Early frontal impairment as a predictor of dementia in Parkinson's disease

To the Editor: The very interesting article of Jacobs et al. [8] on Neuropsychological characteristics of dementia in Parkinson's disease (PD) suggests several ideas. A preclinical phase of parkinsonian dementia can be identified, and this preclinical phase presents a specific neuropsychological pattern that can be distinguished from the pattern seen in Alzheimer's disease. Verbal fluency represents the type of cognitive performance that can best be correlated with subsequent development of dementia, and poor performance on these tests would reflect an executive dysfunction due to an involvement of the frontal-subcortical circuits. On the basis of our own results, an early frontal dysfunction can be considered the best predictive factor for the development of dementia in PD. [2] In particular, in an otherwise unselected sample of parkinsonian patients, we found that four different types of relationships can be observed between a frontal syndrome, dementia and PD: (1) no cognitive abnormalities are revealed by neuropsychological evaluation; (2) the frontal symptomatology is associated with a more generalized cognitive impairment; (3) signs of frontal dysfunction constitute the sole cognitive alteration that can be noted; and (4) the neuropsychological examination reveals abnormal cognitive functions that cannot be attributed to a frontal dysfunction. The first pattern can be …