Magnetic Resonance Imaging (MRI)-Based Hippocampal Volumetry in Patients with Dementia in Anambra State, Nigeria: A Retrospective Study

Background: Dementia is a progressive neurocognitive syndrome associated with structural and functional changes in the brain. The hippocampus plays a central role in memory formation and is particularly vulnerable to neurodegenerative processes, especially those associated with Alzheimer’s disease. Magnetic resonance imaging (MRI)-based hippocampal volumetry may provide a useful quantitative marker for characterising dementia and differentiating its subtypes. However, there is limited local evidence regarding hippocampal volume among patients with dementia in southeastern Nigeria. Aim: To assess hippocampal volume in patients with dementia using MRI, compare right and left hippocampal volumes across dementia subtypes, and determine whether hippocampal volume varies by sex. Methods: A retrospective cross-sectional study was conducted at the MRI Unit of GEM Diagnostic Centre, Onitsha, Anambra State, Nigeria. Seventy-one brain MRI examinations and corresponding medical records of adults with dementia were purposively selected. MRI examinations were retrieved from the Picture Archiving and Communication System. The right and left hippocampi were identified on coronal images, manually delineated across the slices in which they appeared, and their volumes calculated from the summed cross-sectional areas and slice thickness. Data were analysed using SPSS version 21.0. The Shapiro–Wilk test was used to assess normality, while independent-samples t-tests were used for group comparisons. Statistical significance was set at p < 0.05. Results: The patients whose images were evaluated comprised 53 males (74.65%) and 18 females (25.35%). The largest age group was 61–80 years (40.84%). Mean hippocampal volumes were highest among patients with normal pressure hydrocephalus (NPH), measuring 2.343 ± 0.041 cm³ on the right and 2.250 ± 0.102 cm³ on the left. Vascular dementia patients had mean volumes of 2.010 ± 0.071 cm³ on the right and 2.125 ± 0.088 cm³ on the left. Mixed dementia patients had volumes of 1.992 ± 0.119 cm³ on the right and 1.844 ± 0.086 cm³ on the left, while Alzheimer’s disease had the lowest volumes, at 1.856 ± 0.148 cm³ on the right and 1.828 ± 0.070 cm³ on the left. A significant sex difference was observed only in the left hippocampus among patients with Alzheimer’s disease (p = 0.031). Right–left hippocampal volume differences were significant in vascular dementia (p < 0.001) and mixed dementia (p = 0.008), but not in Alzheimer’s disease (p = 0.320) or NPH (p = 0.066). Conclusion: Hippocampal volume varied across dementia subtypes, with the smallest volumes observed in Alzheimer’s disease and the largest in NPH. Significant hippocampal asymmetry was observed in vascular and mixed dementia. MRI-derived hippocampal volumetry may therefore provide useful quantitative information in the structural assessment and differentiation of dementia subtypes.

Keywords: dementia; hippocampus; hippocampal volumetry; magnetic resonance imaging; Alzheimer’s disease; vascular dementia; normal pressure hydrocephalus; Nigeria.

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