Cerebral Blood Flow Velocity and Vasomotor Reactivity Before and after Shunting Surgery in Patients with Normal Pressure Hydrocephalus

Abstract

The purpose of this study was to evaluate pre- and post-shunting haemodynamic changes and their correlation with the clinical results in normal pressure hydrocephalus (NPH). Accordingly, eleven demented patients with clinical signs suggestive of NPH received examinations of cerebral blood flow velocity (BFV) and vasomotor reactivity (VMR) by transcranial Doppler sonography with carbogen testing before and after shunt treatment. Computerized tomography (CT), clinical assessment and neuropsychological grading were performed prior to and at 3 months following 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 the NPH patients did not have significant decreases of BFVs, but had significant decreases of carbogen VMR (P < 0.05). After shunting, there were no significant changes of the BFVs as compared with the pre-shunting data. The post-shunting VMR of the ACA was significantly higher than 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 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, the five patients with gait improvement showed significantly higher values 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 improvement (p < 0.05, respectively). Our study supports the view that patients with NPH had various degrees of impaired VMR in both the ACA and the MCA, but showed insignificant reduction in BFVs, indicating a compensatory mechanism of CBF over time to accommodate the subnormal state 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 alone is associated with symptomatic improvement in mental function and that increase in VMR in both the ACA and the MCA with improvement in gait, respectively.

Magnetic resonance imaging for quantitative flow measurement in infants with hydrocephalus: a prospective study

“…7,36 The increase of CBF after CSF diversion found in adult patients with idiopathic chronic hydrocephalus was ~ 50%, 39 whereas this increase was not significant in patients with NPH. 42,45 According to our study, progressive hydrocephalus in infants leads to greater reduction in CBF than it does in adults with idiopathic chronic hydrocephalus. This may be caused by the shorter existence of the hydrocephalus, the different consistency of the developing parenchyma in infants, and the higher vulnerability of the maturing periventricular white matter in infants.…”

Outcome of Idiopathic Normal-Pressure Hydrocephalus After Surgery With Gravity Valves

“…Hence, a delayed diagnosis can result in irreversible degradation of the patient's cognitive potential. 34 For this reason, sensitive diagnostics ( Fig. 1) and prompt therapy (Fig.…”

Cerebral hemodynamics before and after shunting in normal pressure hydrocephalus

“…Others believe that a fall in cerebral blood flow is a secondary phenomenon resulting from a decrease in cerebral metabolism caused by a decrease in volume of brain tissue in normal pressure hydrocephalus (19–21). Some authors have found no alterations in cerebral hemodynamics after shunt therapy (6–8, 16), whereas others found significant improvement in cerebral blood flow (9–11) and cerebrovascular reactivity (7, 10–12), and a reduction in PI (13). A remarkable observation in our study was the decrease in blood flow velocities in patients with and without clinical improvement after shunt surgery, suggestive for a possible postoperative normalization in intraparenchymal pressure and concomitant relaxation of large arteries.…”

“…Whether changes in cerebral hemodynamics eventually lead to clinical improvement is unclear. The pathophysiologic mechanism underlying clinical improvement after shunt surgery in NPH is still unknown, and may include restoration of regional cerebral blood flow (7, 9–11, 16) and metabolic improvement (18). Higher preoperative cerebral blood flow, measured by means of single photon emission computed tomography, in patients with a favourable outcome has been observed (22).…”

“…Data on cerebral hemodynamics in normal pressure hydrocephalus are scarce and information on changes in cerebral hemodynamics induced by shunt surgery, are conflicting. Some authors have found no changes in one or more cerebral hemodynamic parameters after shunt surgery (6–8), whereas others did find significant improvement in cerebral blood flow (9–11), cerebrovascular reactivity (7, 10–12), and a concomitant decrease in pulsatility index (13). Whether these changes in cerebral hemodynamics are associated with clinical improvement is unknown.…”