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

Glymphatic system dysfunction and its impact on seizure severity, cognitive function, and affective symptoms in patients with generalized tonic-clonic seizures alone

BACKGROUND

Generalized tonic-clonic seizures alone (GTCS alone) represent a distinct idiopathic epilepsy syndrome. Glymphatic system (GS) dysfunction-a brain-wide perivascular clearance pathway-has been proposed as a contributing mechanism in epilepsy and its related comorbidities.

OBJECTIVE

To assess GS function in patients with GTCS alone using the Analysis Along the Perivascular Space (ALPS) index derived from diffusion spectrum imaging (DSI), and to explore its associations with clinical, cognitive, and emotional measures.

METHODS

A total of 101 patients with GTCS alone and 76 demographically matched healthy controls underwent DSI. The ALPS index was calculated and correlated with scores from standardized assessments, including the National Hospital Seizure Severity Scale (NHS3), Epileptic Discharge Index (EDI), Montreal Cognitive Assessment (MoCA), Kilifi Stigma Scale for Epilepsy (KSSE), and Hamilton Depression Rating Scale (HAMD).

RESULTS

Patients with GTCS alone had lower ALPS indices compared to healthy controls (1.43 vs. 1.52, p < 0.01). Among patients, the ALPS index positively correlated with MoCA scores (r = 0.30, p = 0.002) and negatively correlated with age (r = -0.22, p = 0.030), NHS3 (r = -0.27, p = 0.007), KSSE (r = -0.21, p = 0.038), and HAMD (r = -0.20, p = 0.042). The ALPS index was lower in patients with higher antiseizure medication loads (1.36 vs. 1.44, p = 0.042) and elevated EDI values (1.39 vs. 1.45, p = 0.039).

CONCLUSIONS

Glymphatic function is impaired in patients with GTCS alone, as indicated by reduced ALPS indices. These indices are associated with seizure severity, cognitive impairment, depressive symptoms, and perceived stigma. The ALPS index may serve as a noninvasive imaging biomarker of disease burden and a novel tool for understanding pathophysiological mechanisms in GTCS alone.

Choroid plexus enlargement in patients with rapid eye movement sleep behavior disorder: relevance to glymphatic system dysfunction

Choroid plexus volume change has been suggested as a biomarker for the course of various neurological diseases. However, its role in sleep disorders remains unclear. We analyzed choroid plexus volume changes in patients with isolated rapid eye movement sleep behavior disorder (iRBD) compared with healthy controls. We enrolled 27 patients with iRBD and 27 healthy controls. All participants underwent brain magnetic resonance imaging (MRI), including three-dimensional T1-weighted imaging suitable for volumetric analysis. iRBD was diagnosed based on overnight polysomnography and corresponding clinical history. We compared the choroid plexus volume between patients with iRBD and healthy controls, and investigated the relationship between choroid plexus volume and polysomnographic findings. The mean choroid plexus volume was significantly larger in patients with iRBD than in healthy controls (2.379% vs. 2.116%, p = 0.002). No significant correlation was observed between choroid plexus volume and polysomnographic findings in patients with iRBD. Patients with iRBD demonstrated choroid plexus enlargement compared with healthy controls. This finding could be related with glymphatic system dysfunction in this population.

Beyond the cerebellum: perivascular space burden in spinocerebellar ataxia type 3 extends to multiple brain regions

Spinocerebellar ataxia type 3 (SCA3) is an uncommon inherited (autosomal dominant) neurodegenerative disorder caused by abnormal accumulation of ataxin-3 protein. The perivascular space (PVS) burden reflects protein clearance and may worsen in SCA3 disease. This study aimed to quantify the PVS burden and investigate the relationship between the PVS burden and clinical characteristics in individuals with SCA3. This study enrolled 43 SCA3 patients and 43 age- and sex-matched healthy controls (HCs). The cross-sectional study assessed the severity of ataxia in SCA3 patients using the Scale for the Assessment and Rating of Ataxia (SARA) and the International Cooperative Ataxia Rating Scale (ICARS). Various cognitive functions were evaluated in all subjects using the Montreal Cognitive Assessment (MoCA), Rapid Verbal Retrieval (RAR) and Digital Span Test (DST) scales. MRI was used to automatically segment the PVS in all subjects and quantify the PVS burden in 15 brain regions. Compared with the HCs, the SCA3 patients showed a significantly higher PVS burden in the basal ganglia, temporal lobe, right parietal lobe and right cerebellum. There was a positive correlation in motor dysfunction between the PVS volume in the left parietal lobe, right cerebellum and PVS number in the right cerebellum with the SARA and ICARS scores. This study showed that SCA3 patients have an increased PVS burden in many brain regions, leading to motor impairment. The PVS burden could be a new imaging biomarker for disease monitoring and a therapeutic target for SCA3.

Glymphatic system dysfunction as a biomarker of disease progression in Parkinson's disease: neuroimaging evidence from longitudinal cohort studies

BACKGROUND AND OBJECTIVE

The brain glymphatic system is involved in the clearance of misfolded α-synuclein, and the impaired glymphatic system may contribute to the progression of Parkinson's disease (PD). This study aimed to investigate the association between glymphatic function, as assessed by the diffusion tensor image analysis along the perivascular space (DTI-ALPS) index, and disease progression in PD.

METHODS

One hundred thirty nine PD patients and 62 healthy controls (HCs) were enrolled in this prospective cohort study and followed up for 4 years. At baseline and 1-, 2-, and 4-year follow-ups, the enrolled population was examined with DTI scans, and the ALPS index was calculated. Unified Parkinson's Disease Rating Scale (UPDRS)-III and Montreal Cognitive Assessment (MoCA) were used to assess the motor and cognitive functions of the patients, respectively.

RESULT

The ALPS index was significantly lower in PD patients compared with HCs. Receiver operating characteristic curve analysis demonstrated that the ALPS index had a great diagnostic ability on PD, both at baseline and subsequent follow-ups (AUCbaseline: 0.729; AUC1-year: 0.653; AUC2-year: 0.714; AUC4-year: 0.728). The adjusted linear mixed-effects models showed that the ALPS index was significantly associated with UPDRS-III scores (β: - 5.173, 95%CI: - 8.850 to - 1.497, p = 0.006), but this association was lost for MoCA. A lower baseline ALPS index was associated with a faster increase in UPDRS-III, but not for MoCA.

CONCLUSION

The ALPS index could be used as an early potential imaging marker not only to differentiate PD patients from HCs but also to predict longitudinal motor function progression in PD.

T2 MRI visible perivascular spaces in Parkinson's disease: clinical significance and association with polysomnography measured sleep

Poor sleep quality might contribute to the risk and progression of neurodegenerative disorders via deficient cerebral waste clearance functions during sleep. In this retrospective cross-sectional study, we explore the link between enlarged perivascular spaces (PVS), a putative marker of sleep-dependent glymphatic clearance, with sleep quality and motor symptoms in patients with Parkinson's disease (PD). T2-weighted magnetic resonance imaging (MRI) images of 20 patients and 17 healthy control participants were estimated visually for PVS in the basal ganglia (BG) and centrum semiovale (CSO). The patient group additionally underwent a single-night polysomnography. Readouts included polysomnographic sleep features and slow-wave activity (SWA), a quantitative EEG marker of sleep depth. Associations between PVS counts, PD symptoms (MDS-UPDRS scores), and sleep parameters were evaluated using correlation and regression analyses. Intra- and inter-rater reproducibility was assessed with weighted Cohen`s kappa coefficient. BG and CSO PVS counts in both patients and controls did not differ significantly between groups. In patients, PVS in both brain regions was negatively associated with SWA (1-2 Hz; BG: r(15) = -.58, padj = .015 and CSO: r(15) = -.6, padj = .015). Basal ganglia PVS counts were positively associated with motor symptoms of daily living (IRR = 1.05, CI [1.01, 1.09], p = .007, padj = .026) and antidepressant use (IRR = 1.37, CI [1.05, 1.80], p = .021, padj = .043) after controlling for age. Centrum Semiovale PVS counts in patients were positively associated with a diagnosis of REM sleep behavior disorder (IRR = 1.39, CI [1.06, 1.84], p = .018, padj = .11). These results add to evidence that sleep deterioration may play a role in impairing glymphatic clearance via altered perivascular function, potentially contributing to disease severity in PD patients.

