Carpal tunnel syndrome: evaluation of median nerve circulation with dynamic contrast-enhanced MR imaging.

PURPOSE: To identify mechanism(s) responsible for carpal tunnel syndrome (CTS). MATERIALS AND METHODS: At dynamic gadolinium-enhanced magnetic resonance (MR) imaging, the enhancement pattern of the sagittal section of the median nerve in 10 wrists of nine patients with CTS (two men and seven women, aged 43-60 years [mean, 52 years 10 months]) was studied while each wrist was in a neutral, flexed, and/or extended position. Five asymptomatic volunteers (four men and one woman, aged 23-54 years [mean, 31 years 5 months]) also underwent MR imaging to establish the normal enhancement patterns. RESULTS: Two distinctly abnormal patterns of median-nerve enhancement were revealed: marked or no enhancement. Marked enhancement was attributed to nerve edema, and the lack of enhancement was attributed to ischemia. Marked enhancement changed to no enhancement changed to no enhancement when the wrists were in a flexed or extended position. This change was associated with an aggravation of the symptoms of CTS. CONCLUSIONS: CTS may result from a circulatory disturbance rather than from deformation or compression of the nerve.