Alcoholic Polyneuropathy

Alcoholic polyneuropathy is a slowly progressive, length dependent, mainly sensory and painful axonal neuropathy in chronic heavy alcohol users, from direct neurotoxicity and nutritional deficiency (thiamine, folate, B12). It affects 20 to 60% of long term heavy drinkers, and is associated with cumulative lifetime consumption.

Pathophysiology. Ethanol and acetaldehyde injure axons and small fibres, with oxidative stress, and added thiamine deficiency from poor intake and impaired absorption.

Burning pain, numbness and paraesthesia in the feet, with loss of ankle reflexes, sensory loss in a stocking distribution, leg cramps, weakness, sensory ataxia and sometimes autonomic features (erectile dysfunction, orthostatic hypotension). Wernicke encephalopathy, liver disease and cerebellar degeneration may coexist.

Red flags.

• Ataxia, confusion or ophthalmoplegia (Wernicke encephalopathy).
• Rapid progression or marked weakness suggesting another cause.

Clinical diagnosis with a history of sustained alcohol excess. Check vitamin B12, folate, thiamine, glucose, HbA1c, liver tests, thyroid function, renal function, magnesium and full blood count. Nerve conduction studies show axonal sensorimotor neuropathy. Exclude other causes, including HIV, paraprotein and hereditary neuropathy.

Differential diagnosis.

• Diabetic, nutritional, uraemic and toxic neuropathy.
• Vitamin B12 deficiency, hypothyroidism and paraproteinaemic neuropathy.
• Acquired inflammatory neuropathy.

Abstinence is the main treatment. Offer brief intervention, relapse prevention (acamprosate 666 mg three times daily, naltrexone 50 mg daily) and addiction services. Manage withdrawal safely.

Thiamine. If Wernicke encephalopathy is possible: 500 mg IV three times daily for 2 to 3 days, then 250 mg IV daily for 3 to 5 days, then oral 100 mg three times daily. Give before glucose. Otherwise oral thiamine 100 mg three times daily.

Other vitamins. Folic acid 5 mg daily, vitamin B12 as indicated, and a multivitamin. Give nutrition support.

Neuropathic pain. Gabapentin 300 mg daily, increased gradually to 600 to 1200 mg three times daily (adjust to eGFR, monitor misuse), pregabalin, or amitriptyline 10 to 75 mg at night. Avoid opioids. Duloxetine with caution in liver disease.

Foot care and rehabilitation. Footwear, daily inspection, physiotherapy and falls prevention.

Monitoring. Symptoms, alcohol intake, liver function and nutrition.

Referral and escalation. Refer to neurology if atypical, and to addiction services.

Special groups. In pregnancy, advise abstinence, with thiamine and folic acid.