title: Striatal D2 receptor availability after shunting in idiopathic normal pressure hydrocephalus.
abstract: Gait disturbance in idiopathic normal pressure hydrocephalus (iNPH) is reminiscent of parkinsonism. Our recent PET study showed reduction in postsynaptic D(2) receptor binding concomitant with a normality of presynaptic dopamine transporter binding. Here, we investigated the plasticity of D(2) receptor in treating iNPH patients with ventriculoperitoneal (VP) shunting using PET with (11)C-raclopride and discuss the contribution of D(2) receptor to the pathophysiology of iNPH.
  
  
  METHODS
  Eight iNPH patients participated in this study. After evaluation of their neuropsychologic abilities, all patients underwent 3-dimensional MRI and quantitative PET measurements twice before and 1 mo after VP shunting. MRI-based morphometric analyses were performed to examine postoperative variations of the ventricles. Estimation of binding potential (BP) for (11)C-raclopride was based on Logan plot analysis. Region-of-interest analysis was used to examine changes in (11)C-raclopride BP in the striatum. A 2-tailed paired t test was used for evaluating changes in PET and MRI parameters between conditions, and correlation analysis was used to investigate clinicopathophysiologic relevance (clinical vs. in vivo findings).
  
  
  RESULTS
  Clinical evaluation revealed significant recovery in a 5-m back-and-forth navigation test and an affect test and a mild increase in Mini-Mental State Examination scores after VP shunting. Significant postoperative increases in (11)C-raclopride BP were found in the nucleus accumbens and dorsal putamen, and the increases were significantly associated with emotional (Spearman rank r = 0.66, P < 0.05) and navigational improvement (r = 0.72, P < 0.05), respectively. The (11)C-raclopride BP increase in the striaum as a whole correlated significantly with improvement in general cognitive ability. There was a mild ventricular shrinkage after surgery, albeit there was no correlation of its size with clinical and PET parameters.
  
  
  CONCLUSIONS
  Striatal upregulation of D(2) receptor after VP shunting is associated with amelioration of hypokinetic gait disturbance and anhedonic mentation in iNPH patients, indicating that the effect of VP shunting may reside in noninhibition of functionally suppressed D(2) receptor in the striatum. D(2) receptor responsiveness may indicate a mechanism for iNPH pathophysiology.
authors.affiliation: Department of Neurosurgery, Hamamatsu Medical Center, Hamamatsu, Japan.
authors.forename: Teiji
authors.initials: T
authors.lastname: Nakayama
authors.forename: Yasuomi
authors.initials: Y
authors.lastname: Ouchi
authors.forename: Etsuji
authors.initials: E
authors.lastname: Yoshikawa
authors.forename: Genichi
authors.initials: G
authors.lastname: Sugihara
authors.forename: Tatsuo
authors.initials: T
authors.lastname: Torizuka
authors.forename: Keisei
authors.initials: K
authors.lastname: Tanaka
mesh_terms: D000368:Aged; D002250:Carbon Radioisotopes; D005260:Female; D006801:Humans; D006850:Hydrocephalus, Normal Pressure / Q000378:metabolism / Q000473:pathology / Q000601:surgery*; D008279:Magnetic Resonance Imaging; D008297:Male; D020891:Raclopride / Q000378:metabolism; D017448:Receptors, Dopamine D2 / Q000032:analysis*; D017287:Ventriculoperitoneal Shunt
chemical_list: D002250:Carbon Radioisotopes; D017448:Receptors, Dopamine D2; D020891:Raclopride