Study of brain tissue impedance in the hydrocephalic cat.

Impedographic studies were made in cats made hydrocephalic by intracisternal kaolin. Enlargement of the anterior horns preceded that of the body of the lateral ventricles, and there was a selectivity to pressure atrophy among different tissues within the brain. Furthermore, sequential measurement of impedance using chronically implanted electrodes demonstrated a gradual decrease of impedance in the periventricular white matter during the development of hydrocephalus, suggesting an expansion of the extracellular space in the tissue around the ventricular wall.