The object of this report is to present with all possible accuracy the results of the clinical, postmortem and histologic investigations in eight cases of internal hydrocephalus of the obstructive type, bringing special emphasis to bear on the obliterating lesion of the aqueduct of Sylvius as a cause of ventricular distention.
Of this group, examined without selection, all show either complete occlusion of the aqueductus cerebri or obliteration of the fourth ventricle through severe pathologic changes occurring in the ependymal or subependymal tissues of these regions.
The first four cases have already been shown before the New York Pathological Society1 and the records reappear at this time in greater detail, together with the findings in four other cases not reported heretofore.
Beside the congenital, obstructive form of the disease as it appears in this review, a subdivision of this type of hydrocephalus occurs apparently idiopathically, in previously healthy young