Tongue somatosensory-evoked potentials: evaluation of the afferent trigeminal pathway in patients with early multiple sclerosis.

The aim of this study was to determine the efficacy of tongue somatosensory-evoked potentials (tSSEPs) in evaluation of afferent trigeminal pathway in patients with early multiple sclerosis (MS). The tSSEP was performed on 10 healthy volunteers and 10 patients with the first symptom of MS. Data were compared between the groups, and tSSEP findings of patients with MS were correlated with clinical and magnetic resonance imaging (MRI) data. Among 10 patients, 2 (20%) had clinically evident involvement of the brainstem, 5 (50%) had brainstem lesions on brain MRI, while 9 (90%) had prolonged latencies on tSSEP. Of the 8 patients with no clinical evidence of brainstem pathology, 7 (88%) had prolonged latencies/conduction block on tSSEP. Patients had statistically significant prolongation of N1, P1, and N2 latencies for stimulation of the right side and N2 latency for stimulation of the left side compared to healthy controls. The tSSEP is an efficient method for evaluating the afferent trigeminal pathway in patients with early MS. This study provides evidence that lesions of the afferent trigeminal pathway are more frequently found by tSSEP than by clinical examination or MRI.