The "Hedgehog-Halo Sign" Is Associated with Gait Symptom Severity and Tap Response in Normal Pressure Hydrocephalus

BACKGROUND

Reduced cerebrospinal fluid (CSF) clearance may play a vital role in the pathogenesis of normal pressure hydrocephalus (NPH), but the radiologic marker is yet to be elucidated.

OBJECTIVES

This open-label study presents two novel neuroimaging biomarkers based on enlarged perivascular spaces (ePVS) of the sub-insular territory: the Hedgehog and Hedgehog-Halo (H-H) sign, designed to predict gait symptom severity and tap response in NPH.

METHODS

We retrospectively reviewed 203 patients with possible NPH with baseline magnetic resonance imaging and gait analyses before and after lumbar puncture (LP). The Hedgehog/H-H sign was scored using T2-weighted images. The clinical severity at baseline and post-tap gait improvement was compared in patients with and without Hedgehog/H-H sign. The association between Hedgehog/H-H sign and post-tap gait outcomes was assessed using multivariate regression. The diagnostic performance of Hedgehog/H-H sign was compared with conventional radiological markers.

RESULTS

Patients with H-H showed higher global disability and more severe gait impairment than those without any signs. Following LP, patients with Hedgehog/H-H sign significantly improved in various gait parameters, unlike those with neither sign. Additionally, sub-insular ePVS was significantly associated with post-tap gait improvement after adjusting covariates. Finally, the Hedgehog/H-H sign showed a higher performance than conventional markers in predicting post-tap gait response.

CONCLUSIONS

The Hedgehog/H-H sign is a useful neuroimaging biomarker related to the severity and tap response in NPH. This biomarker can be readily applied in clinical practice before undergoing LP, independent of conventional radiological signs. Further research is warranted to determine applicability in predicting post-shunt gait response.

Value of MRI-visible perivascular spaces in predicting levodopa responsiveness of patients with Parkinson's disease

PURPOSE

Inter-individual difference in levodopa responsiveness is a challenge for physicians to administer personalized treatment for patients with Parkinson's disease (PD). Previous studies demonstrated that magnetic resonance imaging (MRI)-visible perivascular spaces (PVS) might lead to an incomplete response to levodopa. This study aimed to investigate the association between MRI-visible PVS and levodopa responsiveness in patients with PD.

METHODS

This cross-sectional study enrolled a total of 327 patients with PD (median age 64.0[57.0-68.0] years, 180 male) who had undergone high-resolution T2-weighted structural MRI at our hospital between 2019 and 2023. An acute levodopa challenge test was performed to evaluate levodopa responsiveness. The patients were divided into two groups: levodopa responsive (MDS-UPDRS-III reduction ≥ 33 %, n = 274) and irresponsive groups (MDS-UPDRS-III reduction < 33 %, n = 53). We employed quantitative and semi-quantitative methods to evaluate MRI-visible PVS in patients with PD, including PVS number, volume fraction, and visual score. Additionally, the imaging features of the levodopa-responsive and irresponsive groups were compared.

RESULTS

There were no significant differences in PVS number, volume fraction, and visual score between the levodopa-responsive and -irresponsive groups. The indicators from quantitative and semi-quantitative analyses of PVS were not found to be independent predictors of levodopa responsiveness. None of the indicators from the quantitative or semi-quantitative analyses of PVS were significantly associated with poor responsiveness to levodopa treatment.

CONCLUSIONS

MRI-visible PVS are not independently associated with levodopa responsiveness, and their value in predicting levodopa responsiveness in patients with PD is limited.

Association of Relative Brain Hyperperfusion Independent of Dopamine Depletion With Motor Dysfunction in Patients With Parkinson Disease

BACKGROUND AND OBJECTIVES

Parkinson disease (PD) exhibits a characteristic pattern of brain perfusion or metabolism, thereby being considered network disorder. Using dual-phase N-(3-fluoropropyl)-2β-carbomethoxy-3β-(4-iodophenyl) nortropane (18F-FP-CIT) PET, we investigated the role of brain perfusion in motor symptoms and disease progression, independent of striatal dopamine depletion.

METHODS

We recruited patients with de novo PD and healthy controls (HCs) who underwent dual-phase 18F-FP-CIT PET and brain MRI. All patients underwent the Unified PD Rating Scale (UPDRS) and were followed up for ≥5 years. A subset of patients (n = 51) underwent follow-up UPDRS and brain MRI. Early-phase images evaluated brain perfusion, while delayed-phase images evaluated dopamine transporter availability. We compared early-phase 18F-FP-CIT uptakes (SUVRE) between PD and HC groups. Then, we investigated the association of SVURE and delayed-phase 18F-FP-CIT uptakes (SUVRD) with motor symptoms in PD. Standardized residuals (SRs) of the SUVRE in the hyperperfusion region (SUVRE-HYPER) were obtained from the linear regression of the SUVRD in the posterior putamen (SUVRD-PP), the main region of dopamine deficit. Subsequently, we investigated the association of the SR with baseline and longitudinal motor symptoms and brain atrophy.

RESULTS

Compared with HC (n = 30), patients with PD (n = 168) showed relative hyperperfusion in the primary motor cortex, thalamus, pons, hippocampus, and cerebellum and relative hypoperfusion in the prefrontal and temporo-parieto-occipital cortices, which is consistent with a PD-related metabolic pattern. Motor symptoms were negatively correlated with SUVRD-PP (standardized β = 0.402, p < 0.001) and positively correlated with SUVRE-HYPER (standardized β = 0.292, p < 0.001), but not with SUVRE in the hypoperfusion regions. Regardless of SUVRD-PP, SUVRE-HYPER was independently associated with motor dysfunction, especially rigidity (standardized β = 0.214, p = 0.012). The SR of SUVRE-HYPER was significantly associated with the UPDRS part III total score. Longitudinally, the baseline SR of SUVRE-HYPER was not associated with long-term motor complications but with an increase in the UPDRS part III total score (p = 0.017) and a decrease in brain volume.

DISCUSSION

These results suggest that aberrant relative brain hyperperfusion, independent of striatal dopamine depletion, was associated with baseline and longitudinal motor deficits and progression of neurodegeneration in PD.

Association of Striatal Dopamine Depletion and Brain Metabolism Changes With Motor and Cognitive Deficits in Patients With Parkinson Disease

BACKGROUND AND OBJECTIVES

Parkinson disease (PD) shows degeneration of dopaminergic neurons in the substantia nigra and characteristic changes in brain metabolism. However, how they correlated and affect motor and cognitive dysfunction in PD has not yet been well elucidated.

