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Definition
A neuromuscular junction disorder characterized by progressive muscular weakness and fatigability on exertion
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Etiology
Autoimmune anti-body mediated attack on ACh receptors at NM junction
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Characteristics
- Muscle strength worse with continuing contraction, improved with rest
- Classified into 4 types
- Course varies = may progress from mild to severe, typically within 18 months
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Four Types
- Ocualar myasthenia (confined to extraocular muscles)
- Mild generalized myasthenia
- Severe generalized myasthenia
- Crisis
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Generalized Myasthenia
Usually involves bulbar (extraocular, facial, and muscle of mastication) and proximal limb-girdle muscles
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Myasthenic Crisis
- Myasthenia gravis with respiratory failure
- Treat as medical emergency
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Examination
- Cranial nerves
- Respiratory function
- Muscle strength
- Functional mobility skills
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Exam: Cranial Nerves
- Diplopia
- Ptosis
- Progressive dysarthria or nasal speech
- Difficulties chewing and swallowing
- Difficulties in facial expression (drooping)
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Exam: Respiratory Function
- Breathing difficulties
- Hoarse voice
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Exam: Muscle Strength
- Prox more involved than distal
- Fatigability characteristic of this disease
- Repeated muscle use results in rapid weakness
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Exam: Functional Mobility Skills
- Stair climbing
- Rising from chair
- Lifting
(difficulties similar to myopathies)
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EMG and Repetitive Nerve Stimulation Studies
- Show abnormal responses to repetitive nerve stimulation
- Failure of transmission
- Decreased EMG-recorded responses
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Medical Intervetntions
- Acetylchoinesterase inhibitors
- Corticosteroids
- Immunosuppressants
- Alternative treatments = plasmapheresis (removal of blood with filtering and separation of cellular elements from plasma); thymectomy
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PT Goals, Outcomes, and Interventions
- Monitor changes in pt's condition (vital signs, respiration, swallowing
- Promote independence in FMS and ADLs
- Teach energy conservation techniques
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