Does Side of Onset Influence the Pattern of Cerebral Atrophy in Parkinson's Disease?

Microstructural Degeneration of the Corpus Callosum in Parkinson's Disease with Unilateral Onset: A Free-Water Imaging Study

Background: Motor symptom laterality is an important clinical feature of PD that not only manifests as lateral limb dysfunction but also affects the nonmotor symptoms and the prognosis in PD patients. Previous studies suggested that the compensatory mechanisms in the dominant hemisphere of the brain may be an underlying explanation. The corpus callosum (CC) is the largest fiber connecting the two hemispheres of the brain. Considering the CC as the pointcut may help elucidate the mechanisms underlying how motor symptom laterality affects nonmotor symptoms and prognosis in PD patients. Purpose: To explore microstructural degeneration of the CC in PD patients with unilateral motor symptom onset and evaluate its relationship with motor and nonmotor performance. Methods: In this study, 201 right-handed PD patients with unilateral motor symptom onset (91 patients with left-onset [LPD] and 110 with right-onset [RPD]) and 100 right-handed healthy controls (HC) were included. A bitensor model of diffusion tensor imaging was applied to analyze free water (FW) as well as fractional anisotropy (FAT) and mean diffusivity (MDT) of the tissue compartment after correcting FW. These provide noninvasive in vivo measures of white matter integrity and pathological processes including atrophy, edema, and neuroinflammation. The CC was divided into halves along the median sagittal line, and each half was manually divided into five functional segments. A total of 10 subregions were obtained and numbered in sequence. The laterality index was calculated to quantify the asymmetry of the CC and its segments. A general linear model was used to compare among groups, and partial correlation analysis was performed to explore the relationships between the diffusion parameters of CC subregions and clinical manifestations. Results: Compared with HC, FW and FAT of the bilateral CC were decreased in the LPD group, whereas MDT in the right hemisphere was increased. In the LPD group, FAT of all CC subregions except for subregions 1, 3, and 6 was significantly lower than HC, and MDT in the anterior and posterior segments of the CC (CC subregions 1, 5-7, and 10) was significantly higher than HC. In the RPD group, FAT of subregion 7 was significantly decreased and MDT was increased than HC. Laterality index analysis of the CC indicated significant interhemispheric FAT asymmetry in the anterior and middle in the RPD group, with a more significant reduction in the right CC. Moreover, degeneration of the CC and its subregions was related to motor and nonmotor symptoms in PD. Conclusions: More extensive CC damage was observed in the LPD group than in the RPD group. Additional, asymmetrical damage was observed in the anterior and middle segments of the CC in the RPD group, suggesting that differences in callosal degeneration patterns may be a potential mechanism underlying how asymmetrical motor symptoms affect the nonmotor symptoms and prognosis in PD.

Does the side of onset influence symptom severity in Parkinson's disease? A systematic review and meta-analysis

Parkinson's disease (PD) is a neurodegenerative movement disorder characterized by motor symptoms that initially manifest unilaterally. Whilst some studies indicate that right-side onset is associated with greater symptom severity, others report no differences between right-side and left-side onset patients. The present meta-analysis was thus designed to reconcile inconsistencies in the literature and determine whether side of onset affects PD symptom severity. Following the PRISMA guidelines 1013 studies were initially identified in database and grey literature searches; following title and abstract, and full text, screening 34 studies met the stringent inclusion criteria (n = 2210). Results of the random-effects meta-analysis indicated no difference in symptom severity between PD patients with left-side (n = 1104) and right-side (n = 1106) onset. As such, the meta-analysis suggests that the side of onset should not be used to predict symptom trajectory or to formulate prognoses for PD patients. The current meta-analysis was the first to focus on the relationship between the side of onset and symptom severity in PD. However, the studies included were limited by the common exclusion of left-handed participants. Future research would benefit from exploring other factors that may influence symptom severity and disease progression in PD, such as asymmetric loss of nigrostriatal dopaminergic neurons.

Effects of spinal cord stimulation on voxel-based brain morphometry in patients with failed back surgery syndrome

OBJECTIVE

Despite the clinical effectiveness of Spinal Cord Stimulation (SCS), potential structural brain modifications have not been explored. Our aim was to identify structural volumetric changes during subsensory SCS, in patients with Failed Back Surgery Syndrome (FBSS).

METHODS

In this cohort study, twenty-two FBSS patients underwent a magnetic resonance imaging protocol before SCS and 3 months after SCS. Clinical parameters were correlated with volumetric changes, calculated with voxel-based morphometry.

RESULTS

After 3 months, a significant volume decrease was found in the inferior frontal gyrus, precuneus, cerebellar posterior lobe and middle temporal gyrus. Significant increases were found in the inferior temporal gyrus, precentral gyrus and the middle frontal gyrus after SCS. Additionally, significant increases in volume of superior frontal and parietal white matter and a significant decrease in volume of white matter underlying the premotor/middle frontal gyrus were revealed after SCS. A significant correlation was highlighted between white matter volume underlying premotor/middle frontal gyrus and leg pain relief.

CONCLUSIONS

This study revealed for the first time that SCS is able to induce volumetric changes in gray and white matter, suggesting the reversibility of brain alterations after chronic pain treatment.

SIGNIFICANCE

Volumetric brain alterations are observable after 3 months of subsensory SCS in FBSS patients.

Morphological Characterization of Functional Brain Imaging by Isosurface Analysis in Parkinson’s Disease

Finding new biomarkers to model Parkinson’s Disease (PD) is a challenge not only to help discerning between Healthy Control (HC) subjects and patients with potential PD but also as a way to measure quantitatively the loss of dopaminergic neurons mainly concentrated at substantia nigra. Within this context, this work presented here tries to provide a set of imaging features based on morphological characteristics extracted from I[Formula: see text]-Ioflupane SPECT scans to discern between HC and PD participants in a balanced set of [Formula: see text] scans from Parkinson’s Progression Markers Initiative (PPMI) database. These features, obtained from isosurfaces of each scan at different intensity levels, have been classified through the use of classical Machine Learning classifiers such as Support-Vector-Machines (SVM) or Naïve Bayesian and compared with the results obtained using a Multi-Layer Perceptron (MLP).

The proposed system, based on a Mann–Whitney–Wilcoxon U-Test for feature selection and the SVM approach, yielded a [Formula: see text] balanced accuracy when the performance was evaluated using a [Formula: see text]-fold cross-validation. This proves the reliability of these biomarkers, especially those related to sphericity, center of mass, number of vertices, 2D-projected perimeter or the 2D-projected eccentricity, among others, but including both internal and external isosurfaces.

Lateralisation in Parkinson disease

Asymmetry of dopaminergic neurodegeneration and subsequent lateralisation of motor symptoms are distinctive features of Parkinson's disease compared to other forms of neurodegenerative or symptomatic parkinsonism. Even 200 years after the first description of the disease, the underlying causes for this striking clinicopathological feature are not yet fully understood. There is increasing evidence that lateralisation of disease is due to a complex interplay of hereditary and environmental factors that are reflected not only in the concept of dominant hemispheres and handedness but also in specific susceptibilities of neuronal subpopulations within the substantia nigra. As a consequence, not only the obvious lateralisation of motor symptoms occurs but also patterns of associated non-motor signs are defined, which include cognitive functions, sleep behaviour or olfaction. Better understanding of the mechanisms contributing to lateralisation of neurodegeneration and the resulting patterns of clinical phenotypes based on bilateral post-mortem brain analyses and clinical studies focusing on right/left hemispheric symptom origin will help to develop more targeted therapeutic approaches, taking into account subtypes of PD as a heterogeneous disorder.