Brainstem lesions decrease heart rate variability

Brainstem is an essential region in the regulation of the autonomic cardiovascular functions. Some authors have reported that medulla oblongata is very important in this regulation, but probably is not the unique because the sympathetic cardiovascular centers are spread in the brainstem. Since some years ago, we are able to measure heart rate variability which is a useful tool for assessing quantitatively both sympathetic and parasympathetic autonomic effects on the heart. The objective is to evaluate the effects of isolated brainstem lesion (IBL) on sympathetic and parasympathetic cardiovascular regulatory functions.

We analyzed the heart rate variability in time and frequency domains in 14 IBL patients and 25 age and sex matched healthy control subjects, measured from 24-h electrocardiogram.

Low frequency power (0.001) and low frequency/high frequency power (0.05) were significantly higher in control subjects independently, all together or in subgroups (medulla oblongata affected or not). High frequency power (0.05) were higher too in control subjects. Variability in time domain (0.001 and 0.01) was lower when the medulla oblongata was affected.

These results confirm that brainstem lesions cause cardiovascular autonomic dysregulation overall when the medulla oblongata is affected. The importance of this region in parasympathetic and sympathetic cardiovascular functions is showed. However, pontine and mesencephalic lesions seem to provoke a decrease only in sympathetic regulation.