White matter hyperintensities and risk of levodopa-induced dyskinesia in Parkinson's disease

Intrinsic brain functional connectivity predicts treatment-related motor complications in early Parkinson's disease patients

BACKGROUND

Treatment-related motor complications may develop progressively over the course of Parkinson's disease (PD).

OBJECTIVE

We investigated intrinsic brain networks functional connectivity (FC) at baseline in a cohort of early PD patients which successively developed treatment-related motor complications over 4 years.

METHODS

Baseline MRI images of 88 drug-naïve PD patients and 20 healthy controls were analyzed. After the baseline assessments, all PD patients were prescribed with dopaminergic treatment and yearly clinically re-assessed. At the 4-year follow-up, 36 patients have developed treatment-related motor complications (PD-Compl) whereas 52 had not (PD-no-Compl). Single-subject and group-level independent component analyses were used to investigate FC changes within the major large-scale resting-state networks at baseline. A multivariate Cox regression model was used to explore baseline predictors of treatment-related motor complications at 4-year follow-up.

RESULTS

At baseline, an increased FC in the right middle frontal gyrus within the frontoparietal network as well as a decreased connectivity in the left cuneus within the default-mode network were detected in PD-Compl compared with PD-no-Compl. PD-Compl patients showed a preserved sensorimotor FC compared to controls. FC differences were found to be independent predictors of treatment-related motor complications over time.

CONCLUSION

Our findings demonstrated that specific FC differences may characterize drug-naïve PD patients more prone to develop treatment-related complications. These findings may reflect the presence of an intrinsic vulnerability across frontal and prefrontal circuits, which may be potentially targeted as a future biomarker in clinical trials.

The impact of cerebral small vessel disease burden and its imaging markers on gait, postural control, and cognition in Parkinson's disease

OBJECTIVE

This study aimed to investigate how cerebral small vessel disease (CSVD) burden and its imaging markers are related to alterations in different gait parameters in Parkinson's disease (PD) and whether they affect attention, information processing speed, and executive function when global mental status is relatively intact.

METHODS

Sixty-five PD patients were divided into the low CSVD burden group (n = 43) and the high CSVD burden group (n = 22). All patients underwent brain magnetic resonance imaging scans, clinical scale evaluations, and neuropsychological tests, as well as quantitative evaluation of gait and postural control. Multivariable linear regression models were conducted to investigate associations between CSVD burden and PD symptoms.

RESULTS

Between-group analysis showed that the high CSVD group had worse attention, executive dysfunction, information processing speed, gait, balance, and postural control than the low CSVD group. Regression analysis revealed that greater CSVD burden was associated with poor attention, impaired executive function, and slow gait speed; white matter hyperintensity was associated with slow gait speed, decreased cadence, increased stride time, and increased stance phase time; the presence of lacune was associated only with poor attention and impaired executive function; enlarged perivascular space in the basal ganglia was associated with gait speed.

CONCLUSIONS

CSVD burden may worsen gait, postural control, attention, and executive function in patients with PD, and different imaging markers play different roles. Early management of vascular risks and treatment of vascular diseases provide an alternate way to mitigate some motor and cognitive dysfunction in PD.

Effects of Dihydropyridines on the Motor and Cognitive Outcomes of Patients with Parkinson's Disease

BACKGROUND

Dihydropyridines (DHPs) may have neuroprotective effects against Parkinson's disease (PD).

OBJECTIVE

This study investigated the effects of DHPs on nigrostriatal dopaminergic denervation and longitudinal motor and cognitive outcomes in PD.

METHODS

We classified 476 patients with drug-naive PD who had undergone dopamine transporter imaging into three groups. They were selected according to a prior diagnosis of hypertension and use of DHPs and were matched using propensity scores: patients without hypertension (HTN-; n = 50) and patients with hypertension treated without DHP (HTN+/DHP-; n = 50) or with DHP (HTN+/DHP+; n = 50). Multiple linear regression and linear mixed model analyses were performed to determine intergroup differences in baseline dopamine transporter availability and longitudinal changes in the levodopa-equivalent dose, respectively. Using Kaplan-Meier analyses, we compared the risks of levodopa-induced dyskinesia, wearing off, and dementia-free survival during the 5.06 years of the mean follow-up period. The Cox regression model determined the independent effects of DHPs on dementia conversion.

