Effect of occupational keyboard typing on magnetic resonance imaging of the median nerve in subjects with and without symptoms of carpal tunnel syndrome.

Abstract

To examine the effects of occupational keyboard typing on median nerve shape and T2 relaxation and on forearm muscle T2 in professional typists with and without symptoms of carpal tunnel syndrome. Based on the Levine Carpal Tunnel Syndrome Symptom Severity scale (LCTSS), 12 female professional typist volunteers were divided into asymptomatic (LCTSS < 1.3, n = 5) and symptomatic (LCTSS > 1.3, n = 7) groups. Magnetic resonance images were acquired from wrist and forearms of all subjects before, immediately after, and 8 hrs after 3 hrs of typing. Forearm muscle T2 and median nerve T2 cross-sectional area and long/short axis ratio were evaluated by blinded observers. There was no difference between groups in any measured variable before typing. Median nerve T2 increased and long/short axis ratio decreased in asymptomatic subjects after typing, but there were no significant changes in symptomatic subjects. T2 increased in finger flexor muscles after typing, but there was no difference in the pattern of muscle T2 changes between groups. In magnetic resonance images of the median nerve at the carpal tunnel, swelling and T2 increases from baseline are a normal response to typing and may be less likely to occur in subjects with symptoms of carpal tunnel syndrome.