The Claustrum and Its Role in Neurodegenerative Diseases-A Narrative Review.

The claustrum is a thin gray matter structure with extensive cortical connections, involved in mechanisms of consciousness and salience processing. Numerous studies have suggested that the claustrum may play an important role in neurodegenerative diseases. In this work, we aimed to review and summarize current evidence on the involvement of the claustrum in neurodegenerative disorders. Our review was conducted following PRISMA 2020 guidelines using databases including Google Scholar, MEDLINE, and Scopus. A total of 2316 studies were screened, and 135 were included in the full-text analysis, focusing on claustral structural changes, connectivity alterations, and their impact on clinical symptoms in neurodegenerative diseases. A total of 30 studies met the inclusion criteria. The strongest pathological evidence of claustral involvement was observed in Parkinson's disease and dementia with Lewy bodies and Alzheimer's disease. Claustral abnormalities were also reported in frontotemporal dementia, in poststroke patients, and in multiple sclerosis. Alterations of the claustrum correlated with clinical symptoms such as cognitive impairment. The claustrum is a structure involved in multiple neurodegenerative disorders. As a network node between cortical regions, it is critically involved in numerous neurodegenerative disorders.