A 35-year-old construction worker presents with complaints of nocturnal parasthesias of the thumb and the index and middle fingers. There is some atrophy of the thenar eminence. Tinel sign is positive. The most likely diagnosis is

(Braunwald, 15/e, pp 1984-1986.) Carpal tunnel syndrome results from median nerve entrapment and is usually due to excessive use of the wrist. The process has been associated with thickening of connective tissue as in acromegaly, or with deposition of amyloid. It also occurs in hypothyroidism, rheumatoid ahritis, and diabetes mellitus. As in this patient, numbness occurs in the distribution of the median nerve. Later in the process, atrophy of the abductor pollicis brevis becomes apparent. The Tinel sign (parasthesia induced in the median nerve distribution by a reflex hammer hitting on the volar aspect of the wrist) is very characteristic. De Quervain's tenosynovitis causes focal wrist pain on the radial aspect of the hand and is due to inflammation of the tendon sheath of the abductor pollicis longus. It should not produce a postive Tinel sign. Amylotrophic lateral sclerosis may present with distal muscle weakness that is diffuse and not focal. Diffuse atrophy and muscle fasiculations would be prominent. Rheumatoid ahritis would not produce these symptoms unless inflammation of the wrist was causing median nerve entrapment in the carpal tunnel.