[Auditory evoked brain stem responses in patients with normal pressure hydrocephalus following subarachnoid hemorrhage and elderly dementia].

There have been many reports that had discussed the effectiveness of shunt surgery in dementia patients. But it is not always reliable to predict such effectiveness before the operation. We used auditory evoked brain stem responses (ABR) to investigate the degree of brain damage in normal pressure hydrocephalus (NPH) and predict the effectiveness of shunt surgery. Fifteen patients with subarachnoid hemorrhage were divided into three groups, 5 cases without any symptoms of NPH, 6 cases with one of three symptoms of NPH and 4 cases with full blown symptoms of NPH which improved after shunt surgery, it is NPH. Eleven cases of aged patients were classified into two groups, Elderly normal (6 cases) and Elderly dementia (5 cases) groups, Younger normal group was composed of 8 healthy persons. Interpeak latencies (IPL's) on ABR was used as indexes of evaluating brain stem function, I-V IPL was used as central transmission time (CTT). CTT of Younger normal group and Elderly normal group were not different. It showed that CTT was a reliable parameter of ABR independently of age. There was significant prolongation of CTT in the patients of NPH and Elderly dementia group in comparison with other groups, However between them significant differences were not present. We concluded that there was some degree of brain stem dysfunction in the patients of NPH as well as dementia patients suggesting one aspect of the pathogenesis of NPH. But we could not distinguish the patients of NPH from other dementia patients by the analysis of ABR.