The spontaneous development of an opening between the third ventricle or the lateral ventricles and the external surface of the brain is so unusual that the following 2 cases are reported. Such openings develop as a consequence of expansion of the cerebral ventricles when there is obstruction to the flow of cerebrospinal fluid. In the only such case with a pathologic study of the brain previously reported in the literature, the obstruction took place at the aqueduct of Sylvius. In the second case reported here the block was at the same site, and in the first case an enormous teratoid tumor in the posterior cranial fossa was responsible for the stoppage.
REPORT OF CASES
Case 1.
—Mrs. M. B., aged 54, who had been referred by Dr. H. T. Haver of Chicago, entered the Billings Hospital in the service of Dr. Percival Bailey on Aug. 12, 1937, in an extremely