THE EFFECT OF INTRACRANIAL HYPOTENSION ON CEREBRAL BLOOD-FLOW IN A FELINE MODEL

Intracranial hypotension is a known clinical entity but its pathophysi ology has been meagerly studied. Any setting with cerebrospinal fluid leakage or drainage can cause intracranial hypotension. A feline model of kaolin induced chronic hydrocephalus with controlled cerebrospinal fluid drainage from a lateral ventricle yields reproducible intracran ial hypotension of up to -15 torr for several hours to -80 torr of abo ut 10 minutes. The magnitude of this hypotension is significantly grea ter than can be attained by cisterna magna drainage. This new model al lows multiple cerebral parameters to be studied during intracranial hy potension. In 11 cats with stable blood pressure and intracranial hypo tension of at least -15 torr, regional blood flow utilizing the hydrog en clearance method in the cerebral cortex and subcortical nuclei was unchanged relative to the baseline. These results imply that: 1) cereb ral vascular autoregulation is maintained during significantly increas ed perfusion pressure due to negative intracranial pressure, 2) the sy mptomatology of clinical intracranial hypotension is not due to decrea sed cerebral perfusion.