Alzheimer Hastalığında Hipokampal Alt Alan Hacim Değişiklikleri: Yaşlı Bireylerde Cinsiyete Göre Ayrıştırılmış Bir MR Çalışması

Öz

Alzheimer hastalığı (AH), hipokampal atrofisinin en erken ve en belirgin yapısal değişikliklerden birini oluşturduğu, ilerleyici bir nörodejeneratif hastalıktır. Bu nedenle, alt alan düzeyinde morfometrik analizler, AH’de hipokampal tutulumun ayrıntılı biçimde karakterize edilmesini sağlayabilir. Bu çalışmanın amacı, alt alan segmentasyonu kullanarak, AH tanılı bireyler ile bilişsel olarak sağlıklı yaşlı bireyler arasında hipokampus ve hipokampal alt alan hacim farklarını; hemisferik asimetri ve cinsiyete özgü örüntüler dâhil olmak üzere incelemektir. Bu kesitsel nörogörüntüleme çalışmasında, AH tanılı bireyler ile bilişsel olarak sağlıklı kontrollerin (SK) hipokampus ve hipokampal alt alan hacimleri, OASIS-1 veri setine ait yapısal manyetik rezonans görüntüleme (MRG) verileri kullanılarak incelendi. Analitik örneklem, 60 yaş ve üzeri toplam 200 katılımcıdan oluşmaktaydı (100 AH, 100 SK). Hipokampus ve alt alanlarının (CA1, CA2–CA3, CA4–dentat girus, subikulum ve SR–SL–SM) segmentasyonu, volBrain platformunun HIPS modülü kullanılarak gerçekleştirildi. Sağlıklı kontrollerle karşılaştırıldığında, AH tanılı bireylerde hipokampal hacimde ve birden fazla hipokampal alt alanda orta ile büyük etki büyüklüklerine sahip anlamlı hacim azalmaları saptandı. Buna karşılık, hipokampal asimetri indeksleri çoklu karşılaştırmalar için düzeltme sonrasında grup düzeyinde farklılık göstermedi. Cinsiyete göre ayrıştırılmış analizler, AH tanılı kadın ve erkek katılımcılarda hipokampus ve alt alan hacim azalmalarının benzer örüntüler sergilediğini ortaya koydu. Bu bulgular, Alzheimer hastalığının yalnızca küresel hipokampal atrofi ile sınırlı kalmayıp, anatomik olarak özgül ve yaygın hipokampal alt alan hacim azalmaları ile ilişkili olduğunu ve bu etkilerin karıştırıcı değişkenler için düzeltme sonrasında da sürdüğünü göstermektedir. Alt alan düzeyindeki morfometrik analizler, AH’de hipokampal tutulumun grup düzeyinde betimlemesini sunmakta olup, klinik öneminin netleştirilebilmesi için boylamsal çalışmalara ihtiyaç vardır.

Anahtar Kelimeler

• Alzheimer hastalığı
• Hipokampus
• Manyetik Rezonans Görüntüleme
• Beyin Haritalama
• Cinsiyet özellikleri

Hippocampal Subfield Volume Alterations in Alzheimer’s Disease: A Sex-Stratified MRI Study in Older Adults

Öz

Alzheimer’s disease (AD) is a progressive neurodegenerative disorder in which hippocampal atrophy represents one of the earliest and most prominent structural alterations. Subfield-level morphometric analysis may therefore provide a more detailed characterization of hippocampal involvement in AD. The aim of this study was to characterize hippocampal and hippocampal subfield volume differences between individuals with AD and cognitively healthy older adults, including hemispheric asymmetry and sex-specific patterns, using automated subfield segmentation. In this cross-sectional neuroimaging study, hippocampal and hippocampal subfield volumes were examined in individuals with AD and cognitively healthy controls (HC) using structural MRI data from the OASIS-1 dataset. The analytic sample consisted of 200 participants aged 60 years and older (100 AD, 100 HC). Automated segmentation of the hippocampus and its subfields (CA1, CA2–CA3, CA4–dentate gyrus, subiculum, and SR–SL–SM) was performed using the HIPS module of the volBrain platform. Compared with HC, individuals with AD showed significant reductions in total hippocampal volume and in multiple hippocampal subfields, with medium to large effect sizes. In contrast, hippocampal asymmetry indices did not demonstrate consistent group-level differences after correction for multiple comparisons. Sex-stratified analyses revealed similar patterns of hippocampal and subfield volume reductions in female and male participants with AD. These findings indicate that AD is associated with widespread, anatomically specific hippocampal subfield volume reductions beyond global hippocampal atrophy and evident after adjustment for key confounders. Subfield-level morphometry provides a refined group-level description of hippocampal involvement in AD, although longitudinal studies are required to clarify its clinical relevance.

Anahtar Kelimeler

• Alzheimer Disease
• Hippocampus
• Magnetic Resonance Imaging
• Brain Mapping
• Sex Characteristics

Kaynakça

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