Quantitative MRI and electrophysiology of preoperative carpal tunnel syndrome in a female population.

The tunnel size is reported to play a role in median neuropathy. The aim of the study was to quantify the volume of the carpal tunnel in a selected population with idiopathic carpal tunnel syndrome (CTS), as the narrowest point of the canal was noted. Twenty-seven patients with CTS and 28 asymptomatic controls were examined. All participants were women. Both groups underwent nerve conduction studies and magnetic resonance (MR) of the wrists. On the MR axial images, the volume of carpal tunnels, the wrists and the thenar muscles were calculated bilaterally in all subjects. The values for the signal intensity of the median nerve from all wrists were also quantified and correlated with the neurophysiological findings. The carpal tunnel volume (CTV) and the wrist volume (WV)/CTV ratio were almost identical in both groups (p = 0.36 and p = 0.45, respectively). The focal narrowest point of the tunnel was similarly located in both populations, and detected at its distal third, about 8 mm from the outlet. The median nerve in the patients emitted a higher signal compared with the controls, p = 0.037. Between the two groups, there were differences in the amplitude and the distal latency of the median sensory branch (p = 0.0001 and p = 0.0001, respectively), as well as in the amplitude and the F-wave latencies of the median motor branch (p = 0.045 and p = 0.017, respectively). There was no difference in the size of the carpal tunnel in women with idiopathic CTS compared with healthy controls, as the focal narrowest point was equally located in both groups near the canal outlet.