Case Series of Right-Hemisphere Nonfluent Variant of Primary Progressive Aphasia.

Background and purpose: Nonfluent variant primary progressive aphasia (nfvPPA) is a neurodegenerative disorder characterized by the progressive deterioration of language functions that typically appears with atrophy predominating in the left peri-insular region (left-nfvPPA) on imaging. While both left-dominant and right-dominant presentations have been reported in semantic variant primary progressive aphasia, the other language presentation of frontotemporal dementia, no case series of nfvPPA with predominantly right-sided atrophy of the peri-insular region (right-nfvPPA) have been reported previously. This study explored whether such entities exist and what their clinical features might be.

Methods: A retrospective review of brain imaging data obtained from an established cohort of patients diagnosed with nfvPPA was performed to identify right-nfvPPA cases, followed by detailed analyses of their clinical profiles and imaging results compared to matched typical left-nfvPPA cases and healthy control group.

Results: Four of 55 individuals meeting the consensus diagnostic criteria for nfvPPA demonstrated right-nfvPPA. No significant differences were noted in their clinical and neuropsychological profiles. Detailed imaging analyses demonstrated that the individuals with right-nfvPPA did not demonstrate atrophy of the anterior cingulate gyrus, unlike those in the left-nfvPPA group.

Conclusions: This study has revealed several intriguing differences between right-nfvPPA and left-nfvPPA, particularly in the prevalence of impairments in motor speech and naming as well as imaging differences. These findings warrant further exploration in a larger cohort to improve our understanding of neural network organization and its dysfunction in neurodegenerative disorders.