Functional and Cognitive Consequences of Silent Stroke Discovered Using Brain Magnetic Resonance Imaging in an Elderly Population

Wolf-Peter Schmidt, MD; Andreas Roesler, MD; Konrad Kretzschmar, PhD; Karl-Heinz Ladwig, PhD; Ralf Junker, MD; Klaus Berger, MD

Disclosures

J Am Geriatr Soc. 2004;52(7) 

In This Article

Discussion

The study revealed a prevalence of silent stroke of 12.7% in an elderly population. Prevalence increased with age and was higher in men than in women. Factors associated with silent stroke were history of hypertension or heart surgery and a moderately higher serum level of CRP. Silent stroke was associated with considerable impairments in cognitive function and reductions in self-perceived health status and independence in ADL.

The results underscore prior findings that silent stroke has functional consequences for affected individuals. One study showed associations between silent stroke and visual field deficits, weakness in walking on heels, history of memory loss, migraine, and worse scores in a test of cognitive function.[23] Another study found showed that participants with silent stroke had poorer scores on the MMSE and on Raven's colored progressive matrices.[11] Recent results from the prospective Rotterdam Scan study demonstrated a clear association between the diagnosis of silent stroke on baseline MRI and subsequent development of dementia and cognitive decline.[24]

The current results confirm that silent stroke is associated with impairments in tests of cognitive function rather than movement-oriented performance tests like rising from a chair. Almost 50% of the silent strokes affected frontal circuit components (frontal cortex, basal ganglia, thalamus). Lesions in these brain structures compromise executive functions and have been related to vascular dementia.[25] However, the existing difference in the IADL score between participants with and without silent stroke did not reach statistical significance in the current study. Because the number of participants was small, the power of the study to detect a significant difference in IADLs was relatively low. The results may also suggest the application of more specific tests of executive function in patients with silent stroke, but it must be considered that affected persons and clinicians may not notice silent strokes because they have little effect on daily life.

Participants with silent stroke had more depressive symptoms than individuals without events. This may indicate that poststroke depression as a common finding after a known stroke event[26] is not only due to limitations imposed by manifest neurological deficits. It also suggests that vascular changes in the brain and silent stroke might be directly related to depression. The results are consistent with the high prevalence of silent stroke of more than 50% in elderly patients with depression.[27] Other studies have found that depressive symptoms decrease processing speed.[28] The differences in procedural speed found in the current study were still significant after adjusting for symptoms of depression. Therefore silent stroke may be an independent risk factor for senile depression and decline in processing speed. The consistent slight impairments in self-perceived health, although not statistically significant in this study, suggest a contribution of silent stroke to the reduced quality of life in affected individuals.

As expected, the prevalence of silent stroke in this study increased with age and was higher in participants with a history of hypertension. In addition, there was a significant association between silent stroke and a history of heart surgery. Although the number of individuals who had undergone cardiac surgery was small, it confirms findings from a prospective study using MRI brain imaging before and after coronary artery bypass grafting intervention.[10] A higher serum level of CRP in participants with silent stroke than in those without any stroke was observed. Elevated CRP concentrations are increasingly recognized as an independent risk factor for cerebrovascular events.[29,30] Whether CRP levels also constitute a predictor for silent stroke deserves further study in a larger population sample and a prospective study design.

This study has several strengths and limitations. It provides a detailed description of the effect of silent stroke on a large number of scales of physical, mental, and emotional health in an elderly population. Diagnoses of ischemic cerebral lesions on brain imaging were made following a standardized MRI reading protocol. The presence or absence of a history of clinically manifest stroke was assessed using a single stroke question, which has been shown to yield a reliable assessment of stroke symptoms. The rating scales used are established for the assessment of performance and health status and frequently applied in studies of geriatric populations. The IADL scale used in this study does not include the higher-order activities that diminished speed performance might affect. The relatively small number of subjects with silent strokes limits the results, restricting the power of the statistical tests used. However, despite nonsignificant P-values, the differences in the rating scales indicate the need for further study. Because of contraindications, MRI scans could be performed on only 69% of the MEMO participants. The 267 persons studied were significantly younger than those without MRI (mean age 72.3 vs 73.7) and had significantly lower systolic blood pressure (139.1 vs 143.6mmHg). There were no significant differences in sex, years of education, or the prevalence of hypertension or myocardial infarction between participants who did and did not undergo an MRI. It seems unlikely that the selection of participants suitable for MRI may have impaired the validity of the study results.

In conclusion, these results confirm that silent stroke has a measurable and considerable effect on cognitive performance and quality of life in those affected. Determining the presence of silent stroke using brain imaging may thus contribute to identifying individuals at risk for developing gradual neurological deficits and cognitive decline. Further evaluation of possible risk factors for asymptomatic cerebral lesions including cardio- and cerebrovascular interventions, as well as serum markers of inflammation, may yield new insights in terms of pathogenesis and prevention.


CLICK HERE for subscription information about this journal.

Comments

3090D553-9492-4563-8681-AD288FA52ACE
Comments on Medscape are moderated and should be professional in tone and on topic. You must declare any conflicts of interest related to your comments and responses. Please see our Commenting Guide for further information. We reserve the right to remove posts at our sole discretion.
Post as:

processing....