Background: Nerve conduction studies (NCS) remain gold standard for carpal tunnel syndrome (CTS) diagnostication. Unfortunately the waiting time for NCS in New Zealand can exceed 6-12 months resulting in delayed diagnosis, treatment and relief of symptoms. Ultrasound (US) assessment of the carpal tunnel has been described as a valid alternative tool internationally. We aimed to investigate if US is a viable investigation tool for CTS locally.
Methods: All patients awaiting carpal tunnel decompression (CTD) under Plastic Surgery at Waikato Hospital were identified and a list of patients who had NCS-confirmed CTS in this cohort was generated. These patients were invited to complete a Boston Carpal Tunnel questionnaire (BCTQ) and US preoperative assessment before surgery. Cross sectional area (CSA) of the median nerve was measured 8cm proximal to the wrist crease (forearm), and at the proximal extent of the carpal tunnel at the area of greatest swelling (wrist). A standardised criteria for US diagnosis of CTS was used(1). A standardised proforma was used for data collection and subsequent analysis.
Results: 20 patients were included in the study (13 female, 7 male) with a median age of 58 +/- 25 years. 19 were right handed, 2 current smokers and 2 ex-smokers. Sensitivity of US was calculated at 90% when CSA of 9 mm2 and above at wrist was used as diagnostic criteria for CTS. This was not improved further when combined with wrist:forearm CSA ratio. BCTQ identified 17 patients as having CTS with a calculated sensitivity of 75% regardless of whether symptom or functional severity score was used. All patients with positive NCS had at least a positive BCTQ or US finding for CTS.
Conclusion: Combined US/BCTQ assessment offers promising potential for US diagnosis of CTS.
(Our ongoing study aims to provide data for specificity of US+ BCTQ by December 2022)