B-waves in healthy persons.

The objective of this study was to determine, whether 0.5-2/min oscillations in intracranial pressure ('B-waves') are a physiological phenomenon. In a group of 5 patients 0.5-2/min oscillations of ventricular pressure simultaneous with oscillations in the middle cerebral artery (MCA) flow velocity, as assessed by transcranial Doppler sonography, were observed. Similar oscillations in MCA blood flow velocity were demonstrated in 8 out of 10 healthy subjects with an amplitude of about 10% of the mean flow velocity. We speculate that oscillations both in ventricular pressure and middle cerebral artery blood flow velocity are caused by rhythmic diameter changes of cerebral vessels with concomitant cerebral blood volume oscillations. Our data support the suggestion that B-waves may be physiological.