MoCA scores as predictor of volumetric differences between MCI patients and cognitively intact older adults

Purpose Mild cognitive impairment (MCI) refers to individuals not yet fulfilling the criteria of Alzheimer disease (AD) but who have impaired cognitive functions compared to other adults their age while activities of daily living remain intact [1]. It has been shown that about 60% of people with diagnosis of MCI progress to dementia in a 5-year period [2,3]. Loss of hippocampal volume is widely used as a biomarker of neurodegeneration in early stage of AD as it is one of the first sites where morphological changes occur [4]. However, volumetric declines due to MCI may not differ from those seen during the normal course of cognitive aging. Nevertheless, neuroimaging studies have demonstrated that the progression of hippocampal atrophy in patients with MCI is a highly precise to predict progression to AD [5]. Earlier studies have indicated that clinical features cross-sectionally correlate with regional or whole brain atrophy using magnetic resonance imaging (MRI) [6,7]. The Montreal Cognitive Assessment (MoCA) is brief screening tool for MCI and extensively used in a variety of contexts [8]. Despite wide application, neuroanatomical correlates associated with cognitive functions on the MoCA remain unclear. The purpose of our study was to examine whether lower scores on MoCA test would predict greater atrophy of the hippocampus and its subfields in MCI patients. Methods and materialsParticipants55 participants were chosen for this study consisting of 28 subjects with MCI (years range 60-80) and 27 cognitively intact older adults (years range 60-75). Participants with MCI were diagnosed using ICD-10 and Petersen criteria [2]. Exclusionary criteria for both groups included diagnosis of dementia, and/or MoCA score ≤16, MRI evidence of brain pathology such as tumor, stroke, or significant trauma, multiple sclerosis, psychiatric illness, history of drug abuse or alcoholism, and MRI contraindications. All participants signed an informed consent document prior to assessment. The study was approved by the local Medical Ethics Committee for Biomedical Research (No. BE-10-7). Neuropsychological testing Neuropsychological testing was done using MoCA which assesses different cognitive domains: attention and concentration, executive functions, memory, language, visuoconstructional skills, conceptual thinking, calculations, and orientation. The total possible score is 30 points; a score of 26 or above is considered normal [8].Magnetic resonance examination and volumetric analysis Magnetic resonance scans were performed using 3T scanner with a 32-channel receiver head coil. A high-resolution T1W structural image (TR = 2200 ms, TE = 2.48 ms, 0.9 mm slice thickness) was used to acquire a 3D magnetization prepared gradient echo. Volumetric analysis of hippocampus (both right and left) was performed using FreeSurfer v7.1.1 (Harvard, MA, USA, http://surfer.nmr.mgh.harvard.edu/). Hippocampal segmentation included hippocampal tail, subiculum head and body, cornu ammonis (CA)1 head and body, CA3 head and body, CA4 head and body, hippocampal fissure, presubiculum head and body, parasubiculum, molecular layer of hippocampus proper (ML-HP) head and body, granule cell and molecular layer of the dentate gyrus (GC-ML-DG) head and body, fimbria, hippocampal-amygdala transition area (HATA), whole hippocampal body, whole hippocampal tail and whole hippocampus (Figure 1). The participants in our study were divided into 2 groups. The first group included MCI patients with MoCA scores ≤25 (MCI ≤25) and healthy controls (HC) with MoCA scores ≥26 (HC ≥26). The second group consisted of MCI patients with MoCA scores ≤24 (MCI ≤24) and HC with MoCA scores ≥27 (MCI ≥27). Demographic characteristics of subjects are shown in Figure 2. Fig. 2 [...]. Selecting MoCA cutoff of 24 for MCI patients revealed statistically significant loss of volume in various hippocampal subfields compared to cognitively intact adults with MoCA scores ≥ 27 (Figure 3). Fig. 3 [...]. Hippocampal volume differences were not present when cutoffs of 25 for MCI patients and 26 for older adults with no MCI were selected (all p ≥ 0.05). Figure 3 presents only statistically significant volume differences of hippocampus and its subfields which became evident when MoCA cutoff of 24 for MCI and 27 for HC was selected. Conclusion MoCA cutoff score of 25 is usually considered to separate patients with MCI from cognitively intact older adults. However, the relationship between MoCA performance and structural brain changes is not fully understood. In our study reduced volume of hippocampus and its subfields became evident when MoCA cutoffs for MCI patients and older adults without MCI were set at 24 and 27, respectively. This could suggest that a cutoff score of 25 may not be sensitive enough to detect structural volumetric differences in hippocampus as a result of MCI.