Alterations of Regional Homogeneity in the Mild and Moderate Stages of Parkinson's Disease

Exploring brain asymmetry in early-stage Parkinson's disease through functional and structural MRI

OBJECTIVE

This study explores the correlation between asymmetrical brain functional activity, gray matter asymmetry, and the severity of early-stage Parkinson's disease (PD).

METHODS

Ninety-three early-stage PD patients (ePD, H-Y stages 1-2.5) were recruited, divided into 47 mild (ePD-mild, H-Y stages 1-1.5) and 46 moderate (ePD-moderate, H-Y stages 2-2.5) cases, alongside 43 matched healthy controls (HCs). The study employed the Hoehn and Yahr (H-Y) staging system for disease severity assessment and utilized voxel-mirrored homotopic connectivity (VMHC) for analyzing brain functional activity asymmetry. Asymmetry voxel-based morphometry analysis (VBM) was applied to evaluate gray matter asymmetry.

RESULTS

The study found that, relative to HCs, both PD subgroups demonstrated reduced VMHC values in regions including the amygdala, putamen, inferior and middle temporal gyrus, and cerebellum Crus I. The ePD-moderate group also showed decreased VMHC in additional regions such as the postcentral gyrus, lingual gyrus, and superior frontal gyrus, with notably lower VMHC in the superior frontal gyrus compared to the ePD-mild group. A negative correlation was observed between the mean VMHC values in the superior frontal gyrus and H-Y stages, UPDRS, and UPDRS-III scores. No significant asymmetry in gray matter was detected.

CONCLUSIONS

Asymmetrical brain functional activity is a significant characteristic of PD, which exacerbates as the disease severity increases, resembling the dissemination of Lewy bodies across the PD neurological framework. VMHC emerges as a potent tool for characterizing disease severity in early-stage PD.

Altered perivascular spaces in subcortical white matter in Parkinson's disease patients with levodopa-induced dyskinesia

Dilated perivascular spaces (PVS) have emerged as a pathological hallmark in various neurological conditions, including Parkinson's disease (PD). Levodopa-induced dyskinesia (LID), an intractable motor complication of PD, remains enigmatic regarding the distribution patterns of PVS. Our objective was to scrutinize the percent PVS (pPVS) changes within PD patients with LID (PD-LID). In total, 132 individuals were enrolled, including PD-LID (n = 42), PD patients without LID (PD-nLID, n = 45), and healthy controls (HCs, n = 45). Employing an automated approach for PVS quantification based on structural magnetic resonance imaging, we comprehensively evaluated total pPVS in subcortical white matter globally and regionally. A significant increase in global pPVS was observed in PD patients versus HCs, particularly evident in PD-LID relative to HCs. Within the PD-LID group, elevated pPVS was discerned in the right inferior frontal gyrus region (rIFG) (pars opercularis), contrasting with PD-nLID and HCs. Moreover, PD patients exhibited increased pPVS in bilateral superior temporal regions compared to HCs. Notably, pPVS in the rIFG positively correlated with dyskinetic symptoms and could well identify LID. Our findings unveiled PVS alternations in subcortical white matter in PD-LID at both global and regional levels, highlighting the increased pPVS in rIFG as a prospective imaging marker for LID.

Behavioral, neural and ultrastructural alterations in a graded-dose 6-OHDA mouse model of early-stage Parkinson's disease

Studying animal models furthers our understanding of Parkinson's disease (PD) pathophysiology by providing tools to investigate detailed molecular, cellular and circuit functions. Different versions of the neurotoxin-based 6-hydroxydopamine (6-OHDA) model of PD have been widely used in rats. However, these models typically assess the result of extensive and definitive dopaminergic lesions that reflect a late stage of PD, leading to a paucity of studies and a consequential gap of knowledge regarding initial stages, in which early interventions would be possible. Additionally, the better availability of genetic tools increasingly shifts the focus of research from rats to mice, but few mouse PD models are available yet. To address these, we characterize here the behavioral, neuronal and ultrastructural features of a graded-dose unilateral, single-injection, striatal 6-OHDA model in mice, focusing on early-stage changes within the first two weeks of lesion induction. We observed early onset, dose-dependent impairments of overall locomotion without substantial deterioration of motor coordination. In accordance, histological evaluation demonstrated a partial, dose-dependent loss of dopaminergic neurons of substantia nigra pars compacta (SNc). Furthermore, electron microscopic analysis revealed degenerative ultrastructural changes in SNc dopaminergic neurons. Our results show that mild ultrastructural and cellular degradation of dopaminergic neurons of the SNc can lead to certain motor deficits shortly after unilateral striatal lesions, suggesting that a unilateral dose-dependent intrastriatal 6-OHDA lesion protocol can serve as a successful model of the early stages of Parkinson's disease in mice.

