[Slow pressure waves during intracranial hypertension].

Intracranial pressure waves include fast waves (pulse and respiration) and slow waves. Only the latter are considered here. Since the definition of three wave types in the pioneering works of Janny (1950) and Lundberg (1960), their study of frequential characteristics shows they are included in a spectrum where three contiguous frequency bands are individualised: the B wave band (BW) between 8 x 10(-3) Hz and 50 x 10(-3) Hz; the Infra B band (IB) below 8 x 10(-3) Hz; and the Ultra B band (UB) beyond 50 x 10(-3) Hz to 200 x 10(-3) Hz. The origin of these waves is vascular and some may be physiological. They are probably generated by central neuro-pacemakers and/or cyclic phenomena of cerebral autoregulation. They are linked with slow peripheral arterial pressure waves, with biological rhythms and with biomechanics and vasomotricity in the craniospinal enclosure. They are pathological for the slowest (IB), particularly if they are plateau waves, but the physiologic-pathologic boundary is not yet established for each type of slow waves. They can cause severe consequences if they result in major cerebral perfusion pressure changes, and if they induce or worsen herniations.