METHODS

In this single-site cross-sectional study, we enrolled patients with PD who underwent N-(3-[18F]fluoropropyl)-2β-carbomethoxy-3β-(4-iodophenyl)nortropane (18F-FP-CIT) PET, 18F-fluorodeoxyglucose (18F-FDG) PET, the Movement Disorder Society-sponsored Unified PD Rating Scale examination, and detailed neuropsychological testing. General linear models and mediation analyses were implemented to investigate the association between striatal dopamine transporter availability, brain metabolism, and parkinsonian motor subscores or domain-specific cognitive scores. Healthy controls (HCs) who underwent 18F-FP-CIT and 18F-FDG PET were also enrolled.

RESULTS

Compared with HCs (n = 38, mean age 67.3 ± 5.9 years; 19 women), patients with PD (n = 143, mean age 69.0 ± 9.0 years; 69 women) characteristically showed relative brain hypermetabolism and hypometabolism that correlated with striatal dopamine transporter availability. As the loss of putaminal dopamine transporter availability increased, brain metabolism relatively increased from the paracentral lobule, pons, and limbic system to the cerebellum and anterior cingulate cortex, whereas brain metabolism relatively decreased from the lateral temporal and frontal cortices to the occipital and inferior parietal cortices. Reduced putaminal dopamine was associated with a higher rigidity subscore by the mediation of relative hypermetabolism in the paracentral lobule (standardized indirect effect, β = -0.070, p = 0.025) and directly associated with a higher bradykinesia subscore (β = -0.274, p = 0.011). Reduced caudate dopamine was associated with a higher axial subscore (β = -0.125, p = 0.004) and lower executive (β = 0.229, p = 0.004), visuospatial (β = 0.139, p = 0.006), and memory (β = 0.140, p = 0.004) domain scores by the mediation of relative brain hypometabolism. The tremor subscore and language and attention scores were not associated with striatal dopamine availability or brain metabolism.

DISCUSSION

Our findings suggest that in PD, striatal dopamine depletion and altered brain metabolism are closely linked, that changes in brain metabolism occur in specific spatial patterns depending on the degree of dopamine depletion, and that both differentially affect motor and cognitive dysfunction depending on each symptom.

Evaluating the robustness of DTI-ALPS in clinical context: a meta-analytic parallel on Alzheimer's and Parkinson's diseases

In recent years, the glymphatic system has received increasing attention due to its possible implications in biological mechanisms associated with neurodegeneration. In the field of human brain mapping, this led to the development of diffusion tensor image analysis along the perivascular space (DTI-ALPS) index. While this index has been repeatedly used to investigate possible differences between neurodegenerative disorders and healthy controls, a comprehensive evaluation of its stability across multiple measurements and different disorders is still missing. In this study, we perform a Bayesian meta-analysis aiming to assess the consistency of the DTI-ALPS results previously reported for 12 studies on Parkinson's disease and 11 studies on Alzheimer's disease. We also evaluated if the measured value of the DTI-ALPS index can quantitatively inform the diagnostic process, allowing disambiguation between these two disorders. Our results, expressed in terms of Bayes' Factor values, confirmed that the DTI-ALPS index is consistent in measuring the different functioning of the glymphatic system between healthy subjects and patients for both Parkinson's disease (Log10(BF10) = 30) and Alzheimer's disease (Log10(BF10) = 10). Moreover, we showed that the DTI-ALPS can be used to compare these two disorders directly, therefore providing a first proof of concept supporting the reliability of taking into consideration this neuroimaging measurement in the diagnostic process. Our study underscores the potential of the DTI-ALPS index in advancing our understanding of neurodegenerative pathologies and enhancing clinical diagnostics.

Regional Burden of Enlarged Perivascular Spaces and Cognition and Neuropsychiatric Symptoms in Drug-Naive Patients With Parkinson Disease

BACKGROUND AND OBJECTIVES

Although the potential role of enlarged perivascular spaces (EPVSs) in Parkinson disease (PD) is increasingly recognized, whether EPVSs located in different anatomical regions exert differential effects on clinical manifestation remains uncertain. We investigated the regional EPVS burden and its association with cognition and neuropsychiatric symptoms (NPSs) in newly diagnosed PD population.

METHODS

In this retrospective, cross-sectional study, EPVS in the temporal lobe (T-EPVS), centrum semiovale (CS-EPVS), and basal ganglia (BG-EPVS) were visually rated in drug-naive patients with PD who underwent magnetic resonance imaging, dopamine transporter (DAT) scans, neuropsychological assessments, and Neuropsychiatric Inventory Questionnaire at baseline. Cognitive performance, NPS burden, vascular risk factors, small vessel disease (SVD) imaging markers, and DAT availability were compared across groups dichotomized by their regional EPVS burden (cutoff for high-degree vs low-degree: >10 for T-EPVS/BG-EPVS and >20 for CS-EPVS).

RESULTS

A total of 480 patients with PD (123 without cognitive impairment, 291 with mild cognitive impairment, and 66 with dementia) were included. The proportion of high-degree T-EPVS (p for trend <0.001) and BG-EPVS (p for trend = 0.001) exhibited an increasing trend across the cognitive spectrum, corresponding to worsening cognition. Compared with the low-degree group, the high-degree BG-EPVS group showed higher SVD burden (moderate-to-severe white matter hyperintensity [14.8% vs 40.5%, p < 0.001], lacune [10.3% vs 30.7%, p < 0.001], and cerebral microbleeds [8.1% vs 22.2%, p < 0.001]), greater atrophy in cortical gray matter (40.73% ± 1.09% vs 39.96% ± 1.20% of intracranial volume, p < 0.001), and lower cognitive performance (in language [-0.22 ± 1.18 vs -0.53 ± 1.29, p = 0.013], and visual memory domains [-0.24 ± 0.97 vs -0.61 ± 0.96, p = 0.009]). The high-degree T-EPVS group presented with greater NPS burden in decreased motivation (0.61 ± 1.78 vs 1.35 ± 2.36, p = 0.007), affective dysregulation (0.88 ± 2.13 vs 2.36 ± 3.53, p < 0.001), and impulse dyscontrol (0.43 ± 1.67 vs 1.74 ± 4.29, p < 0.001), compared with the low-degree T-EPVS group. Meanwhile, the burden of CS-EPVS did not reveal any differences in cognition or NPS.

DISCUSSION

BG-EPVS and T-EPVS seem to exert differential effects on cognition and NPS in patients with PD. Investigating the EPVS profile in distinct anatomical regions may be useful in disentangling the heterogeneity within PD.

