of the biceps; nerve conduction evaluation of the common peroneal nerve and its branches

Tibial Nerve Injury at the Knee

• Pathogenesis:
  • Baker's cyst; ganglia; trauma to the knee; traction injuries from ankle sprains
• Clinical presentation:
  • Weakness of foot plantar flexion
  • Sensory loss on bottom of the foot
• EMG:
  • Denervation in tibial innervated muscles below the knee
• Lumbar plexopathy:
  • General features:
    • Occurs with pelvic surgery; retroperitoneal hematoma ; prolonged labor; metastatic disease
• Clinical presentation:
  • Weak ankle inversion
  • Weak toe flexion
  • Normal plantar flexion
  • Well demarcated to the L5 dermatoma
  • AJ present unless the S1 root is involved
  • Pain is common and may be radicular

Deep Peroneal Mononeuropathy at the Ankle

Sciatic Mononeuropathy Affecting the Peroneal Nerve Selectively

• General features:
  • Lateral (peroneal division is affected more frequently than the medial tibial division
  • Peroneal division injured during:
    • Hip trauma; fracture dislocation; femoral fracture
    • Hip joint replacement; coma, abnormal positions
    • Gluteal injection ( penicillin , Na²++, Fe²); gluteal compartment syndrome
    • Peroneal division has fewer and larger nerve fascicles with less supportive tissue
    • Peroneal nerve is fixed at the sciatic notch and fibular neck (more taut than the tibial nerve)
• Clinical presentation:
  • Similar to lesions at the fibular neck:
    • Subtle tibial nerve involvement
    • Absent or depressed AT (due to tibial nerve involvement)
    • Weak ankle inversion (due to partial tibial nerve involvement)
    • Sensory loss on the sole (concomitant tibial nerve involvement)
    • Sensory loss in the upper lateral third of the leg (territory of the lateral cutaneous nerve of the calf originates from the common peroneal nerve proximal to the fibular neck)
  • EMG:
    • Short head of the biceps femoris is the only hamstring muscle innervated by the peroneal nerves

Superficial Peroneal Nerve

• General features:
  • Injured 10 cm proximal to lateral malleolus (pierces the fascia and become superficial)
  • Runner or other athletic pursuits
• Clinical presentation:
  • Numbness lateral distal 1/3 of the leg

Differential Diagnosis of Peroneal Mononeuropathy

• L5 radiculopathy:
  • L5 radiculopathy; usual cause is an herniated nucleus pulposus (HNP); back pain and sciatic nerve radiations (hip pain and great toe; dorsum of the foot)
  • Inversion weakness of the foot (posterior tibialis nerve) not innervated by the peroneal nerve
  • Sensory loss above the midpoint of the calf (laterally) is peroneal mononeuropathy. Upper part of the calf is supplied by a separate sensory branch from the popliteal fossa.
  • Greater weakness of EHL than AT suggests an L5 lesion (it has more of innervation)
  • Ankle jerk is intact. Primarily innervated from S1

Deep Peroneal Neuropathy at the Ankle (Anterior Tarsal Tunnel Syndrome)

• General features:
  • Floor is the fascia overlying the talus and navicular bones, roof is the inferior extensor retinaculum
  • Lesion of the distal segment of deep peroneal nerve
• Clinical presentation:
  • May be unilateral or bilateral; more common in women than men
  • Numbness and paresthesias deep peroneal sensory distribution (web space of the first and second toe)
  • Wasting of EDB
  • Ankle and foot pain worse at night
• Pathogenesis:
  • Pressure from straps, shoe rims, ganglion cyst, pes cavus; osteophytes of the talonavicular bones, plantar flexion of the foot with extension of the toe (high heels); extreme inversion of the foot as occurs in dystonia or spasticity
• EMG:
  • Neurogenic MUAP and denervation of EDB
  • Prolongation of peroneal motor distal latency to EDB
• Differential diagnosis:
  • Lateral division alone: foot pain may be combined with arthritis, ligament damage, bone abnormalities; EDB is atrophied in ATT syndrome
  • Superficial peroneal nerve; no motor loss; sensory loss of the dorsum of the foot and base of the lateral toes
  • L5 root: S1 may be heel pain alone; L5 dorsum of the foot

