Neuromuscular Disease

Anterior horn

• spinal muscular atrophy
• amyotrophic lateral sclerosis
  • asymmetric limb or bulbar signs
    • markedly / early atrophy
    • fasciculations / cramps
    • nil sensory involvement
    • reduced / increased reflexes

Peripheral nerve

• symmetrical, distal signs; moderate atrophy
• sensory involvement: paraesthesia, hypoesthesia
• reflexes reduced out of proportion to weakness

Neuromuscular junction (NMJ)

• extraocular / bulbar / proximal limb
• diurnal fluctuation
• nil atrophy, sensory involvement, reflexes normal

Muscle e.g. Duchenne

• symmetric limb signs, nil sensory involvement
• atrophy
• reflexes reduced in proportion to weakness (∴ absent only late)

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Acute Generalised Weakness (within 24 hours)

• < 1 hour – metabolic / toxin of NMJ / muscle
• electrolyte, metabolic, toxic
• acute inflammatory myopathy (neuropathy)

Subacute Weakness (over days – peripheral neuropathies, neuromuscular junction)

• Guillain Barre Syndrome, Toxic neuropathies
• Myasthenia Gravis
• Polymyositis / Dermatomyositis (only when severe)

Slowly Progressive Weakness

• Proximal: polymyositis / dermatomyositis / endocrinopathies
  • > 1 year: muscular dystrophies, Myasthenia Gravis
• Distal: Peripheral Neuropathy, Anterior Horn, Myotonic Dystrophy
• Bulbar: Anterior Horn; NMJ