High Frequency of Crossed Aphasia in Dextral in an Italian Cohort of Patients with Logopenic Primary Progressive Aphasia

Background: Primary progressive aphasia (PPA) has been described as a neurodegenerative language disorder mainly affecting the left hemisphere. Few cases of right hemisphere damage in right-handed PPA subjects have been reported. This condition, named crossed aphasia in dextral (CAD), is relatively rare and probably related to an alteration during neurodevelopment of language networks. Objective: To explore the prevalence of CAD in an Italian cohort of 68 PPA patients, in order to evaluate whether right hemisphere language lateralization could be a risk factor for PPA. Methods: Clinical-demographic and cerebral [F-18]-fluorodeoxyglucose positron emission tomography ([F-18]FDG-PET) scan were analyzed, resulting in 23 logopenic variant (lvPPA) patients, 26 non-fluent variant (nfvPPA) patients, and 19 semantic variant (svPPA) patients. SPM single subject routine was performed for diagnostic purposes in order to identify the hypometabolic pattern of each patient. Based on brain metabolic profile, PPA patients were divided in right and left lvPPA, nfvPPA, and svPPA. [F-18]FDG-PET group analyses were performed with SPM two-sample t-test routine. Results: 26% of lvPPA cases were identified as CAD based on right hypometabolic pattern. CAD patients did not differ from left lvPPA regarding demographic features and general cognitive performance; however, they performed better in specific working memory tasks and showed brain hypometabolism limited to the superior, middle, and supramarginal temporal gyri. Conclusion: Atypical lateralization of language function could determine a vulnerability of the phonological language loop and in that way could be a risk factor for lvPPA.