Differential Diagnosis in Neurology

6.2. Disc Disease

Cervical Disc

• General features:
  • A bulging disc extends beyond the margin of the end plate of the vertebral body but the annulus fibrosis is intact
  • A disc extrusion is an extension of the nucleus pulposus through the annulus; usually remains anterior to the posterior longitudinal ligament (rarely it extends through it).
  • A sequestered fragment is completely separated from the nucleus pulposus. This segment may migrate up or down the spinal cord.
  • Cervical spine roots exit horizontally from the cord to the neural foramina and entrap the root corresponding to the vertebral body directly below it.
  • The ventral and dorsal roots join distal to the DRG and form a spinal nerve; the dorsal ramus supplies the paraspinal muscles and is the cutaneous innervation of 1.5 – 2 inches lateral to the spinous process; the ventral rami form the cervical and lumbar plexus
  • Posterolateral disc herniation often compresses the root that will exit one level below. The root at the level of the herniation has already exited. A far lateral disc may trap the root at the specific level. The exiting nerve root is lateral to the descending root. A posterior or large HNP may compress the cauda equina and compress many descending nerve roots.
  • Disc disease occurs at motion segments:
    • C4–C5; C5–C6; C6–C7 at cervical levels
    • L4–L5; L5–S1 at lumbar levels
  • Disc herniation may cause bilateral symptoms. The foraminal exit may be compressed (superiorly) as the disc desiccates, extends and does not maintain its normal height. The side with direct nerve root compression is affected to a much greater degree
• Clinical Presentation:
  • The pain emanates from the neck and radiates primarily to the spine and the shoulder. C4–C5 disease radiates to the cap of the shoulder. C5–C6 to the shoulder and biceps. C6–C7 to the spine medially and lateral forearm [C6 and posterior (triceps area, C7)]. Radiation of cervical disc to the hand is rare (C6 thumb and index finger; C7 third finger; extremely rarely C8. Median nerve compression involves all fingers clinically. It should split the fourth finger (median nerve side medially). Ulnar nerve lesions at the cubital tunnel radiates pain to the last 1/2 4th and complete 5th finger. The ulnar nerve has only a small innervation area; one inch above the wrist and the last two 4th/5th fingers. The lateral cord of the brachial plexus radiates pain to the thumb, index, and radial part of the third finger. Posterior interosseous nerve from the posterior cord and middle trunk of the brachial plexus is a pure motor nerve. The medial forearm radiations are primarily from the medial cord.
  • Limitation of neck movement due to pain is common with disc disease; Spurling's maneuver (extending and rotating the neck to the side of the lesion and then pressing it downward) may irritate the involved root. Neck extension induces posterior disc bulging and lateral flexions and rotation narrows the ipsilateral neural foramina. A position of comfort is for a patient with cervical radiculopathy to place the arm over the head which decompresses the nerve root sleeve. Thus maneuver severely exacerbates brachial plexus pain by stretching sensitized nerve roots. Valsalva maneuvers exacerbate the pain of disc disease by causing further protrusion.
  • The C5 root radiates to the neck and cap of the shoulder; weakness is seen in shoulder abduction, external rotation, elbow flexion and forearm supination. There is depression of the biceps and brachioradialis reflex.
  • The C6 root radiates pain to the neck, shoulder, lateral forearm and rarely the thumb and index finger. Strength is diminished similarly to C5 involvement but, there is added pronation weakness of the arm.
  • The C7 radiates to neck, triceps, medial spine and rarely the long finger. Weakness is noted in elbow and wrist extension, forearm pronation and wrist flexion. The triceps reflex is depressed.
  • The C8 root is rarely affected by disc disease as it is not a movement segment. Pain and paresthesias are noted in the medial forearm and fourth and fifth fingers. Weakness occurs in the muscles of the thenar eminence, most prominently thumb flexion. There is concomitant weakness of finger and wrist extension (ulnar side) distal finger flexion and minimal dorsal and volar interossei function. The finger flexion reflex is lost.
  • The T1 root is rarely injured by disc disease as it is also not a motion segment. There is medial arm (usually T2) and forearm pain. Finger abduction and adduction and muscles of the hypothenar eminence are most severely involved. Rarely there is anterior chest wall pain. This is most often a reflection of sensitization of the intercostico-brachial nerve that derives from the medial cord of the brachial plexus. There is no reflex abnormality that can be elicited.

