Correct Answer: B. Carpal tunnel syndrome, Durkan's test
Carpal tunnel syndrome (CTS) presents with paresthesias in the lateral 3.5 digits (thumb, index, middle, and radial half of ring finger)—the distribution of the median nerve. The patient's nocturnal symptoms and relief with arm hanging (gravity-dependent drainage of edema) are classic CTS features. Durkan's test (carpal compression test) is the gold standard clinical assessment: sustained pressure over the carpal tunnel for 30 seconds reproduces paresthesias with 87% sensitivity and 95% specificity. This test directly compresses the median nerve within the carpal tunnel, making it the most reliable bedside diagnostic maneuver. Froment's test assesses the ulnar nerve (adductor pollicis function), not the median nerve. The clinical presentation—nocturnal paresthesias in median nerve distribution relieved by positional changes—combined with Durkan's test (which specifically compresses the median nerve at the wrist) makes option B the correct answer. Per Bailey & Love and standard orthopedic practice in India, Durkan's test is preferred over Phalen's test for its superior sensitivity in CTS diagnosis.
Why the other options are wrong
A. Carpal tunnel syndrome, Froment's test — While CTS diagnosis is correct, Froment's test is wrong. Froment's test assesses ulnar nerve function (adductor pollicis strength during thumb adduction against resistance), not median nerve compression. This is an NBE trap pairing the correct diagnosis with an incorrect test—students may recognize CTS but confuse the diagnostic test. Durkan's test, not Froment's, is the gold standard for CTS. C. Guyon's canal syndrome, Durkan's test — Guyon's canal syndrome affects the ulnar nerve (superficial and deep branches), causing paresthesias in the medial 1.5 digits (ulnar side of ring finger and little finger), not the lateral 3 digits. The patient's presentation clearly indicates median nerve involvement. Although Durkan's test is correct, the diagnosis is wrong—this option misdirects students who may know the test but misidentify the nerve distribution. D. Guyon's canal syndrome, Froment's test — This option is doubly incorrect. Guyon's canal syndrome affects the ulnar nerve (not median), causing symptoms in the medial 1.5 digits, not lateral 3 digits. Froment's test is appropriate for ulnar nerve assessment, but the patient's clinical presentation—lateral 3 digits with nocturnal paresthesias—is pathognomonic for CTS (median nerve), not Guyon's syndrome. This is a complete mismatch.
High-Yield Facts
- Carpal tunnel syndrome presents with paresthesias in the lateral 3.5 digits (median nerve distribution: thumb, index, middle, radial ring finger).
- Durkan's test (carpal compression test): sustained pressure over the carpal tunnel for 30 seconds; sensitivity 87%, specificity 95%—gold standard bedside test for CTS.
- Nocturnal paresthesias relieved by arm hanging (gravity-dependent edema drainage) is the classic CTS presentation that distinguishes it from other peripheral neuropathies.
- Froment's test assesses ulnar nerve function (adductor pollicis); positive when thumb IP joint flexes during pinch—used for Guyon's canal syndrome and ulnar nerve palsy.
- Guyon's canal syndrome affects ulnar nerve distal to wrist, causing paresthesias in medial 1.5 digits (ulnar side of ring finger and little finger) with preserved sensation at thumb.
Mnemonics
CTS vs Guyon's: Digit Distribution LAM = Lateral 3.5 digits = Affected in Median nerve (CTS). MUG = Medial 1.5 digits = Ulnar nerve = Guyon's canal. Use when differentiating sensory loss patterns in hand paresthesias. CTS Diagnostic Tests: DCP Durkan's (gold standard), Carpal compression, Phalen's (less sensitive). Durkan's is the most reliable single test—remember it as the 'direct compression' test that mimics the pathology. Use when choosing between CTS diagnostic maneuvers.
NBE Trap
NBE pairs CTS (correct diagnosis) with Froment's test (ulnar nerve test) to trap students who recognize the clinical presentation but confuse diagnostic tests across different nerve compressions. The lateral 3 digits and nocturnal symptoms are unmistakable CTS clues, but students may default to Froment's if they recall it as a "hand nerve test" without specificity.
Clinical Pearl
In Indian orthopedic practice, CTS is the most common nerve compression syndrome, especially in women and repetitive workers (garment industry, IT professionals). Durkan's test is preferred in busy OPDs because it requires no equipment and can be performed in 30 seconds—making it the practical gold standard for ruling in CTS before EMG confirmation.
_Reference: Bailey & Love Ch. 68 (Hand Surgery); Harrison Ch. 379 (Peripheral Neuropathies)_