Leveraging Structural Magnetic Resonance Imaging in the Evaluation of Parahippocampal Region: An Aid to Alzheimer’s Diagnosis

Abstract

Introduction: Alzheimer’s, a prevalent degenerative dementia, succeeds Mild Cognitive Impairment (MCI), a variable precursor. The need to distinguish between them has grown with the advent of new disease-modifying treatments. Entorhinal cortex neurons collect sensory inputs from primary and association cortices, transmitting them to the hippocampus via the Perforant pathway-a White Matter (WM) tract in the parahippocampal region. Aim: To demonstrate the significance of Structural Magnetic Resonance Imaging (MRI) in distinguishing between individuals with Alzheimer’s Disease (AD) and those with MCI compared to a control group (CN). Materials and Methods: The present cross-sectional study was conducted in the Department of Radiodiagnosis at ACS Medical College and Hospital in Chennai, Tamil Nadu, India, from June 2022 to December 2022. Participants ranging in age from 45 to 82 years, underwent clinical evaluations and were subsequently classified based on their Mini-Mental State Examination (MMSE) scores. Those with MMSE scores below nine were diagnosed with AD, scores between 18 and 23 were indicative of MCI, and scores ranging from 24 to 30 signified inclusion in the healthy control group. The sample involved 30 healthy controls, 20 individuals with MCI, and 30 patients previously diagnosed with AD. Each participant underwent a comprehensive MRI scan. The diagnosis of AD and MCI was made using a novel technique that elaborates the dimensions of the parahippocampus on oblique coronal T1-weighted images. Results: The mean age of the participants was 65±5.5 years, ranging from 45 to 82 years. Among the 80 cases, 32 (40%) were males, and 48 (60%) were females. Ratios of the parahippocampal region were categorised as follows: ≤0.30 for AD, 0.31-0.39 for MCI, and ≥0.40 for cognitively normal individuals (CN). Patients with AD displayed ratios <0.3, corresponding to MMSE scores <9; those with MCI had ratios between 0.31 and 0.39, aligned with MMSE scores 18-23; while normal controls showed ratios ≥0.40, corresponding to MMSE scores 24-30. Conclusion: Using structural MRI to assess parahippocampal dimensions, effectively identifies neurological biomarkers linked to AD and MCI. This comprehensive approach not only enhances diagnostic precision but also lays the groundwork for pioneering treatment strategies aimed at tackling these cognitive conditions.

Keywords

• control group
• dementia
• mild cognitive impairment
• perforant pathway