Freezing of gait in Parkinson's disease is associated with altered functional brain connectivity

•Freezing of gait (FOG) is a common gait abnormality in Parkinson's disease (PD).•Functional imaging correlates of FOG in patients with PD are not known.•We analyzed functional brain connectivity in PD patients with and without FOG.•Reduced interhemispheric connectivity of left parietal opercular cortex was a major finding.•Our study suggests altered functional brain connectivity in PD patients with FOG.

BackgroundPatients with Parkinson's disease (PD) may develop several gait disturbances during the course of illness and Freezing of gait (FOG) is one of them. Several neuroimaging studies have been conducted to identify the neural correlates of FOG but results have not been uniform. Resting state functional MRI (rs-fMRI) is relatively less explored in PD patients with FOG. This study aims to compare the whole brain resting state connectivity of PD patients with and without FOG using rs-fMRI.Methodsrs-fMRI was obtained for 28 PD patients (15 with and 13 patients without FOG) who were matched for various demographic and clinical characteristics. Seed to voxel analysis was performed at whole brain level and compared between the two groups.ResultsWhen compared to patients without FOG, the patients with FOG had reduced functional connectivity across multiple seeds. Major finding was reduced inter-hemispheric connectivity of left parietal opercular cortex with multiple regions of the brain primarily involving the primary somatosensory and auditory areas, which also negatively correlated with the FOGQ scores.ConclusionOur findings suggest that alterations in the resting state functional connectivity of the opercular parietal cortex may be one of the substrates of FOG. Reduced interhemispheric connectivity probably is the reason for impairment of control and coordination in bilateral leg movements while walking.