Hand Numbness

Hand numbness is a localisation problem: which fingers are numb identifies which nerve is involved. Carpal tunnel syndrome, compression of the median nerve at the wrist, causes numbness in the thumb, index, middle and half the ring finger, classically worse at night and relieved by shaking the hand. Cubital tunnel syndrome compresses the ulnar nerve at the elbow, affecting the little finger and the other half of the ring finger. Cervical radiculopathy from a pinched nerve root in the neck radiates into the arm and hand, often with neck pain. These mechanical causes account for most cases. The systemic causes matter because they are common and treatable: diabetes produces a glove-distribution peripheral neuropathy, vitamin B12 deficiency causes numbness with balance and cognitive features, hypothyroidism both causes neuropathy and predisposes to carpal tunnel, and alcohol produces a length-dependent neuropathy. Numbness in both hands symmetrically suggests a systemic cause; one hand suggests a local one. Red flags include sudden onset, progressive weakness, or numbness with facial involvement or speech disturbance, which point to stroke rather than nerve compression.

• •Numbness or tingling in the thumb, index and middle fingers, worse at night — carpal tunnel pattern
• •Numbness in the little and ring fingers, worse with elbow flexion — ulnar pattern
• •Waking at night to shake the hand for relief
• •Radiating pain or numbness from neck into arm and hand
• •Symmetrical numbness in both hands, suggesting a systemic cause
• •Clumsiness, dropping objects or weak grip in advanced compression
• •Associated balance problems or cognitive change suggesting B12 deficiency

• •Carpal tunnel syndrome — the most common cause
• •Cervical radiculopathy from disc or arthritic compression in the neck
• •Cubital tunnel syndrome at the elbow
• •Diabetic peripheral neuropathy
• •Vitamin B12 deficiency, including from metformin and vegan diets
• •Hypothyroidism
• •Alcohol-related neuropathy
• •Pregnancy-related fluid retention causing transient carpal tunnel
• •Rheumatoid arthritis causing wrist synovitis
• •Vibration exposure from tools
• •Amyloidosis and other rarer infiltrative causes

Peripheral nerves signal through electrical conduction that fails under compression, ischaemia or metabolic injury. In carpal tunnel, pressure within the wrist tunnel compresses the median nerve, first affecting the large sensory fibres that carry touch. In metabolic neuropathies, axons die back from the longest nerves first — which is why symptoms start in the feet or hands in a glove-and-stocking pattern. B12 deficiency damages the myelin sheath itself, affecting both peripheral nerves and the spinal cord.