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Updated Jan 2009 by Charles Gomersall
Causes
Upper motor neuron lesion (early stages)
Brainstem
Acute myelopathy
Lower motor neuron lesion
Anterior horn cell
Peripheral neuropathy
- Guillain-Barré
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Critical illness neuropathy
- Vasculitic neuropathy
- Heavy metals, biological toxins, drugs
- Acute intermittent porphyria
- Diptheritic neuropathy
- Post-rabies vaccine neuropathy
- Lymphomatous neuropathy
Disorder of neuromuscular transmission
Muscle disorders
- hypokalaemia
- hypophosphataemia
- inflammatory myopathy
- acute rhabdomyolysis
- trichinosis
- periodic paralysis
Clues to the cause of weakness
| Suggestive clinical features |
Diagnosis |
| Fluctuating weakness, fatigability, ptosis |
Myasthenia gravis |
| Preceding infection, vaccination, diarrhoea, sensory symptoms |
Guillain Barre |
| Skin rash |
Dermatomyositis,
vasculitis |
| Episodic abdominal pain, psychiatric illness |
Porphyria |
| History of mosquito bites, asymmetric flaccid weakness,
encephalopathy |
West Nile virus infection |
| Family history, retinitis pigmentosa, fits, mental retardation,
deafness |
Mitochondrial myopathy |
| Critical illness, particularly sepsis |
Critical illness
polyneuropathy & myopathy |
Drugs which induce weakness
| Clinical syndrome |
Possible culprit drugs |
| Myasthenia like syndrome |
Antibiotics: aminoglycosides, quinolones, imipenem, erythromycin,
polymyxins |
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Neuromuscular blockers |
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Antiarrhythmics: quinidine, procainamide |
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Calcium channel blockers: verapamil, diltiazem |
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Beta blockers |
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Magnesium (including magnesium containing laxatives and antacids) |
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Phenytoin |
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Corticosteroids |
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Lithium |
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D-penicillamine |
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Interferon alpha |
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Chloroquine |
| Myopathy |
Statins, D-penicillamine, zidovudine, lamivudine, stavudine |
| Rhabdomyolysis |
Fibrates |
Further reading
Maramattom BV, Wijdicks EFM. Acute neuromuscular weakness in the intensive
care unit. Crit Care Med, 2006; 34(11): 2835-2841
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