[The mechanism of the development of spontaneous fluctuations in the cerebrospinal fluid pressure ("plateau" and B waves)].

The peculiarities of the development of spontaneous fluctuations of the c.s.f. pressure (CSFP) (B- and plato-waves) in the early postoperative period in 169 neurosurgical patients were studied according to the location of the pathological process and the severity of the clinical condition. The dependence between the CSPF spontaneous fluctuations, the changes of intracerebral pressure, and the dynamics of bioelectrical activity of the brain was studied. The development of spontaneous wave CSFP fluctuations was found to be dependent on the location of the tumor and the severity of the clinical condition. These fluctuations occurred most frequently in patients who were in a critical state (12-8 marks on Glasgow's scale) with the process located in the diencephalo-stem brain areas. A hypothesis is suggested, according to which the cause of the wave CSFP fluctuations of the B-wave type is connected with the change of the vasomotor center to the cyclic regimen of work: the neurogenic change of the vascular tonus, causing in succession constriction and dilatation of the vessels, leads to rhythmic CSFP oscillations. CSFP plato-waves occur in cases in which the constriction phase fails to appear after the dilatation phase, i.e., the tonic pressor effect of the vasomotor center does not occur, which may be due to its exhaustion. In death of the brain and in terminal states the vasomotor center loses the ability to cause neurogenic regulation of the vascular tonus, to provide the pressor effect in particular, which leads to the disappearance of spontaneous CSFP fluctuations.