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Somatosensory evoked potentials elicited by trigeminal nerve stimulation (TSEPs) allow the study of the trigeminal system, its peripheral to its central portion. As a routine clinical testing procedure, however, this method has not yet received greater attention and still has to wait to become a part of the diagnostic workup in multiple sclerosis (MS).A patient diagnosed as MS was presented with selective involvement of the left trigeminal nerve. Neurophysiologically, the most prominent and persistent abnormalities were found in the TSEPs. The presumed diagnosis of MS was subsequently confirmed by MRI showing evidence of demyelinating disease.There has been a scarcity of references on TSEP. Our study emphasizes its usefulness and a plea is being made for the inclusion of TSEP in protocols for the diagnostic workup in patients with MS.

The brain-stem involvement in Friedreich's ataxia (FA) was studied by using brain-stem auditory evoked potentials (BAEPs) and the blink reflex. Ten out of 18 patients had abnormal BAEPs, the main abnormality being complete absence of responses and disappearance of wave V. Combined degeneration of the peripheral and central acoustic pathways probably accounts for these findings. The blink reflex was abnormal in 50% of the cases. The outstanding abnormality was bilateral delay of late responses with normal early response, which could be correlated with the known pallor of the descending trigeminal tracts. In contrast with BAEP findings, blink reflex abnormalities did not correlate with either the age of patients or the severity and duration of the disease. These data suggest a difference in susceptibility to degeneration between the auditory system and neuronal system subserving the blink reflex. We conclude that systematic BAEP and blink reflex recording is useful in the electrophysiological evaluation of FA patients.