The physiology and pathology of herniation of the cerebrum through the incisura tentorii.

This study was originally planned in an attempt to explain the mechanism involved in fixed dilatation of the pupil resulting from ipsilateral cerebral compression. It soon became evident, however, that the pupillary changes constituted but one element of complete oculomotor nerve palsy. An investigation has been made of eleven clinical cases, seven of whom failed to recover and were examined at necropsy, and of fifteen experimental procedures carried out on Macacus Rhesus monkeys. Each clinical case examined at necropsy and each successful experimental animal showed signs of ipsilateral third nerve palsy, and in each there was found a herniation of the ipsilateral hippocampal gyrus over the free edge of the tentorium cerebelli pressing on the third nerve. As the work progressed it became evident that there were two other features sometimes associated with ipsilateral third nerve signs and herniation of the hippocampal gyrus. These were ipsilateral hemiplegia and infarction of the occipital lobes. The former was present in one clinical case and in two of the experimental animals. The latter was discovered at necropsy in four patients but it was not found in any of the experimental animals. Both these features have already been described in the literature, and although not entirely original as far as this work is concerned, it has been considered fitting to include them in this report [...