Objective: Carpal tunnel syndrome (CTS) is common among patients receiving hemodialysis and deeply influences the daily life. Amyloid deposits are considered as the main reason for median nerve compression but the prevalence is unclear. In this study, to determine the main region of amyloid deposit inside carpal tunnel, we measured cross-sectional area (CSA) of each composition of carpal tunnel in preoperative MRI. Materials and Methods: In all, 41 hemodialysis patients (HD) and age, sex-matched 41 nonhemodialysis patients (NHD), who underwent the first surgery for CTS in Tsuchiya General Hospital (Hiroshima, Japan) from 2005 to 2015, were retrospectively collected. CTS was diagnosed from clinical and electromyographic (EMG) findings. CSA of carpal tunnel, each flexor tendon and median nerve at the level of hook of hamate, were measured in T1-weighted axial image in preoperative MRI, by using Synapse OP-A software. Statistical analysis was performed by student’s t test and Pearson’s chi-square test. This study was approved by institutional review board. Results: HD was 64.3 years and the dialysis duration was 21.9 (11-35) years, and NHD was 65.5 years. CSA of carpal tunnel (HD: 204.2 mm2, NHD: 191.3 mm2, P = .01), flexor tendon (HD: 101.2 mm2, NHD: 92.7 mm2, P = .03), and flexor digitorum profundus tendon (FDP; HD: 57.3 mm2, NHD: 49.8 mm2, P = .04) were bigger in HD group, but median nerve, flexor digitorum superficialis tendon, and flexor pollicis longus tendon were not significantly different from NHD group. Dialysis duration or age to each CSA did not show any strong correlation. In one dialysis patient, accessory tendon of FDP was dissected during the surgery to reduce the pressure of carpal tunnel, and then it was histologically analyzed. Amyloid deposition was confirmed not only around but inside the tendon itself by Dylon stain. Conclusions: We identified hemodialysis caused CSA expansion of carpal tunnel due to amyloid deposition as previously described. Also CSA expansion of flexor tendon, especially FDP, was happened, possibly because amyloid deposited not only around but inside the tendon. We could not identify why it happened to FDP mostly from this study. Great progress had been made on the technique of Beta 2-microglobulin removal in these years, and it is a possible reason why we could not find any correlation between duration of hemodialysis or age to any CSA.
