Diabetic Neuropathy

Diabetic neuropathy is nerve damage attributable to diabetes, present in up to 50% of patients over time.

• Forms: distal symmetric polyneuropathy (commonest), autonomic neuropathy (cardiovascular, gastrointestinal, genitourinary), mononeuropathies (CN III, VI, carpal tunnel), radiculoplexus neuropathy (amyotrophy), treatment induced neuropathy.
• Pathogenesis: hyperglycaemia, oxidative stress, microvascular ischaemia, advanced glycation end products.
• Risk factors: duration, poor control, hypertension, dyslipidaemia, smoking, alcohol.
• Complications: foot ulcers, Charcot arthropathy, amputation, falls, silent ischaemia.

• Stocking glove numbness, burning pain, paraesthesia, allodynia, worse at night.
• Loss of ankle reflexes, vibration and pinprick sensation, claw toes, dry skin.
• Autonomic: orthostatic hypotension, resting tachycardia, gastroparesis, erectile dysfunction, neurogenic bladder, hypoglycaemia unawareness.
• Acute painful neuropathy after rapid glucose improvement.

• 10 g monofilament, 128 Hz tuning fork, pinprick, ankle reflexes annually.
• Exclude other causes: B12 deficiency (especially on metformin), hypothyroidism, alcohol, uraemia, CIDP, paraproteinaemia.
• Nerve conduction studies for atypical or asymmetric disease; skin biopsy for small fibre neuropathy.
• Autonomic testing: heart rate variability, lying and standing blood pressure.

• Optimise glycaemia gradually, control lipids and blood pressure.
• Neuropathic pain first line: duloxetine 30 to 60 mg daily, pregabalin 75 to 300 mg twice daily, gabapentin 300 to 1200 mg three times daily, amitriptyline 10 to 75 mg at night.
• Topical: capsaicin 8% patch, lidocaine 5% plaster. Tapentadol or tramadol for refractory pain.
• Foot care: daily inspection, protective footwear, podiatry.
• Orthostatic hypotension: fludrocortisone 0.1 to 0.2 mg, midodrine 2.5 to 10 mg three times daily. Gastroparesis and bladder management as relevant.
• B12 replacement if deficient.