PET-Studies in Idiopathic Chronic Hydrocephalus before and after Shunt-Treatment: The Role of Risk Factors for Cerebrovascular Disease (CVD) on Cerebral Hemodynamics

Aim

To investigate the impact of cerebrovascular risk factors in idiopathic chronic hydrocephalus concerning cerebral hemodynamics and clinical outcome after shunting.

Global cortical cerebral blood flow (CBF) and cerebrovascular reserve capacity (CVR) in 53 patients (67 ±11 yrs) were determined by 15-0-water-PET studies before and after administration of aceta-zolamide (1 g) prior (pre), one week (7 d) and seven months (7 m) after shunting. According to the prevalence of vascular risk factors (American subcommittee on reporting standards for cerebrovascular disease) patients were classified into a “low-risk” (n = 27) and “high-risk” (n = 20) group; patients with a history of stroke (n = 6) were separated. After 7 months, clinical outcome was assessed according to Stein and Langfitt.

While CBF in “high-risk” patients prior to surgery was significantly lower in clinical responder compared to non-responder (32 ± 5 vs. 42 ± 15 ml/100 ml/min; p < 0.05), CVR was marginal in both outcome groups (< 30%). One week after shunting, CVR in responder of “high-risk” significantly increased (64 ± 30 vs. 31 ± 10% pre; p < 0.01). In “low-risk” patients, differences in CVR prior to shunting were found: CVR was lower in clinical responder than in non-responder (36 ± 11 vs. 47 ± 22% pre; p > 0.05) and deteriorated in non-responder (29 ± 15% vs. 47 ± 22 pre; p < 0.02) one week after shunting.

Different peri-operative characteristics in global CVR regarding clinical response after shunting between both “risk-groups” were observed. Pathophysiological mechanisms upon clinical sequels after shunting in idiopathic hydrocephalus may not be unique.