RESULTS

Dopamine transporter availability in all striatal subregions was comparable between the HTN-, HTN+/DHP-, and HTN+/DHP+ groups. The risks of levodopa-induced dyskinesia and wearing off, as well as longitudinal changes in the levodopa-equivalent dose, did not differ between the groups. The HTN+/DHP+ group had a lower risk of developing dementia than the HTN+/DHP- (Bonferroni-corrected P_log-rank  = 0.036) group. The use of DHP was independently associated with a lower risk of dementia conversion after controlling for other antihypertensive drugs and confounding factors (hazard ratio, 0.242; 95% confidence interval, 0.087-0.668; P = 0.006).

CONCLUSIONS

DHPs may be associated with better long-term cognitive outcomes in hypertensive patients with PD. © 2023 International Parkinson and Movement Disorder Society.

Quantitative Transcranial Sonography Evaluation of Substantia Nigra Hyperechogenicity Is Useful for Predicting Levodopa-Induced Dyskinesia in Parkinson Disease

Levodopa-induced dyskinesia (LID) is a common motor complication in Parkinson disease (PD). Abnormal substantia nigra hyperechogenicity (SN+), detected by transcranial sonography (TCS), plays an important role in the differential diagnosis of PD. The purpose of this study was to investigate the predictive performance of quantitative SN+ evaluations for LID. Five hundred sixty-two individuals were included in our analysis, and 198 individuals were followed up. These individuals were divided into two groups at baseline: the PD with LID (PD+LID) group and the PD without LID (PD-LID) group. The association between total hyperechogenic area of the SN on both sides (SN_T) and LID was analyzed by binary logistic analysis. A binary logistic regression model including SN_T was applied to establish a model for discriminating LID. At baseline, 105 (18.7%) individuals were diagnosed with LID. The PD+LID group had a longer disease duration, shorter education duration, higher levodopa equivalent doses, greater disease severity and larger SN_T. A model combining clinical features and SN_T was further established with better efficiency (area under the receiver operating characteristic curve = 0.839). One hundred ninety-eight individuals were followed up; individuals with a larger SN_T and a higher predicted probability were more likely to develop LID in our follow-up. Our study determined that quantitative TCS evaluation of SN echogenicity is useful in predicting LID in PD.

Patterns of striatal dopamine depletion and motor deficits in de novo Parkinson's disease

The background of this study is to investigate whether striatal dopamine depletion patterns (selective involvement in the sensorimotor striatum or asymmetry) are associated with motor deficits in Parkinson's disease (PD). We enrolled 404 drug-naïve patients with early stage PD who underwent dopamine transporter (DAT) imaging. After quantifying DAT availability in each striatal sub-region, principal component (PC) analysis was conducted to yield PCs representing the spatial patterns of striatal dopamine depletion. Subsequently, multivariate linear regression analysis was conducted to investigate the relationship between striatal dopamine depletion patterns and motor deficits assessed using the Unified PD Rating Scale Part III (UPDRS-III). Mediation analyses were used to evaluate whether dopamine deficiency in the posterior putamen mediated the association between striatal dopamine depletion patterns and parkinsonian motor deficits. Three PCs indicated patterns of striatal dopamine depletion: PC1 (overall striatal dopamine deficiency), PC2 (selective dopamine loss in the sensorimotor striatum), and PC3 (symmetric dopamine loss in the striatum). Multivariate linear regression analysis revealed that PC1 (β = - 1.605, p < 0.001) and PC2 (β = 3.201, p < 0.001) were associated with motor deficits (i.e., higher UPDRS-III scores in subjects with severe dopamine depletion throughout the whole striatum or more selective dopamine loss in the sensorimotor striatum), whereas PC3 was not (β = - 0.016, p = 0.992). Mediation analyses demonstrated that the effects of PC1 and PC2 on UPDRS-III scores were indirectly mediated by DAT availability in the posterior putamen, with a non-significant direct effect. Dopamine deficiency in the posterior putamen was most relevant to the severity of motor deficits in patients with PD, while the spatial patterns of striatal dopamine depletion were not a key determinant.

