Intellectual impairment in Parkinson's disease--correlation with cerebral cortical blood flow

A contribution of cerebral cortical damage to the development of intellectual impairment in patients with Parkinson's disease (PD) has been suspected. We studied the relationship between intellectual impairment and cerebral cortical blood flow in 28 treated idiopathic parkinsonian patients. Mean IQ score as evaluated by applying the Suzuki-Binet test in patients with PD was 70.7 (+/- 12.7) and 78.6% of the patients showed abnormal score (below 80). The intellectual deficits were characterized by impairment of memory and abstract thinking, and showed a significant correlation with the severity of motor symptoms. Mean hemispheric cortical blood flow measured by using the 133xenon intravenous injection technique in patients with PD was significantly lower than that for 18 age-matched controls. Prefrontal cortical blood flow in PD was also significantly reduced compared with that in age-matched controls, showing a partial loss of hyperfrontal pattern. However, there was no significant correlation between IQ score and either mean hemispheric cortical blood flow or prefrontal cortical blood flow values. These results suggest that, although the patients with PD demonstrated a high prevalence of intellectual impairment, the impairment is not necessarily of cortical origin.