Linguistic analysis in the differential diagnosis between cognitive impairment and functional cognitive impairment (depression): a pilot study.

The differential diagnosis between cognitive impairment and functional cognitive impairment (depression) is complex and difficult, especially in the early stages of the disease. The aim of our study was to test linguistic analysis as a diagnostic tool to support clinical, and test-based diagnoses for this differential diagnosis. We enrolled 13 patients, requesting a diagnostic consultation in a Alzheimer Evaluation Unit. A provisional diagnosis through a neuropsychological evaluation (interview and neuropsychological tests) was made at baseline, while a definitive diagnosis was provided after six months, or, if not possible, after 12 months. The linguistic analysis was performed at T0 in blind by a linguist. Patients' language was studied at linguistic (morphological, syntactical, lexical literal and textual) and conversational (verbiage and humor) level. The correspondence rate between the linguistic analysis at T0 and the definitive diagnosis was 76.9%, compared to 58.4% between the neuropsychological équipe analyses at T0 and definitive diagnosis. There is no single patognomonic phenomenon for cognitive impairment or depression, but rather a linguistic cluster can lead to a diagnosis with a fairly good reliability.