Neuropathy — Causes, Symptoms, Diagnosis & Treatment Guide — Symptoms, Causes & Treatment | MyMedicPlus

Peripheral neuropathy is a disorder of the peripheral nervous system — the network of motor, sensory, and autonomic nerves connecting the central nervous system to the rest of the body. Damage to these nerves disrupts signal transmission, causing a range of symptoms from pain and numbness to weakness and autonomic dysfunction. Neuropathy affects approximately 2-7% of the general population, rising to 50% of people with long-standing diabetes — making diabetic peripheral neuropathy the single most common form worldwide. Neuropathy may be focal (affecting single nerves — mononeuropathy), multifocal (several individual nerves — mononeuropathy multiplex), or generalised (polyneuropathy — affecting the longest fibres first, producing a 'glove and stocking' distribution). Identifying and treating the underlying cause is the priority, as many neuropathies are potentially reversible if the cause is corrected early.

Metabolic causes: diabetes mellitus (most common — chronic hyperglycaemia damages small blood vessels supplying nerves), hypothyroidism, uraemia (chronic kidney disease), and liver disease. Nutritional deficiencies: vitamin B12 deficiency (subacute combined degeneration — posterior and lateral column involvement), vitamin B1 (thiamine — Wernicke-Korsakoff from alcohol excess), vitamin B6 toxicity (excess supplementation), vitamin E deficiency. Toxic causes: alcohol (most common toxic neuropathy), chemotherapy agents (vincristine, cisplatin, paclitaxel, oxaliplatin), isoniazid, metronidazole, and heavy metal poisoning (arsenic, lead, mercury). Autoimmune/inflammatory: Guillain-Barré syndrome (acute demyelinating polyneuropathy — often post-infectious), chronic inflammatory demyelinating polyneuropathy (CIDP), vasculitis-related mononeuritis multiplex. Hereditary: Charcot-Marie-Tooth disease (commonest hereditary neuropathy). Infections: HIV, Lyme disease, leprosy (most common infectious cause globally).

Symptoms reflect which nerve fibre types are affected. Small fibre neuropathy: burning, stabbing, or shooting pain — particularly severe at night; allodynia (pain from light touch); and autonomic symptoms (postural hypotension, erectile dysfunction, sweating abnormalities, gastroparesis, bladder dysfunction). Large fibre neuropathy: loss of vibration and position sense causing imbalance and falls, diminished tendon reflexes, and loss of protective sensation. Motor involvement: distal muscle weakness and wasting (foot drop — inability to dorsiflex the foot — causing a high-stepping gait), difficulty with fine motor tasks, and in severe cases proximal weakness. In diabetic neuropathy: symmetrical distal sensorimotor neuropathy in a 'glove and stocking' distribution develops insidiously over years. Acute painful neuropathy can occur with rapid changes in glycaemic control. Mononeuropathy multiplex (vasculitis, diabetes): asymmetric, stepwise involvement of individual named nerves.

Clinical history and neurological examination establish the pattern and distribution of neuropathy. Nerve conduction studies (NCS) and electromyography (EMG): NCS measures motor and sensory conduction velocity and amplitude, distinguishing demyelinating (slowed conduction — Charcot-Marie-Tooth, CIDP) from axonal (reduced amplitude — diabetes, toxins) neuropathy. EMG assesses muscle denervation. Small fibre neuropathy may have normal NCS — diagnosed by skin punch biopsy (intraepidermal nerve fibre density), quantitative sensory testing (QST), or SUDOSCAN. Blood tests to identify cause: fasting glucose/HbA1c, serum B12 and folate, TSH, renal and liver function, serum protein electrophoresis (SPEP for paraprotein), ANA and ANCA (vasculitis), anti-ganglioside antibodies (GM1 — MMNCB; GQ1b — Miller Fisher), hepatitis B/C, HIV. Lumbar puncture for CSF analysis in suspected GBS (elevated protein without pleocytosis) or CIDP. Genetic testing for hereditary neuropathies. Nerve or muscle biopsy in select cases.

Treat the underlying cause: strict glycaemic control slows progression of diabetic neuropathy (DCCT and UKPDS trials); B12 replacement for deficiency; cessation of alcohol or neurotoxic medications; IVIG or plasma exchange for GBS and CIDP; immunosuppression (prednisolone, azathioprine, rituximab) for vasculitic or autoimmune neuropathies. Neuropathic pain management — first-line agents: duloxetine (60-120 mg daily — SNRI, evidence for diabetic and chemotherapy-induced neuropathy), amitriptyline (25-75 mg at night — evidence for post-herpetic neuralgia and diabetic neuropathy), pregabalin (150-600 mg/day) and gabapentin (900-3,600 mg/day). Topical agents: capsaicin 8% patch (capsaicin desensitises TRPV1 pain receptors), lidocaine patches for localised neuropathic pain. Opioids reserved for refractory pain. Physical therapy prevents deformity, improves proprioception, and reduces fall risk. Orthotics for foot drop. Transcutaneous electrical nerve stimulation (TENS) and spinal cord stimulation provide additional options for refractory neuropathic pain not responding to pharmacological therapy.

Severe peripheral neuropathy causes profound loss of protective sensation — inability to feel pain, heat, or pressure means injuries go unnoticed and untreated. In diabetic neuropathy, this is the primary mechanism behind diabetic foot ulcers (affecting 25% of diabetics over their lifetime) — 85% of all lower limb amputations are preceded by a foot ulcer. Charcot arthropathy (progressive joint destruction from repeated unnoticed trauma) causes permanent foot deformity. Autonomic neuropathy causes orthostatic hypotension (falls), gastroparesis (delayed gastric emptying causing vomiting and malnutrition), urinary retention, sexual dysfunction, and diabetic autonomic neuropathy — associated with sudden cardiac death. Chronic neuropathic pain severely impairs sleep, mood, and quality of life in 20-30% of affected patients.

Diabetic neuropathy prevention: maintain HbA1c below 7.0% through lifestyle, oral hypoglycaemics, and insulin — intensive glycaemic control in the DCCT trial reduced neuropathy by 60% in Type 1 diabetes. Regular foot examinations (at least annually) are essential for early detection of neuropathic ulcers in diabetic patients. Alcohol-related neuropathy: abstinence from alcohol and thiamine supplementation. Toxic neuropathy: prevent by monitoring for neurotoxicity during chemotherapy, adjusting doses when necessary, and using neuroprotective supplements (acetyl-L-carnitine) where evidenced. B12 monitoring for long-term metformin users and vegans/vegetarians. Avoid neurotoxic drugs where possible. Genetic counselling for inherited neuropathies (Charcot-Marie-Tooth). Regular neurological reassessment monitors progression or improvement.

Seek urgent neurological review if neuropathy develops rapidly over days to weeks (could be Guillain-Barré syndrome — ascending weakness with areflexia is a medical emergency requiring ICU monitoring for respiratory failure). See a doctor promptly if you develop foot numbness, burning pain, or loss of protective sensation in the feet — particularly if diabetic, as this represents a significant risk for foot ulceration and amputation. Consult a neurologist if neuropathy is progressive, causing functional impairment or falls, or if the cause is unexplained. Seek immediate care for acute foot ulcers or wounds that are not healing in patients with known neuropathy. Autonomic features such as postural dizziness, fainting, or bladder/bowel dysfunction also warrant specialist assessment.