CEREBRAL BLOOD-FLOW VELOCITY AND VASOMOTOR REACTIVITY BEFORE AND AFTER SHUNTING SURGERY IN PATIENTS WITH NORMAL-PRESSURE HYDROCEPHALUS

The purpose of this study was to evaluate pre- and post-shunting haemo dynamic changes and their correlation with the clinical results in nor mal pressure hydrocephalus (NPH). Accordingly, eleven demented patient s with clinical signs suggestive of NPH received examinations of cereb ral blood flow velocity (BFV) and vasomotor reactivity (VMR) by transc ranial Doppler sonography with carbogen testing before and after shunt treatment. Computerized tomography (CT), clinical assessment and neur opsychological grading were performed prior to and at 3 months followi ng surgery. A control group consisting of 10 patients was included to establish baseline data. The pre-operative CBF studies in the anterior cerebral artery (ACA) and the middle cerebral artery (MCA) revealed t he NPH patients did not have significant decreases of BFVs, but had si gnificant decreases of carbogen VMR (P < 0.05). After shunting, there were no significant changes of the BFVs as compared with the pre-shunt ing data. The post-shunting VMR of the ACA was significantly higher th an the pre-shunting one (p < 0.05), but there was no variation in that of the MCA. Both the values of post-shunting VMR in ACA and the post- shunting increase in VMR in MCA of the the 7 shunt-responsive patients who improved mentally and in other symptoms were significantly higher than those of patients without improvement (p < 0.05). In addition, t he five patients with gait improvement showed significantly higher val ues of post-shunting VMR of ACA and the post-shunting increase of VMR for both ACA and MCA when compared with those patients without gait im provement (p < 0.05, respectively). Our study supports the view that p atients with NPH had various degrees of impaired VMR in both the ACA a nd the MCA, but showed insignificant reduction in BFVs, indicating a c ompensatory mechanism of CBF over time to accommodate the subnormal st ate of cerebral perfusion pressure. Shunt placement would improve the VMR in responsive patients. Postoperatively, an increase of VMR tends to accompany improvement of the functional state: that in the MCA alon e is associated with symptomatic improvement in mental function and th at increase in VMR in both the ACA and the MCA with improvement in gai t, respectively.