Differential Diagnosis of Unilateral Foot Drop

• HSMN/CMT:
  • Flat foot (rocker bottom): foot and ankle weakness in all fields of movements; usually bilateral:
    • Hereditary sensory motor neuropathies
  • Weakness of ankle and toe dorsiflexion with intact plantar flexion is a true foot drop
• Deep peroneal neuropathy
• Common peroneal palsy at the fibular neck
• L4 and L5 radiculopathy (not as severe as nerve injury)
• Poliomyelitis and postpolio syndrome (usually pain in the latter and weakness occurs after period of stability)
• Cerebral vascular disease:
  • Anterior cerebral artery (shoulder involved)
  • Corona radiata (medullary arteries)
  • Ventral pons (lacunar infarction)
• ALS (common painless foot drop; fasciculations and hyperactive reflexes)
• Anterior compartment syndrome of the leg (repetitive exercise; snake bite; rhabdomyolysis)
• Lumbosacral plexopathy (weak toe and plantar flexion)
• Hereditary neuropathy with sensitivity to pressure palsy (concomitant involvement of other nerves)
• Mononeuritis multiplex (setting of autoimmune disease)
• Multifocal motor neuropathy with conduction block (GM1 gangliosidosis; usually upper extremities affected first)
• Parasagittal meningioma (presents with seizure in one leg)

Differential Diagnosis of Bilateral Foot Drop

• Neuropathies:
  • GBS (subacute; usually with numbness)
  • CIDP (Facial numbness; depressed reflexes-throughout)
  • MMNCB (GMI, asymmetric; upper extremity often first)
  • Bilateral peroneal lesions (autoimmune pathologies)
  • Bilateral sciatic compressive lesions
  • Bilateral lumbosacral plexopathies (metastasis, lymphoma, metastasis, retroperitoneal hemorrhage)
• Anterior Horn Cell:
  • ALS (usually unilateral; weakness at onset; associated upper motor signs and symptoms)
  • Spinomuscular atrophy (SMA)
  • Poliomyelitis
  • Leukemia and lymphoma
  • Radiculopathies:
    • Cauda equina syndrome (disc; spondylolisthesis)
    • Conus medullaris (cancer; glioma, syrinx; bladder and bowel predominant over motor loss)
    • S1 greater than L5 root suggestive of intraspinal tumor
  • Myopathies:
    • Myotonic dystrophy (concomitant masseter, neck and distal arm weakness)
    • Fascioscapulohumeral dystrophy (face severe involvement)
    • Scapuloperoneal dystropy (upper shoulder girdle dramatically atrophic)
    • Distal congenital myopathies:
      • Welander
      • Nonaka
      • Markesburry–Griggs – UDD
      • Liang

Tibial Nerve

• General features:
  • Innervates all of the hamstring muscles except the short head of the biceps femoris (common peroneal nerve)
  • Sural branch given off in the upper popliteal fossa; in 80% of patients, the common peroneal nerve gives off a medial branch that joins the sural nerve
  • In the upper calf the tibial nerve lies under the tendinous arch of the soleus muscle (innervate FDP, FHL, gastrocnemius, soleus and tibialis posterior muscles)
  • At the ankle passes posterior to the medial malleolus in the tarsal tunnel
  • Terminal branches are:
    • Calcaneal branch
    • Medial plantar nerve
    • Lateral plantar nerve
  • Interdigital branches arise from the medial and lateral plantar nerves on the soles of the foot

