Brain activity during lower limb movements in Parkinson's disease patients with and without freezing of gait

In this study, we assessed brain functional MRI (fMRI) activity during a foot movement task in Parkinson's disease patients with (PD-FoG) and without freezing of gait (PD-noFoG). Twenty-seven PD patients (17 PD-FoG) and 18 healthy controls (HC) were recruited. PD-FoG cases were divided into nine with mild and eight with moderate FoG according to the FoG questionnaire. Patients underwent motor and neuropsychological evaluations. Both patients and controls performed an fMRI task consisting of alternate dorsal/plantar foot flexion movements according to an auditory stimulus of 0.5 Hz. PD-FoG and PD-noFoG patients were similar for all motor variables (except for the presence of FoG). PD-FoG patients performed worse in executive, attention and working memory, visuospatial, language and memory cognitive tests relative to HC and in executive and language functions compared with PD-noFoG patients. While PD-noFoG patients showed an increased recruitment of the fronto-striatal circuit relative to HC during the fMRI task, PD-FoG subjects showed an increased activity of the parieto-occipital and cerebellar areas compared with HC and a reduced basal ganglia activity when compared with PD-noFoG patients. Within the PD-FoG group, patients with more severe FoG scores showed a decreased recruitment of fronto-parietal areas relative to less severe cases. fMRI modifications correlated with FoG severity and with executive-attentive and visuospatial deficits in PD-FoG patients. This study revealed the presence of two different patterns of brain activity during a foot movement task in PD-FoG and PD-noFoG patients, suggesting a possible compensatory role of parieto-occipital networks to overcome the fronto-striatal failure in PD-FoG cases.