Cerebral blood flow and metabolism in experimental hydrocephalus

Cerebral blood flow and metabolism were studied in experimental hydrocephalus which was produced by intracisternal injection of kaolin in cats, rabbits and rats. Measurements were carried out in varied stages of hydrocephalus. Local cerebral blood flow (l-CBF) was measured by the hydrogen clearance method. Assessment of cerebral metabolism was made biochemically in the brain tissues of various regions, including water content, Na, K, lactate, pyruvate, lipids, ATP, cyclic AMP, catecholamines and monoamine metabolites. Blood flow studies were performed in the cerebral cortex, periventricular white matter, thalamus and midbrain reticular formation in hydrocephalic cats. In all of these regions, l-CBF decreased to about half of the control in both acute and chronic stages of hydrocephalus. CO2 reactivity to CBF was impaired only in the acute stage, while autoregulation of CBF was preserved in the hydrocephalic brain. Water content of the brain tissue increased temporarily only within the periventricular white matter of hydrocephalic rabbits concomitant with increase in Na and decrease in K. Transient increase in the lactate and lactate/pyruvate ratios was also observed in the frontal lobe tissue. In hydrocephalic rats, decrease in phospholipids and cholesterol was observed parallel with the degree of ventricular dilatation. ATP and cyclic AMP decreased biphasically in both acute and chronic stages. On the other hand, increase in concentrations of norepinephrine, dopamine, homovanillic acid, and 5-hydroxyindoleacetic acid became evident in the chronic stage of hydrocephalus. From the above results, it is concluded that the hydrocephalic brain sustained considerable disturbance of metabolism in all modalities in association with decreased blood flow, which is sufficient to explain the clinical symptoms of hydrocephalus.