Clinical correlations of motor and somatosensory evoked potentials in neuromyelitis optica

Background: Motor and somatosensory evoked potentials (MEPs and SSEPs) are sensitive tools for detecting subclinical lesions, assessing disease severity, and determining the prognosis for outcomes of patients with inflammatory neurological diseases such as multiple sclerosis. However, their roles in neuromyelitis optica (NMO), a severe inflammatory neurological disease that predominantly involves optic nerves and spinal cord, have not yet been clarified. Methods and Findings: Clinical symptoms and examination findings at relapses of 30 NMO patients were retrospectively reviewed. Abnormal MEPs were observed in 69.2% of patients. Patients with abnormal motor central conduction time (CCT) of the lower limbs had higher Kurtzke Expanded Disability Status Scale (EDSS) scores than those with normal responses (P=0.027). Abnormal SSEPs were found in 69.0% of patients. Patients with abnormal lower limb sensory CCT had higher EDSS scores than those with normal responses (P=0.019). In 28 patients followed up more than 6 months, only one of 11 patients (9.1%) with normal SSEPs of the lower limbs had new relapses within 6 months, whereas 8 of 17 patients (47.1%, P=0.049) with abnormal SSEPs of the lower limbs had new relapses. Conclusions: These results indicate MEPs and SSEPs of the lower limbs are good indicators for the disability status at relapses of NMO. Lower limb SSEPs may be a good tool for reflecting the frequency of relapses of NMO.