MRI analysis of carpal tunnel syndrome in hemodialysis patients versus non-hemodialysis patients: a multicenter case-control study.

BACKGROUND: Carpal tunnel syndrome (CTS) is common among patients receiving hemodialysis and deeply influences their daily life. Amyloid deposits are considered the main reason for median nerve compression, but its prevalence is unclear. Therefore, to determine the main region of amyloid deposition inside the carpal tunnel, we measured the cross-sectional area (CSA) of each component of the carpal tunnel in preoperative magnetic resonance imaging (MRI).

METHODS: Thirty-five hemodialysis patients (HD group) and age- and sex-matched 35 non-hemodialysis patients (non-HD group), who underwent the first surgery for CTS in registered hospitals from 2005 to 2015, were retrospectively enrolled. CTS was diagnosed from clinical and electromyographic (EMG) findings. The CSA of carpal tunnel, each of the flexor tendons, and the median nerve at the level of the hook of hamate were measured in T1-weighted axial images in preoperative MRI, by using Synapse OP-A software. Statistical analysis was performed using the Student's t test and Pearson's chi-squared test.

RESULTS: The mean age of the HD group was 65.9 years and the dialysis duration was 21.9 (11-35) years. The mean age of the non-HD group was 65.3 years. The CSA of carpal tunnel (p = 0.006), flexor tendon (p = 0.03), and flexor digitorum profundus (FDP) tendon (p = 0.04) were bigger in the HD group. However, the median nerve, the flexor digitorum superficialis (FDS) tendon, and the flexor pollicis longus tendon (FPL) were not significantly different between the two groups. The dialysis duration or age at surgery did not show any strong correlation to each CSA.

CONCLUSIONS: We confirmed that hemodialysis caused expansion of the carpal tunnel due to amyloid deposition as previously described. Hemodialysis also caused expansion of the CSA of the flexor tendon, especially the FDP, possibly because of amyloid deposition inside the tendon. Furthermore, the duration of dialysis or age did not correlate with any CSA, which could be due to the good progress of the beta 2-microglobulin removal technique. Based on our results, FDS excision could be considered in case severe deposition of amyloid in FDP is observed during surgery.