Noninvasive Magnetic Resonance Imaging Measures of Glymphatic System Activity

The comprehension of the glymphatic system, a postulated mechanism responsible for the removal of interstitial solutes within the central nervous system (CNS), has witnessed substantial progress recently. While direct measurement techniques involving fluorescence and contrast agent tracers have demonstrated success in animal studies, their application in humans is invasive and presents challenges. Hence, exploring alternative noninvasive approaches that enable glymphatic research in humans is imperative. This review primarily focuses on several noninvasive magnetic resonance imaging (MRI) techniques, encompassing perivascular space (PVS) imaging, diffusion tensor image analysis along the PVS, arterial spin labeling, chemical exchange saturation transfer, and intravoxel incoherent motion. These methodologies provide valuable insights into the dynamics of interstitial fluid, water permeability across the blood-brain barrier, and cerebrospinal fluid flow within the cerebral parenchyma. Furthermore, the review elucidates the underlying concept and clinical applications of these noninvasive MRI techniques, highlighting their strengths and limitations. It addresses concerns about the relationship between glymphatic system activity and pathological alterations, emphasizing the necessity for further studies to establish correlations between noninvasive MRI measurements and pathological findings. Additionally, the challenges associated with conducting multisite studies, such as variability in MRI systems and acquisition parameters, are addressed, with a suggestion for the use of harmonization methods, such as the combined association test (COMBAT), to enhance standardization and statistical power. Current research gaps and future directions in noninvasive MRI techniques for assessing the glymphatic system are discussed, emphasizing the need for larger sample sizes, harmonization studies, and combined approaches. In conclusion, this review provides invaluable insights into the application of noninvasive MRI methods for monitoring glymphatic system activity in the CNS. It highlights their potential in advancing our understanding of the glymphatic system, facilitating clinical applications, and paving the way for future research endeavors in this field. EVIDENCE LEVEL: 3 TECHNICAL EFFICACY: Stage 5.

The relationship between inflammation, impaired glymphatic system, and neurodegenerative disorders: A vicious cycle

The term "glymphatic" emerged roughly a decade ago, marking a pivotal point in neuroscience research. The glymphatic system, a glial-dependent perivascular network distributed throughout the brain, has since become a focal point of investigation. There is increasing evidence suggesting that impairment of the glymphatic system appears to be a common feature of neurodegenerative disorders, and this impairment exacerbates as disease progression. Nevertheless, the common factors contributing to glymphatic system dysfunction across most neurodegenerative disorders remain unclear. Inflammation, however, is suspected to play a pivotal role. Dysfunction of the glymphatic system can lead to a significant accumulation of protein and waste products, which can trigger inflammation. The interaction between the glymphatic system and inflammation appears to be cyclical and potentially synergistic. Yet, current research is limited, and there is a lack of comprehensive models explaining this association. In this perspective review, we propose a novel model suggesting that inflammation, impaired glymphatic function, and neurodegenerative disorders interconnected in a vicious cycle. By presenting experimental evidence from the existing literature, we aim to demonstrate that: (1) inflammation aggravates glymphatic system dysfunction, (2) the impaired glymphatic system exacerbated neurodegenerative disorders progression, (3) neurodegenerative disorders progression promotes inflammation. Finally, the implication of proposed model is discussed.

The glymphatic system and multiple sclerosis: An evolving connection

Multiple sclerosis (MS) is a complex autoimmune disorder that affects the central nervous system, resulting in demyelination and an array of neurological manifestations. Recently, there has been significant scientific interest in the glymphatic system, which operates as a waste-clearance system for the brain. This article reviews the existing literature, and explores potential links between the glymphatic system and MS, shedding light on its evolving significance in the context of MS pathogenesis. The authors consider the pathophysiological implications of glymphatic dysfunction in MS, the impact of disrupted sleep on glymphatic function, and the bidirectional relationship between MS and sleep disturbances. By offering an understanding of the intricate interplay between the glymphatic system and MS, this review provides valuable insights which may lead to improved diagnostic techniques and more effective therapeutic interventions.

Enlarged Perivascular Space and Index for Diffusivity Along the Perivascular Space as Emerging Neuroimaging Biomarkers of Neurological Diseases

The existence of lymphatic vessels or similar clearance systems in the central nervous system (CNS) that transport nutrients and remove cellular waste is a neuroscientific question of great significance. As the brain is the most metabolically active organ in the body, there is likely to be a potential correlation between its clearance system and the pathological state of the CNS. Until recently the successive discoveries of the glymphatic system and the meningeal lymphatics solved this puzzle. This article reviews the basic anatomy and physiology of the glymphatic system. Imaging techniques to visualize the function of the glymphatic system mainly including post-contrast imaging techniques, indirect lymphatic assessment by detecting increased perivascular space, and diffusion tensor image analysis along the perivascular space (DTI-ALPS) are discussed. The pathological link between glymphatic system dysfunction and neurological disorders is the key point, focusing on the enlarged perivascular space (EPVS) and the index of diffusivity along the perivascular space (ALPS index), which may represent the activity of the glymphatic system as possible clinical neuroimaging biomarkers of neurological disorders. The pathological link between glymphatic system dysfunction and neurological disorders is the key point, focusing on the enlarged perivascular space (EPVS) and the index for of diffusivity along the perivascular space (ALPS index), which may represent the activity of the glymphatic system as possible clinical neuroimaging biomarkers of neurological disorders.

A meta-analysis identifies factors predicting the future development of freezing of gait in Parkinson's disease

Freezing of gait (FOG) is a debilitating problem that is common among many, but not all, people with Parkinson's disease (PD). Numerous attempts have been made at treating FOG to reduce its negative impact on fall risk, functional independence, and health-related quality of life. However, optimal treatment remains elusive. Observational studies have recently investigated factors that differ among patients with PD who later develop FOG, compared to those who do not. With prediction and prevention in mind, we conducted a systematic review and meta-analysis of publications through 31.12.2022 to identify risk factors. Studies were included if they used a cohort design, included patients with PD without FOG at baseline, data on possible FOG predictors were measured at baseline, and incident FOG was assessed at follow-up. 1068 original papers were identified, 38 met a-priori criteria, and 35 studies were included in the meta-analysis (n = 8973; mean follow-up: 4.1 ± 2.7 years). Factors significantly associated with a risk of incident FOG included: higher age at onset of PD, greater severity of motor symptoms, depression, anxiety, poorer cognitive status, and use of levodopa and COMT inhibitors. Most results were robust in four subgroup analyses. These findings indicate that changes associated with FOG incidence can be detected in a subset of patients with PD, sometimes as long as 12 years before FOG manifests, supporting the possibility of predicting FOG incidence. Intriguingly, some of these factors may be modifiable, suggesting that steps can be taken to lower the risk and possibly even prevent the future development of FOG.

The Application of Deep Brain Stimulation for Parkinson's Disease on the Motor Pathway: A Bibliometric Analysis across 10 Years

BACKGROUND AND OBJECTIVE

Since its initial report by James Parkinson in 1817, Parkinson's disease (PD) has remained a central subject of research and clinical advancement. The disease is estimated to affect approximately 1% of adults aged 60 and above. Deep brain stimulation, emerging as an alternative therapy for end-stage cases, has offered a lifeline to numerous patients. This review aimed to analyze publications pertaining to the impact of deep brain stimulation on the motor pathway in patients with PD over the last decade.

METHODS

Data were obtained from the Web of Science Core Collection through the library of Huazhong University of Science and Technology (China). The search strategy encompassed the following keywords: "deep brain stimulation", "Parkinson's disease", "motor pathway", and "human", from January 1, 2012, to December 1, 2022. Additionally, this review visualized the findings using the Citespace software.

RESULTS

The results indicated that the United States, the United Kingdom, Germany, and China were the primary contributors to this research field. University College London, Capital Medical University, and Maastricht University were the top 3 research institutions in the research area. Tom Foltynie ranked first with 6 publications, and the journals of Brain and Brain Stimulation published the greatest number of relevant articles. The prevailing research focal points in this domain, as determined by keywords "burst analysis", "encompassed neuronal activity", "nucleus", "hyper direct pathway", etc. CONCLUSION: This study has provided a new perspective through bibliometric analysis of the deep brain stimulation therapy for treating patients with PD, which can shed light on future research to advance our comprehension of this particular field of study.

