Prefrontal thickening in PD with levodopa-induced dyskinesias: new evidence from cortical thickness measurement.

PURPOSE: Neurodegenerative processes in Parkinson's disease (PD) patients with levodopa-induced dyskinesias (LID) are still a matter of debate. Recently, we demonstrated that this clinical phenotype is associated with an abnormal gray matter increase in the prefrontal cortex when compared to PD without LID. This evidence was found by using voxel-based morphometry (VBM). However, VBM may not be the most appropriate procedure to assess cortical pathology, since its normalization/smoothing steps reduce the ability to anatomically characterize sulci and gyri. The aim of this study is to better delineate the LID-related anatomical abnormalities by using an advanced neuroimaging method that provides a direct and objective measure of the cortical morphology.
METHODS: Surface-based investigation of cortical mantle (cortical thickness) was carried out by using Freesurfer in two groups of treated PD patients with LID (no 29) and without LID (no 30), and one group of age- and sex-matched controls (no 24).
RESULTS: Cortical thickness analysis revealed a pronounced increase of thickness in the right inferior frontal sulcus in PD patients with LID with respect to PD patients without LID. DISCUSSION: The current study confirms our previous morphological findings on the role of the prefrontal cortex in the pathophysiology of LID and delineates with more precision the anatomical abnormalities characterizing this clinical phenotype.