Nerve Conduction Studies of Median Motor Nerve and Median Sensory Branches According to the Severity of Carpal Tunnel Syndrome

OBJECTIVE: To evaluate each digital branch of the median sensory nerve and motor nerves to abductor pollicis brevis (APB) and 2nd lumbrical (2L) according to the severity of carpal tunnel syndrome (CTS). METHODS: A prospective study was performed in 67 hands of 41 patients with CTS consisting of mild, 23; moderate, 27; and severe cases, 17. Compound muscle action potentials (CMAPs) were obtained from APB and 2L, and median sensory nerve action potentials (SNAPs) were recorded from the thumb to the 4th digit. Parameters analyzed were latency of the median CMAP, latency difference of 2L and first palmar interosseous (PI), as well as latency and baseline to peak amplitude of the median SNAPs. RESULTS: The onset and peak latencies of the median SNAPs revealed significant differences only in the 2nd digit, according to the severity of CTS, and abnormal rates of the latencies were significantly lower in the 2nd digit to a mild degree. The amplitude of SNAP and sensory nerve conduction velocities were more preserved in the 2nd digit in mild CTS and more affected in the 4th digit in severe CTS. CMAPs were not evoked with APB recording in 4 patients with severe CTS, but obtained in all patients with 2L recording. 2L-PI showed statistical significance according to the severity of CTS. CONCLUSION: The branch to the 4th digit was mostly involved and the branch to the 2nd digit and 2L were less affected in the progress of CTS. The second digit recorded SNAPs and 2L recorded CMAPs would be valuable in the evaluation of severe CTS.

Dorsal Digital Branch of the Thumb: An Anatomical Study / Nervio Digital Dorsal del Pulgar: Estudio Anatómico

The level of origin of digital branch to thumb (DBT) of superficial branch of radial nerve (SBRN) and its relationship to brachioradialis muscle tendon (BRT) and its fascial sheath (FS) were studied on both sides of upper extremities of 50 cadavers (n=100). The DBT of SBRN originated in the middle third of forearm in 3 cases (3%), distal third of forearm in 10 cases (10%) and in wrist and dorsum of hand in 87 cases (87%). All cases having origin in the middle third of forearm and half of the cases having origin in the distal third of forearm were closely related to BRT or its FS. The clinical importance of the study lies in the fact that the DBT supplies dorsum of the thumb and first web space which has least cutaneous overlapping. Any injury or entrapment of this nerve may lead to painful neuritis. Anatomical knowledge of such variations are important for neurologists and surgeons performing operative procedures in Quervain's release, arthroscopy and Wartenberg's disease.

Fue estudiado en los miembros superiores de 50 cadáveres, el origen del nervio digital dorsal para el pulgar (NDDP) desde el ramo superficial del nervio radial (RSNR) y sus relaciones con el tendón del músculo braquiorradial (TMB) y su vaina fascial (VF). El NDDP del RSNR se originó en el tercio medio del antebrazo en 3 casos (3%), en el tercio distal del antebrazo en 10 casos (10%) y en la muñeca y dorso de la mano en 87 casos (87%). En todos los casos en que el NDDP se originaba en el tercio medio del antebrazo y en la mitad de los casos en que se originaba en el tercio distal del antebrazo, tenía relaciones estrechas con el TMB o su VF. La importancia clínica de este estudio se basa en que el NDDP suple el dorso del pulgar y primer espacio interdigital, el cual tiene pequeñísima superposición cutánea. Alguna herida o compresión de este nervio puede llevar a neuritis dolorosa. El conocimiento anatómico de estas variaciones son importantes para neurólogos y cirujanos durante los procedimientos de liberación de Quervain, artroscopía y enfermedad de Wartenberg.