Hand-Arm Vibration-Associated Neuropathy

Hand arm vibration associated neuropathy is the sensorineural component of hand arm vibration syndrome. It presents with numbness, tingling and loss of dexterity in the fingers after prolonged exposure to hand transmitted vibration, often alongside vascular changes.

Exposure. Chainsaws, grinders, impact wrenches, pneumatic and rotary hammers, drills and sanders in forestry, construction, mining, foundry and metal work.

Epidemiology. Sensorineural symptoms are very common in long term exposed workers, and often outlast vascular symptoms. Carpal tunnel syndrome is more frequent in this group.

Staging. Stage 0SN: exposed with no symptoms. Stage 1SN: intermittent numbness with or without tingling. Stage 2SN: intermittent or persistent numbness with reduced sensory perception. Stage 3SN: intermittent or persistent numbness with reduced tactile discrimination or manipulative dexterity.

Course. Early disease may improve when exposure falls. Advanced loss is usually permanent.

Pathophysiology.

Vibration damages digital nerves and mechanoreceptors, with perineural oedema, demyelination and fibrosis. Ischaemia of the vasa nervorum contributes.

Entrapment at the carpal tunnel and ulnar sites adds to the deficit, and vibration also impairs central sensory processing.

• Numbness, tingling and burning of the fingers, often at night, with clumsiness.
• Reduced grip strength, difficulty with buttons and small objects.
• Reduced temperature and touch perception, with injuries going unnoticed.
• Coexisting finger blanching in vascular disease.

Red flags.

• Thenar wasting, fixed sensory loss or progressive weakness.
• Symptoms proximal to the wrist, bilateral proximal or lower limb features.
• Systemic features such as weight loss or fever.

• Detailed exposure history: tools, vibration magnitude, daily trigger time and years of work.
• Examination of sensation, dexterity, Tinel and Phalen signs, and thenar bulk.
• Quantitative tests: vibrotactile and thermal perception thresholds, monofilament testing, two point discrimination and a pegboard dexterity test.
• Nerve conduction studies to confirm carpal tunnel or ulnar entrapment and to exclude other neuropathy.
• Blood tests: glucose or HbA1c, vitamin B12, TSH, renal and liver function, and alcohol review.

Differential diagnosis. Carpal tunnel syndrome from other causes, cervical radiculopathy, ulnar neuropathy, diabetic and other polyneuropathies, vitamin B12 deficiency, hypothyroidism, thoracic outlet syndrome, multiple sclerosis.

• Reduce vibration exposure: low vibration tools, limited trigger time, rest breaks, job rotation and well maintained tools; transfer from vibration work when symptoms are moderate or severe.
• Keep the hands warm; stop smoking.
• Night wrist splints in neutral for 6 weeks when carpal tunnel syndrome coexists.
• Neuropathic pain or paraesthesia: pregabalin orally, 75 mg twice daily, increased after 3 to 7 days to 300 mg daily and, if needed after a further 7 days, to a maximum of 600 mg daily. Review at 4 weeks and stop if there is no meaningful benefit; withdraw over at least 1 week. Monitor sedation, dizziness, peripheral oedema, weight gain, mood and misuse. Adjust for renal function: creatinine clearance 30 to 60 mL/min, 75 to 300 mg daily in 2 or 3 divided doses; 15 to 30 mL/min, 25 to 150 mg daily; under 15 mL/min, 25 to 75 mg daily. Avoid in pregnancy unless benefit outweighs risk. Evidence for benefit in this condition is limited.
• Carpal tunnel decompression for persistent entrapment with motor loss or failure of splinting.
• Correct treatable contributors: diabetes, hypothyroidism and B12 deficiency.

Monitoring. Review at 6 to 12 months with staging and dexterity testing; yearly health surveillance for exposed workers.

Referral and escalation. Occupational physician; neurophysiology and hand surgery for entrapment; neurology for atypical or progressive disease; notification and compensation where required.