EXPLORATION OF BRAINSTEM FUNCTION THROUGH VESTIBULAR AND TRIGEMINAL REFLEXES IN HEALTHY PEOPLE AND IN PATIENTS WITH MULTIPLE SCLEROSIS

The acoustic-masseteric reflex (AMR) and the vestibulo-masseteric reflex (VMR) were recently characterized, but their normal values have not been standardized yet. In addition, their use to test brainstem (BS) function in neurological diseases has never been considered before. This study purposed a) to standardize normal values of VMR and AMR in healthy subjects, in whom vestibulo-collic (VCR) and trigemino-collic (TCR) reflexes were also recorded; b) to evaluate such brainstem reflexes (BSR) in multiple sclerosis (MS) patients comparing their data with controls; c) to correlate BSR data to those obtained from clinical, evoked potential (EP) and neuroimaging (MRI) assessment. AMR, VMR, VCR and TCR were investigated in 43 controls and in 39 patients with relapsing-remitting MS, who underwent additional neurological, EP and MRI assessment. The frequency of altered BSR was significantly different (p=0.00001) in controls and in MS, who showed BSR abnormalities in 92.3% of cases. The True Positive Fraction of having at least 1, 2, 3 or 4 altered reflexes was 92.3%,74.4%,43.6% and 17.9% respectively. By comparison, clinical, EP and MRI procedures detected BS involvement in 46.4%, 76.9% and 74.4% of MS, respectively. BSR under study test different pathways from the pons to the most caudal part of the medulla. Data suggest that their combined assessment may provide additional functional evaluation of BS integrity that may well assist conventional testing.