Does a volume reduction of the parietal lobe contribute to freezing of gait in Parkinson's disease?

BACKGROUND: Freezing of gait (FOG) is as a brief, episodic absence or marked reduction of forward progression of the feet despite the intention to walk. Structural neuroimaging studies on FOG in PD using volumetric techniques yielded variable and partially conflicting findings, probably reflecting the heterogeneity and complexity of the phenomenon. The aim of this study was to further explore the differences in local gray matter (GM) volume in patients with PD with and without FOG by using Voxel-Based Morphometry (VBM). MATERIALS AND METHODS: We enrolled 26 patients (7 women and 19 men) with a diagnosis of PD in stable treatment with dopaminergic therapy. Thirteen patients classified as FOG+ were matched with thirteen non-freezer (FOG-) PD patients. All 26 participants underwent a detailed neuropsychological assessment as well as a VBM analysis derived from T1 weighted 3T MRI. RESULTS: The patient groups did not significantly differ for age, disease duration, H&Y stage, UPDRS part-III or educational attainment. No significant differences of cognitive profile emerged. PD-FOG+ patients showed a pattern of relative GM atrophy in left posterior parietal gyrus compared with PD-FOG-. DISCUSSION: Our results suggest that a specific pattern of cortical volume reduction involving posterior parietal cortex contributes to the occurrence of FOG in PD. These data agree with the growing body of evidence considering the parietal posterior cortex as an associative area involved in spatial control of motor behavior, par-taking in response selection to sensory evaluation.