Frontotemporal dementia refers to a dementia syndrome in which middle-aged and elderly patients slowly develop personality changes, speech disorders, and abnormal behaviors. Neuroimaging shows atrophy of the frontotemporal lobes, but pathological examinations do not reveal Pick bodies and Pick cells. Pick disease is difficult to distinguish from frontotemporal dementia in the absence of pathological evidence. Currently, many advocate that Pick disease be classified as frontotemporal dementia. Clinical studies have found that frontotemporal dementia may be the most common neurodegenerative dementia syndrome after Alzheimer's disease, accounting for about 1/4 of all dementia patients. Some people believe that frontotemporal dementia actually includes Pick disease with Pick bodies in pathology, as well as other Pick syndromes with similar clinical manifestations but without Pick bodies, the latter including frontal dementia and primary progressive aphasia.