Frontal Pole Hypometabolism Linked to Reduced Prosocial Sexual Behaviors in Frontotemporal Dementia and Corticobasal Syndrome

Background: Changes in sexual behaviors in frontotemporal dementia (FTD) are common and multifaceted, but not well characterized. Objective: To characterize changes in sexual behaviors and intimacy in FTD compared to corticobasal syndrome (CBS) and normal controls (NC), and to evaluate the neuroanatomical associations of these changes. Methods: Spouses of 30 FTD patients, 20 CBS patients, and 35 NC completed the Sexual Symptoms in Neurological Illness and Injury Questionnaire (SNIQ), which captures changes in sexual interest, inappropriate sexual behaviors, and prosocial sexual behaviors. 25 patients with FTD and 14 patients with CBS also received 18-flouorodeoxyglucose positron-emission topography (18FDG-PET) scans to determine the metabolic changes associated with these symptoms. Results: FTD patients showed a greater increase in inappropriate sexual behaviors than CBS patients [p = 0.009] and NC [p < 0.001] and a greater decrease in prosocial sexual behaviors than CBS patients [p = 0.026] and NC [p < 0.001]. Groups did not differ in change in sexual interest. Among both patient groups, the most common change was decreased prosocial sexual behaviors p < 0.01. Hypometabolism in Brodmann's Area 10 (BA10), within the right frontal pole, correlated with decreased prosocial sexual behaviors [p(FWE-corr) <0.05, k = 44]. No anatomical associations were found with other sexual changes. Conclusion: Decreased prosocial sexual behavior was associated with hypometabolism in BA 10, an area tied to social knowledge and theory of mind, supporting the idea that changes reflect social-cognitive deficits due to frontal dysfunction.