What is the likely diagnosis and initial treatment for numbness affecting the thumb, index and middle fingers?

Carpal Tunnel Syndrome

The most likely diagnosis is carpal tunnel syndrome (CTS), and initial treatment should be wrist splinting (especially at night) combined with local corticosteroid injection for patients with moderate symptoms, reserving surgical decompression for those who fail 4-6 months of conservative therapy or present with severe disease. 1, 2

Clinical Presentation

Numbness affecting the thumb, index, and middle fingers follows the classic distribution of median nerve compression at the wrist. 1, 2

• The median nerve innervates the palmar aspect of the thumb, index, middle, and radial half of the ring finger—matching this presentation exactly. 1
• Patients typically report nocturnal pain with tingling and numbness in this distribution, often relieving symptoms by "flicking" the hand (flick sign). 1, 3
• CTS is more common in middle-aged women, patients with obesity or diabetes, and those with occupations involving keyboards, computer mouse use, heavy machinery, or vibrating tools. 2, 3

Diagnostic Approach

Physical examination maneuvers should include:

• Durkan test: Apply firm digital pressure across the carpal tunnel to reproduce symptoms (64% sensitive, 83% specific). 2
• Phalen maneuver: Maximal wrist flexion for 60 seconds to provoke symptoms. 4, 1
• Tinel's sign: Tap over the median nerve at the wrist to elicit paresthesias. 4, 1
• Median nerve compression test: Direct compression over the carpal tunnel. 1

Electrodiagnostic testing (nerve conduction studies and EMG) is indicated when:

• Clinical presentation is atypical or diagnosis is uncertain (>80% sensitive, 95% specific). 2, 3
• Surgical decompression is planned, to determine severity and surgical prognosis. 1
• Proximal median nerve compression or other compressive neuropathies need exclusion. 2, 5

Patients with typical symptoms and positive physical examination findings do not require electrodiagnostic studies before initiating conservative treatment. 1

Initial Treatment Algorithm

For mild to moderate CTS:

1. Wrist splinting in neutral position, particularly at night, as first-line therapy. 1, 2
2. Local corticosteroid injection provides relief for more than one month and delays surgery at one year—particularly effective when combined with immobilization (72% symptom relief). 1, 2
3. Consider physical therapy, therapeutic ultrasound, or yoga as adjunctive measures. 1

Avoid ineffective therapies:

• NSAIDs, diuretics, and vitamin B6 are not effective for CTS. 1

For severe CTS or failed conservative therapy:

• Offer surgical decompression (open or endoscopic carpal tunnel release) if symptoms persist after 4-6 months of conservative treatment. 1, 2
• Patients with severe disease (thenar atrophy, constant numbness, or weakness of thumb opposition) should be offered early surgical consultation. 1, 2
• Endoscopic and open techniques are equally effective, though endoscopic repair allows return to work approximately one week earlier. 1

Critical Differential Diagnoses to Exclude

Proximal median nerve compression (pronator syndrome or anterior interosseous nerve syndrome):

• Presents with variable symptoms along the median nerve distribution but typically includes forearm pain and lacks nocturnal predominance. 5
• Requires electrodiagnostic testing to differentiate from CTS. 2, 5

Cervical radiculopathy (C6-C7):

• May cause hand numbness but typically involves neck pain, dermatomal sensory loss, and reflex changes. 4
• Requires cervical spine imaging if suspected. 4

Common Pitfalls to Avoid

• Do not attribute bilateral symmetric hand numbness to CTS if the patient has diabetes or is on chemotherapy—consider diabetic neuropathy or chemotherapy-induced peripheral neuropathy, which present in a "stocking-glove" distribution. 6, 7
• Do not assume unilateral presentation excludes systemic causes—stroke or TIA should be considered with sudden onset and vascular risk factors. 4
• Do not delay surgical referral in patients with severe CTS (thenar atrophy or constant numbness), as prolonged compression leads to irreversible nerve damage. 1, 2