Cerebral blood flow in patients with normal pressure hydrocephalus.

Mean cerebral blood flow (CBF) of the whole brain was measured in 48 patients who underwent cerebrospinal fluid shunt surgery for normal pressure hydrocephalus (NPH) by performing first-pass radionuclide angiography using 99Tcm-hexamethylpropylene amine oxime. Patients were divided according to outcome into an 'excellent' improvement group, a 'good' improvement group, a 'fair' improvement group and a 'poor' improvement group. Patients with excellent and good improvement had a preoperative mean CBF of 40.4 +/- 3.9 ml.100 g-1.min-1 and 37.1 +/- 5.5 ml.100 g-1.min-1, respectively, both of which were significantly (P < 0.005) higher than that in 11 patients who showed fair improvement (30.8 +/- 3.2 ml.100 g-1.min-1) and six patients who showed poor improvement (31.8 +/- 2.5 ml.100 g-1.min-1). Patients with a clinical improvement after shunting had an increased postoperative mean CBF. We conclude that patients with a preoperative mean CBF of over 35 ml.100 g-1.min-1 can show favourable improvement after a shunting procedure, and that the preoperative mean CBF of 32 ml.100 g-1.min-1 can be considered the critical level for treatment.