What causes numbness in the palm?

Causes of Palm Numbness

Carpal tunnel syndrome is the most common cause of palm numbness, resulting from median nerve compression at the wrist, and typically affects the palmar aspect of the thumb, index, middle fingers, and radial half of the ring finger. 1

Primary Diagnostic Considerations

Carpal Tunnel Syndrome (Most Common)

• Median nerve compression at the wrist causes numbness in the thumb, index, middle fingers, and radial half of the ring finger on the palmar surface. 1
• Patients typically experience paresthesias (tingling, pins-and-needles sensation) along with numbness in this characteristic distribution. 1
• Physical examination findings that support this diagnosis include:
  • Positive flick sign (patient shakes hand to relieve symptoms) 1
  • Positive Phalen maneuver (wrist hyperflexion reproduces symptoms) 1, 2
  • Positive median nerve compression test (direct pressure over carpal tunnel reproduces symptoms) 1
• Risk factors include diabetes, smoking, alcohol consumption, rheumatoid arthritis, and hypothyroidism, though these typically produce bilateral symptoms. 2

Systemic Neuropathies Affecting the Palm

Diabetic peripheral neuropathy presents with large-fiber involvement causing numbness in a stocking-glove distribution, beginning distally in the fingertips and progressing proximally. 3 However, this typically affects both feet first before hands and involves all fingers symmetrically rather than isolated median nerve distribution. 3, 4

Chemotherapy-induced peripheral neuropathy (CIPN) causes primarily sensory neuropathy with numbness and tingling in a stocking-glove distribution beginning distally in fingers and toes. 5, 3 This affects all fingertips symmetrically rather than following a specific nerve distribution. 5

Vascular Causes (Rare but Important)

Thrombosis of a persistent median artery can cause acute carpal tunnel syndrome with numbness in median nerve distribution, often accompanied by coldness and acute hand swelling. 6, 7 This is a rare anatomical variant but should be considered when symptoms are acute and associated with vascular features. 6

Diagnostic Algorithm

Step 1: Determine Distribution Pattern

• If numbness affects thumb, index, middle, and radial half of ring finger (palmar surface): Think carpal tunnel syndrome or median nerve pathology. 1, 2
• If numbness affects little finger and ulnar aspect of ring finger: Consider ulnar nerve compression (cubital tunnel syndrome at elbow or ulnar tunnel syndrome at wrist). 2
• If numbness affects all fingertips symmetrically in both hands: Consider systemic polyneuropathy from diabetes or chemotherapy. 3, 4

Step 2: Assess Timing and Associated Features

• Gradual onset with nocturnal worsening and relief with hand shaking: Classic for carpal tunnel syndrome. 1
• Acute onset with hand swelling and coldness: Consider thrombosed persistent median artery requiring urgent ultrasound Doppler. 6, 7
• Progressive symmetric symptoms in stocking-glove pattern: Evaluate for diabetes (check HbA1c, perform monofilament testing) or recent chemotherapy exposure. 3

Step 3: Physical Examination Maneuvers

• Perform Phalen maneuver (hold wrists in full flexion for 60 seconds): Positive if reproduces numbness. 1, 2
• Perform Tinel sign (percussion over median nerve at wrist): Positive if produces tingling. 1, 2
• Test pinprick sensation in median nerve distribution versus ulnar distribution to confirm pattern. 2
• For suspected diabetic neuropathy: Perform 10-g monofilament testing, vibration perception with 128-Hz tuning fork, and temperature sensation. 3

Step 4: Confirmatory Testing When Needed

• Patients with typical carpal tunnel syndrome symptoms and positive examination findings do not need additional testing for diagnosis. 1
• Obtain electrodiagnostic studies (EMG/nerve conduction studies) if:
  • Symptoms are atypical or diagnosis is uncertain 1
  • Surgical decompression is planned (to determine severity and prognosis) 1
  • Need to differentiate from cervical radiculopathy or other nerve entrapments 2
• Obtain ultrasound Doppler if acute onset with vascular features (coldness, swelling) to evaluate for persistent median artery thrombosis. 6, 7

Common Pitfalls to Avoid

• Do not assume all hand numbness is carpal tunnel syndrome. Cervical radiculopathy, thoracic outlet syndrome, and proximal median nerve compression can mimic carpal tunnel syndrome but require different management. 2
• Do not overlook bilateral symptoms in patients with diabetes, hypothyroidism, or rheumatoid arthritis, as these conditions predispose to nerve entrapment but also cause systemic neuropathy. 2
• Do not miss acute vascular causes. If a patient presents with acute numbness, hand swelling, and coldness, urgent ultrasound is needed to rule out persistent median artery thrombosis, which may require anticoagulation or surgery. 6, 7
• Isolated single-digit numbness (e.g., only middle finger) is atypical for common causes and warrants consideration of focal trauma, compression, or vascular compromise specific to that digit. 4