Updates on brain regions and neuronal circuits of movement disorders in Parkinson's disease

Parkinson's disease (PD) is a progressive neurodegenerative disease with a global burden that affects more often in the elderly. The basal ganglia (BG) is believed to account for movement disorders in PD. More recently, new findings in the original regions in BG involved in motor control, as well as the new circuits or new nucleuses previously not specifically considered were explored. In the present review, we provide up-to-date information related to movement disorders and modulations in PD, especially from the perspectives of brain regions and neuronal circuits. Meanwhile, there are updates in deep brain stimulation (DBS) and other factors for the motor improvement in PD. Comprehensive understandings of brain regions and neuronal circuits involved in motor control could benefit the development of novel therapeutical strategies in PD.

Association of choroid plexus volume with motor symptoms and dopaminergic degeneration in Parkinson's disease

BACKGROUND

The choroid plexus (CP) is involved in the clearance of harmful metabolites from the brain, as a part of the glymphatic system. This study aimed to investigate the association between CP volume (CPV), nigrostriatal dopaminergic degeneration and motor outcomes in Parkinson's disease (PD).

METHODS

We retrospectively searched drug-naïve patients with early-stage PD who underwent dopamine transporter (DAT) scanning and MRI. Automatic CP segmentation was performed, and the CPV was calculated. The relationship between CPV, DAT availability and Unified PD Rating Scale Part III (UPDRS-III) scores was assessed using multivariate linear regression. We performed longitudinal analyses to assess motor outcomes according to CPV.

RESULTS

CPV was negatively associated with DAT availability in each striatal subregion (anterior caudate, β=-0.134, p=0.012; posterior caudate, β=-0.162, p=0.002; anterior putamen, β=-0.133, p=0.024; posterior putamen, β=-0.125, p=0.039; ventral putamen, β=-0.125, p=0.035), except for the ventral striatum. CPV was positively associated with the UPDRS-III score even after adjusting for DAT availability in the posterior putamen (β=0.121; p=0.035). A larger CPV was associated with the future development of freezing of gait in the Cox regression model (HR 1.539, p=0.027) and a more rapid increase in dopaminergic medication in the linear mixed model (CPV×time, p=0.037), but was not associated with the risk of developing levodopa-induced dyskinesia or wearing off.

CONCLUSION

These findings suggest that CPV has the potential to serve as a biomarker for baseline and longitudinal motor disabilities in PD.

Levodopa-induced dyskinesia: interplay between the N-methyl-D-aspartic acid receptor and neuroinflammation

Parkinson's disease (PD) is a common neurodegenerative disorder of middle-aged and elderly people, clinically characterized by resting tremor, myotonia, reduced movement, and impaired postural balance. Clinically, patients with PD are often administered levodopa (L-DOPA) to improve their symptoms. However, after years of L-DOPA treatment, most patients experience complications of varying severity, including the "on-off phenomenon", decreased efficacy, and levodopa-induced dyskinesia (LID). The development of LID can seriously affect the quality of life of patients, but its pathogenesis is unclear and effective treatments are lacking. Glutamic acid (Glu)-mediated changes in synaptic plasticity play a major role in LID. The N-methyl-D-aspartic acid receptor (NMDAR), an ionotropic glutamate receptor, is closely associated with synaptic plasticity, and neuroinflammation can modulate NMDAR activation or expression; in addition, neuroinflammation may be involved in the development of LID. However, it is not clear whether NMDA receptors are co-regulated with neuroinflammation during LID formation. Here we review how neuroinflammation mediates the development of LID through the regulation of NMDA receptors, and assess whether common anti-inflammatory drugs and NMDA receptor antagonists may be able to mitigate the development of LID through the regulation of central neuroinflammation, thereby providing a new theoretical basis for finding new therapeutic targets for LID.

Association between choroid plexus volume and cognition in Parkinson disease

BACKGROUND AND PURPOSE

The choroid plexus (CP) clears harmful metabolites from the central nervous system as part of the glymphatic system. We investigated the association of CP volume (CPV) with baseline and longitudinal cognitive decline in patients with Parkinson disease (PD).

METHODS

We retrospectively reviewed the medical records of 240 patients with newly diagnosed PD who had undergone detailed neuropsychological tests and high-resolution T1-weighted structural magnetic resonance imaging during the initial assessment. The CPV of each patient was automatically segmented, and the intracranial volume ratio was used in subsequent analyses. The relationship between CPV and baseline composite scores of each cognitive domain was assessed using multivariate linear regression analyses. A Cox proportional hazards model was used to compare the risk of dementia conversion with CPV.

RESULTS

CPV negatively correlated with composite scores of the frontal/executive function domain (β = -0.375, p = 0.002) after adjusting for age, sex, years of education, and parkinsonian symptom duration. The Cox regression model revealed that a larger CPV was associated with a higher risk of dementia conversion (hazard ratio [HR] = 1.509, p = 0.038), which was no longer significant after adjusting for the composite scores of the frontal/executive function domain. A mediation analysis demonstrated that the effect of CPV on the risk of dementia conversion was completely mediated by frontal/executive function (direct effect: HR = 1.203, p = 0.396; indirect effect: HR = 1.400, p = 0.015).

CONCLUSIONS

Baseline CPV is associated with baseline frontal/executive function, which subsequently influences dementia conversion risk in patients with PD.

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.

Aging reduces calreticulin expression and alters spontaneous calcium signals in astrocytic endfeet of the mouse dorsolateral striatum

Aging-related impairment of the blood brain barrier (BBB) and neurovascular unit (NVU) increases the risk for neurodegeneration. Among various cells that participate in BBB and NVU function, calcium signals in astrocytic endfeet are crucial for maintaining BBB and NVU integrity. To assess if aging is associated with altered calcium signals within astrocytic endfeet of the dorsolateral striatum (DLS), we expressed GCaMP6f in DLS astrocytes of young (3-4 months), middle-aged (12-15 months) and aging (20-30 months) mice. Compared to endfeet in young mice, DLS endfeet in aging mice demonstrated decreased calreticulin expression, and alterations to both spontaneous membrane-associated and mitochondrial calcium signals. While young mice required both extracellular and endoplasmic reticulum calcium sources for endfoot signals, middle-aged and aging mice showed heavy dependence on endoplasmic reticulum calcium. Thus, astrocytic endfeet show significant changes in calcium buffering and sources throughout the lifespan, which is important for understanding mechanisms by which aging impairs the BBB and NVU.

Molecular and Cellular Interactions in Pathogenesis of Sporadic Parkinson Disease

An increasing number of the population all around the world suffer from age-associated neurodegenerative diseases including Parkinson’s disease (PD). This disorder presents different signs of genetic, epigenetic and environmental origin, and molecular, cellular and intracellular dysfunction. At the molecular level, α-synuclein (αSyn) was identified as the principal molecule constituting the Lewy bodies (LB). The gut microbiota participates in the pathogenesis of PD and may contribute to the loss of dopaminergic neurons through mitochondrial dysfunction. The most important pathogenetic link is an imbalance of Ca²⁺ ions, which is associated with redox imbalance in the cells and increased generation of reactive oxygen species (ROS). In this review, genetic, epigenetic and environmental factors that cause these disorders and their cause-and-effect relationships are considered. As a constituent of environmental factors, the example of organophosphates (OPs) is also reviewed. The role of endothelial damage in the pathogenesis of PD is discussed, and a ‘triple hit hypothesis’ is proposed as a modification of Braak’s dual hit one. In the absence of effective therapies for neurodegenerative diseases, more and more evidence is emerging about the positive impact of nutritional structure and healthy lifestyle on the state of blood vessels and the risk of developing these diseases.

