Impairment of cerebrovascular reactivity to acetazolamide in patients withnormal pressure hydrocephalus

Cerebrovascular reactivity (CVR) to acetazolamide was investigated in 41 pa tients with normal pressure hydrocephalus (NPH). The aetiology was subarach noid haemorrhage in 20 patients, trauma in nine, brain tumour in three and idiopathic in nine. Mean cerebral blood flow (CBF) of the whole brain was m easured by performing first-pass radionuclide angiography using Tc-99(m)-he xamethylpropylene amine oxime. CerebrovascuIar reactivity was measured as t he percentage change from the baseline mean CBF value after the administrat ion of 500 mg of acetazolamide. Cerebrovascular reactivity was significantl y (P < 0.001) reduced in patients with the complete triad of NPH (1.4+/-3.1 %), regardless of the aetiology, compared with normal controls (14.7+/-3.3% ). Patients with the incomplete triad also showed significantly (P<0.05) re duced CVR (9.6+/-5.4%). Patients with the complete triad had significantly (P < 0.001) lower CVR than those with the incomplete triad. Post-operative CVR in both groups (20 patients with the complete triad and 9 patients with the incomplete triad) increased significantly, from 1.5+/-3.5% to 10.0+/-5 .5% (P < 0.001) and from 8.7+/-4.9% to 14.9+/-5.4% (P<0.05), respectively. Cerebrovascular reactivity is impaired in patients with NPH regardless of t he aetiology and improves after shunting. ((C) 2000 Lippincott Williams & W ilkins).