engleski

Dynamics of transmantle pressure gradient in cats with acute aqueductal blockage

It is not quite clear whether pressure gradient of cerebrospinal fluid (CSF) between brain ventricles and cortical subarachnoid space is necessery for development of hydrocephalus. Some recent results in patients with noncommunicating hydrocephalus show that such a transmantle pressure gradient is not present (1). We have investigated in cats with acute occlusion of aqueduct whether transmantle pressure can be developed. In chloralose anaesthetized cats the aqueduct was totally occluded by implantation of plastic cannula with tip covered by cyanoacrylate glue through a small tunnel in vermis of cerebellum and the CSF pressure recorded in both isolated ventricles and cisterna magna after hermetic reconstruction of skull. The head of cat was fixed in stereotaxic holder and CSF pressures were recorded under control conditions and during infusion of arteficial CSF (aCSF) either in isolated ventricles or in cisterna magna. The CSF pressure in isolated ventricles and cisterna magna were not different from control value and cerebral transmantle pressure gradient did not develop over 120 min. Infusion of aCSF in cisterna magna at rates of 13 and 52 µ l/min (n=4) during 5 min increased proportionally the CSF pressures in both cisterna magna and isolated ventricles without development of transmantle gradient. However, when aCSF was infused in isolated ventricles for 5 min at rate of 13 and 52 µ l/min (n=4), the transmantle gradients of 2 and 15 cm H2O were developed, respectively. Acute occlusion of aqueduct does not cause transmantle pressure gradient during 2 hours, while a such gradient develops very soon during infusion of aCSF in isolated ventricles. However, during infusion of aCSF in cisterna magna the CSF pressure increase in cranial subarachnoid space is immediately transmitted across brain parenchyma to isolated ventricles preventing development of any pressure gradient. Thus, it would appear that transmantle pressure gradient in noncommunicating hydrocephalus can develop only in pathological conditions which cause an acute increase of intraventricular pressure but not by aqueductal occlusion itself.

dynamics ; transmantle pressure ; gradient ; cats ; acute aqueductal blockage

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