Association of enlarged perivascular spaces with upper extremities and gait impairment: An observational, prospective cohort study

BACKGROUND AND OBJECTIVE

Gait disturbances are common in the elderly and can lead to the loss of functional independence and even death. Enlarged perivascular space (EPVS) and motor performance may be related, but only few studies have explored this relationship. The aim of our study was to investigate the effects of both the severity and location of EPVS on movement disorders.

METHOD

Two hundred and six participants aged between 45 and 85 years old with complete magnetic resonance imaging (MRI) data were included in our analysis. EPVS were divided into basal ganglia (BG) and centrum semiovale (CSO), and their grades were measured. Gait was assessed quantitatively using a 4-m walkway and TUG test as well as semi-quantitatively using the Tinetti and SPPB tests. The function of upper extremities was evaluated by 10-repeat pronation-supination, 10-repeat finger-tapping, and 10-repeat opening and closing of the hands.

RESULTS

Both high-grade EPVS, whether in BG and CSO, were independently correlated with gait parameters, the TUG time, Tinetti, and SPPB tests. The EPVS located in BG had a significant association with 10-repeat finger-tapping time (β = 0.231, P = 0.025) and a similar association was also observed between CSO-EPVS and 10-repeat pronation-supination time (β = 0.228, P = 0.014).

CONCLUSION

Our results indicated that EPVS was associated with gait disturbances, and a further investigation found that EPVS has an association with upper extremities disorder. EPVS should be considered as a potential target for delaying gait and upper extremities damage since CSVD can be prevented to some extent.

Glymphatic System Dysfunction and Sleep Disturbance May Contribute to the Pathogenesis and Progression of Parkinson’s Disease

Parkinson’s disease (PD) is a multisystem alpha-synucleinopathic neurodegenerative disease and the most prevalent neurodegenerative disorder after Alzheimer’s disease with a high incidence rate in the elderly population. PD is highly multifactorial in etiology and has complex and wide-ranging pathogenic mechanisms. Environmental exposures and genetic predisposition are prominent risk factors. However, current evidence suggests that an intimate link may exist between the risk factor of sleep disturbance and PD pathogenesis. PD is characterized by the pathological hallmarks of alpha-synuclein aggregations and dopaminergic neuron degeneration in the substantia nigra. The loss of dopamine-producing neurons results in both motor and non-motor symptoms, most commonly, bradykinesia, tremor, rigidity, psychiatric disorders, sleep disorders and gastrointestinal problems. Factors that may exacerbate alpha-synuclein accumulation and dopamine neuron loss include neuroinflammation and glymphatic system impairment. Extracellular alpha-synuclein can induce an inflammatory response which can lead to neural cell death and inhibition of neurogenesis. The glymphatic system functions most optimally to remove extracellular brain solutes during sleep and therefore sleep disruption may be a crucial progression factor as well as a risk factor. This literature review interprets and analyses data from experimental and epidemiological studies to determine the recent advances in establishing a relationship between glymphatic system dysfunction, sleep disturbance, and PD pathogenesis and progression. This review addresses current limitations surrounding the ability to affirm a causal link between improved glymphatic clearance by increased sleep quality in PD prevention and management. Furthermore, this review proposes potential therapeutic approaches that could utilize the protective mechanism of sleep, to promote glymphatic clearance that therefore may reduce disease progression as well as symptom severity in PD patients.

Association of Enlarged Perivascular Spaces With Amyloid Burden and Cognitive Decline in Alzheimer Disease Continuum

BACKGROUND AND OBJECTIVES

To investigate the effects of enlarged perivascular space (EPVS) on amyloid burden and cognitive function in Alzheimer disease (AD) continuum.

METHODS

We retrospectively reviewed 208 patients with AD across the cognitive continuum (preclinical, prodromal, and AD dementia) who showed amyloid deposition on 18F-florbetaben PET scans and 82 healthy controls. EPVSs were counted for each patient in the basal ganglia (BG), centrum semiovale (CSO), and hippocampus (HP) on axial T2-weighted images. Patients were then classified according to the number of EPVSs into the EPVS+ (>10 EPVSs) and EPVS- (0-10 EPVSs) groups for the BG and CSO, respectively. In terms of HP-EPVS, equal or more than 7 EPVSs on bilateral hemisphere were regarded as the presence of HP-EPVS. After adjusting for markers of small vessel disease (SVD), multiple linear regression analyses were performed to determine the intergroup differences in global and regional amyloid deposition and cognitive function at the time of diagnosis of AD continuum. A linear mixed model was used to assess the effects of EPVSs on the longitudinal changes in the Mini-Mental State Examination (MMSE) scores.

RESULTS

Amyloid burden at the time of diagnosis of AD continuum was not associated with the degree of BG-, CSO-, or HP-EPVS. BG-EPVS affected language and frontal/executive function via SVD markers, and HP-EPVS was associated with general cognition via SVD markers. However, CSO-EPVS was not associated with baseline cognition. A higher number of CSO-EPVS was significantly associated with a more rapid decline in MMSE scores (β = -0.58, standard error = 0.23, p = 0.011) independent of the amyloid burden. In terms of BG and HP, there was no difference between the EPVS+ and EPVS- groups in the rate of longitudinal decreases in MMSE scores.

DISCUSSION

Our findings suggest that BG-, CSO-, and HP-EPVS are not associated with baseline β-amyloid burden or cognitive function independently of SVD at the diagnosis of AD continuum. However, CSO-EPVS appears to be associated with the progression of cognitive decline in an amyloid-independent manner. Further studies are needed to investigate whether CSO-EPVS is a potential therapeutic target in patients with AD continuum.

Ophthalmologic problems correlates with cognitive impairment in patients with Parkinson's disease

Objective

Visual impairment is a common non-motor symptom (NMS) in patients with Parkinson's disease (PD) and its implications for cognitive impairment remain controversial. We wished to survey the prevalence of visual impairment in Chinese Parkinson's patients based on the Visual Impairment in Parkinson's Disease Questionnaire (VIPD-Q), identify the pathogens that lead to visual impairment, and develop a predictive model for cognitive impairment risk in Parkinson's based on ophthalmic parameters.

Methods

A total of 205 patients with Parkinson's disease and 200 age-matched controls completed the VIPD-Q and underwent neuro-ophthalmologic examinations, including ocular fundus photography and optical coherence tomography. We conducted nomogram analysis and the predictive model was summarized using the multivariate logistic and LASSO regression and verified via bootstrap validation.

Results

One or more ophthalmologic symptoms were present in 57% of patients with Parkinson's disease, compared with 14% of the controls (χ²-test; p < 0.001). The visual impairment questionnaire showed good sensitivity and specificity (area under the curve [AUC] = 0.918, p < 0.001) and a strong correlation with MoCA scores (Pearson r = −0.4652, p < 0.001). Comparing visual impairment scores between pre- and post-deep brain stimulation groups showed that DBS improved visual function (U-test, p < 0.001). The thickness of the retinal nerve fiber layer and vessel percentage area predicted cognitive impairment in PD.

Interpretation

The study findings provide novel mechanistic insights into visual impairment and cognitive decline in Parkinson's disease. The results inform an effective tool for predicting cognitive deterioration in Parkinson's based on ophthalmic parameters.

