Patients with the akinetic-rigid (AR) subtype of Parkinson disease (PD) have widespread decreased local gyrification indices (LGI) compared with healthy controls (HCs), according to study findings published in Neurology.
Previous data have indicated distinct cerebellar morphologic alterations for the 2 subtypes of PD (AR and tremor-dominant [TR]). The study researchers sought to determine whether the 2 subtypes are associated with different patterns of cortical gyrification changes and whether those changes are related to white matter (WM) abnormalities.
Within the cohort of PD without dementia (n=102), patients were divided into TD subtype (n=26) and AR subtype (n=64), and mixed subtype (n=12). 56 HCs participated in the study. There were significantly more males in the AR subtype (males, 40; females, 24) than in the other groups (TD: males, 8; females, 18; HC: males, 19; females, 37).
The patients underwent the unified PD Rating Scale (UPDRS), the Hoehn and Yahr disability scale (H&Y), the Mini-Mental State Examination (MMSE), the Montreal Cognitive Assessment (MoCA) test, and brain magnetic resonance imaging (MRI) scans when they were clinically off medication.
Study researchers used LGI to measure cortical gyrification. They compared LGI maps at vertex level among the groups. Each between-group contrast was initially thresholded at a conservative vertex-wise P <.001 and corrected at cluster level for comparisons. Fractional anisotropy (FA) maps were compared at voxel level among the groups.
Patients with AR subtype showed significantly lower LGI in widespread cortical regions, including the bilateral precentral gyrus, medial and lateral orbitofrontal cortex, inferior and superior parietal lobule, precuneus, posterior cingulate cortex, cuneus and nearby visual cortices, middle and superior temporal gyrus, left inferior, middle and superior frontal gyrus, left anterior cingulate cortex, right postcentral gyrus, and right supramarginal gyrus.
Findings indicated that LGI of a significant cluster, involving the left inferior and middle frontal gyrus, was correlated with the MMSE and H&Y score, respectively, in patients with AR subtype.
Compared with HC patients, patients with the AR subtype displayed significantly lower FA in multiple WM tracts, involving bilaterally the corticospinal tract, inferior longitudinal fasciculus, inferior fronto-occipital fasciculus, superior longitudinal fasciculus, forceps minor, forceps major, and anterior thalamic radiation.
Mean LGI of clusters with LGI decrease was positively correlated with mean FA of the WM with FA decrease in patients with the AR subtype.
Limitations of the study included a relatively small sample size of patients with TD subtype compared with those with AR subtype and HCs, differences in gender distribution among the groups, the cross-sectional nature of the study, and the existence of other subtype classifications.
Study researchers concluded that their findings “suggest that cortical gyrification changes in PD are motor phenotype-specific and are possibly mediated by the microstructural abnormalities of the underlying WM tracts.”
Tang X, Zhang Y, Liu D, Hu Y, Jiang L, Zhang J. Association of gyrification pattern, white matter changes, and phenotypic profile in patients with Parkinson Disease. Neurol. Published online March 25, 2021. doi:10.1212/WNL.0000000000011894