Peripheral neuropathy - acquired
Description
- Characterise before you investigate. Four questions settle the differential:
- 1. Pattern - symmetric length-dependent | mononeuritis multiplex | radiculoplexus | non-length-dependent (ganglionopathy)
- 2. Fibre type - motor | large-fibre sensory | small-fibre | autonomic
- 3. Physiology - axonal vs demyelinating (NCS decides)
- 4. Tempo - acute (<4 wk) | subacute | chronic (>8 wk)
Pattern -> cause
| Pattern | Think |
|---|---|
| Distal symmetric, length-dependent ("glove and stocking") | Diabetes, alcohol, CKD, B12, drugs, idiopathic. Legs before arms; arms involved once legs affected to the knee |
| Mononeuritis multiplex | Vasculitis, diabetes, leprosy, sarcoid, amyloid, HNPP, HIV, malignancy |
| Demyelinating, proximal + distal | GBS, CIDP, anti-MAG, CMT1, HNPP |
| Sensory ganglionopathy (non-length-dependent, ataxic, arms early) | Paraneoplastic (anti-Hu, SCLC), Sjogren's, cisplatin, B6 toxicity |
| Pure motor | GBS, multifocal motor neuropathy, lead, porphyria, dapsone, CMT (HMSN), MND (not a neuropathy) |
| Small fibre | Diabetes/prediabetes, amyloid, HIV, Sjogren's, Fabry, sodium channel variants, idiopathic |
| Autonomic-predominant | Amyloid, diabetes, paraneoplastic, GBS, porphyria, HIV |
| Painful, rapidly progressive, asymmetric | Vasculitis - a medical emergency |
Large vs small fibre
- Large - vibration, proprioception, reflexes, motor. Sensory ataxia, Romberg positive, pseudoathetosis
- Small - pinprick, temperature, burning/dysaesthetic pain, autonomic. NCS are NORMAL - a normal NCS does not exclude neuropathy
6 more sections, plus exam facts
Premium unlocks every note across every specialty, and the full exam fact library behind it.
Get premium access