An etiological aspect of normal pressure hydrocephalus. With special reference to diagnostic significance of continuous intracranial pressure monitoring

Abstract

In order to elucidate the mechanism of the normal pressure hydrocephalus (NPH), results of continuous intracranial pressure monitoring were analyzed. The subjects were 37 patients, consisting of 23 with NPH symptoms and 14 without, in whom continuous intracranial pressure monitoring was performed. In patients with cerebral aneurysm the monitoring was performed through the ventricular drainage within one week after operation. In 6 of these patients, the monitoring was repeated after the recurrence of NPH symptoms. Shunt operations were carried out in 16 patients. The pre and post-operative sizes of the ventricle were compared with each other by computerized tomography (CT) scan. The results indicated that 19 patients manifested pressure waves, and 8 were without NPH symptoms. No difference was found between the results of two monitorings in any of the 6 aneurysmal patients. The shunt was effective in all 6 patients with pressure waves, and in 4 out of 10 patients without pressure waves. Reduction of the ventricular size was observed in 6 patients by CT scan, 5 of whom had shown pressure waves. CT scan disclosed frontal damage in most of the NPH patients. Thus, the pressure wave frequently appeared even in patients without NPH symptoms. Though the efficacy rate of shunt operation wa: higher in patients with a pressure wave, some effects were observed even in the patients without z pressure wave. The pressure wave might not indicate an abnormal circulation or absorption of cerebrospina: fluid but the functional capacity of the brain itself. Occurrence of NPH appears to be dependent tc some extent on factors such as the severity and site of the brain damage and the preexisting functional capacity of the brain itself as well as the circulation of cerebrospinal fluid.