Kaolin-induced hydrocephalus in the hamster: temporal sequence of changes in intracranial pressure, ventriculomegaly and whole-brain specific gravity

The development of kaolin-induced hydrocephalus in adult hamsters was monit ored by measuring changes in intracranial pressure (ICP), ventriculomegaly (VG) and whole-brain specific gravity (SG). Controls were intact or sham op erated animals. Relative to controls, ICP of experimental animals increased at 24 h post intracisternal kaolin injection (by approximately 7-fold), re ached a maximum on day 6 (by approximately 12-fold) and remained markedly e levated through day 15 (by approximately 5-fold). Ventricles differed in ti me of onset of; distension (third: day 1, lateral: day 2, fourth: day 4) an d in time of maximum ventriculomegaly (fourth: day 6; third: day 7; and lat eral: day 9). Ventricular distension resulted in alterations in the ependym a; cilia were lost and apical cell surfaces were distorted. The ependyma wa s ruptured and the subjacent neuropil was exposed to the cerebrospinal flui d in some regions. Whole-brain SG remained constant in controls but decline d in hydrocephalic hamsters after day 3 post-kaolin injection and reached i ts nadir on day 9 when whole-brain water content was 18% greater than in co ntrols. Consistent with the fact that causal relationships exist between in creased ICP, ventricular distension and brain edema, the alterations in eac h parameter occurred sequentially rather than simultaneously, and the time- course of each manifestation of hydrocephalus differed. The data suggest th at the pathophysiology of kaolin-induced hydrocephalus in the hamster is tr i-phasic: an initial period of rapid change, a brief interval of maximum al teration, and a subsequent period of compensation.