Transthyretin amyloidosis (ATTR) is an underdiagnosed condition that can present early as carpal tunnel syndrome, sometimes preceding cardiac involvement by several years. The recent emergence of new treatments underscores the importance of early diagnosis. Synovial biopsy performed during open carpal tunnel surgery is considered the gold standard for local screening, but it is less accessible, more difficult, and riskier to perform via endoscopy-a minimally invasive surgical technique that is currently the standard at our center and is becoming increasingly widespread.

The anterior annular ligament of the carpus constitutes an alternative tissue to the synovium, easily accessible via endoscopy, safe, and standardizable.

In this study, the systematic performance of an annular ligament biopsy in conjunction with a synovial biopsy during endoscopic carpal tunnel surgery would allow for the evaluation of the diagnostic concordance of the ligament biopsy by comparing it to the results obtained using the gold standard method. This strategy would also provide an opportunity to analyze the feasibility of systematic screening for ATTR on the ligament during endoscopic procedures.

This approach could offer a practical and innovative method for the early identification of at-risk patients and facilitate appropriate and timely management of the condition.

Inclusion Criteria:

• Adult patient with Health Insurance
• Clinical diagnosis + carpal tunnel EMG
• Validated indication for carpal tunnel surgery
• Signed informed consent
• Patient at risk for postoperative complications (bilateral carpal tunnel syndrome, heart failure, atrial fibrillation, elderly patients)

Exclusion Criteria:

• Need for open carpal tunnel surgery.
• Pregnant women
• Adults under guardianship