Ultra High-Resolution Ultrasound Features of Carpal Tunnel Syndrome in Transthyretin Amyloidosis: A Cross-Sectional Study

Introduction/Aims: Transthyretin amyloidosis (ATTR), including hereditary (hATTR) and wild-type (wtATTR), often presents initially as carpal tunnel syndrome (CTS), often preceding systemic symptoms by several years. Ultra high-resolution ultrasound (UHRUS) offers detailed visualization of peripheral nerve morphology, but its application in ATTR-related CTS is unexplored. This study evaluated UHRUS features in ATTR-related CTS. Methods: This cross-sectional study enrolled 20 individuals with hATTR or wtATTR confirmed by genetic testing, biopsy, or cardiac pyrophosphate scan. Clinical evaluation included assessment for CTS symptoms and Boston Carpal Tunnel Questionnaire scores. Electrodiagnostic studies followed AANEM guidelines to diagnose median neuropathy at the wrist. UHRUS (48–70 MHz) assessed median nerve cross-sectional area (CSA), fascicle count, flexor retinaculum, and epineural thickness, as well as characteristics of paraneural tissue and tenosynovial tissue. Result: Clinical CTS was present in 17 patients (85%) and was electrodiagnostically confirmed in 85% of symptomatic wrists. Median nerve cross-sectional area (CSA) was significantly larger in wrists with both clinical and electrodiagnostic evidence of CTS compared to those without; however, 13 median nerves demonstrated normal CSA (< 12 mm2) despite clinical CTS. Additionally, several atypical ultrasonographic findings were noted: hyperechoic areas within five median nerves, thickened and hyperechoic paraneural tissue surrounding 15 median nerves and increased echogenicity of the flexor retinaculum in two wrists. Discussion: This pilot study identified several sonographic changes in ATTR-related CTS. These preliminary findings can provide a foundation for future research aimed at validating these patterns and developing a diagnostic tool to facilitate early detection in ATTR patients.