Extrapyramidal features in Alzheimer's disease

In many cases of Alzheimer’s disease (AD), extrapyramidal signs (EPS) occur at some point in the illness [1–29]. Pearce first reported EPS in pre-senile dementia in 1974 [1]. Epidemiological reports suggested that EPS in AD herald a more ominous clinical course, with a more rapid rate of cognitive [2, 7] and functional decline [3, 6], a greater risk of institutionalization [3, 8, 9] and shorter survival [3, 8, 10, 11]. We do not know whether these signs describe a distinct subset of AD patients or act as a marker of advanced disease; nor do we know if EPS are risk factors for adverse outcomes. Earlier clinicopathological studies need to be re-examined in light of the recent clinical and pathologic guidelines for the diagnosis of dementia with Lewy bodies (DLB) [30]. In order to interpret the significance of EPS in AD patients, the data need to be critically synthesized. The objectives of this review are to summarize and clarify what is known about the epidemiology, clinical relevance and pathological correlates of EPS in AD. I therefore conducted a systematic search of MEDLINE from January 1966 until December 1997 of all studies relating to parkinsonian signs, parkinsonism or extrapyramidal features in AD. Research reports from English language peer-reviewed journals were considered for abstraction. References from these articles were also reviewed for relevant studies. I examined multiple reports from a single cohort only once and conducted a qualitative synthesis of the data from independent studies.