[The role of computerized rheoencephalography in the assessment of normal pressure hydrocephalus. Preliminary report].

BACKGROUND AND PURPOSE

It is generally agreed that the positive result of lumbar cerebrospinal fluid (CSF) withdrawal offers a reliable means for selection of patients likely to respond to shunting in normal pressure hydrocephalus (NPH). However the studies of cerebral hemodynamics in NPH are performed Routinely only in few neurosurgical centers. We therefore studied the effect of CSF withdrawal on cerebrovascular autoregulation (CVA) in this condition by means of computerized rheoencephalography [REG].

MATERIAL AND METHODS

The study group consisted of 27 patients with presumed posttraumatic NPH. In each patient both the tap test and infusion test were performed. Psychometric tests and rheoencephalographic examinations were made twice: before and after CSF withdrawal. The obvious restoration of the functional state of CVA after CSF withdrawal was considered as a positive result of the tap test.

RESULTS

Fourteen patients with a positive tap test and/or with resistance to CSF outflow (Rout) of more than 11 mmHg/ml/min were shunted. The improvement was obtained in 10 of them. Only one patient with a positive tap test did not improve.

CONCLUSIONS

Our study suggests that restoration of CVA after CSF withdrawal is associated with high likelihood of shunt success, but not vice versa. Evaluation of CVA using REG seems to offer a new diagnostic tool in selecting patients likely to respond to shunting. Further studies are necessary to optimize the amount of CSF withdrawal, the delay between CSF withdrawal and control examinations and methodology of neuropsychological examinations.