DENVER, CO (American Academy of Neurology) -- Significant cognitive impairment and hallucination are relatively common among advanced Parkinson's disease patients. Some medications that augment the therapeutic effects of dopamine replacement drugs may in fact exacerbate neuropsychiatric symptoms experienced by these patients. Researchers have discovered that rivastigmine (a cholinesterase inhibitor) has a positive effect on these symptoms without a worsening of motor control, according to a presentation today at the Annual Meeting of the American Academy of Neurology.

In an open exploratory study, 12 patients with established Parkinson's disease, persistent hallucinations and moderate cognitive impairment were given rivastigmine for six weeks at maximum tolerated doses before withdrawal. "On drug treatment, we saw significant improvements regarding these patients' hallucinations and cognitive abilities," said study author Paul Reading, Ph.D., of the Regional Neurosciences Centre of Newcastle General Hospital in the United Kingdom. "After rivastigmine therapy was withdrawn, there was a corresponding deterioration in their symptoms."

Parkinson's patients' performance was also enhanced while on the medication, with faster reaction times and better attention in tasks measuring numerical working memory and vigilance. Caregiver distress was also improved.

"We are encouraged by the fact that these benefits of rivastigmine therapy did not seem to come at the expense of patients' motor control," said Reading.

Further study will be required to investigate the potentially reversible cholinergic deficits in this patient group and their likely involvement in neuropsychiatric symptomology.