NATURAL-HISTORY OF MEDIAN NERVE SENSORY CONDUCTION IN INDUSTRY - RELATIONSHIP TO SYMPTOMS AND CARPAL-TUNNEL SYNDROME IN 558 HANDS OVER 11 YEARS

We evaluated the natural history of median nerve sensory conduction, h and/wrist symptoms, and carpal tunnel syndrome (CTS) in an 11-year lon gitudinal study of 289 workers from four industries. Twenty hands whic h had carpal tunnel release surgery were excluded, leaving 558 hands f or the primary study group. Overall, the trend was for mean sensory la tencies and prevalence of slowing to increase, the prevalence of sympt oms to decrease, and the prevalence of CTS to remain unchanged. Among individual hands, nerve conduction abnormalities tended to persist (82 % 11-year persistence), while symptoms fluctuated widely (13% Ii-year persistence). There was a strong, direct linear correlation between in itial severity of slowing and subsequent development of CTS; however, most workers who developed de novo slowing did not develop symptoms or CTS. We conclude that changes in conduction status of the median nerv e occur naturally with increasing age and do not necessarily lead to s ymptoms and CTS. (C) 1998 John Wiley & Sons, Inc.