If the ventral roots are primarily involved in root disease there is atrophy and wasting of the affected myotome to a greater degree than sensory loss. This is more characteristic of bony defects such as cervical spondylosis and osteophytes of the foramina. Fasciculations may be induced by movement or percussion of the affected myotome (rare) with severe ventral root compressions.

Clinical Features of Lumbar Disc Disease

• L5–S1 greater than L4–L5 segments are the motion segments and are primarily involved. The L5 disc may be subject to the greatest intradiscal pressure with sitting and standing. L1–L3 root involvement suggests medical illness.
• Compression of the affected interspace may be painful; there may be slight decrease of sensation in a 1 1/2 inch cutaneous area from the spine laterally (cutaneous territory of the dorsal rami).
• Mechanical stretch maneuvers are positive. The straight leg raising maneuver with concomitant Laségue's sign (extension of the ankle with the leg extended) elicits pain. The patient may have referred pain to all aspects of the sciatic distribution, but usually it is proximal in the posterior thigh and back. It may radiate pain to the great toe (L5) or the little toe (S1). Pain may be more prominent when the leg is lowered. Raising the normal leg may refer pain to the affected leg.
• Tinel's signs are positive over the nerve that carries the specific root; the sciatic nerve (L4–S2) is most frequently involved with disc disease. Tinel's signs (mechanical pressure over the nerve elicits pain) are positive at the sciatic notch, in the posterior popliteal fossa and at the interspinous process at the affected level.
• There is muscle tenderness of the muscles that are innervated by the specifically sensitized root. The disc compression more proximally has sensitized the deep poly modal C-fiber and A-delta nociceptors such that mechanical pressure rather than tissue destructive stimuli will depolarize them.
• Pain radiations of L5-(usual):
  • Interspace at L4–L5; L5 S1
  • Buttock
  • Lateral thigh
  • Posterior popliteal fossa
  • Top of the foot
  • Great toe
• Additional radiations of L5:
  • Hip
  • Top of the thigh:
    • Somatic referred pain from the innervation of the anterior disc capsule
    • Dura at L5; the innervation of the recurrent nerve of Spurling at that level
  • Scrotum
  • Rarely the anterior lower abdominal wall

• Painful radiation of S1:
  • Usual
    • Interspace of L5–S1 in the back
    • Buttock
    • Posterior thigh; laterally S1; medially S2
    • Posterior popliteal fossa
    • Heel and sole of the foot
    • Little toe and lateral lower leg
    • Calf
  • Unusual
    • Groin
    • Tip of the penis (rare)
    • Ipsilateral vagina (rare)
    • Anus (argument; some feel there is S5)

• Pain radiations of L4:
  • Inside the lower leg (saphenous nerve distribution)
  • Band around the ankle
• Severe L4–L5; L5–S1 disc disease:
  • Increased frequency of urination
  • Slight decrease of bladder emptying (S1 root)
  • Pain increased during menstruation (convergent innervation from the uterus, fallopian tubes and ovary to L5, S1. DRG (somatic-visceral convergence)
• Exacerbating factors for the pain:
  • Flexion and extension posture; sitting; driving a car
  • Valsalva maneuvers
  • Sleep (veins that overlie the root compress the sensitized root; patients awakens with back pain at 4–5 AM. Inability to lie down suggests intraparenchymal spinal cord tumor (patients sleep upright in a chair). Awakening slightly earlier at night suggests a subarachnoid cyst compressing the spinal cord
  • Leg feels as if it will suddenly "give away" and will not support the body weight.

