Multimodal MRI and tau PET findings from the Autosomal Dominant Alzheimer’s disease cohort caused by the A431E PSEN1 Jalisco mutation

Abstract

AbstractBackgroundThe A431E mutation in PSEN1 is a cause of Autosomal Dominant Alzheimer’s disease (ADAD) that represents a founder effect, apparently arising from the state of Jalisco, Mexico, with over 100 superficially distinct families being affected. The median age of symptom onset is 41 years, with about 40% of cases having an atypical presentation of substantial spastic paraparesis. This study aimed to identify the neuroimaging features associated with the A431E PSEN1 Jalisco mutation to elucidate its pathophysiology and to inform future clinical studies.MethodThirty‐one participants with or known to be at‐risk for the A431E PSEN1 mutation were enrolled in a comprehensive genetic, clinical, and imaging protocol including MRI and flortaucipir PET scans. Diffusion MRI and flortaucipir PET studies were conducted on sub‐samples of the cohort along with appropriate control participants.ResultPeak flortaucipir standard uptake value ratio (SUVR) among A431E mutation carriers was predominantly in the lateral parietal cortices relative to the medial temporal lobes with disproportionate signal in motor and sensory cortex relative to persons with late onset AD. Flortaucipir SUVR in 6 brain regions (i.e., medial orbitofrontal, caudal and rostral anterior cingulate, parahippocampal, precuneus, and lateral occipital) were associated with neuropsychiatric symptoms in persons with or at risk for the A431E PSEN1 mutation. Among 21 A431E PSEN1 mutation carriers with available diffusion MRI images, the Ashworth score of spastic paraparesis correlated with mean diffusivity in several brain regions, particularly left inferior parietal, superior parietal, and paracentral lobules (r’s>0.8, p’s< 0.001). In a subset of 10 clinically impaired A431E PSEN1 mutation carriers, mean diffusivity in white matter tracts underlying multiple cortical areas was higher relative to 8 impaired persons with late onset AD or ADAD mutations that do not cause spastic paraparesis.ConclusionThe pattern of flortaucipir distribution was atypical with disproportionate involvement of sensorimotor areas and parietal cortex. Higher flortaucipir signal was associated with more neuropsychiatric symptoms. Microstructural changes in white matter were more pronounced in persons with the A431E PSEN1 mutation and likely underlie the associated spastic paraparesis. The distinct neuroimaging features and associated neuropsychiatric manifestations observed in this cohort highlight the importance of comprehensively characterizing heterogeneous AD subtypes.