Local striatal volume and motor reserve in drug-naïve Parkinson's disease

Motor reserve (MR) may explain why individuals with similar pathological changes show marked differences in motor deficits in Parkinson's disease (PD). In this study, we investigated whether estimated individual MR was linked to local striatal volume (LSV) in PD. We analyzed data obtained from 333 patients with drug naïve PD who underwent dopamine transporter scans and high-resolution 3-tesla T1-weighted structural magnetic resonance images. Using a residual model, we estimated individual MRs on the basis of initial UPDRS-III score and striatal dopamine depletion. We performed a correlation analysis between MR estimates and LSV. Furthermore, we assessed the effect of LSV, which is correlated with MR estimates, on the longitudinal increase in the levodopa-equivalent dose (LED) during the 4-year follow-up period using a linear mixed model. After controlling for intracranial volume, there was a significant positive correlation between LSV and MR estimates in the bilateral caudate, anterior putamen, and ventro-posterior putamen. The linear mixed model showed that the large local volume of anterior and ventro-posterior putamen was associated with the low requirement of LED initially and accelerated LED increment thereafter. The present study demonstrated that LSV is crucial to MR in early-stage PD, suggesting LSV as a neural correlate of MR in PD.

Development of Parkinson Disease and Its Relationship with Incidentally Discovered White Matter Disease and Covert Brain Infarction in a Real-World Cohort

OBJECTIVE

This study aimed to examine the relationship between covert cerebrovascular disease, comprised of covert brain infarction and white matter disease, discovered incidentally in routine care, and subsequent Parkinson disease.

METHODS

Patients were ≥50 years and received neuroimaging for non-stroke indications in the Kaiser Permanente Southern California system from 2009 to 2019. Natural language processing identified incidentally discovered covert brain infarction and white matter disease and classified white matter disease severity. The Parkinson disease outcome was defined as 2 ICD diagnosis codes.

RESULTS

230,062 patients were included (median follow-up 3.72 years). A total of 1,941 Parkinson disease cases were identified (median time-to-event 2.35 years). Natural language processing identified covert cerebrovascular disease in 70,592 (30.7%) patients, 10,622 (4.6%) with covert brain infarction and 65,814 (28.6%) with white matter disease. After adjustment for known risk factors, white matter disease was associated with Parkinson disease (hazard ratio 1.67 [95%CI, 1.44, 1.93] for patients <70 years and 1.33 [1.18, 1.50] for those ≥70 years). Greater severity of white matter disease was associated with increased incidence of Parkinson disease(/1,000 person-years), from 1.52 (1.43, 1.61) in patients without white matter disease to 4.90 (3.86, 6.13) in those with severe disease. Findings were robust when more specific definitions of Parkinson disease were used. Covert brain infarction was not associated with Parkinson disease (adjusted hazard ratio = 1.05 [0.88, 1.24]).

INTERPRETATION

Incidentally discovered white matter disease was associated with subsequent Parkinson disease, an association strengthened with younger age and increased white matter disease severity. Incidentally discovered covert brain infarction did not appear to be associated with subsequent Parkinson disease. ANN NEUROL 2022;92:620-630.

White matter connectivity networks predict levodopa-induced dyskinesia in Parkinson's disease

BACKGROUND

Although levodopa-induced dyskinesia-relevant white matter change has been evaluated, it is uncertain whether these changes may reflect the underlying predisposing conditions leading to the development of levodopa-induced dyskinesia.

OBJECTIVE

To elucidate the role of white matter connectivity networks in the development of levodopa-induced dyskinesia in drug-naïve Parkinson's disease.

METHODS

We recruited 30 patients who developed levodopa-induced dyskinesia within 5 years from MRI acquisition (vulnerable-group), 47 patients who had not developed levodopa-induced dyskinesia within 5 years (resistant-group), and 28 controls. We performed comparative analyses of whole-brain white matter integrity and connectivity using tract-based spatial and network- and degree-based statistics. We evaluated the predictability of levodopa-induced dyskinesia development and relationship with its latency, using the average connectivity strength as a predictor in Cox- and linear-regression, respectively.

RESULTS

Mean-diffusivity was lower mainly at the left frontal region in the vulnerable-group compared to the resistant-group. Network-based statistics identified a subnetwork consisting of the bilateral fronto-striato-pallido-thalamic and lateral parietal regions (subnetwork A) and degree-based statistics identified four subnetworks (hub-subnetwork) consisting of edges centered on the left superior frontal gyrus, left putamen, left insular, or left precentral gyrus, where the vulnerable-group had stronger connectivity compared to the resistant-group. Stronger connectivity within the subnetwork A and hub-subnetwork centered on the left superior frontal gyrus was a predictor of levodopa-induced dyskinesia development independent of known risk factors and had an inverse relationship with its latency.

CONCLUSIONS

Our data suggest that white matter connectivity subnetworks within corticostriatal regions play a pivotal role in the development of levodopa-induced dyskinesia.

