[Clinical and experimental study on false lateralizing sign (author's transl)].

Clinical study is based upon the results of 68 cases of infratentorial tumor which have been examined in the Dept. of Neurosurgery, Tokyo Jikeikae University Hospital during the year 1967--1977. False lateralizing signs (F.L.S.) were studied of 57 cases except 11 pontine tumors. The incidence of this peculiar signs was 19.2% in 57 cases of infratentorial tumors, including 31.5% in 19 cases of cerebellopontine angle tumors, and 23.8% in 21 cases of cerebellar hemisphere tumor. A number of hypotheses have been proposed in the literature with regard to false lateralizing sign. The author presented the idea that elevated counter pressure elicited at a distance from the tumor may play significant role in producing this peculiar signs. Then the author undertook three-dimensional experiment on counter pressure mechanism, in order to elucidate the idea in cooperation with Material section, Trial production No. 1, Nissan Motor Car. Co. Ltd. The result showed that high counter pressure was observed at the contralateral cerebellopontine angle than the ipsilateral one to the compression. This means that when a mass grows at the posterior fossa on one side, lower cranial nerves of the contralateral side are easily compressed by the counter pressure mechanism from purely physical point of view. Therefore, there is a fair chance for the manifestation of false lateralizing signs.