Alpha-Synuclein RT-QuIC in Idiopathic Normal Pressure Hydrocephalus

This study quantified the occurrence of an underlying synucleinopathy in 50 patients with idiopathic normal pressure hydrocephalus by means of real-time quaking-induced conversion, a highly sensitive and specific technique capable of detecting and amplifying misfolded aggregated forms of α-synuclein in the cerebrospinal fluid. Seven patients were positive and they did not differ from negative cases, except for a more frequent L-dopa responsiveness and gait characterized by a wider base. The two groups did not differ in terms of response rate to tap test or shunt surgery, although step length and gait velocity improved by a lesser extent in positive cases. This article is protected by copyright. All rights reserved.

The interplay between small vessel disease and Parkinson disease pathology: A longitudinal study

BACKGROUND

Cerebral small vessel disease (SVD) related brain changes have been found associated with various clinical symptoms of Parkinson disease (PD). On the other hand, PD pathology and treatment may also accelerate SVD progression.

OBJECTIVE

The aim of this study is to explore the interplay between SVD and PD pathology using longitudinal dataset.

METHODS

We screened 66 healthy controls (HCs) and 114 patients from the Parkinson Progression Markers Initiative (PPMI) database. The peak width of skeletonized mean diffusivity (PSMD) was quantified from diffusion tensor images to reflect vascular pathologies at baseline and 24 months follow-up, and dopamine transporter (DAT) imaging data was used to represent the extent of dopaminergic neuronal degeneration at the same point time. We compared the PSMD between PD patients and HCs, and analyzed whether PSMD and DAT availability could predict each other's progression using multiple regression analyses in PD patients.

RESULTS

PSMD at baseline had no significant difference between the HCs and patients with PD (P = 0.169). Higher baseline PSMD was associated with less DAT reduction in the caudate (β = 0.216, P = 0.029), but not the putamen (β = 0.058, P = 0.552) in PD patients. Baseline caudate and putamen DAT availability had no significant association with PSMD progression (β = -0.006, P = 0.950; β = 0.017, P = 0.860, respectively).

CONCLUSIONS

Mild SVD might slow down PD pathology progression, while the effect of PD pathology on the progression of SVD was not significant.

Enlarged perivascular spaces are linked to freezing of gait in Parkinson's disease

Objective

Freezing of gait (FOG) is one of common and disabling gait impairments of Parkinson's disease (PD). White matter hyperintensity (WMH) and lacunes, as common manifestations of cerebral small vessel diseases (CSVD), have been reported to be associated with gait function in PD patients. However, in the cases with FOG which present with extensive WMH or lacunes, it actually is difficult to distinguish pure PD pathology from vascular origin or combined effects. So far little is known about the correlation between enlarged perivascular space (PVS) and FOG in PD patients. This study aims to explore the role of enlarged PVS in FOG in PD patients.

Methods

A total of 95 patients with PD in the absence of obvious WMH and lacunes were included in our study, which were divided into PD-FOG (+) group and PD-FOG (-) group. Demographic and clinical data were investigated. Enlarged PVS in the centrum semiovale (CSO) and basal ganglia (BG) were assessed. The association between enlarged PVS and FOG in patients with PD was analyzed using the multivariate models and the Spearman's correlation.

Results

There were 36 PD patients grouped into PD-FOG (+) (37.9%), with an older age, a longer PD disease duration, and larger numbers of enlarged PVS in CSO and BG compared with PD-FOG (-) group. The highest-severity degree of enlarged PVS burden in CSO was independently associated with FOG in patients with PD [adjusted odds ratio (OR), 3.869; p = 0.022 in multivariable model]. The percentages of FOG case increased accompanied by the aggravation of enlarged PVS located in CSO. The grade and count of enlarged PVS in CSO and BG both correlated with FOGQ score in PD patients.

Conclusion

Enlarged PVS, particularly in CSO, are associated with FOG in patients with PD, which provides a novel perspective for the mechanisms of FOG in PD.

Association of Cerebral Small Vessel Disease With Gait and Balance Disorders

Cerebral small vessel disease (CSVD) is a common cerebrovascular disease and an important cause of gait and balance disorders. Gait and balance disorders can further lead to an increased risk of falls and a decreased quality of life. CSVD can damage gait and balance function by affecting cognitive function or directly disrupting motor pathways, and different CSVD imaging features have different characteristics of gait and balance impairment. In this article, the correlation between different imaging features of sporadic CSVD and gait and balance disorders has been reviewed as follows, which can provide beneficial help for standardized management of CSVD.

Post-mortem correlates of Virchow-Robin spaces detected on in vivo MRI

The purpose of our study is to quantify the extent to which Virchow-Robin spaces (VRS) detected on in vivo MRI are reproducible by post-mortem MRI.Double Echo Steady State 3T MRIs were acquired post-mortem in 49 double- and 32 single-hemispheric formalin-fixed brain sections from 12 patients, who underwent conventional diagnostic 1.5 or 3T MRI in median 22 days prior to death (25% to 75%: 12 to 134 days). The overlap of in vivo and post-mortem VRS segmentations was determined accounting for potential confounding factors.The reproducibility of VRS found on in vivo MRI by post-mortem MRI, in the supratentorial white matter was in median 80% (25% to 75%: 60 to 100). A lower reproducibility was present in the basal ganglia, with a median of 47% (25% to 75%: 30 to 50).VRS segmentations were histologically confirmed in one double hemispheric section.Overall, the majority of VRS found on in vivo MRI was stable throughout death and formalin fixation, emphasizing the translational potential of post-mortem VRS studies.

Enlarged Perivascular Spaces in the Basal Ganglia Independently Related to Gait Disturbances in Older People With Cerebral Small Vessel Diseases

Background and Objective

Gait disturbances are common in older people and are associated with adverse consequences, e.g., falls and institutionalization. Enlarged perivascular spaces in the basal ganglia (BG-EPVS) are considered an magnetic resonance imaging (MRI) marker of cerebral small vessel diseases (CSVD). However, the consequences of BG-EPVS are largely unknown. Previous studies showed that other CSVD markers were related to gait disturbances. However, the relation between BG-EPVS and gait performance is unclear. Therefore, we aimed to explore the relation between BG-EPVS and gait performance in elderly individuals.

Methods

We recruited older people with CSVD in the Neurology Department of our hospital from December 1, 2020 to October 31, 2021. Participants with BG-EPVS &gt; 20 on the unilateral side of the basal ganglia slice containing the maximum number were classified into the BG-EPVS group (n = 78), and the rest were classified into the control group (n = 164). Quantitative gait parameters and gait variability were provided by the Intelligent Device for Energy Expenditure and Activity (IDEEA; MiniSun, United States) gait analysis system. Semiquantitative gait assessment was measured with the Tinetti test. Point-biserial correlation and multivariate linear regression analysis were performed to investigate the association between BG-EPVS and gait performance.

Results

The BG-EPVS group had a slower gait speed and cadence, shorter stride length, longer stance phase percentage, smaller pre-swing angle and footfall, and lower Tinetti gait test and balance test scores compared with those in the control group (P &lt; 0.05). There were no statistical differences in stride length variability and stride time variability between the two groups (P &gt; 0.05). A correlation analysis showed that BG-EPVS were negatively related to gait speed, cadence, stride length, pre-swing angle, and footfall (γrange = −0.497 to −0.237, P &lt; 0.001) and positively related to stance phase percentage (γ = 0.269, P &lt; 0.001). BG-EPVS was negatively related to the score of the Tinetti gait test (γ = −0.449, P &lt; 0.001) and the balance test (γ = −0.489, P &lt; 0.001). The multiple linear regression analysis indicated that BG-EPVS was an independent risk factor for gait disturbances and poor balance after adjusting for confounders, including other CSVD markers.

