Aim: 

AMR and VMR have been recently characterized in man but possible uses in assessment of BS circuits in physiologic and pathologic conditions have not been considered yet.

Methods: 

We compared AMR and VMR to the acoustic brainstem responses (ABR) and to the vestibulocollic reflex (VC) which depend on the same receptors as the AMR (choclea) and VMR (otoliths). Reflex investigation was made in controls and in multiple sclerosis patients (MS). In MS neurophysiologic and MRI findings were compared. AMR, VMR, VC and ABR were assessed in 15 controls and MS (EDSS<5). MRI was done in MS within 2 weeks from clinical and reflex examination. Mann-Whitney U test and Spearman correlation (p<0.05) analysis were performed.

Results: 

Reflex distribution was significantly different in controls and MS. In MS reflex latency and/or amplitude abnormalities were found as follow: AMR 80%; VMR 60%; VC 13% and ABR 55% of patients. MRI showed that BS lesion side was consistent with the side of reflex alterations (p<0.03). VMR and VC data in MS suggest that in our sample BS structures mediating the VMR were more affected than vestibulospinal pathways, in agreement with MRI data reporting that lesion load mostly involved rostral medulla. AMR abnormalities correlated with ABR alterations (p<0.03) and showed higher sensitivity in detecting lower pons lesions.

Conclusion: 

These preliminary data suggest that VMR and AMR additional assessment may assist BS circuit testing. To draw anatomic-neurophysiologic conclusions a larger sample is needed.