Glucocerebrosidase Mutations and Motor Reserve in Parkinson's Disease

BACKGROUND

The concept of motor reserve explains the individual differences in motor deficits despite similar degrees of nigrostriatal dopamine depletion in Parkinson's disease (PD).

OBJECTIVE

To investigate glucocerebrosidase (GBA) variants as potential determinants of motor reserve for exploratory purposes.

METHODS

A total of 408 patients with drug-naïve PD were enrolled from the Parkinson's Progression Markers Initiative cohort database. All patients underwent SPECT dopamine transporter (DAT) scans and had results for Sanger sequencing of GBA. Parkinsonian motor deficits were assessed using the Movement Disorders Society Unified Parkinson's Disease Rating Scale Part III (MDS-UPDRS-III). We compared MDS-UPDRS-III scores while adjusting for DAT availability in the putamen (i.e., motor reserve) between the PD groups according to the presence of GBA mutations.

RESULTS

Fifty-four (13.2%) patients carried GBA mutations. PD patients with GBA mutations were younger than those without mutations. There were no significant differences in sex, disease duration, years of education, and striatal DAT availability between the PD groups. PD patients with GBA mutations had higher MDS-UPDRS-III scores for the less affected side than those without mutations, despite similar levels of DAT availability in the contralateral putamen. The MDS-UPDRS-III sub-scores of the more affected side did not differ between the two PD groups.

CONCLUSION

The results of this study demonstrated the detrimental effect of GBA variants on individual capacity to cope with PD-related pathologies, with different impacts depending on the motor laterality.

Parkinsonism and cerebrovascular disease

The relationship between cerebrovascular disease and parkinsonism is commonly seen in everyday clinical practice but remains ill-defined and under-recognised with little guidance for the practising neurologist. We attempt to define this association and to illustrate key clinical, radiological and pathological features of the syndrome of Vascular Parkinsonism (VaP). VaP is a major cause of morbidity in the elderly associated with falls, hip fractures and cognitive impairment. Although acute parkinsonism is reported in the context of an acute cerebrovascular event, the vast majority of VaP presents as an insidious syndrome usually in the context of vascular risk factors and radiological evidence of small vessel disease. There may be an anatomic impact on basal ganglia neuronal networks, however the effect of small vessel disease (SVD) on these pathways is not clear. There are now established reporting standards for radiological features of SVD on MRI. White matter hyperintensities and lacunes have been thought to be the representative radiological features of SVD but other features such as the perivascular space are gaining more importance, especially in context of the glymphatic system. It is important to consider VaP in the differential diagnosis of Parkinson disease (PD) and in these situations, neuroimaging may offer diagnostic benefit especially in those patients with atypical presentations or refractoriness to levodopa. Proactive management of vascular risk factors, monitoring of bone density and an exercise program may offer easily attainable therapeutic targets in PD and VaP. Levodopa therapy should be considered in patients with VaP, however the dose and effect may be different from use in PD. This article is part of the Special Issue "Parkinsonism across the spectrum of movement disorders and beyond" edited by Joseph Jankovic, Daniel D. Truong and Matteo Bologna.

Current Knowledge on the Background, Pathophysiology and Treatment of Levodopa-Induced Dyskinesia-Literature Review

Levodopa remains the primary drug for controlling motor symptoms in Parkinson’s disease through the whole course, but over time, complications develop in the form of dyskinesias, which gradually become more frequent and severe. These abnormal, involuntary, hyperkinetic movements are mainly characteristic of the ON phase and are triggered by excess exogenous levodopa. They may also occur during the OFF phase, or in both phases. Over the past 10 years, the issue of levodopa-induced dyskinesia has been the subject of research into both the substrate of this pathology and potential remedial strategies. The purpose of the present study was to review the results of recent research on the background and treatment of dyskinesia. To this end, databases were reviewed using a search strategy that included both relevant keywords related to the topic and appropriate filters to limit results to English language literature published since 2010. Based on the selected papers, the current state of knowledge on the morphological, functional, genetic and clinical features of levodopa-induced dyskinesia, as well as pharmacological, genetic treatment and other therapies such as deep brain stimulation, are described.

Perivascular Spaces in the Basal Ganglia and Long-term Motor Prognosis in Newly Diagnosed Parkinson Disease

OBJECTIVE

To investigate the association between enlarged perivascular spaces (PVS) in the basal ganglia (BG-PVS) and long-term motor outcomes in Parkinson disease (PD).

