Causes of neuromuscular weakness at NMJ level

1. Myasthenia Gravis
2. Lambert-Eaton syndrome
3. Organophosphate poisoning
4. Botulism

Myasthenia gravis

Myasthenia gravis is an autoimmune disorder resulting in insufficient functioning acetylcholine receptors at the postsynaptic membrane.

Antibodies to acetylcholine receptors are seen in 90% of cases*. Myasthenia is more common in women (2:1)

The key feature is muscle fatigability - muscles become progressively weaker during periods of activity and slowly improve after periods of rest:

Ask the patient to clench the fist around your finger repeatedly => weakness in upper extremities

• extraocular muscle weakness: diplopia (double vision)
• proximal muscle weakness: face, neck, limb girdle
• Speech - dysphonia - mushy or nasal quality
• Face - snarling appearance when smiling
• ptosis
• dysphagia/ difficulty chewing
• As disease progresses, weakness may become generalized, involving proximal muscles in an asymmetric pattern
• Deep tendon reflexes are intact (in contrast to botulism)
• Pupillary responses are normal