Radiology: Ultrasound bests EDT for carpal tunnel syndrome diagnosis

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Color Doppler ultrasonography (US) can be used as a noninvasive alternative to electrodiagnostic testing (EDT) to accurately diagnose carpal tunnel syndrome (CTS), according to a study published online in Radiology Sept. 7.

The study used the presence of intraneural vascularity, evaluated with color Doppler US, to diagnose CTS with comparable or higher sensitivity and specificity than EDT.

According to Ahmad Reza Ghasemi-Esfe, MD, of the Tehran University of Medical Sciences in Tehran, Iran, and colleagues, the conventional approach to treating a patient exhibiting characteristics of CTS is to confirm the diagnosis with EDT, but the accuracy of EDT has been called into question since reported sensitivity and specificity of EDT in the diagnosis of CTS are 70 percent and 82 percent, respectively.

“Therefore, [EDT] cannot help diagnose approximately 20 percent to 30 percent of CTS cases,” wrote Ghasemi-Esfe and colleagues. “US is the technique that has been most commonly discussed in CTS diagnosis owing to its lower cost and greater comfort.”

The study demonstrated that US can be more accurate than EDT, in addition to providing cost and comfort advantages. The sensitivity and specificity of intraneural vascularity measured by US was 83 percent and 89 percent, respectively.

Intraneural vascularity was seen in 91.4 percent of patients with mild CTS and 100 percent of patients with moderate or severe CTS, according to Ghasemi-Esfe et al. By processing the Doppler images and counting the number of pixels in the intraneural vascular area, the severity of CTS also can be determined.

One hundred and one patients with evidence of CTS and 55 control subjects were enrolled in the study.

Prior to the current study, most research was focused on gray-scale US and resulted in inconsistent findings regarding the accuracy of US in diagnosing CTS, according to Ghasemi-Esfe et al. The authors chalked up these discrepancies to varying criteria used to select patients and healthy control subjects.

Ghasemi-Esfe and colleagues also noted that results could vary for a number of other reasons. Changes in the color Doppler gain or depth of the image can affect the number of pixels shown in the intraneural vascular area. Different US units may vary in sensitivity, which could also affect the sum of pixels detected. The procedure is also dependent on operator experience and technique, and for this reason, the authors suggested continued assessment of the variability of their findings.

The authors said that with a well-designed, standard protocol, US is a reliable tool for measuring median nerve characteristics.