Obstructive lesions within the ventricular system characteristically result in dilatation of the ventricles proximal to the obstruction. This ventricular enlargement occurs at the expense of the surrounding cerebral tissue, most notably the cerebral mantle, which may be markedly thinned.1-3 After removal of the obstruction or mechanically bypassing it with a shunt, the ventricular dilatation and concomitant cerebral thinning may be reversed.4 The "mobile" components of the cerebrum which permit this fluctuation in size have not been defined. In an effort to better understand this tissue change, chemical and morphological studies have been performed upon the cerebrum of dogs in whom obstructive hydrocephalus has been created.
Methods
Because of the marked variation in water and lipid content of the maturing brain only adult mongrel dogs were used.5 Cisternal punctures were performed using sodium pentobarbital anesthesia (30 mg. per kilogram). Intracisternal pressures were recorded, and a volume of cerebrospinal