High Tibial Nerve Injury

• General features:
  • Most often the nerve is injured in or near the popliteal fossa
• Clinical presentation:
  • Foot pain and numbness; increased by dorsi or plantar flexion of the foot
  • Tenderness and a positive Tinel's sign in the posterior popliteal fossa
  • Weakness of plantar and toe flexion and inversion of the foot
  • Absent ankle jerk
• Pathogenesis:
  • Synovial cyst or superior tibial-fibular ganglion cyst
  • Fibrous band or aponeurotic arch of the soleus
  • Knee surgery
  • Schwannomas and neurofibromas
• EMG:
  • Low or absent MUAP of the abductor hallices and abductor digit minimi pedis muscles
  • Sural nerve SNAP may be absent depending on the location of the take off of the nerve in the popliteal fossa

Tibial Nerve Injury at the Ankle Tarsal Tunnel Syndrome

• General features:
  • Compression of tibial nerve or its terminal branches under the flexor retinaculum
  • Usually insidious onset
  • Women greater than men in frequency
  • 10–20% of patients it is bilateral
  • Anatomy: the root is the lancinate ligament extends between the medial malleolus and the calcaneum (flexor retinaculum; posterior tibial artery, tendons of the tibialis posterior, FDL, FHL
• Pathogenesis:
  • Injured in runners and dancers
  • Rheumatoid arthritis
  • Acromegaly
  • Diabetes mellitus
  • SLE
  • Hyperlipidemia
  • Hypothyroidism
  • Ganglion cyst
  • Lipoma
  • Schwannoma
  • Varicose veins
  • Heel varus and valgus deformities
  • Hypertrophic or anomalous abductor hallices muscles
  • Mobile pes planus
• Clinical presentation:
  • Burning pain and numbness on the sole of the foot and heel; may radiate to the calf
  • Nocturnal pain
  • Increases with rest after activity
  • May be exacerbated by walking or jogging
  • May be in medial plantar, lateral plantar or calcaneal branch distributions
  • Tinel's sign is positive over the tunnel
  • In 40% of patients, the calcaneal branch is spared as it takes off proximal to the retinaculum
  • 25% of patients have the sensory loss only in medial branch; 10% only in the lateral branch
  • Rare weakness of FHB; FDB (medial plantar); quadratus plantar; interossei (lateral plantar); impairs pushing off phase of walking; weakness of plantar flexion of the lateral toes
• EMG:
  • Decreased conduction of distal posterior tibial nerve
  • Decreased SNAP, slowed NCVs of the medial and lateral plantar nerves
  • Rare denervation of the abductor hallices and abductor digiti pedia quinti

Differential Diagnosis of Tarsal Tunnel Syndrome

• Plantar fasciitis (entree sole equally involved)
• Stress fractures (lateral metatarsals > medial)
• Bursitis (insertion of the anterior tibial muscle)
• Rheumatoid arthritis (severe joint deformities)
• Chronic regional pain syndrome II (severe allodynia, hyperalgesia, autonomic dysregulation)
• Proximal tibial mononeuropathy (compression by the tendinous arch of the soleus muscle); plantar flexion weakness; decreased AJ
• Tibial component of the sciatic nerve (nerve sheath tumor); calf weakness, decreased AJ
• S1 and S2 radiculopathy; concomitant weakness these root muscles and back pain
• Peripheral neuropathy (usually bilateral which is rare with TTS)
• Entrapment of the medial plantar nerve (area of insertion of AT which originates from the calcaneus)
• Burning in the sole and aching in the arch ; medial plantar nerve against the tuberosity of the navicular bone

Lesions of the Medial Plantar Branch of the Tibial Nerve

• Bunion surgery
• Pes cavus
• Synovial cyst of the first metatarsal phalangeal joint
• Schwannoma
• Running

Lateral Plantar Nerve Injury of the Tibial Nerve

• Trauma
• Fracture
• Schwannoma

Joplin's Neuroma

• Medial plantar proprius digital nerve to the great toe:
  • Cutaneous innervation of the medial aspect of the great toe
  • Due to ill-fitting shoes, trauma, or bunion
  • Positive Tinel's sign at the first metatarsophalangeal joint

Morton's Neuroma (Interdigital Neuropathy)

