Occlusion of the sagittal sinus in craniectomized rabbits

Most attempts at production of hydrocephalus in experimental animals by obstructing the venous sinuses have failed. In adult humans, venous sinus occlusion usually results in the clinical syndrome of pseudotumor cerebri with small or normal sized ventricles. However, in children less than 18 month old with venous sinus hypertension, ventriculomegaly has been reported. We examined the change in ventricular size in craniectomized animals (simulating children with open sutures) with occlusion of the superior sagittal sinus. New Zealand rabbits weighing 1500-1800 g were anesthetized with an intramuscular injection of 2 ml 7:3 ketamine (100 mg/ml): Rompun (xylazine) (20 mg/ml) solution. The scalp was shaved, prepped with Betadine, and infiltrated with 1% lidocaine, and a midline scalp incision made. The periosteum was reflected laterally and a craniectomy performed with microscopic magnification. The dura was exposed overlying both cerebral hemispheres and the superior sagittal sinus from its origin to the torcular. In five control animals, the scalp was then closed. In ten experimental animals, small incisions were made in the dura just lateral to the superior sagittal sinus with a no. 11 scalpel and then with microscopic magnification the sinus was coagulated with bipolar cautery and transected; the scalp was then closed. All animals were allowed 5-7 days to recover, then ultrasound was used to assess ventricular size. We observed a small but statistically significant increase in ventricular size in the experimental group compared to the control group. This model provides evidence that venous sinus occlusion in animals with expandable crania can produce ventriculomegaly.