The most common types of dementia are Alzheimer disease Vascular dementia Dementia with Lewy bodies Frontotemporal dementias HIV-associated dementia Dementia also occurs in patients with Parkinson disease, Huntington disease, progressive supranuclear palsy, Creutzfeldt-Jakob disease, Gerstmann-Sträussler-Scheinker syndrome, other prion disorders, neurosyphilis, a traumatic brain injury (eg, chronic traumatic encephalopathy), or certain brain tumors located in cortical or subcortical brain areas involved in cognition.