NEFL and Atrophy: Taken together, these results are compatible with a model where non‐Aβ and non‐tau pathologies (which may include vascular pathology, TDP‐43, Lewy bodies and other pathologies) are associated with high NFL levels, expansion of ventricles, and some degree of hippocampal atrophy at baseline, but the progressive hippocampal volume loss seen in people harboring Aβ pathology is independent of NFL and is instead reflected by increased CSF levels of T‐tau and Ng.