Abstract
Simultaneous radioisotope (RI) and metrizamide computed tomography (CT) cisternographies were studied and compared to obtain a precise diagnosis of normal pressure hydrocephalus (NPH). RI cisternography demonstrated more prolonged visualization of the cerebrospinal fluid (CSF) dynamics including persistent ventricular reflux. However, these two methods are apparently comparable and complement each other when they are performed simultaneously.
Twenty-six cases presenting dementia and hydrocephalus were included in this study, 12 cases of which were operated and the other 14 were observed conservatively. Eight of the 12 cases operated showed an excellent result, but the other 4 did not. Retrospective analysis of the findings obtained from the cisternograms demonstrated in NPH patients that a block at the convexity, more prolonged ventricular reflux and faster RI clearance were noted. These findings apparently indicate an accelerated absorption from the collateral pathway of CSF in NPH. By contrast, cisternograms of non-NPH patients demonstrated delayed RI clearance and RI accumulation over the cortex, indicating moderate congestion or slowing of CSF dynamics. Therefore, RI clearance seems to be the most valuable method for differentiating NPH from non-NPH.