Relieving Factors for L4–S1 Disc Disease

• Rest; supine posture with flexed knees
• Heat over the affected interspace
• Some patients improve with exercise (heat may decrease conduction in sensitized nerve roots)

Motor Weakness of L4–S1 radiculopathy of Disc Disease (Differential Diagnosis)

• L4: weakness of the quadriceps, tibialis anterior and hip adductors; depressed knee jerk. Need to r/o lumbosacral plexopathy and femoral neuropathy.
• L5: weakness of the anterior tibialis; extensor hallices longus; weakness of ankle inversion (absent in peroneal palsy). Weakness of the gluteus minimus and medius localizes the lesion proximal to the sciatic nerve, but L5 could still be a component of lumbosacral plexopathy.
• S1: weakness is primarily of the gastrocnemius and soleus muscles > hamstrings and glutei. Gluteus maximus weakness localizes the lesions prior to the sciatic nerve. Deficient ankle jerk. Need to rule out lumbosacral plexopathy, tibial and sciatic neuropathy.
• Lower sacral radiculopathy:
  • Usually S2–S5 are involved concomitantly; often from central disc herniations
  • Pain and sensory loss in the perineal area; usually asymmetric; "saddle anesthesia"
  • Urinary and fecal incontinence
  • Decreased sensation of the S1–S5 dermatomes in an unequal distribution
  • Weakness of gluteal muscles with S1–S2 involvement; toe flexor weakness with S3 involvement; atrophy of EDB with S1–S2 lesions; soleus and gastrocnemius are weak if S1 is compressed
  • Reduced or absent anal sphincter tone, decreased bulbocavernosus and anal wink reflexes with S1–S5 involvement.

High Lumbar Root

In general, the L1–L3 are not affected by disc disease as they are not motion segments. They are involved in diabetic plexopathy, ilioinguinal and genitofemoral nerve injury from surgical procedures (hernia, catheterization of the femoral artery), intra-abdominal surgical procedures; lymphoma, retroperitoneal hematoma and autoimmune processes.

L1 Root: Pain and paresthesias in the inguinal area; slight weakness of the iliopsoas (hip flexion).

L2 Root: Anterolateral thigh pain and weakness of the iliopsoas muscle; differential diagnosis includes high lumbar plexopathy, neuralgia paraesthetica or femoral neuropathy. In general, femoral neuropathy is associated with quadriceps weakness and a decreased knee jerk.

L3 Radiculopathy: Pain in the anterior thigh to the knee; iliopsoas and quadriceps weakness; a plexus lesion usually involves the hip adductor muscles (L3 root) and the obturator nerve. There is a depressed knee jerk. The distribution overlaps the projected pain from the recurrent nerve of the Spurling at L5 (dural radiation at this level). Diabetic amyotrophy (most often a lumbosacral plexopathy) frequently involves this root).

Cervical and Lumbar Spondylosis

• General features of cervical spondylosis:
  • Involves the disc, the uncovertebral and facet joints.
  • Age related changes occur in the annulus fibrosus and disc proteoglycan composition with desiccation and narrowing of the intervertebral space.
  • The marrow of the vertebral body undergoes fibrovascular changes and fatty replacement. This is often most evident at the end plates of the vertebra (eburnation).
  • Osteophyte formation occurs at the margins of the vertebral bodies and in the foramina. Osteophyte formation also occurs at the uncinate joint.
  • Facet joint degeneration occurs with widening of the synovial space and internal rotation into the foraminal exit canal.
  • Bony changes predominate at upper cervical levels and disc degeneration at C5–C6; C6–C7 the major motion segments.
  • At upper cervical levels (C4–C5 and C5–C6) the DRG's may contribute to foraminal exit stenosis as they may be intraspinal.