• General features:
  • Generally refers to interdigital neuropathy between the 3rd and 4th toes; may occur between web space of all toes
  • Anatomy: metatarsal tunnels are between the deep and transverse metatarsal and superficial ligaments that connect the metatarsal heads
  • Medial plantar nerves, arteries and veins transverse the metatarsal tunnel of the first, second and third toes
  • Lateral plantar nerves supply the IV, Vth toes
  • Chronic compression of the interdigital nerve between the metatarsal head; hyperextension of the metatarsophalangeal joint exacerbates the angulation of the nerve
• Pathogenesis:
  • Distortion of the metatarsophalangeal joints
  • Trauma; high heels
  • Fractures
  • Subluxation of the joint
  • Rheumatic inflammatory disease
  • Synovial cysts
  • Hyperextension of the toes narrows the canals and compresses the nerves
  • Flexion contraction of the hip and knees causes toe hyperextension
  • Dystonia and spasticity
• Clinical presentation:
  • Lancinating electric-like pain in the territory of the involved interdigital nerve
  • Triggered by pressure between III, IV metatarsal head (classic)
  • Hypoesthesias in the distribution of the involved digital nerve
  • Arch pain
  • Exacerbated by standing and walking
  • Pain may radiate to the ankle and calf
  • Web space compression test is positive
• Differential diagnosis of Morton's Neuroma:
  • Bursitis
  • Plantar fasciitis
  • Arthritis (head of joint is tender not the web space)
  • TTS may involve only one plantar nerve

Diagnostic Evaluation

• Ultrasound demonstrates an ovoid hypoechoic non-parallel to the long axis of the metatarsal bone
• Decreased sensory NCV's of the interdigital nerves

Sural Nerve Injury

• General features:
  • Branch of the distal sciatic from both divisions in the posterior popliteal fossa
  • Injured at the ankle or calf
  • Post operative complications following biopsy of the sural nerve are common (approximately 50% of patients)
  • Sural neuralgia may occur in 5% of patients after surgical procedure and biopsy (neuroma)
• Clinical presentation:
  • Pain and paresthesias in the lateral ankle and foot; sensory loss in the lateral sole to the base of the Vth toe
  • Normal AJ and gastrocnemius strength (differentiate it from S1 radiculopathy)
  • Tinel's sign after its emergence 20–25 cm above the foot
• EMG:
  • Low amplitude or absent SNAP

