№ 11Differential Diagnostic Topics18 min read
Differential diagnosis of muscle weakness
1. Big picture
Muscle weakness is a symptom, not a diagnosis. The first exam task is to decide whether the patient has true loss of power or only fatigue, pain, dyspnea, depression, or deconditioning.
The second task is localization:
Brain/spinal cord
→ anterior horn cell
→ nerve root / plexus / peripheral nerve
→ neuromuscular junction
→ muscle
→ electrolyte/endocrine/systemic cause
The dangerous diagnoses to recognize immediately are:
- Stroke or spinal cord compression
- Guillain-Barré syndrome with respiratory failure
- Myasthenic crisis
- Severe hypo-/hyperkalemia
- Rhabdomyolysis
- Thyrotoxic periodic paralysis
- **Sepsis/critical
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