Young‐onset dementia	Magnetic resonance imaging: areas affected	Positron emission tomography: areas affected	Other imaging modalities
Alzheimer disease	Hippocampus Medial temporal lobes	Precuneus Posterior cingulate Parietotemporal	Amyloid‐β positron emission tomography
Posterior cortical atrophy	Posterior/occipital regions	Parietooccipital cortices	Amyloid‐β positron emission tomography
Behavioural variant frontotemporal dementia	Frontal (medial, orbitofrontal, anterior insula)	Frontotemporal
Semantic frontotemporal dementia	Anterior temporal	Frontal midline structure (cingulate, orbitofrontal and anterior medial cortices, insula)
Progressive non‐fluent aphasia		Frontotemporal region of left side: inferior frontal region, dorsolateral prefrontal, Broca and Wernicke area, and inferior temporal regions