Femoral Nerve

• General features:
  • Formed by the posterior divisions of the ventral rami of L2, L3, L4 spinal roots
  • Innervate psoas muscle; passes between the psoas and iliacus muscle; covered by the iliacus fascia (roof of the iliacus compartment)
  • Passes under the inguinal ligament; innervates the iliacus muscle (4–5 cm proximal to the ligament)
  • After the ligament it innervates:
    • Four heads of the quadriceps and the sartorius muscle
    • The medial and the intermediate cutaneous nerve of the thigh (innervates the anterior thigh) and the saphenous nerve; the saphenous nerve is posteromedial in the femoral triangle and passes through the adductor canal; it is the origin of the infrapatellar branch that innervates the skin of the anterior patella; the saphenous nerve become subcutaneous 10 cm proximal and medial to the knee (pierces the fascia between the sartorius and gracilis muscle); crosses the pes anserinus bursa at the upper medial tibia. In the lower third of the leg it divides into two terminal branches that innervate the medial surface of the knee, leg, medial malleolus and medial arch of the foot.
• Clinical presentation:
  • Usually unilateral; exception is lithotomy position with concomitant pressure on the adductor canal (during delivery or GYN surgery)
  • Acute thigh weakness
  • Weakness and atrophy of the quadriceps
  • Sensory loss over the anterior thigh and medial calf
  • Hip, flexor weakness (L1–L3) suggests lumbar plexus weakness
  • Unstable leg; knee buckles when partially flexed; frequent falls
  • Sensory loss in the medial and intermediate femoral cutaneous nerve distribution
  • Acutely, groin and thigh pain; later on deep pain
  • Femoral nerve involvement from retroperitoneal hematoma has severe back abdominal, groin, buttock and anterior thigh pain; position of comfort is a flexed thigh
  • Hip flexion weakness (iliopsoas involvement with intrapelvic lesion); spared if lesion is at the inguinal ligament (lithotomy position)
  • Positive reversed straight leg raising test (particularly with proximal lesions)
  • Depressed or absent knee jerk
• Pathogenesis:
  • Primarily injured during surgical or diagnostic procedures; retractor compresses the nerve against the pelvic wall
  • Pelvic injury:
    • Abdominal hysterectomy
    • Prostatectomy
    • Renal transplantation
    • Colectomy
    • Inguinal herniorrhaphy
    • Lumbar sympathetectomy
    • Tubal ligation
    • Aortic aneurysm surgery
  • Retroperitoneal hematoma:
    • Fascial layer pressure; blood is trapped over the iliacus muscle beneath the femoral triangle and under the fascia
    • Renal transplantation (bleeding)
    • Hemophilia
    • Anticoagulation
    • Coagulopathy
    • Ruptured abdominal aneurysms
    • Femoral artery catheterizations
    • Large hemorrhages extend into the psoas muscle and retroperitoneal space that compromises lumbar or lumbosacral plexus
    • Femoral artery or vein catheterization:
      • Approximately 0.5% of femoral artery catheterization for coronary artery disease bleed; often there is concomitant use of anticoagulation); approximately 1/3 lead to lumbar plexopathy or femoral nerve injury
  • Compression at the inguinal ligament:
    • Prolonged lithotomy position (hip flexion and external rotation):
      • Associated with vaginal delivery
      • Vaginal hysterectomy, prostatectomy and laparoscopy
    • Inguinal hematoma
  • Total hip replacement:
    • Nerve injury may occur up to 2–3% of patients
    • Anterior acetabular retraction compress the nerve
    • Most common in revisions and complicated reconstruction of the hip
  • Lymphadenopathy at the inguinal area
  • Pelvic mass lesions:
    • Lymphoma
    • Metastatic tumor (ovary, prostate, colon)
    • Abscess
    • Aortic or iliac aneurysm
  • Neurapraxia injuries (stretch)
  • Radiation therapy
  • Laceration (blood drawing, cauterization)
  • Diabetic femoral neuropathy (radicular plexopathy)
  • Femoral nerve tumors; neurofibroma, schwannoma and neurogenic sarcoma
• EMG:
  • Slowing of motor nerve conduction at the inguinal ligament
  • Decreased SNAP of the saphenous nerve
  • Denervation of femoral nerve innervated muscles
• Differential diagnosis:
  • L2, L3, L4 radiculopathy (rare disc disease)
  • Lumbar plexopathy (L2, L3, L4); if the thigh adductors are denervated the lesion is proximal to the femoral nerve (obturator nerve)
  • Weakness of ankle dorsiflexion (L4 and L5) from the peroneal nerve suggests L4 radiculopathy or lumbar plexopathy; back and buttock pain with positive reverse straight leg raising test favor radiculopathy; maybe positive as well with retroperitoneal hematoma or mass lesion

Saphenous Nerve Injury

• General features:
  • Courses through the adductor canal; penetrates the fascia above the knee
  • Supplies the medial calf; medial malleolus and medial arch of the foot
• Clinical presentation:
  • Pain or numbness in the distribution of the nerve; medial calf most noticeable
  • Tinel's sign over the site of entrapment
  • Entrapment often occurs at exit from Hunter's canal (10 cm above the medial femoral condyle)
  • Knee pain is common
  • Infrapatellar branch entrapment causes anterior, anteromedial or anterolateral knee pain
• Pathogenesis:
  • Stripping of the long saphenous vein as well as harvesting the vein for coronary bypass
  • Superficial femoral thromboendarterectomies
  • Femoropopliteal bypass grafts
  • Meniscectomies
  • Arthroscopic procedures
  • Infrapatellar branch maybe entrapped behind the sartorius tendon
  • Medial knee trauma
  • Schwannoma
• EMG:
  • Low or absent saphenous SNAP
• Differential diagnosis:
  • L4 radiculopathy
  • Lumbar plexopathy
  • Femoral neuropathy

