Progressive ventricular enlargement in cats in the absence of transmantle pressure gradients.

Intracranial pressure (ICP) was measured simultaneously at multiple sites in cats to determine if transmantle pressure gradients were present in progressive hydrocephalus. The cats underwent craniectomy and intracisternal injection of kaolin; 4 to 9 weeks later ICP was measured at the ventricle, cisterna magna, and convexity subarachnoid space, and in the brain tissue and the sagittal sinus. In 13 cats in which ventricular size conformed to previously established norms for duration of hydrocephalus, there were no demonstrable gradients of pressure at any of the sites of measurement according to one-way analysis of variance (p greater than 0.05). The mean (+/- standard error of the mean) peak and trough pressures (in mm Hg) at each site were: ventricle, 12.7 +/- 0.7 and 12.0 +/- 0.6; cisterna magna, 12.9 +/- 0.8 and 12.3 +/- 0.7; subarachnoid space, 12.7 +/- 0.8 and 12.1 +/- 0.7; brain tissue, 12.9 +/- 0.9 and 12.4 +/- 0.9; and sagittal sinus, 13.1 +/- 0.8 and 11.9 +/- 0.8. These results indicate that ventricular expansion can progress without measurable transmantle pressure gradients.