What causes hand numbness and how is it treated?

Hand Numbness: Causes and Treatment

Primary Diagnostic Considerations

Hand numbness requires systematic evaluation starting with the most common causes: carpal tunnel syndrome (median nerve compression), peripheral neuropathy, cervical radiculopathy, and thoracic outlet syndrome. 1, 2

Most Common Causes

• Carpal tunnel syndrome is the most frequent nerve entrapment condition, causing decreased pain sensation and numbness in the thumb, index, and middle fingers 2, 3
• Peripheral neuropathy from diabetes, chemotherapy, vitamin B12 deficiency, or thyroid dysfunction presents with numbness and tingling, often in a "glove and stocking" distribution 4, 1
• Cervical radiculopathy can cause decreased sensation in specific finger distributions depending on the nerve root involved 2
• Thoracic outlet syndrome results from compression of the brachial plexus, causing chronic arm and hand paresthesia, numbness, or weakness 4, 5

Risk Factors to Assess

• Diabetes mellitus, smoking, alcohol consumption, rheumatoid arthritis, and hypothyroidism are risk factors for nerve entrapment 2
• History of chemotherapy (taxane-based or platinum-based regimens cause neuropathy in 30-40% of patients) 4
• Repetitive upper-extremity movement activities (swimming, throwing, volleyball) predispose to nerve compression 4, 6

Initial Clinical Assessment

History and Physical Examination

• Obtain a comprehensive history characterizing the numbness: onset, distribution (which fingers), progression, exacerbating factors, and associated symptoms like pain or weakness 1, 7
• Assess pain using a simple pain scale and document characteristics (burning, tingling, etc.) 4, 1
• Perform specific provocative tests for carpal tunnel syndrome: symptoms reproduced by wrist hyperflexion (Phalen's test) and median nerve percussion (Tinel's sign) 2
• Test sensation in specific distributions: decreased sensation in thumb, index, and middle fingers suggests median nerve involvement; little finger and ulnar aspect of ring finger suggests ulnar nerve or C8 radiculopathy 2
• Evaluate for thoracic outlet syndrome with positional testing during extreme shoulder abduction, which naturally narrows the costoclavicular space 4

Neurological Examination

• Perform 10-g monofilament testing, vibration testing with 128-Hz tuning fork, pinprick sensation testing, and ankle reflex assessment to identify loss of protective sensation 7
• Assess proprioception by testing joint position sense of the great toe or fingers with eyes closed, moving from distal to proximal joints 8
• Evaluate for intrinsic muscle weakness which may indicate ulnar nerve compression or cervical radiculopathy 2

Laboratory and Imaging Workup

Essential Laboratory Tests

• Fasting blood glucose and hemoglobin A1c to assess for diabetes mellitus 1, 7
• Vitamin B12 level to evaluate for deficiency-related neuropathy 1, 7
• Thyroid function tests (TSH, free T4) to assess for thyroid dysfunction 1, 7
• Complete blood count to evaluate for anemia 7

Imaging When Indicated

• Electromyography and nerve conduction studies help differentiate between cervical radiculopathy, thoracic outlet syndrome, and peripheral nerve entrapments 2
• MRI of the cervical spine if cervical radiculopathy is suspected based on dermatomal distribution 4
• CT or MRI of the thoracic outlet in neutral and stressed (abducted) positions when thoracic outlet syndrome is suspected 4

Treatment Approach

For Carpal Tunnel Syndrome

• Volar splinting and corticosteroid injection often ameliorate symptoms and should be first-line conservative treatment 2
• Surgical decompression is indicated when conservative measures fail 3

For Peripheral Neuropathy

• First-line medications include pregabalin, duloxetine, and gabapentin for neuropathic pain, numbness, and tingling 1
• Duloxetine specifically is recommended for patients with chemotherapy-induced peripheral neuropathy 4, 1
• Physical activity has been shown in multiple RCTs to improve neuropathic symptoms 4, 1
• Acupuncture has demonstrated efficacy in decreasing pain intensity in meta-analyses of RCTs 4
• Optimize glucose control in diabetic neuropathy to prevent progression 1

For Thoracic Outlet Syndrome

• The central objective is to preserve the digits and hand without sacrificing vascular access (in dialysis patients) 4
• Diagnostic arteriography of the extremity is foundational before determining surgical management 4
• Combined transaxillary first rib resection followed by transcervical anterior and middle scalenectomy has shown approximately 95% improvement in symptoms in surgical series 5

Non-Pharmacological Interventions

• Physical therapy, including stretching and exercises, has been shown effective for managing musculoskeletal symptoms 4
• Cognitive behavioral therapy may be recommended as an adjunct for neuropathic pain management 1

Critical Pitfalls to Avoid

• Do not rely on a single test for diagnosing peripheral neuropathy - at least two tests should be performed 7
• Do not overlook non-diabetic causes of peripheral neuropathy even in patients with diabetes 7
• Do not fail to assess for vascular compromise in patients with neuropathic symptoms, particularly in thoracic outlet syndrome where arterial steal can cause ischemia 4
• Recognize that approximately 40-50% of patients with thoracic outlet syndrome have associated peripheral nerve compression symptoms, making this one of the most overlooked and misdiagnosed conditions 5
• In patients with cervical spinal cord injury without fracture/dislocation, early surgical intervention may not be necessary or may even be harmful - close consultation with the patient is essential 4

Specialist Referral Indications

• Refer to endocrinology for diabetes management in diabetic neuropathy 1, 7
• Refer to hand surgery for suspected carpal tunnel syndrome requiring surgical intervention 3
• Refer to vascular surgery for thoracic outlet syndrome with arterial involvement 4
• Refer to podiatry for foot care in patients with diabetic neuropathy and loss of protective sensation 7