Lateral Femoral Cutaneous Nerve Injury

• General features:
  • Sensory fibers of dorsal rami of L2 and L3 spinal roots
  • Passes within or under the inguinal ligament anterior or medial to its insertion at the anterior superior iliac spine. There are significant anatomical variations of its passage
  • Pierces the fascia lata to innervate the lateral thigh
• Clinical presentation:
  • Numbness and paresthesias in the lateral thigh (burning); never below the knee
  • Hyperesthesias and dynamic and static mechanoallodynia may occur
  • Exacerbated by standing, walking or turning and relieved by hip flexion
  • "Wind-up phenomenon" present; increasing dysesthesias with temporal summation
  • Alopecia maybe present in the area of sensory loss
• Pathogenesis:
  • Entrapment of the LFCN through or under the inguinal ligament (meralgia paresthetica):
    • Diabetes
    • Pregnancy
    • Obesity
    • Constricting belts
  • Direct injury
    • Iliac bone grafts
    • Injections
    • Renal transplantation
    • Gastric bypass surgery
    • Herniorrhaphy
    • Intrapelvic retraction injury
    • Abnormal positioning (hip flexion)
    • Blunt trauma (seat belt; avulsion of the anterior superior iliac spine)
    • Metastasis to iliac crest
    • Abdominal aortic aneurysm
• EMG:
  • Decrease SNAP and NCVs of the nerve
• Differential Diagnosis:
  • Lumbar radiculopathy:
    • Not as well circumscribed sensory loss
    • Associated back and groin pain
  • Femoral neuropathy:
    • Numbness involves the anterior thigh; may extend medially and to the leg
    • Weakness of the quadriceps and depressed KJ exclude the diagnosis
  • Lumbar plexopathy:
    • Anterior thigh pain
    • Weakness; loss of KJ
  • Lumbar spinal stenosis:
    • "Simian" forward, flexed posture
    • Weakness primarily in the L4–S1 distribution
    • Loss of AJ at times; other patients have increased reflex due to concomitant cervical stenosis
  • Tensor fascia lata bursitis:
    • Lateral thigh pain often with specific point tenderness

Ilioinguinal Nerve Injury

• General features:
  • Originates from T12–L1 spinal roots; pierces the transverse and internal oblique muscles and passes along the inguinal canal
  • Associated with the genital branch of the genital femoral nerve and the spermatic cord in men; the round ligament in women
  • Innervates the lower abdominal muscle
  • Cutaneous innervation along the ilial ligament and the labia majora in women and base of the penis and scrotum in men
  • Entrapment usually slightly medial to the anterior iliac spine with a positive Tinel's sign
• Clinical presentation:
  • Burning pain in the lower abdomen; inner portion of the thigh; scrotum; labia majora
  • Bulging of the anterior abdominal wall (transversalis; internal oblique muscle weakness)
  • Pain is exacerbated with extension of the thigh or hip; position of comfort is a flexed hip
  • Tinel's sign elicited by tapping the lower abdomen
• Pathogenesis:
  • Laparoscopy
  • Hernia repair
  • Appendectomy
  • Bladder suspension
  • Pfannenstiel incision
  • Blunt trauma
  • Entrapment medial to the anterior superior iliac spine
• EMG:
  • Denervation of lower abdominal muscles
• Differential diagnosis:
  • High lumbar radiculopathy (L1 or L2)
  • Iliohypogastric neuropathy
  • Genitofemoral neuropathy

