The role of evoked potential and MR imaging in assessing multiple sclerosis: a comparative study

The role of evoked potential (EP) in evaluating multiple sclerosis (MS) has changed with the advent of magnetic resonance (MR) imaging. Given the possibly varied nature and distribution of pathologic lesions in Asian MS, this study compared the diagnostic usefulness of EPs to that of MR imaging among Chinese subjects.

This was a retrospective study of MS patients treated at the Kwong Wah Hospital, Hong Kong, between June 2004 and June 2009. The visual (VEPs), brainstem auditory (BAEPs), somatosensory (SEPs) and trigeminal (TSEPs) EPs were compared with MR imaging for correlation and usefulness using the chi-square test. Sensitivities and specificities were calculated.

The results showed that abnormalities were detected in the three modalities of EP among the 17 patients studied (VEP 82 percent, median and tibial SEP 65 percent, BAEP 47 percent). Compared with MR imaging, VEP was far more useful at detecting optic nerve lesions, while SEP was less sensitive at detecting cord lesions. BAEP was able to localise lesions along the auditory pathways at a rate that was almost similar to that of MR imaging (non-inferiority). Both TSEP and MR imaging for trigeminal nerves were negative in the two patients with trigeminal neuralgia. In some instances, EPs yielded abnormalities that were undetected by conventional MR imaging, and the sensitivity increased with the number of EP modalities.

EP may be considered in clinical situations in which MR imaging is negative or cannot be performed. They may also be performed when evaluating treatment response, long-term prognosis and nonspecific changes on MR imaging.