Alterations in brain-stem auditory responses induced by head down tilting in hypertensives with supine brain-stem disorders.

The influence of head down (HD) tilting on brain-stem auditory evoked responses (BAER) was studied in hypertensives with supine brain-stem disorders (occipital headache, vertigo, nausea, diplopia, blurred vision occurring after night recumbency), in hypertensives without such phenomena and in normotensives. In the latter two categories of subjects HD tilting had no effect on BAER. On the contrary, in hypertensives with supine brain-stem disorders the manoeuvre induced a constant prolongation of I-V and III-V intervals and a depression in the amplitude of wave V; the alterations of BAER produced by HD tilting reveal probably a dysfunction of the superior brain-stem area and might be due to the impaired cerebral venous draining subsequent to the manoeuvre. The study of BAER after HD tilting seems to be a proper means to attest the supine brain-stem disorders displayed by some hypertensives.