Iliohypogastric Nerve Injury

• General features:
  • Originates from T12–L1 spinal roots; crosses the psoas and quadratus lumborum muscles; passes through and innervates transverse and internal oblique muscles
  • Two terminal cutaneous branches that innervate lateral buttock (lateral branch) and over and along the pubic symphysis (anterior branch)
• Clinical presentation:
  • Pain and sensory loss above the symphysis pubis
  • Rarely weakness of the abdominal wall
  • Lateral buttock numbness (strip)
• Pathogenesis:
  • Most often injured with the ilioinguinal nerve
  • Appendectomy
  • Hernia repair
  • Pfannenstiel incision (gynecologic surgery)
  • Abdominoplasty
• EMG:
  • Denervation of the lower abdominal muscles
• Differential diagnosis:
  • Ilioinguinal neuropathy
  • Genitofemoral neuropathy
  • L1 and L2 radiculopathy

Genitofemoral Nerve Injury

• General features:
  • Originates from L1 and L2 spinal roots; passes through the psoas muscles; divides into femoral and genital branches at the inguinal ligament
  • Femoral branch innervates small area of anterior thigh; genital branch innervates scrotum and labia majora
  • Innervates the cremasteric muscle
• Clinical presentation:
  • Pain in the medial inguinal area, scrotum or labia majora
  • Sensory loss may overlap with that of ilioinguinal nerve
  • Absent cremasteric reflex
• Pathogenesis:
  • Appendectomy
  • Inguinal herniorrhaphy
  • Nephrectomy
  • Cesarean section
  • Abdominal trauma
  • Adhesions and scarring (delayed presentations)
  • Concomitant genital branch and ilioinguinal nerve injury occurs at the inguinal ligament
• EMG:
  • No NCS have been delineated from this nerve
• Differential diagnosis:
  • L1–L2 radiculopathy
  • Ilioinguinal neuropathy:
    • No anterior femoral distribution

Posterior Cutaneous Nerve of the Thigh Injury

• General features:
  • Origin is S1–S3 spinal roots
  • Exits the pelvis with the inferior gluteal nerve through the sciatic notch under the pyriformis muscles
  • Cutaneous innervation of the lower buttock, posterior thigh, popliteal fossa and at times the proximal 1/3 of the calf; perineal, scrotal and labia majora branches
  • Injured with sciatic and inferior gluteal nerves
• Clinical presentation:
  • Paresthesias of the lower buttock and posterior thigh; exacerbated with sitting or lying down
• Pathogenesis:
  • Gun shot and laceration wounds
  • Colorectal tumors
  • Venous malformations
  • Bicycle riding; specific compressions
  • Intramuscular injections
• EMG:
  • Decreased SNAP of the nerve
• Differential diagnosis:
  • S1 or S2 radiculopathy
  • Sacral plexopathy: the above root lesions would be accompanied by a depressed or absent ankle jerk; sciatic nerve lesions would have concomitant hamstring or gastrocnemius muscle weakness

Obturator Nerve Injury

• General features:
  • Origin is the ventral divisions of L2, L3, L4 spinal roots; courses at the medial edge of the psoas muscle and over the sacroiliac joint and divides into anterior and posterior divisions at the obturator canal
  • Innervate the adductor longus, brevis and magnus (also innervated by the sciatic)
  • Cutaneous innervation of part of the inner thigh
• Clinical presentation:
  • Pain in the medial thigh (often in athletes or associated with obturator hernia); adductor muscle weakness
  • Pain may radiate to the medial calf; exacerbated by extension or lateral leg movement
  • Adductor weakness causes destabilization of the hip joint; difficulty with walking; wide based gait
• Pathogenesis:
  • Lumbar plexopathy (accompanies femoral nerve lesions; it arises from the dorsal divisions of the same roots)
  • Pelvic trauma (fractures)
  • Hip surgery:
    • Retractor blade
    • Cement extrusion
    • Fixation screws
  • Aorta femoral bypass
  • Oophorectomy
  • Laparoscopic lymphadenectomy
  • Vaginal delivery (forceps)
  • Obturator hernia
  • Endometriosis
  • Pelvic malignancy
  • Rare; entrapment under adductor fascia
  • Schwannoma
  • Sacroiliac joint lesion may impinge on the nerve
• EMG:
  • Adductor denervation
  • Fibrillation potentials and large MUAP
• Differential diagnosis:
  • L3, L4 radiculopathy
  • Lumbar plexopathy (diabetes, infection, malignancy, collagen vascular disease)

The above are ruled out by iliopsoas, quadriceps weakness, loss of knee jerks and ankle jerks. Medial thigh sensory loss is seminal. Symphysis pubis lesions may radiate to the medial thigh.

