Abstract
BackgroundIn addition to nerve conduction studies (NCSs), ultrasonography has been widely used as an alternative tool for diagnosing carpal tunnel syndrome (CTS). Although the results of NCSs are influenced by local skin temperature, few studies have explored the effects of skin temperature on ultrasonography of the median nerve. Since swelling and intraneural blood flow of the median nerve might be influenced by local temperature changes, the aim of this study was to evaluate the cross-sectional area (CSA) and intraneural blood flow of the median nerve under three skin temperatures (30 °C, 32 °C, 34 °C).MethodsFifty patients with CTS and 50 healthy volunteers were consecutively recruited from a community hospital. Each participant received physical examinations and NCSs and underwent ultrasonography, including power Doppler, to evaluate intraneural vascularity.ResultsThe CSA of the median nerve in the CTS patients was significantly larger than that in the healthy controls at all three temperatures. However, significant differences in the power Doppler signals of the median nerve between the two studied groups were observed only at 30 and 32 °C, not at 34 °C.ConclusionThe significant difference in the intraneural vascularity of the median nerve between the patients with CTS and the healthy subjects was lost at higher temperatures (34 °C). Therefore, the results of power Doppler ultrasonography in diagnosing CTS should be cautiously interpreted in patients with a high skin temperature or those who reside in warm environments.
Highlights
Ultrasound examination has gained increasing popularity as a useful tool to evaluate patients with carpal tunnel syndrome (CTS)
Among the within-group results measured at 30, 32 and 34 °C in both studied groups, no significant differences were found in the sonographic findings of the median nerve, including the cross-sectional area (CSA) and the power Doppler signal (Table 3)
We demonstrated that there was no significant difference in the resistive index (RI) or time-averaged mean velocity (TAMEAN) of the ulnar artery measured by spectral Doppler ultrasound between patients with CTS and control participants, which was consistent with previous findings in CTS patients with diabetes [33]
Summary
Ultrasound examination has gained increasing popularity as a useful tool to evaluate patients with carpal tunnel syndrome (CTS). Using power Doppler ultrasonography to evaluate the intraneural vascularity of the median nerve, on the other hand, has emerged in recent years as another method to assist in diagnosing CTS [10, 11]. Dejaco, et al semiquantitatively graded intraneural power Doppler signals as a score of 0 to 3, and the results showed that a score of 2 (two or three single vessels or two confluent vessels within the median nerve) or above had a specificity of 90% for the diagnosis of CTS [10]. One recent study calculated the total area of the vascularity on power Doppler images of each median nerve, and the results showed that the sensitivity and specificity of CSA and hypervascularization in detecting CTS were 90.9, 94.0, 93.4, and 90.0%, respectively [11]. Since swelling and intraneural blood flow of the median nerve might be influenced by local temperature changes, the aim of this study was to evaluate the cross-sectional area (CSA) and intraneural blood flow of the median nerve under three skin temperatures (30 °C, 32 °C, 34 °C)
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