Carpal tunnel syndrome

Abstract

Abstract Carpal tunnel syndrome (CTS) is a compressive focal neuropathy of the median nerve (NM) at the wrist. We hypothesize that reverse Phalen’s test rather than the previously commonly proposed classic Phalen’s maneuver was a logical maneuver in the diagnosis of CTS from the anatomic, pathophysiological and electrophysiological viewpoint. Dorsal flexion of the hand results in an increase in the flexor retinaculum tension (RFT), extension of the finger long flexor muscle tendons and consequential NM entrapment between the tendons and flexor retinaculum (RF). Thus, the carpal tunnel (CT) volume is reduced, the intra-tunnel pressure is increased, while the RF to NM distance is decreased. On Phalen’s maneuver, the forced palmar hand flexion entails opposite consequences i.e. reduced RFT, relaxation of the finger long flexor muscle tendons, decreased pressure upon NM, slight increase in the CT volume, decreased intra-tunnel pressure and increased RF to NM distance. The hypothesis can be tested by a conductive NM study, preferably at three positions: mid-position (palmar/volar angle 180 degrees); forced dorsal flexion (palmar/volar angle about 270 degrees); and forced palmar (volar) flexion (palmar/volar angle about 90 degrees). Relative to mid-position, “deterioration” of electroneurography (ENG) finding is observed in dorsal flexion, whereas “improvement” of ENG finding is recorded in palmar flexion.