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(Stroke. 2009;40:983.)
© 2009 American Heart Association, Inc.

Research Letters

Interhemispheric Distribution of Alzheimer Disease and Vascular Pathology in Brain Aging

Panteleimon Giannakopoulos, MD; Enikö Kövari, MD; François R. Herrmann, MD, MPH; Patrick R. Hof, MD Constantin Bouras, MD

From the Departments of Psychiatry (E.K., C.B., P.G.) and Geriatrics (F.R.H.), University of Geneva Faculty of Medicine, Geneva, Switzerland; the Division of Old Age Psychiatry (P.G.), University of Lausanne School of Medicine, Lausanne, Switzerland; and the Department of Neuroscience (P.R.H.), Mount Sinai School of Medicine, New York, NY.

Correspondence to Enikö Kövari, Department of Psychiatry, Division of Neuropsychiatry, University of Geneva Hospitals, 1225 Chêne-Bourg, Switzerland. E-mail eniko.kovari{at}hcuge.ch

Background and Purpose— Most of the neuropathological studies in brain aging were based on the assumption of a symmetrical right–left hemisphere distribution of both Alzheimer disease and vascular pathology. To explore the impact of asymmetrical lesion formation on cognition, we performed a clinicopathological analysis of 153 cases with mixed pathology except macroinfarcts.

Methods— Cognitive status was assessed prospectively using the Clinical Dementia Rating scale; neuropathological evaluation included assessment of Braak neurofibrillary tangle and Aß deposition staging, microvascular pathology, and lacunes. The right–left hemisphere differences in neuropathological scores were evaluated using the Wilcoxon signed rank test. The relationship between the interhemispheric distribution of lesions and Clinical Dementia Rating scores was assessed using ordered logistic regression.

Results— Unlike Braak neurofibrillary tangle and Aß deposition staging, vascular scores were significantly higher in the left hemisphere for all Clinical Dementia Rating scores. A negative relationship was found between Braak neurofibrillary tangle, but not Aß staging, and vascular scores in cases with moderate to severe dementia. In both hemispheres, Braak neurofibrillary tangle staging was the main determinant of cognitive decline followed by vascular scores and Aß deposition staging. The concomitant predominance of Alzheimer disease and vascular pathology in the right hemisphere was associated with significantly higher Clinical Dementia Rating scores.

Conclusions— Our data show that the cognitive impact of Alzheimer disease and vascular lesions in mixed cases may be assessed unilaterally without major information loss. However, interhemispheric differences and, in particular, increased vascular and Alzheimer disease burden in the right hemisphere may increase the risk for dementia in this group.

Key Words: Alzheimer • cerebral infarct • cognition • white matter disease