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Approach to peripheral neuropathy
In every neuropathy first set the pattern — length-dependent distal symmetric, multifocal, acute or mainly motor — then the cause; most neuropathies are distal and symmetric, and the most common cause is diabetes.
Why it matters in the exam
Questions present a patient with "glove and stocking" numbness, burning feet or foot drop, and ask about the first tests, the likely cause (diabetes, alcohol, B12 deficiency, chemotherapy, isoniazid) and treatment of neuropathic pain. The highest-yield blood tests are glucose (or HbA1c), B12, and serum protein electrophoresis with immunofixation. A pattern of several separate nerves (mononeuritis multiplex) suggests vasculitis and requires urgent work-up. Small-fibre neuropathy presents as burning with a normal conduction study and is diagnosed by skin biopsy. A common distractor is opioids as first-line for neuropathic pain. Always ask about alcohol, drugs, occupational exposure and family history, and examine the feet at every visit of a diabetic patient, because loss of protective sensation is the main cause of ulcers and amputations.
Key points
- Set the pattern first, then the cause.
- The common pattern is distal symmetric, and the common cause is diabetes.
- Basic tests: glucose or HbA1c, B12 and electrophoresis with immunofixation.
- Several separate nerve lesions require urgent vasculitis work-up.
- Neuropathic pain: duloxetine, pregabalin, gabapentin or amitriptyline, not opioids.
Summary table
| Pattern | Main causes | Work-up or treatment |
|---|---|---|
| Distal symmetric length-dependent | Diabetes, alcohol, B12 deficiency, hypothyroidism, kidney failure, chemotherapy (platinum, taxanes, vincristine), isoniazid | Glucose or HbA1c, B12, electrophoresis with immunofixation; vitamin B6 with isoniazid |
| Several separate nerves | Vasculitis, diabetes, leprosy, sarcoidosis | ESR, ANCA, electrical study; sometimes nerve biopsy; urgent treatment of vasculitis |
| Acute and progressive | GBS, porphyria, toxins | Admission and respiratory monitoring |
| Small fibre | Diabetes and prediabetes, amyloidosis, autoimmune causes | Normal conduction study; skin biopsy for fibre density |
| Hereditary | Charcot-Marie-Tooth disease (CMT1A — PMP22 duplication) | Pes cavus, hammer toes, family history |
| Neuropathic pain | Duloxetine, pregabalin, gabapentin or amitriptyline; topical capsaicin | Avoid opioids as first-line; foot care and ulcer prevention |
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Sources
- AAN Practice Parameter: Evaluation of Distal Symmetric Polyneuropathy — Role of Laboratory and Genetic Testing, 2009 — Screening laboratory tests
- AAN Practice Guideline: Oral and Topical Treatment of Painful Diabetic Polyneuropathy, 2022 — Recommended drug classes
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-06. The text may contain errors; when in doubt, check the source.