Intracranial pressure B-waves precede corresponding arterial blood pressure oscillations in patients with suspected normal pressure hydrocephalus

B-waves are rhythmic oscillations of intracranial pressure (ICP) with a wav elength of 0.5-2 min. These oscillations are accompanied by corresponding f luctuations of arterial blood pressure (BP). There is controversy in the li terature whether the ICP oscillations precede or follow the BP oscillations . This relationship, however, is important for the understanding of the ori gin and the interactions of ICP B-waves with other parameters. ICP and BP w ere monitored continuously for one night in nine patients with suspected sy mptomatic normal pressure hydrocephalus (NPH). forty-five B-waves were iden tified and the time delays between the peaks and the onsets of B-waves and their BP-equivalents were measured. The mean (+/- standard deviation) of th e time delays between the peaks of ICP B-waves and corresponding BP-oscilla tions was 4.2 +/- 2.4 sec and between the onsets of the oscillations 10.3 /- 6.6 sec. In all but two B-waves, the ICP peak preceded the BP peak in al l the 45 B-waves the onset of the ICP increase preceded the BP increase (p < 0.004). Our study demonstrates that ICP B-waves precede concomitant chang es in BP by several seconds.