Guillain-Barré Syndrome vs Myasthenia Gravis
Guillain-Barré Syndrome and Myasthenia Gravis are easy to mix up on the boards. Here's a side-by-side comparison — presentation, workup, imaging, and first-line treatment — drawn from our full outlines.
Guillain-Barré Syndrome vs Myasthenia Gravis at a glance
- Guillain-Barré Syndrome: Acute immune-mediated ascending demyelinating polyneuropathy; can cause respiratory failure.
- Myasthenia Gravis: Autoimmune neuromuscular junction disease with fluctuating fatigable weakness.
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Side-by-side comparison
| Feature | Guillain-Barré Syndrome | Myasthenia Gravis |
|---|---|---|
| At a glance | Acute immune-mediated ascending demyelinating polyneuropathy; can cause respiratory failure. | Autoimmune neuromuscular junction disease with fluctuating fatigable weakness. |
| Classic presentation | Acute ascending symmetric weakness + areflexia + antecedent infection + albuminocytologic dissociation in CSF (elevated protein with normal cell count).; Symmetric ascending weakness beginning in the legs, progressing over hours to days (peak by 2-4 weeks); Distal paresthesias and pain (often missed by clinicians but very common — back… | Fatigable ptosis and diplopia worse at end of day, improving with rest.; Fluctuating, fatigable weakness — worse with use, better with rest; Symptoms typically worse at the end of the day; Ocular (initial in ~50%, eventually in ~85%): ptosis (often asymmetric), diplopia; Bulbar: dysphagia, dysarthria, nasal speech, jaw fatigue (chewing… |
| Workup / key labs | Clinical: progressive symmetric weakness + areflexia, peak by 4 weeks, exclusion of alternative causes. Supportive: CSF albuminocytologic dissociation, electrodiagnostic features of demyelination.; CBC, BMP, LFTs, ESR, CRP, HIV, HBV, HCV; Antiganglioside antibodies (anti-GM1, anti-GD1a, anti-GQ1b — Miller Fisher); Stool for… | Clinical features + positive antibodies (AChR or MuSK) and/or supportive electrodiagnostics (decremental RNS, abnormal single-fiber EMG).; Acetylcholine receptor (AChR) antibodies — binding, blocking, modulating (binding most useful); If AChR negative: anti-MuSK antibodies; If both negative: anti-LRP4 antibodies (low yield); TSH, free… |
| Imaging | MRI spine with gadolinium — exclude compressive lesion; nerve root enhancement (especially cauda equina) supports GBS; Nerve conduction studies / EMG: slowed conduction velocities, prolonged distal latencies, conduction block, F-wave abnormalities (early), low amplitudes (axonal variants); Lumbar puncture: albuminocytologic dissociation… | CT chest with contrast (or MRI) — evaluate for thymoma in ALL patients with confirmed MG; Repetitive nerve stimulation: decremental response (>10% drop in CMAP amplitude) at low frequency; Single-fiber EMG: most sensitive — increased 'jitter' and blocking; Ice pack test, edrophonium (Tensilon) test (rarely used now due to side effects) |
| First-line treatment | ICU admission for any patient with autonomic instability, bulbar weakness, or rapidly progressive disease; Frequent pulmonary monitoring (FVC, NIF q4-8h); intubate at 20/30/40 thresholds — do not wait for hypoxia; IVIG 0.4 g/kg/day × 5 days (total 2 g/kg) — first-line, equivalent efficacy to PLEX, easier to administer; Plasma exchange… | Symptomatic: pyridostigmine (acetylcholinesterase inhibitor) 30-60 mg PO every 4-6 hours, titrate to effect — improves transmission but does not modify disease; Immunosuppression: prednisone (initiate gradually — high doses can transiently worsen weakness; start low and titrate up, or hospitalize for monitoring); Steroid-sparing agents:… |
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