What causes finger numbness and tingling?

Finger Numbness and Tingling: Causes and Diagnostic Approach

Finger numbness and tingling most commonly results from nerve compression (particularly carpal tunnel syndrome affecting the median nerve), peripheral neuropathy from systemic diseases (diabetes, chemotherapy, vitamin B12 deficiency), or medication side effects, with the distribution pattern and associated symptoms guiding the specific diagnosis.

Primary Causes by Distribution Pattern

Median Nerve Distribution (Thumb, Index, Middle, and Radial Half of Ring Finger)

• Carpal tunnel syndrome is the most common cause, presenting with numbness and tingling in the thumb, index, middle, and radial ring fingers, often worse at night 1
• The Durkan maneuver (firm digital pressure across the carpal tunnel) is 64% sensitive and 83% specific for diagnosis 1
• Symptoms are reproduced by wrist hyperflexion and median nerve percussion 2
• Risk factors include female sex, obesity, diabetes, and occupations involving keyboards, computer mouse, heavy machinery, or vibrating tools 1

Ulnar Nerve Distribution (Little Finger and Ulnar Half of Ring Finger)

• Decreased sensation in the little finger and ulnar aspect of the ring finger suggests ulnar nerve compression at the elbow (cubital tunnel syndrome) or wrist (ulnar tunnel syndrome) 2
• May be accompanied by intrinsic muscle weakness 2

Symmetric "Stocking-Glove" Distribution (Both Hands)

• Peripheral neuropathy presents with bilateral, symmetric numbness and tingling starting distally in the fingers 3, 4
• Common descriptors include burning pain, electrical shock sensations, uncomfortable tingling, and contact pain (allodynia) 3

Systemic Causes of Peripheral Neuropathy

Diabetic Peripheral Neuropathy

• Affects up to 50% of diabetic patients with long disease duration 3
• Assess small-fiber function (pinprick, temperature), large-fiber function (vibration, 10-g monofilament), and protective sensation 3
• Symptoms include numbness, tingling, burning pain, and altered temperature perception, characteristically worse at night 3
• Consider other causes: vitamin B12 deficiency, hypothyroidism, renal disease, alcohol, neurotoxic medications 3

Chemotherapy-Induced Peripheral Neuropathy (CIPN)

• Occurs in 30-40% of patients receiving taxane-based or platinum-based chemotherapy 3
• Paclitaxel causes primarily sensory neuropathy more prominent in lower extremities initially 3
• Oxaliplatin symptoms are more severe in upper extremities during treatment, with a "coasting phenomenon" where neuropathy worsens for 2-3 months after cessation 3
• Numbness and tingling appear earlier and are more prominent than pain 3

Medication-Induced Neuropathy

• Metformin causes vitamin B12 deficiency leading to peripheral neuropathy, especially at doses of 2g daily 4
• Presents as numbness and tingling in a stocking-glove distribution with impaired vibratory sensation and proprioception 4
• Monitor patients on long-term metformin for B12 deficiency 4
• Bortezomib (multiple myeloma treatment) causes predominantly sensory neuropathy with stinging sensations or numbness initially affecting toes, sometimes fingers 3
• Thalidomide causes bilateral symmetric sensory disorders with distal paresthesia and hyperesthesia after prolonged exposure 3

Hepatitis C-Related Neuropathy

• Up to 50% of HCV-infected patients develop peripheral sensory, motor, or sensorimotor polyneuropathies 3
• Most common symptoms are sensory loss, paresthesias, numbness, cramps, burning feet, and tingling 3
• Onset is often subacute with distal, symmetric presentation 3

Diagnostic Workup

Clinical Assessment

• History: Determine distribution pattern (median vs. ulnar vs. symmetric), timing (worse at night suggests carpal tunnel), progression, and associated symptoms 3
• Physical examination: Test sensory function in specific nerve distributions, perform Durkan maneuver for carpal tunnel, assess for intrinsic muscle weakness 1, 2
• Identify risk factors: Diabetes, chemotherapy exposure, metformin use, occupational exposures, alcohol consumption, smoking, rheumatoid arthritis, hypothyroidism 1, 2

Laboratory Evaluation

• For suspected peripheral neuropathy, exclude: vitamin B12 deficiency, hypothyroidism, renal disease, diabetes (if not already diagnosed) 3
• Consider HCV testing if other risk factors present 3
• Electrodiagnostic testing (EMG/nerve conduction studies) is >80% sensitive and 95% specific for carpal tunnel syndrome when diagnosis is unclear or proximal compression suspected 1

Specialized Testing

• Electromyography with peripheral nerve neurophysiological tests for suspected peripheral neuropathy 3
• Nerve conduction studies predominantly reveal low amplitude sensory action potentials in chemotherapy-induced neuropathy 3
• Intraepidermal nerve fiber density testing for small fiber neuropathy when indicated 3

Common Pitfalls

• Distinguishing diabetic neuropathy from metformin-induced B12 deficiency neuropathy is challenging as both present similarly; check B12 levels in all diabetic patients on metformin with neuropathy symptoms 4
• Bilateral symptoms suggest systemic causes (diabetes, medications, toxins) rather than focal nerve compression 2
• Night-time worsening strongly suggests carpal tunnel syndrome rather than peripheral neuropathy 3
• Seek immediate medical attention if numbness is accompanied by weakness, severe pain, rapid progression, confusion, memory problems, or difficulty walking 4