The general aim of this research is to gain insight in the role of SSCT in the etiology and progression of CTS. We hypothesize that (degenerative) damage of the SSCT occurs early on in the pathogenesis of CTS. Fibrotic damage to the SSCT will lead to altered morphology and biomechanical characteristics. This eventually may lead to damage of the median nerve. To examine the SSCT an ultrasound technique described by Van Doesburg et al. 2012 will be used First, the reliability of the US technique to characterize morphology of the SSCT will be investigated. Secondly, cross-sectional data will be collected in healthy subjects and CTS patients to provide descriptive parameters and to describe differences between patients and controls. In the final part a prospective study will be conducted to look at changes of SSCT thickness over time and after treatment.

Inclusion Criteria:

• For CTS patients
• Human adults, 18 years and older
• Complaints compatible with CTS (Katz Hand Diagram[31] rating of 'classic', 'probable' or 'possible' or typical clinical signs)
• Indication for electrodiagnostic testing
• Informed consent to participate
• For Healthy subjects
• Human adults, 18 years and older
• Negative electrodiagnostic testing and scoring 'unlikely' at Katz Hand diagram
• Informed consent to participate

Exclusion Criteria:

• Pregnancy
• History of renal disease, diabetes, chemotherapy, tumors, other neurological diseases (e.g., polyneuropathy), thyroid disease
• Problems of the upper limb, e.g., degenerative and inflammatory joint disease, gout, tendinopathy at the wrist, acute trauma of the upper limb

Subjects with and without carpal tunnel syndrome