Private pins and needles clinic in London, same-day specialist medicine.

What the pattern means

• Thumb, index, middle and half the ring finger, worse at night, shaking the hand helps — carpal tunnel syndrome.
• Little finger and half the ring finger, worse with the elbow bent — ulnar nerve at the elbow.
• Both feet, symmetrically, in a stocking distribution, creeping up over months — peripheral neuropathy.
• Down one leg past the knee, with back pain — nerve root compression (sciatica).
• One arm, in a band or stripe, with neck pain — cervical nerve root.
• Outer thigh, a patch — meralgia paraesthetica, from a compressed nerve at the groin.
• Around the mouth and both hands together, with anxiety — usually hyperventilation.
• Patchy, migrating, both sides, with other neurological symptoms — needs neurological assessment.

Causes of peripheral neuropathy

• Diabetes — the commonest cause in the UK, and it can be the presenting feature of undiagnosed diabetes.
• Vitamin B12 deficiency — entirely treatable, and damage becomes permanent if left.
• Alcohol — a common and under-acknowledged cause.
• Underactive thyroid, kidney disease, and coeliac disease.
• Medicines — some chemotherapy agents, metronidazole, isoniazid, and long-term metformin (via B12 depletion).
• Inflammatory and autoimmune conditions, and less commonly inherited neuropathies.
• In a proportion no cause is found despite full investigation.

What gets tested

• Blood tests — HbA1c or glucose, B12, folate, ferritin, thyroid function, kidney and liver function, full blood count, inflammatory markers, coeliac screening
• Examination of sensation, power, reflexes and gait, which localises the problem
• Nerve conduction studies where compression or neuropathy needs confirming
• MRI of the neck or back where a nerve root or the spinal cord is implicated
• Further testing for inflammatory or inherited causes where indicated

Meanwhile