Bipolar disorder among patients diagnosed with frontotemporal dementia

Abstract

Objective: Previous studies have documented manic and hypomanic symptoms in behavioral variant frontotemporal dementia (bvFTD), suggesting a relationship between bipolar disorder and bvFTD. Methods: The investigators conducted a literature review as well as a review of the psychiatric histories of 137 patients with bvFTD, and patients with a prior diagnosis of bipolar disorder were identified. The clinical characteristics of pa-tients’ bipolar disorder diagnosis, family history, features of bvFTD, and results from fluorodeoxyglucose positron emission tomography (FDG-PET), as well as autopsy find-ings, were evaluated. Results: Among the 137 patients, 14 (10.2%) had a psychiatric diagnosis of bipolar disorder, eight of whom met criteria for bipolar disorder (type I, N=6; type II, N=2) 6–12 years preceding onset of classic symptoms of progressive bvFTD. Seven of the eight patients with bipolar disorder had a family history of mood disorders, four had bitemporal predominant hypometabolism on FDG-PET, and two had a tauopathy involving temporal lobes on autopsy. Three additional patients with late-onset bipolar I disorder proved to have a nonprogressive disorder mimicking bvFTD. The remaining three patients with bvFTD had prior psychiatric symptoms that did not meet criteria for a diagnosis of bipolar disorder. The literature review and the findings for one patient further suggested a shared genetic mutation in some patients. Conclusions: Manic or hypomanic episodes years before other symptoms of bvFTD may be a prodrome of this de-mentia, possibly indicating anterior temporal involvement in bvFTD. Other patients with late-onset bipolar disorder ex-hibit the nonprogressive frontotemporal dementia pheno-copy syndrome. Finally, a few patients with bvFTD have a genetic predisposition for both disorders.