Ipsilateral hippocampal atrophy is associated with long-term memory dysfunction after ischemic stroke in young adults

Abstract

Memory impairment after stroke in young adults is poorly understood. In elderly stroke survivors memory impairments and the concomitant loss of hippocampal volume are usually explained by coexisting neurodegenerative disease (e.g., amyloid pathology) in interaction with stroke. However, neurodegenerative disease, such as amyloid pathology, is generally absent at young age. Accumulating evidence suggests that infarction itself may cause secondary neurodegeneration in remote areas. Therefore, we investigated the relation between long-term memory performance and hippocampal volume in young patients with first-ever ischemic stroke. We studied all consecutive first-ever ischemic stroke patients, aged 18-50 years, admitted to our academic hospital center between 1980 and 2010. Episodic memory of 173 patients was assessed using the Rey Auditory Verbal Learning Test and the Rey Complex Figure and compared with 87 stroke-free controls. Hippocampal volume was determined using FSL-FIRST, with manual correction. On average 10 years after stroke, patients had smaller ipsilateral hippocampal volumes compared with controls after left-hemispheric stroke (5.4%) and right-hemispheric stroke (7.7%), with most apparent memory dysfunctioning after left-hemispheric stroke. A larger hemispheric stroke was associated with a smaller ipsilateral hippocampal volume (b=-0.003, P<0.0001). Longer follow-up duration was associated with smaller ipsilateral hippocampal volume after left-hemispheric stroke (b=-0.028 ml, P=0.002) and right-hemispheric stroke (b=-0.015 ml, P=0.03). Our results suggest that infarction is associated with remote injury to the hippocampus, which may lower or expedite the threshold for cognitive impairment or even dementia later in life.

Keywords: episodic memory; hippocampal volume; ischemic stroke; young adults.

Figure 1

Lesion probability maps in patients with left‐hemispheric stroke, right‐hemispheric stroke, and infratentorial stroke. The color overlay created on top of the MNI standard brain template shows the probability of each voxel containing a lesion in each patient group. The color bar denotes the probability range. [Color figure can be viewed in the online issue, which is available at http://wileyonlinelibrary.com.]

Figure 2

Unadjusted mean hippocampal volume (±SEM) 10 years after ischemic stroke in young adults compared with stroke‐free controls. Significant differences are shown after adjusting for age at follow‐up and sex. *P<0.05, **P<0.01, ***P<0.001.