Magnetic Resonance Imaging (MRI) can be used to visualize abnormalities in the shape and dimensions of the median nerve. This accounts for its high sensitivity (96%)1 for detecting mild median nerve compression, but these abnormalities have also been described in people without CTS, which explains the low specificity (33-38%).1 This limits its diagnostic usefulness. Essentially, MRI of the wrist is most useful if a space-occupying lesion is suspected from the history or physical examination.
Ultrasound may be used to quantitatively measure the cross-sectional area of the median nerve. Certainly, the lower cost and time requirement favor ultrasound over MRI, but variable sensitivity and specificity1 limit its use in practice.
Ultrasound may be used to quantitatively measure the cross-sectional area of the median nerve. Certainly, the lower cost and time requirement favor ultrasound over MRI, but variable sensitivity and specificity1 limit its use in practice.
Currently, neither MRI or ultrasound is superior to EMG in terms of diagnosis. However, in the future these investigations may become more clinically useful in the diagnosis of CTS.
1Kleopa KA, Bird SJ. Carpal Tunnel Syndrome. STAT!Ref Online Electronic Medical Library: ACP PIER & AHFS DI Essentials 2009.
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