Neural functional network of early Parkinson's disease based on independent component analysis

This work explored neural network changes in early Parkinson's disease: Resting-state functional magnetic resonance imaging was used to investigate functional alterations in different stages of Parkinson's disease (PD). Ninety-five PD patients (50 early/mild and 45 early/moderate) and 37 healthy controls (HCs) were included. Independent component analysis revealed significant differences in intra-network connectivity, specifically in the default mode network (DMN) and right frontoparietal network (RFPN), in both PD groups compared to HCs. Inter-network connectivity analysis showed reduced connectivity between the executive control network (ECN) and DMN, as well as ECN-left frontoparietal network (LFPN), in early/mild PD. Early/moderate PD exhibited decreased connectivity in ECN-LFPN, ECN-RFPN, ECN-DMN, and DMN-auditory network, along with increased connectivity in LFPN-cerebellar network. Correlations were found between ECN-DMN and ECN-LFPN connections with UPDRS-III scores in early/mild PD. These findings suggest that PD progression involves dysfunction in multiple intra- and inter-networks, particularly implicating the ECN, and a wider range of abnormal functional networks may mark the progression of the disease.

Drooling disrupts the brain functional connectivity network in Parkinson's disease

AIMS

This study aimed to investigate the causal interaction between significant sensorimotor network (SMN) regions and other brain regions in Parkinson's disease patients with drooling (droolers).

METHODS

Twenty-one droolers, 22 PD patients without drooling (non-droolers), and 22 matched healthy controls underwent 3T-MRI resting-state scans. We performed independent component analysis and Granger causality analysis to determine whether significant SMN regions help predict other brain areas. Pearson's correlation was computed between imaging characteristics and clinical characteristics. ROC curves were plotted to assess the diagnostic performance of effective connectivity (EC).

RESULTS

Compared with non-droolers and healthy controls, droolers showed abnormal EC of the right caudate nucleus (CAU.R) and right postcentral gyrus to extensive brain regions. In droolers, increased EC from the CAU.R to the right middle temporal gyrus was positively correlated with MDS-UPDRS, MDS-UPDRS II, NMSS, and HAMD scores; increased EC from the right inferior parietal lobe to CAU.R was positively correlated with MDS-UPDRS score. ROC curve analysis showed that these abnormal ECs are of great significance in diagnosing drooling in PD.

CONCLUSION

This study identified that PD patients with drooling have abnormal EC in the cortico-limbic-striatal-cerebellar and cortio-cortical networks, which could be potential biomarkers for drooling in PD.

Abnormal intra- and inter-network functional connectivity of brain networks in early-onset Parkinson's disease and late-onset Parkinson's disease

Objective

The purpose of this study is to look into the altered functional connectivity of brain networks in Early-Onset Parkinson's Disease (EOPD) and Late-Onset Parkinson's Disease (LOPD), as well as their relationship to clinical symptoms.

Methods

A total of 50 patients with Parkinson' disease (28 EOPD and 22 LOPD) and 49 healthy controls (25 Young Controls and 24 Old Controls) were admitted to our study. Employing independent component analysis, we constructed the brain networks of EOPD and Young Controls, LOPD and Old Controls, respectively, and obtained the functional connectivity alterations in brain networks.

Results

Cerebellar network (CN), Sensorimotor Network (SMN), Executive Control Network (ECN), and Default Mode Network (DMN) were selected as networks of interest. Compared with their corresponding health controls, EOPD showed increased functional connectivity within the SMN and ECN and no abnormalities of inter-network functional connectivity were found, LOPD demonstrated increased functional connectivity within the ECN while decreased functional connectivity within the CN. Furthermore, in LOPD, functional connectivity between the SMN and DMN was increased. The functional connectivity of the post-central gyrus within the SMN in EOPD was inversely correlated with the Unified Parkinson's Disease Rating Scale Part III scores. Age, age of onset, and MMSE scores are significantly different between EOPD and LOPD (p < 0.05).

Conclusion

There is abnormal functional connectivity of networks in EOPD and LOPD, which could be the manifestation of the associated pathological damage or compensation.

The Cerebellum is Involved in Motor Improvements After Repetitive Transcranial Magnetic Stimulation in Parkinson's Disease Patients

Accumulating evidence indicates that repetitive transcranial magnetic stimulation (rTMS) ameliorates motor symptoms in patients with Parkinson's disease (PD); however, patients' responses to rTMS are different. Here, we aimed to explore neural activity changes in patients with PD exhibiting different responses to high-frequency rTMS treatments using functional magnetic resonance imaging (fMRI). We treated 24 patients with PD using 10-session rTMS (10 Hz) over the supplementary motor area (SMA) for 10 days. Resting-state functional magnetic resonance imaging (rs-fMRI), the Unified Parkinson's Disease Rating Scale Part III (UPDRS-III) and other neuropsychological scales were performed at the baseline and endpoint of rTMS treatment. The changes in the fractional amplitude of low-frequency fluctuation (fALFF) were calculated. Significant improvements were observed in motor symptoms, especially in the sub-symptoms of bradykinesia. All the participants were subsequently stratified into responders and non-responders according to the UPDRS-III reduction. We identified increased fALFF values in the left Crus II of the cerebellar hemisphere and bilateral thalamus as responsive signs to rTMS. Furthermore, the motor response to rTMS over the SMA, measured by the reduction in UPDRS-III and bradykinesia scores, was positively associated with increased fALFF values in the left Crus2 of cerebellar hemisphere, left lobule VIIB of cerebellar hemisphere, right lobule VI of the cerebellar hemisphere, and the right postcentral gyrus. These findings provide evidence for the involvement of cerebellar activity in the motor response to rTMS treatment.