METHODS

We reviewed the medical records of 248 patients with drug-naive early-stage PD (follow-up >3 years, mean age 67.44 ± 8.46 years, 130 female) who underwent brain MRI and dopamine transporter (DAT) scans at initial assessment. The number of baseline enlarged BG-PVS was counted on axial T2-weighted images. Then, patients were divided into 2 groups: a PD group with a low number (0-10) of enlarged PVS (PD-EPVS-; n = 156) and a PD group with a high number (>10) of enlarged PVS (PD-EPVS+; n = 92). We used Cox regression models to compare the levodopa-induced dyskinesia (LID)-, wearing-off-, and freezing of gait (FOG)-free times between groups. We also compared longitudinal increases in levodopa-equivalent dose per body weight between groups using a linear mixed model.

RESULTS

Patients in the PD-EPVS+ group were older (72.28 ± 6.07 years) and had greater small vessel disease burden than those in the PD-EPVS- group (64.58 ± 8.38 years). The PD-EPVS+ group exhibited more severely decreased DAT availability in all striatal subregions except the ventral striatum. The risk of FOG was higher in the PD-EPVS+ group, but the risk of LID or wearing-off was comparable between groups. The PD-EPVS+ group required higher doses of dopaminergic medications for effective symptom control compared to the PD-EPVS- group.

CONCLUSION

This study suggests that baseline enlarged BG-PVS can be an indicator of the progression of motor disability in PD.

White Matter Hyperintensities, Dopamine Loss, and Motor Deficits in De Novo Parkinson's Disease

BACKGROUND

White matter hyperintensities, prevalent in patients with Parkinson's disease (PD), significantly affect parkinsonian motor symptoms. The objective of this study was to investigate the relationship between white matter hyperintensities and nigrostriatal dopamine depletion and their interaction or mediating effects on motor symptoms in patients with drug-naive early-stage PD.

METHODS

This cross-sectional study enrolled 501 patients with de novo PD who initially underwent [¹⁸ F] N-(3-fluoropropyl)-2β-carbonethoxy-3β-(4-iodophenyl) nortropane positron emission tomography and brain magnetic resonance imaging scans between April 2009 and September 2015 in a tertiary-care university hospital. We quantified dopamine transporter availability in each striatal subregion and assessed the severity of periventricular and lobar white matter hyperintensities using the Scheltens scale. The relationship between white matter hyperintensities, dopamine transporter availability in the posterior putamen, and Unified Parkinson's Disease Rating Scale (UPDRS) motor scores was assessed using multivariate linear regression and mediation analyses.

RESULTS

Periventricular and frontal white matter hyperintensities were generally associated with dopamine transporter availability in striatal subregions after adjusting for age at symptom onset, sex, disease duration, and vascular risk factors. There was an interaction effect between periventricular white matter hyperintensities and dopamine transporter availability in the posterior putamen for the axial motor score. The effect of white matter hyperintensities on UPDRS total score and bradykinesia subscore was indirectly mediated by dopamine transporter availability in the posterior putamen, whereas the axial sub-score was directly affected by white matter hyperintensities.

CONCLUSIONS

This study suggests that the detrimental effect of white matter hyperintensities on parkinsonian motor symptoms is more relevant and independent for axial motor impairments in the status of mildly decreased striatal dopamine transporter availability. © 2021 International Parkinson and Movement Disorder Society.

Emerging Concepts of Motor Reserve in Parkinson's Disease

The concept of cognitive reserve (CR) in Alzheimer's disease (AD) explains the differences between individuals in their susceptibility to AD-related pathologies. An enhanced CR may lead to less cognitive deficits despite severe pathological lesions. Parkinson's disease (PD) is also a common neurodegenerative disease and is mainly characterized by motor dysfunction related to striatal dopaminergic depletion. The degree of motor deficits in PD is closely correlated to the degree of dopamine depletion; however, significant individual variations still exist. Therefore, we hypothesized that the presence of motor reserve (MR) in PD explains the individual differences in motor deficits despite similar levels of striatal dopamine depletion. Since 2015, we have performed a series of studies investigating MR in de novo patients with PD using the data of initial clinical presentation and dopamine transporter PET scan. In this review, we summarized the results of these published studies. In particular, some premorbid experiences (i.e., physical activity and education) and modifiable factors (i.e., body mass index and white matter hyperintensity on brain image studies) could modulate an individual's capacity to tolerate PD pathology, which can be maintained throughout disease progression.