CARPAL-TUNNEL SYNDROME - ARE THE MR FINDINGS A RESULT OF POPULATION SELECTION BIAS

OBJECTIVE. Previous descriptions of MR imaging of carpal tunnel syndro me used limited study populations and volunteers as controls, We reeva luated these descriptions to determine their sensitivity and specifici ty when applied to a large consecutive clinical series in which the in cidence of carpal tunnel syndrome was small. SUBJECTS AND METHODS. In 196 consecutive wrists for which supplemental axial conventional spin- echo T1-weighted and fast spin-echo T2-weighted images were obtained a t 1.5 T with a dedicated wrist coil, 165 studies were available for re view. Previously described signs of carpal tunnel syndrome such as pro ximally increased size, flattening of the median nerve, increased medi an nerve signal intensity, flexor tenosynovitis, retinacular bowing, d ecreased deep tendon fat, and deep palmar bursitis were retrospectivel y and independently evaluated by two observers who were unaware of pat ient diagnosis. RESULTS. None of the previously described signs was se nsitive for the diagnosis of carpal tunnel syndrome. However, specific ity was high for retinacular bowing (94%), median nerve flattening (97 %), and deep palmar bursitis (95%). CONCLUSION. Most previously descri bed MR imaging signs of carpal tunnel syndrome are insensitive and non specific. Exceptions include retinacular bowing, median nerve flatteni ng, and deep palmar bursitis, which in our study proved to have specif icities greater than or equal to 94%.