Date Published: May 1, 2018
Publisher: BioMed Central
Author(s): Basil H. Ridha, Sebastian Crutch, Dawn Cutler, Christopher Frost, William Knight, Suzie Barker, Norah Epie, Elizabeth K. Warrington, Riitta Kukkastenvehmas, Jane Douglas, Martin N. Rossor.
The study investigated whether donepezil exerts symptomatic benefit in patients with posterior cortical atrophy (PCA), an atypical variant of Alzheimer’s disease.
A single-centre, double-blind, placebo-controlled, cross-over clinical trial was performed to assess the efficacy of donepezil in patients with PCA. Each patient received either donepezil (5 mg once daily in the first 6 weeks and 10 mg once daily in the second 6 weeks) or placebo for 12 weeks. After a 2-week washout period, each patient received the other treatment arm during the following 12 weeks followed by another 2-week washout period. The primary outcome was the Mini-Mental State Examination (MMSE) at 12 weeks. Secondary outcome measures were five neuropsychological tests reflecting parieto-occipital function. Intention-to-treat analysis was used. For each outcome measure, carry-over effects were first assessed. If present, then analysis was restricted to the first 12-week period. Otherwise, the standard approach to the analysis of a 2 × 2 cross-over trial was used.
Eighteen patients (13 females) were recruited (mean age 61.6 years). There was a protocol violation in one patient, who subsequently withdrew from the study due to gastrointestinal side effects. There was statistically significant (p < 0.05) evidence of a carry-over effect on MMSE. Therefore, the analysis of treatment effect on MMSE was restricted to the first 12-week period. Treatment effect at 6 weeks was statistically significant (difference = 2.5 in favour of donepezil, 95% CI 0.1 to 5.0, p < 0.05). Treatment effect at 12 weeks was close, but not statistically significant (difference = 2.0 in favour of donepezil, 95% CI –0.1 to 4.5, p > 0.05). There were no statistically significant treatment effects on any of the five neuropsychological tests, except for digit span at 12 weeks (higher by 0.5 digits in favour of placebo, 95% CI 0.1 to 0.9). Gastrointestinal side effects occurred most frequently, affecting 13/18 subjects (72%), and were the cause of study discontinuation in one subject. Nightmares and vivid dreams occurred in 8/18 subjects (44%), and were statistically more frequent during treatment with donepezil.
In this small study, there was no statistically significant treatment effect of donepezil on the primary outcome measure (MMSE score at 12 weeks) in PCA patients, who appear to be particularly susceptible to the development of nightmares and vivid dreams when treated.
Trial registration: Current Controlled Trials ISRCTN22636071. Retrospectively registered 19 May 2010
Alzheimer’s disease (AD) typically presents with progressive impairment of episodic memory as a result of degeneration of medial temporal lobe structures before the involvement of other cortical regions causing widespread global cognitive impairment. Cholinesterase inhibitors (AChEI) have been shown to provide symptomatic benefit in patients with mild to moderate AD . A small but significant proportion of patients with AD-type pathology present with visual perceptual or visual spatial dysfunction, apraxia, dyscalculia or alexia reflecting posterior cortical dysfunction, with relative preservation of episodic memory. Structural brain imaging in these patients reveals parieto-occipital atrophy (posterior cortical atrophy (PCA)) . Only one case report suggested potential therapeutic benefit from taking AChEI in a patient with PCA . Otherwise, there have been no studies assessing the effectiveness of AChEI specifically in patients with PCA due to underlying AD.
All patients screened met the inclusion and exclusion criteria. Patients with PCA due to underlying AD were already known to the clinical investigators as they were under their clinical care. This allowed rigorous pre-screening based on their clinical assessment, and so only patients who were highly likely to fulfil the study criteria were invited to participate.
This small, double-blind, placebo-controlled, cross-over study found no statistically significant treatment effect on the MMSE at 12 weeks (primary outcome measure) in patients with PCA.