Early functional MRI changes in a prodromal semantic variant of primary progressive aphasia: a longitudinal case report

Objective: To assess longitudinal patterns of brain functional MRI (fMRI) activity in a case of prodromal semantic variant of a primary progressive aphasia (svPPA). Methods: Clinical, cognitive and neuroimaging data (T1-weighted and task-based fMRI during silent naming [SN] and object knowledge [OK]) were obtained at baseline, month 8 and month 16 from a 49-year-old lady presenting with anomias and evolving to overt svPPA in 8 months. Results: At baseline, the patient showed isolated anomias and mild left anterior temporal pole atrophy. During SN–fMRI, she showed bilateral temporal and left inferior frontal gyri (iFG) activations. During OK–fMRI, we observed normal performance and the recruitment of bilateral posterior hippocampi, iFG and left middle orbitofrontal gyrus (mOFG). At month 8, the patient received a diagnosis of svPPA and showed isolated right iFG activity during SN–fMRI, and a borderline performance during OK–fMRI together with a disappearance of mOFG recruitment. At the last visit (after 7-month language therapy), the patient showed a stabilization of naming disturbances, and, compared to previous visits, an increased left iFG recruitment during SN–fMRI. During OK–fMRI, she performed abnormally and did not show the activity of mOFG and iFG. Across all visits, brain atrophy remained stable. Conclusions: This case report showed longitudinal fMRI patterns during semantic-related tasks from prodromal to overt svPPA. Frontal brain recruitment may represent a compensatory mechanism in patients with early svPPA, which is likely to be reinforced by language-therapy. Brain fMRI is more sensitive compared with structural MRI to detect progressive brain changes associated with disease and treatment.