General Clinical Characteristics of Cervical Spondylosis

• Clinical Presentation (cervical spondylosis)
  • Mechanical signs:
    • Forward flexed neck (spondylitic posture) with restricted movement to all planes
    • Proximal > distal weakness in the upper extremities; a C5–C6, C6–C7 disease
    • Weakness and atrophy of deltoid cap, supraspinatus and rhomboids > biceps
    • Trapezius ridge prominent; pain (C4–C6) C8–T1 innervated muscles are generally spared
    • C5–C6 sensory loss rare; primarily a motor illness; fasciculations, reflex depression of C5–C6, C7 may be hyperactive
    • Decreased biceps with increased triceps and finger flexion reflex. The inverted radial reflex is often present. There is concomitant spinal compression at C4–C5. Neural foraminal exit osteophyte.
    • Poor tandem gait; compression of the dorsal and ventral spinocerebellar tracts which are lateral in the spinal cord. This occurs late in the course of the disease.
    • Neurogenic bladder
• General Clinical Characteristics of Lumbar Spondylosis:
  • Combination of degenerative disc disease (desiccation of the disc; hard disc) with foraminal exit arthritic changes (osteophytes)
  • Weakness, sensory loss, atrophy and decreased reflexes in the involved myotomes and dermatomes
  • Mechanical signs are prominent (positive straight leg raising test)
  • Almost always associated with lumbar spondylosis
  • May have increased KJ and AJ which are due to associated cervical stenosis

Lumbar Spondylolysis

• Fracture through or maldevelopment of the pars interarticularis of the posterior vertebral elements (usually at L4–L5; L5–S1)
• Asymptomatic unless there is spondylolisthesis (malalignment)
• Jumping down or minimal trauma frequently displaces or breaks the malformed pars interarticularis
• Minimal non-radiating back pain initially

Lumbar Spondylolisthesis

• Spondylolysis from pars interarticularis disease initiates the process
• Retrograde or antegrade movement of the superior vertebrae over the inferior one (or the reverse); lumbar pain radiating into sciatic nerve distributions
• Congenital flat pelvis with typical stance (pelvis shifted forward)
• Bilateral radicular pain exacerbated by standing or particular postures (high heeled shoes)
• Often occurs in childhood and progresses through the teenage years
• Dramatically positive mechanical signs; flexion and extension posture exacerbates the pain
• Weakness and wasting of the affected myotome with associated reflex loss

Cervical Spondylolisthesis

• Occurs frequently following trauma and may be in association with "jumped" (overriding facet joints)
• Usual levels are C4–C5; C5–C6; C6–C7's unusual to have process at higher cervical levels but it does occur
• Severe pain in the neck with guarding and restriction of movement
• Often there is bilateral a increase of reflexes at the appropriate level due to pain; if the root is compromised there is asymmetric loss of the specific segmental reflex

Cervical Stenosis

• General features:
  • The confines of the cervical spinal canal are:
    • Laminae and ligamentum flavum posterolaterally
    • Pedicles anterolaterally
    • Discs and vertebral bodies anteriorly
  • The dimensions of the cervical spinal canal at C1–C3 (16–30 mm); C4–C7 (14–23 mm)
  • Extension reduces the canal 2–3 mm
• Pathology of cervical canal stenosis:
  • Congenitally small canal
  • Disc herniation with concomitant facet and uncovertebral joint osteoarthritic overgrowth
  • Hypertrophy of the posterior longitudinal ligament; particularly common in Japanese patients
• Clinical Presentation:
  • Occurs concomitantly with lumbar stenosis
  • Preserved muscle mass, hyperactive reflexes, poor balance (lateral compression of the DSCT and VSCT)
  • Neurogenic bladder
  • Hyperactive reflexes and Babinski signs
  • Concomitant root involvement from spondylosis may give myotomal atrophy and muscle weakness
  • Venous congestion contributes to myelomalacia with spinal cord signs and symptoms

Lumbar Spinal Stenosis

• General features:
  • A combination of desiccated disc disease with central bulge, facet and ligament hypertrophy that cause trefoil canal compression
  • L4–L5 > L5–S1 level-most frequent levels that are stenosed
  • Congenitally small canal; acquired stenosis occurs one level above a surgical fusion
  • Claudication may be caused by a combination of venous congestion and occlusion of the vaso vasorum. Radicular arteries are patent.