Gluteal Nerve Syndromes

• General features:
  • The superior and inferior gluteal nerves originate from the lumbosacral plexus and traverse the infrapiriform and suprapiriform foramen
  • The foramen is bounded by: superior edge of the piriform muscle, the lower edge of the gluteus medius muscle, ischium of the greater sciatic notch; the piriformis muscle divides the sciatic notch into a superior and inferior foramen
  • Inferior gluteal nerve course through the:
    • L5, S1 and S2 roots; exit through the infra piriformis foramen
    • Innervate the gluteus maximus muscle; supplies hip capsule
  • Superior gluteal nerve:
    • Origin is L4, L5, S1; exits the pelvis through the suprapiriform foramen in juxta position with the sciatic and posterior femoral cutaneous nerve
    • Innervates the gluteus medius, minimus, and the tensor fascia lata
• Pathogenesis:
  • Superior gluteal nervi is injured with misplaced injections
  • Inferior gluteal nerve is injured by intrapelvic mass lesion, lymphoma or colorectal cancer and iliac artery aneurysms
  • Both inferior and superior nerves may be damaged following hip replacement
  • Superior gluteal nerve is rarely entrapped by the piriformis muscle
  • Inferior gluteal nerve may be compressed by the sciatic nerve
  • Pelvic fracture may damage both nerves
  • Prolonged traction during hip replacement
• Clinical presentation:
  • Superior gluteal nerve: pelvic tilt to the opposite side during walking or standing on the affected leg (Trendelenburg sign); waddling gait; weakness of hip abduction
  • Inferior gluteal nerve:
    • Difficulty climbing stairs; standing from a sitting position
    • Pain in the gluteus muscle that radiates into the posterior thigh
    • Weakness of hip extension
    • Atrophy of the buttock
• EMG:
  • Fibrillation potentials and loss of MUAP in the tensor fascia lata and gluteus medius are noted with superior gluteal nerve lesions
  • Inferior gluteal nerve lesions demonstrate denervation of the gluteus maximus
• Differential diagnosis:
  • Disease of the hip joint
  • L5 and L1 radiculopathy

Unusual Entrapments

Lumbosacral Tunnel Syndrome

• General features:
  • L5 root entrapped across the sella of the sacrum or under the lumbosacral ligament
  • Lumbosacral ligament: fibrous bone originates from the fifth lumbar vertebra and inserts on the upper border of the sella of the sacrum
  • L5 root courses under the ligament with the iliolumbar artery and vein
• Pathogenesis:
  • Thickening of the ligament
  • Bony osteophytes
  • Tumor
  • Artery or venous disease
• Clinical presentation:
  • Sensory loss and pain in L5 dermatome without objective findings

Rectus Abdominis Syndrome

• General features:
  • Trapped branches of the T7–T12 intercostal nerves within the rectus muscles
• Clinical presentation:
  • Localized pain in the abdominal wall
  • Aggravated by direct pressure or leg elevation in the supine position

Cheiralgia Paraesthetica

• General features:
  • Superficial branch of the radial nerve
• Clinical presentation:
  • Pain and sensory loss over the dorsum of the lateral aspect of the wrist and first two fingers

Gonyalgia Paraesthetica

• General features:
  • Infrapatellar branch of the saphenous nerve
• Clinical presentation:
  • Numbness and paraesthesias over the patella (often medial)
  • Sharp lancinating pain induced by nerve stretch