Utility of the Mattis dementia rating scale to assess the efficacy of rivastigmine in dementia associated with Parkinson's disease

Introduction The severe, cortical, cholinergic depletion accompanying Parkinson's disease (PD) is considered as a highly probable correlate of cognitive and behavioural dysfunction. Recent studies have demonstrated that cholinesterase inhibitors (notably rivastigmine) are beneficial in patients suffering from dementia associated with PD (PDD). However, the primary efficacy variables used in such work came from scales designed for Alzheimer's disease (AD), even though the cognitive symptoms in PD and AD dementia do not overlap completely. The aim of the present study (a double-blind, placebo-controlled clinical trial) was to determine the utility of the Mattis dementia rating scale - the most commonly used scale in PD patients - to assess the efficacy of a 24-week rivastigmine treatment. Methods Twenty-eight patients with PD, who constituted a subgroup of patients enrolled to the EXPRESS study (Emre et al, N Engl J Med 2004) participated in this study. They suffered from mild to moderately severe dementia (MMSE scores above 10 and below 24), with an onset of cognitive symptoms occurring at least two years after the diagnosis of PD. Patients were randomly assigned to treatment with rivastigmine (3 to 12 mg per day) or placebo. The Mattis dementia rating scale was administered to patients from six centres in France at the baseline and end-point visits. Results Compared with placebo, a 24-week rivastigmine treatment led to a significant improvement in the overall score on the Mattis dementia rating scale (p = 0.031), with a trend towards a significant improvement in the "Attention" subscale score (p = 0.061). Correlation analysis showed that in the rivastigmine group, performance on the Mattis "Attention" and "Initiation" subscales appeared to contribute heavily to the improvement in the overall score. Moreover, the latter was also related to an improvement in activities of daily living and a reduction in behavioural disturbances. Discussion By using the Mattis dementia rating scale (which comprises items that are sensitive to executive dysfunction), the present study confirmed that rivastigmine has a beneficial effect on cognitive function in PDD. Despite our study's small sample size, the Mattis scale was able to detect this improvement and could thus be considered as an interesting outcome measure in further work.