Prevalence of potentially reversible dementias and actual reversibility in a memory clinic cohort

Abstract

BACKGROUND: Although clinics for the evaluation of cognitive dysfunction have typically emphasized the detection and treatment of the reversible causes of dementia, it remains unclear whether the treatment of such causes results in reversal of the dementia. Therefore, the appropriate work-up for dementia is in dispute. METHODS: A chart review was performed with records from an urban tertiary care referral-based memory clinic. The records for 196 patients with dementia or suspected dementia, seen between October 1991 and December 1993, were examined to determine the prevalence of potentially reversible dementias and whether the cognitive dysfunction improved or resolved after treatment. Data abstracted from the medical charts included demographic information, medication use, presence of depression, and results of neuropsychological tests, blood work and neuroimaging. The clinical diagnosis, the response to treatment, if applicable, and the outcome (mean follow-up period 16 months) were analysed. The recommendations of the 1989 Canadian Consensus Conference on the Assessment of Dementia (CCCAD) on the use of CT were retrospectively applied in each case. RESULTS: Of the 196 patients, 45 (23.0%) had a potentially reversible condition identified by history, physical examination, blood testing or CT; in only 7 (3.6% of the total) did treatment result in improvement or resolution of the dementia. These 7 patients had higher results for the Mini-Mental State examination (mean result 26) and exhibited only mild cognitive deficits. Potentially reversible lesions were found in the CT scans of 6 (3.1%) patients: 4 had normal-pressure hydrocephalus and 2 had a brain tumour. If the CCCAD recommendations had been followed, CT would have been performed in 76 (38.8%) of the patients, and 1 of the 6 patients with a lesion would have been missed. INTERPRETATION: Both potential and actual reversibility of dementia was low in these memory clinic patients. The patients whose condition improved with intervention had early and milder cognitive deficits, which suggests that thorough evaluation of early memory loss is warranted.