The Higher Positive Amyloid Deposition in Electrophysiologically Proven Idiopathic Carpal Tunnel Syndrome Patients

Background: Carpal tunnel syndrome (CTS) due to amyloid deposition was reported to precede fatal cardiac amyloidosis by several years. Although nerve conduction study (NCS) supports CTS diagnosis, the incidence of positive amyloid deposition in electrophysiologically proven CTS is unclear. Methods: We retrospectively analysed the demographic data including age, gender, bilateral hand involvement, amyloid deposition and NCS results, of 111 consecutive CTS patients with postoperative symptom improvement (mean 71.1 years old, male/female ratio: 44/67) who simultaneously underwent carpal tunnel release (CTR) and biopsy for amyloid deposition. Results: Electrophysiologically proven CTS patients were 102 (91.9%) out of 111 patients. Amyloid deposition was detected in 62 hands (55.9%), of which 51 were transthyretin amyloid. The NCS severity was associated with a higher prevalence of positive amyloid deposition (p < 0.01). The NCS severity also showed an increased trend between reported risk factors for positive amyloid deposition such as older age, male gender and bilateral hand symptoms (p < 0.01). Conclusions: The prevalence of positive amyloid deposition was higher than previous reports in this study. Abnormal NCS findings in CTS, such as an increased distal motor latency (DML) of abductor pollicis brevis compound muscle action potentials (APB-CMAP) or absent APB-CMAP, may help to increase the pre-test probability of amyloid deposition in tenosynovial biopsy. Level of Evidence: Level IV (Diagnostic Study).