Differential Diagnosis in Neurology

7.6. Unusual Causes of Brachial Plexus Pathology

Infections Affecting the Brachial Plexus

• Lyme disease (C5, C6 roots, upper trunk)
• Ehrlichiosis caninessis (entire plexus)
• HIV (entire plexus)
• Coxsackie virus (C5, C6 roots/upper trunk)
• EBV (C5, C6 roots/upper trunk)
• Neurologic amyotrophy (preceding upper respiratory infection); any components of the plexus; individual components or neuropathy
• Diphtheria
• Bacterial pneumonia
• Influenza
• Scrub typhus
• Typhoid
• Brucellosis
• Hepatitis C

Neuralgic Amyotrophy

• General clinical features :
  • Preceding nonspecific upper respiratory illness
  • Abrupt onset of pain in the shoulder girdle
  • Weakness and wasting of any extremity muscle but primarily C5, C6 and cervical roots; associated with cervical plexus involvement
• Sporadic form :
  • Preceding Events:
    • Post infection
    • Post vaccination
    • Post IV serum treatments
    • During hospitalization for varied treatments
    • IV chemotherapy
    • Childbirth
    • Imaging procedures
    • Allergic desensitization
    • IV heroin use
    • Severe exercise
• Incidence:
  • 1.64/100,000 patients
  • Young to middle aged adults
  • Male predominance; has been seen in epidemics

Clinical Signs and Symptoms of Unusual Cause Brachial Plexopathy

• General Features:
  • No constitutional features (fever or weight loss)
  • Pain which may begin abruptly (even during sleep); hours to 3–4 weeks after the event:
    • Maximal at onset
    • Severe and constant
    • Localizes often to trapezius ridge, lateral deltoid, medial scapular border and its tips (notalgia)
    • Associated muscle tenderness
    • Exacerbated by movement
    • Arm splinted in adduction and internal rotation
    • Severe pain for hours to two weeks; replaced by dull ache
    • Severe deep ache in the lateral forearm; if anterior interosseous nerve is involved, pain localizes to the antecubital fossa
  • Weakness:
    • Starts when acute pain diminishes
    • May be maximal at onset but may progress over 2–3 weeks
    • Deltoid, spinatus, rhomboids are most frequently involved; branch nerves to individual muscles; may be involved; diaphragm (occasionally involved) laryngeal, spinal accessory, long thoracic, suprascapular axillary, anterior and posterior interosseous nerves are most often affected
  • Sensory loss:
    • Infrequent
    • Small area of the lateral deltoid; lateral antebrachial cutaneous nerve (usually the most severely affected sensory nerve)
  • Normal or depressed deep tendon reflexes
  • CSF is normal
  • EMG evaluation:
    • Sensory NCV greater involvement than motor
    • Amplitudes primarily affected
    • Axon loss in affected muscles
    • Bilateral findings in 15–30% of patients
  • Bilateral clinical involvement occurs sequentially
  • Good recovery in majority of patients (80% within two years)
  • Rarely: serratus anterior; spinal accessory, anterior interosseous and phrenic nerves involved severely isolation
    • AD deletion on chromosome 17q25
• Clinical Presentation:
  • Onset in childhoods; may occur 2nd or 3rd decades
  • Several acute episodes over years; usually with recovery
  • Weakness preceded by pain in the affected extremity
  • Pain: severe, lancinating, burning in quality
    • Exacerbated by movement
    • Arm is usually splinted
  • Weakness ensues after pain
    • Progresses over days to weeks
    • Reaches maximum by one month
  • Associated involvement of cranial nerves and lower extremities may occur (lumbosacral plexus involvement)
  • Upper trunk of brachial plexus most commonly affected; any muscle of plexus may be involved
  • Atrophy and fasciculations develop over months
  • Recovery begins weeks to months after onset and may continue for up to two years
  • Recurrent episodes more common than that seen in neurologic amyotrophy
  • Patients may suffer separate attacks of upper or lower limb plexopathy
  • Bilateral brachial plexopathy occurs
  • Cranial nerve involvement: V, VII, and VII, X; Horner's syndrome; may occur separately or with attacks of upper extremity weakness
  • Dysmorphic features that may be associated:
    • Hypotelorism
    • Epicanthic folds
    • Cleft palate
    • Syndactyly
    • Short stature
  • Precipitating factors noted:
    • Infection
    • Strenuous exercise
    • Pregnancy and puerperium
  • The first episode may occur in the first decade; sporadic form of the disease presents in the third and fourth decade

Differential Diagnosis of Conditions with Sensitivity to Pressure

• Diabetes mellitus
• Chronic inflammatory demyelinating neuropathy
• Tangiers's disease
• Partial deficiency of IgA or IgE
• CMT-1 (chromosome17 deletion); HNNP

Rare Illnesses with Brachial Plexopathy

• Estrogen Dependent brachial plexopathy
• Adrenoleukodystrophy
• Adrenomyeloneuropathy
• Ehlers-Danlos syndrome
• Migratory sensory neuropathy

Immune Mediated Causes of Brachial Plexopathy

• AIDP
• CIDP
• Graft versus host disease (GVHD)
• Interleukin 2 (IL-2) therapy
• Administration of anti-immune serum
• Post vaccination
• Associated with collagen vascular disease:
  • SLE
  • Periarteritis nodosa
• Following generalized allergic reactions

Differential Diagnosis of Brachial Plexus Lesions

• Neuropraxic injuries of the supraclavicular brachial plexus:
  • Contusion or parenchymal spinal cord injury
  • Head injury
  • Dislocated shoulder (usually anterior)
  • Rotator cuff injury
  • Fracture of the humerus
  • Cervical disc, spondylolisthesis, jumped or rotary dislocated facets
• Obstetric plexus lesions
• Congenital absence of roots
• Roo's bands (12 in number)
• Humeral osteomyelitis
• Neonatal hemangiomatosis
• Neoplasms
• Congential varicella
• Arthrogryposis multiplex congenita
• Cervical spinal cord amyotrophy (bilateral)
• Post sternotomy surgery:
  • C8 radiculopathy
  • Ulnar neuropathy
  • Medial antebrachial cutaneous neuropathy
• Cervical-rib band (true-N-TOS):
  • CTS
  • Ulnar neuropathy at the cubital tunnel
  • Monomelic ALS
  • ALS
• Benign neoplasms:
  • Lipoma
  • Cyst
• Malignant neoplasm
• Metastasis to adjacent bone
• Differential diagnosis of neuralgia amyotrophica:
  • Orthopedic shoulder disease:
    • Dislocation
    • Rotator cuff lesions
    • Humeral fractures
• Pack paralysis:
  • Monomelic ALS
  • Neurologic amyotrophy
• Rapidly progressing plexopathy:
  • Hematoma
  • Aneurysm
  • Autoimmune causes
  • HNPP (deletion of chromosome 17)