Neurology · Peripheral Neuropathy
The facts most likely to be tested
Carpal tunnel syndrome results from median nerve compression at the wrist within the carpal tunnel.
Patients classically present with nocturnal paresthesias and numbness in the first three digits and the radial half of the fourth digit.
Physical examination reveals thenar eminence atrophy in chronic, severe cases due to denervation of the abductor pollicis brevis.
The Phalen maneuver and Tinel sign are the most common provocative clinical tests used to support the diagnosis.
Nerve conduction studies and electromyography (EMG) are the gold standard diagnostic tests to confirm the diagnosis and assess severity.
Initial management for mild to moderate cases includes wrist splinting in a neutral position, particularly at night.
Conditions associated with increased risk include pregnancy, hypothyroidism, diabetes mellitus, rheumatoid arthritis, and obesity.
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A 45-year-old female presents with a 3-month history of numbness and tingling in her right hand that frequently wakes her from sleep. She works as a data entry clerk and reports that the symptoms are relieved by shaking her hand. On physical exam, there is decreased sensation over the palmar aspect of the thumb, index, and middle fingers. Tinel sign is positive at the wrist, and there is mild thenar muscle wasting.
What is the most appropriate initial diagnostic test to confirm the suspected diagnosis?
Nerve conduction studies
The patient's presentation of nocturnal paresthesias in the median nerve distribution is classic for carpal tunnel syndrome, which is confirmed via nerve conduction studies showing slowed conduction across the carpal tunnel.
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Etiology / Epidemiology
Common in repetitive wrist motion, pregnancy, diabetes, and hypothyroidism.
Clinical Manifestations
Paresthesias in the median nerve distribution; thenar atrophy is a late, pathognomonic sign.
Diagnosis
Electromyography (EMG) and nerve conduction studies are the gold standard for confirmation.
Treatment
Splinting is first-line; surgical decompression is indicated for refractory cases.
Prognosis
Early intervention prevents permanent thenar muscle wasting.
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Epidemiology & Etiology
Prevalence peaks in middle-aged women, often associated with occupational overuse. Systemic risk factors include diabetes mellitus, hypothyroidism, and rheumatoid arthritis. Fluid retention states like pregnancy frequently precipitate acute symptoms.
Pertinent Anatomy
The carpal tunnel is formed by the carpal bones and the transverse carpal ligament. The median nerve is the sole structure compressed within this rigid space, leading to sensory and motor deficits.
Pathophysiology
Increased pressure within the tunnel causes nerve ischemia and impaired axonal transport. Chronic compression leads to demyelination and eventually Wallerian degeneration. This manifests as progressive sensory loss followed by motor weakness.
Clinical Manifestations
Patients report nocturnal paresthesias in the thumb, index, and middle fingers. Phalen's maneuver and Tinel's sign are classic physical exam findings. Thenar muscle atrophy indicates severe, chronic nerve damage requiring urgent evaluation.
Diagnosis
The nerve conduction study is the gold standard, showing prolonged distal latency (>4.2 ms). Clinical diagnosis is supported by positive Phalen's and Tinel's tests. Ultrasound may show nerve cross-sectional area >10 mm² at the tunnel inlet.
Treatment
Initial management includes nocturnal wrist splinting in neutral position. Corticosteroid injections provide temporary relief for moderate cases. Avoid repetitive strain during recovery. Surgical carpal tunnel release is the definitive treatment for persistent symptoms or motor loss.
Prognosis
Most patients improve with conservative care. Failure to treat leads to permanent thenar atrophy and loss of fine motor function. Post-surgical nerve conduction velocity improvement is expected in successful cases.
Differential Diagnosis
Cervical radiculopathy: pain radiates from the neck
Pronator teres syndrome: proximal forearm tenderness
Diabetic neuropathy: typically bilateral and stocking-glove distribution
De Quervain tenosynovitis: positive Finkelstein test
Thoracic outlet syndrome: vascular symptoms and ulnar distribution