MAPT and early-onset autosomal dominant Alzheimer disease: Recent updated Braak staging of Alzheimer’s disease (AD) implicates the brainstem as the first site of tau-related pathology, with the locus coeruleus (LC) the first nucleus to demonstrate signs of pretangles (i.e., precursors to neurofibrillary tangle pathology) (Braak and Del Tredici 2015).