The effect of severe brainstem injury on heart rate and blood pressure oscillations.

To determine whether an intact brainstem is essential for the generation of neurogenically mediated fluctuations of R-R intervals and blood pressure, three patients with cerebellar lesions causing severe brainstem compression or death, one patient with a large pontine infarct and one patient with a pontine haemorrhage, were studied. Time-frequency maps (based on a modified Wigner distribution) were constructed from blood pressure and R-R interval signals in these patients with brainstem injury and were compared with maps of normal control subjects. Low frequency sympathetically mediated rhythms (0.01-0.12 Hz) in systolic and diastolic pressure remained detectable but attenuated in patients with brainstem injury whereas there was an almost complete loss of normal R-R intervals rhythmicity over 0.01 to 0.5 Hz range. These data suggest that fluctuations in R-R intervals require an intact brainstem, whereas low frequency approximately 0.06 +/- 0.02 Hz blood pressure rhythms may be preserved by spinal sympathetic circuitry.