• Clinical Presentations:
  • Neurogenic claudication
  • Often bilateral radicular pain
  • Unable to move immediately after arising; patients stand at the side of the bed for a minute
  • Characteristic "simian" stance; spine forward flexed arms forward
  • Very positive straight leg raising signs; paraspinal muscle rigidity
  • Strength of muscles preserved; minimal atrophy of involved muscle
  • Reflexes increased in upper and lower extremities as cervical stenosis frequently accompanies that at lumbar levels; may be absent if there is accompanying spondylosis
  • Poor tandem gait (cervical stenosis)
  • Positive Babinski's (if concomitant cervical stenosis)

Associated Processes of Spinal Stenosis:

Facet Hypertrophy

• Uncovertebral joints at C4–C5; C5–C6 and C6–C7 in the cervical spine
• L4–L5; L5–S1 at lumbar levels
• Pain is constant at the affected levels; often burning in quality
• Present during movement and at rest
• Atrophy, sensory loss and weakness at the affected level

Lateral Recess Syndrome

• Exit foramina stenosis at L5 is narrowed (3-4 mm from the cord)
• Pain, atrophy, weakness, reflex depression at the affected level

Synovial Cyst of the Facet Joint

• Usually at L4–L5; L5–S1 may irritate the nerve root as it exits
• Often midline back pain
• May occur concomitantly with degenerative osteoarthritis at the same level
• May present with radicular symptoms at the involved level

Posterolateral Disc Herniation

• Interspace level and location of the disc protrusion determine the root that is affected
• Posterolateral protrusion at L4–L5 may compromise the L5 root prior to its exit at the L5–S1 foramen

Far Lateral Disc Herniation

• Compromises the root leaving the exit foramina at that level

Central Disc Herniation

• May affect roots bilaterally
• Bilateral pain
• Bowel and bladder paralysis if at sacral levels
• Perineal anesthesia (saddle anesthesia); S1–S5 roots
• Anterior tibialis, extensor hallucis longus, everter and intrinsic foot weakness
• Cauda equina syndrome (often acute)
• Medial disc protrusions compress roots that will exit at a lower level; may also compress exiting root at that level

Cauda Equina Syndrome

• General Features:
  • More than two contiguous nerve roots are involved
  • Bilateral lumbar or sacral radiculopathies
• Clinical Presentation:
  • Midline variant:
  • Compression of nerve roots of the central cauda equina
  • Acute or gradual onset
  • Acute onset:
    • Disc herniation (L4–L5 most common); sacral roots are positioned most medially and therefore are involved first
    • Severe pain; usually asymmetric sacral root involvement
    • Perineal ("saddle anesthesia")
    • Bladder and bowel incontinence
    • Leg weakness; primarily L5–S2 innervated muscles
    • Progressive
  • Neurogenic Claudication:
    • Back, thigh and leg pain with walking (often 2–3 blocks)
    • Relieved by rest in 2–3 minutes; neurogenic cramps of the calf
    • Rarely pain is induced only with standing without exercise
    • Walking through pain induces weakness and paraesthesias in lumbosacral roots
    • Sitting or raising one leg and bending at the waist are relieving maneuvers
    • Neurologic examination is that of lumbar spinal stenosis

Thoracic Disc

• Rare; usually T8–T11
• Midline back pain; 50% have radiculopathy at the affected level
• Dangerous due to small canal at these levels (if acute HNP)
• Early leg weakness, bowel and bladder involvement with cord compression
• Symptoms are frequently chronic
• Bilateral Babinski's signs with cord compression
• Valsalva maneuver and pressure on the shoulders (extrusion of disc and compression of the spinal cord) increases radicular pain and myelopathy
• Lateral protrusion causes intercostal radicular pain
• C8–T1 disc may affect ipsilateral sympathetics to cause Horner's syndrome
• Medical causes of thoracic discs:
  • Diabetes mellitus
  • Syphilis (denervated disc capsule; paretic joint)
  • Amyloid (painless joint; small fiber loss)
  • Ochronosis (homogentisic aciduria); calcified discs; "Rugger Jersey" disc
• Usually requires severe trauma or heavy lifting
• Early leg weakness, bowel and bladder involvement