Ultrasound evaluation of carpal tunnel syndrome in patients with bifid median nerve

2016-11-22T23-05-36Z
Source: International Journal of Research in Medical Sciences
Smiti Sripathi, Anurag Ayachit, Rebin Bos.
Background: Patients with high division of the median nerve proximal to carpal tunnel, or bifid median nerve, may present with carpal tunnel syndrome (CTS). Ultrasound (US) measurements indicative of CTS in this subset of patients differ from those in patients with non-bifid median nerve. The objectives were to evaluate the parameter ∆CSA [difference between the maximum cross-sectional area of bifid median nerve within carpal tunnel (CSAc) and outside tunnel (CSAp)] in the diagnosis of CTS, to compare sensitivity and specificity of ∆CSA with nerve conduction velocity studies (NCS), and to compare the cross-sectional area (CSAc, CSAp & ∆CSA) of bifid median nerve in CTS patients with that in asymptomatic controls. Methods: 20 wrists with bifid median nerves and symptoms suggestive of CTS were included in the study group. Nerve conduction velocity studies (NCS) were performed in all cases. 4 wrists of asymptomatic age-matched subjects had bifid median nerves and normal NCS and were included in the control group. High resolution ultrasonography was performed for all wrists and findings documented. Statistical Analysis: Receiver Operating Characteristics curves were used to obtain the level of significance (p-value) and assessment of correlation between ∆CSA and NCS findings. Results: There was significant correlation between ∆CSA and NCS. A cut-off value of 2.3mm2 gave the best calculated sensitivity (76.9 %) and specificity (100%). Conclusions: CSA criteria for diagnosing CTS in patients with bifid median nerves are different from those in patients with non-bifid median nerve. ∆CSA is a sensitive and specific parameter for confirming the diagnosis of CTS in patients with bifid median nerve with sensitivity approaching that of NCS.


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