Rivastigmine for the treatment of dementia in patients with progressive supranuclear palsy: Clinical observations as a basis for power calculations and safety analysis

Cognitive decline and dementia are present in about 50% of patients with progressive supranuclear palsy (PSP). Based on the known involvement of the cholinergic system in PSP patients, and because rivastigmine, in contrast to other cholinesterase inhibitors, inhibits both acetylcholinesterase and butyrylcholinesterase, we discuss clinical observations of five patients suffering from PSP and dementia who were all treated with rivastigmine over a period of 3 to 6 months. We found a slight improvement in specific cognitive function that may justify further controlled studies. A calculation of sample size revealed that a study on the effect of rivastigmine in PSP should include about 31 patients to detect a significant effect. In subtests, meaningful results can be obtained with even lower numbers (five patients for a verbal fluency test, and 14 patients for a logical memory task).