Motor Signs Progress Rapidly in Alzheimer Disease

Home>
Specialty Care>
Neurology>
Summary and Comment

Motor Signs Progress Rapidly in Alzheimer Disease

Motor signs become increasingly prevalent as AD progresses and can be caused by the Alzheimer pathology itself.

Many patients with Alzheimer disease (AD) eventually develop extrapyramidal motor signs, such as rigidity, postural changes, and bradykinesia (slowness of movement). Such motor dysfunction challenges caregivers and is associated with higher rates of patient institutionalization and death. Major causes -- the comorbid presence of dementia with Lewy bodies, the direct effect of Alzheimer changes on motor regions, and the use of neuroleptics -- are well known. However, how motor sign prevalence changes during the course of the disease is not well understood. In this, the largest study to date of motor signs in AD, researchers analyzed data on 474 patients with probable AD who were followed for up to 13 years (mean, 3.6 years) in three U.S. and two European centers. Patients with neuroleptic-induced motor signs were excluded from the study.

At least one motor sign was found in 13% of patients at enrollment and in 36% by last assessment. Among the 99 patients who came to autopsy, 93% had AD changes and 22% had comorbid Lewy body dementia. Lewy bodies were found in 24% of patients with motor signs and in 13% of patients without motor signs. The presence of an ApoE ${epsilon}$ 4 allele was associated with lower rates of motor signs. The authors suggest that patients with AD who have that allele may have a reduced prevalence of Lewy body pathology.

Comment: These findings confirm and extend the observation that motor signs frequently develop in patients with Alzheimer disease as the disease progresses. Although about 25% of the time they are related to comorbid Lewy body dementia, most of the time they are directly related to AD changes. Questions remain about the rate of progression in patients with motor signs related to different pathologies. For example, does the motor impairment worsen the disease prognosis, or is it a marker of a more rapidly progressive pathology? This study confirms that motor signs are frequent in AD and that pure Alzheimer pathology is sufficient to cause them.

— Daniel Press, MD

Dr. Press is Instructor in Neurology, Harvard Medical School, and Staff Neurologist, Beth Israel Deaconess Medical Center, Boston.

Published in Journal Watch Neurology December 10, 2004