Makindo Medical Notes"One small step for man, one large step for Makindo" |
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Weakness in adults can result from disorders of muscle, nerve, or neuromuscular transmission. The key challenge is distinguishing **acute life-threatening conditions** (e.g. Guillain-Barré, botulism, MG crisis) from **chronic progressive diseases** (e.g. ALS, muscular dystrophies). A systematic approach with careful history, examination, and time course analysis is essential.
Time Course | Likely Causes |
---|---|
Acute (hours–days) | GBS, botulism, myasthenic crisis, stroke, electrolyte derangements (K+, Ca2+) |
Subacute (weeks) | CIDP, inflammatory myopathies (polymyositis, dermatomyositis), drug-induced myopathy |
Chronic (months–years) | ALS, muscular dystrophies, inherited neuropathies, metabolic myopathies |
Condition | Pathophysiology | Clinical Features | Diagnosis |
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💊 Myasthenia Gravis | Autoantibodies to post-synaptic ACh receptors → ↓ transmission | Fluctuating weakness, ptosis, diplopia, dysphagia, fatigability | Anti-AChR antibodies, EMG, CT/MRI for thymoma |
⚡ Guillain-Barré Syndrome | Immune-mediated demyelination post-infection | Ascending symmetrical weakness, areflexia, respiratory failure risk | NCS, CSF (↑ protein, normal WCC) |
🧠 Amyotrophic Lateral Sclerosis | Degeneration of UMN & LMN | Progressive weakness, wasting, fasciculations, spasticity, hyperreflexia | EMG, NCS, MRI (exclude mimics) |
🧬 Muscular Dystrophies | Inherited dystrophin defects | Proximal weakness, pseudohypertrophy, progressive disability | Genetic testing, muscle biopsy, ↑ CK |
☠️ Botulism | Toxin blocks presynaptic ACh release | Descending paralysis, CN palsies, respiratory weakness | Toxin assays, NCS, exposure history |
🔥 Polymyositis / Dermatomyositis | Autoimmune inflammation & necrosis | Proximal weakness, dysphagia; dermato = heliotrope rash, Gottron’s papules | ↑ CK, muscle biopsy, autoantibodies |
🎯 Lambert-Eaton Syndrome | Antibodies to presynaptic VGCC (often paraneoplastic) | Proximal leg weakness, autonomic signs, improves with activity | Anti-VGCC Abs, EMG, cancer screening |
🌀 CIDP | Chronic autoimmune demyelination | Symmetrical weakness + sensory loss ≥8 weeks | NCS/EMG, CSF (↑ protein) |