Phonemic Verbal Fluency and Midbrain Atrophy in Progressive Supranuclear Palsy

Background: The neuropsychological profile of progressive supranuclear palsy (PSP) patients is mainly characterized by executive dysfunction, but the relationship between the latter and midbrain atrophy is still unclear. Objective: The aims of the study were to investigate which test evaluating executive functioning is more frequently impaired in PSP patients and to evaluate the relationship between midbrain-based MRI morphometric measures and executive dysfunction. Methods: PSP patients who had undergone a neuropsychological battery assessing executive functioning with the Frontal Assessment Battery (FAB), the phonemic verbal fluency F-A-S, the Raven's Progressive Colored Matrix, and the Stroop word colors test (time and errors) were enrolled in the study. A group of Parkinson's disease (PD) patients matched by age, sex, education, and global cognitive status was selected. All the enrolled patients also underwent a volumetric T1-3D brain MRI. Results: Thirty-five PSP patients and 35 PD patients were enrolled. Patients with PSP as compared to patients with PD showed a significant greater impairment in verbal fluency (16.0±7.9 and 23.4±8.7 words/180 s; p<0.001) and a significant lower score at the FAB total score (11.5±3.8 and 13.7±3.4; p=0.013). Midbrain area was significantly smaller in PSP patients than in PD patients (83.9±20.1 and 134.5±19.9 mm2; p<0.001). In PSP patients, a significant positive correlation between verbal fluency and the midbrain area (r=0.421; p=0.028) was observed. Conclusion: Our findings suggest that the phonemic verbal fluency is among the most frequently impaired executive functions in PSP patients and is strongly correlated to midbrain atrophy.