PURPOSE: We prospectively evaluated the regional cerebral metabolic rate of 
glucose (CMRglu) before and after ventricular shunt placement in idiopathic 
normal-pressure hydrocephalus (iNPH) patients, to investigate whether some brain 
regions are more involved than others; we also correlated the individual 
variations of CMRglu with the clinical scale score assessment after shunting.
METHODS: Twenty iNPH patients (12 men; mean age 73 ± 9 years) underwent clinical 
scale score assessment and F-FDG PET-CT before and 1 week after shunting.
RESULTS: Before shunting, CMRglu values were similar in right and left brain 
regions, as well as after shunting. After shunting, 17 of 20 iNPH patients were 
clinically improved; all scale scores decreased, and CMRglu significantly 
increased in all regions (P < 10). In 3 of 20 iNPH patients, the symptoms 
persisted, the scale scores did not change, and CMRglu increased only in 3 
regions: left frontal, left putamen, and right thalamus. Before shunting, no 
difference in global CMRglu between clinically improved (n = 17) and not 
improved (n = 3) iNPH patients was found. After shunting, a significant (P = 
0.01) correlation between individual variations of CMRglu and clinical 
assessment was found.
CONCLUSIONS: These findings confirm that iNPH is a disease involving all 
cerebral regions almost in the same way, and shunt procedure has a similar 
effect on regional cerebral metabolism almost in the same way. Individual 
variations of CMRglu are more important than absolute values and correlate with 
clinical status after shunting. Clinical improvement depends not only on the 
capability to restore the cerebrospinal fluid dynamic, but also on the ability 
of cerebral parenchyma to recover the metabolic function.