Conclusion

Large numbers of BG-EPVS were independently related to gait disturbances in older people with CSVD. This finding provides information about the consequences of BG-EPVS and risk factors for gait disturbances.

Association Between Large Numbers of Enlarged Perivascular Spaces in Basal Ganglia and Motor Performance in Elderly Individuals: A Cross-Sectional Study

Background and Objective

Motor dysfunction is common in the elderly, and is associated with adverse consequences. Enlarged perivascular spaces in basal ganglia (BG-EPVSs) are considered an MRI marker of cerebral small-vessel diseases. However, the consequences of BG-EPVSs are largely unknown. In the present study, we aimed to explore the association between large numbers of BG-EPVSs and motor performance.

Methods

We prospectively recruited elderly individuals in the Neurology Department of our hospital from December 1, 2020 to January 31, 2022. Participants with >20 BG-EPVSs on the unilateral side of the slice containing the most EPVSs were classified as the BG-EPVS group (n=99) and the rest as controls (n=193). Motor performance was assessed by quantitative gait analysis, Tinetti test, timed up-and-go (TUG) test, and the Short Physical Performance Battery (SPPB). Spearman correlation analysis and multivariate linear regression analysis were performed to investigate the association between BG-EPVSs and motor performance.

Results

Compared with the control group, the BG-EPVS group had lower gait speed and cadence, shorter stride length, longer TUG duration, and lower Tinetti gait test, Tinetti balance test, and SPPB scores (P<0.01). Spearman correlation analysis showed that BG-EPVSs were negatively related to gait speed, gait cadence, stride length, and Tinetti gait test, Tinetti balance test, and SPPB scores (ρ= –0.539 to –0.223, P<0.001) and positively related to TUG duration (ρ=0.397, P<0.001). Regression analysis indicated that BG-EPVSs were an independent risk factor of lower gait speed, shorter stride length, poor balance, and poor general physical performance after adjusting for confounders (β= –0.313 to –0.206, P<0.01).

Conclusion

Large numbers of BG-EPVSs were independently related to poor gait, balance, and general physical performance in elderly individuals, which provides information about the consequences of BG-EPVSs and risk factors for motor dysfunction.

Poor Sleep Quality Associated With Enlarged Perivascular Spaces in Patients With Lacunar Stroke

Background and Objective

Enlarged perivascular spaces (EPVSs) are considered as an MRI marker of cerebral small vessel diseases and were reported to be associated with brain waste clearance dysfunction. A previous study found that interstitial fluid clearance in the mouse brain occurred mainly during sleep. However, the relationship between sleep quality and EPVS in humans has not been well-understood. Thus, we aimed to investigate the relationship between sleep and EPVS in humans.

Methods

This retrospective study was conducted in patients with lacunar stroke in the Neurology Department of Beijing Chaoyang Hospital. Patients with EPVS >10 on one side of the basal ganglia (BG) and white matter slice containing the maximum amount were defined as the BG-EPVS group and the white matter (WM)-EPVS group, respectively. Patients with EPVS <10 in the slice containing the maximum amount were defined as the control group. Sleep quality was evaluated by the Pittsburgh Sleep Quality Index (PSQI) including seven components, where a score of 6 or higher indicated poor sleep quality. Spearman's correlation analysis and the binary logistic regression analysis were performed to analyze the relationship between poor sleep quality and BG-EPVS and WM-EPVS, respectively.

Results

A total of 398 patients were enrolled in this study, including 114 patients in the BG-EPVS group and 85 patients in the WM-EPVS group. The proportion of poor sleep quality in the BG-EPVS group was higher than that in the control group (58.8 vs. 32.5%, p < 0.001). The score of PSQI, subjective sleep quality, sleep latency, sleep duration, and sleep efficiency were higher in the BG-EPVS group than that in the control group (p < 0.05). The proportion of poor sleep quality was also higher in the WM-EPVS group than that in the control group (50.6 vs. 35.3%, p = 0.031). The score of sleep duration and sleep disturbances was higher in the WM-EPVS group than that in the control group. Spearman's correlation analysis showed that poor sleep quality was positively associated with BG-EPVS (ρ = 0.264, p < 0.001) and WM-EPVS (ρ = 0.154, p = 0.044). The binary logistic regression analysis showed that poor sleep quality, longer sleep latency, and less sleep duration were independently related to BG-EPVS and poor sleep quality, less sleep duration, and more serious sleep disturbances were independently related to WM-EPVS after adjusting for confounders (P < 0.05).

Conclusion

Poor sleep quality was independently associated with EPVS in BG and WM.

Mesenchymal stromal cells: what have we learned so far about their therapeutic potential and mechanisms of action?

Mesenchymal stromal cells (MSCs) have been found to be safe and effective in a wide range of animal models of human disease. MSCs have been tested in thousands of clinical trials, but results show that while these cells appear to be safe, they tend to lack efficacy. This has raised questions about whether animal models are useful for predicting efficacy in patients. However, a problem with animal studies is that there is a lack of standardisation in the models and MSC therapy regimes used; there appears to be publication bias towards studies reporting positive outcomes; and the reproducibility of results from animal experiments tends not to be confirmed prior to clinical translation. A further problem is that while some progress has been made towards investigating the mechanisms of action (MoA) of MSCs, we still fail to understand how they work. To make progress, it is important to ensure that prior to clinical translation, the beneficial effects of MSCs in animal studies are real and can be repeated by independent research groups. We also need to understand the MoA of MSCs to assess whether their effects are likely to be beneficial across different species. In this review, we give an overview of the current clinical picture of MSC therapies and discuss what we have learned from animal studies. We also give a comprehensive update of what we know about the MoA of MSCs, particularly in relation to their role in immunomodulation.

Cholinergic Receptor Modulation as a Target for Preventing Dementia in Parkinson's Disease

Parkinson’s disease (PD) is a neurodegenerative condition characterized by the loss of dopaminergic neurons in the substantia nigra pars compacta (SNpc) in the midbrain resulting in progressive impairment in cognitive and motor abilities. The physiological and molecular mechanisms triggering dopaminergic neuronal loss are not entirely defined. PD occurrence is associated with various genetic and environmental factors causing inflammation and mitochondrial dysfunction in the brain, leading to oxidative stress, proteinopathy, and reduced viability of dopaminergic neurons. Oxidative stress affects the conformation and function of ions, proteins, and lipids, provoking mitochondrial DNA (mtDNA) mutation and dysfunction. The disruption of protein homeostasis induces the aggregation of alpha-synuclein (α-SYN) and parkin and a deficit in proteasome degradation. Also, oxidative stress affects dopamine release by activating ATP-sensitive potassium channels. The cholinergic system is essential in modulating the striatal cells regulating cognitive and motor functions. Several muscarinic acetylcholine receptors (mAChR) and nicotinic acetylcholine receptors (nAChRs) are expressed in the striatum. The nAChRs signaling reduces neuroinflammation and facilitates neuronal survival, neurotransmitter release, and synaptic plasticity. Since there is a deficit in the nAChRs in PD, inhibiting nAChRs loss in the striatum may help prevent dopaminergic neurons loss in the striatum and its pathological consequences. The nAChRs can also stimulate other brain cells supporting cognitive and motor functions. This review discusses the cholinergic system as a therapeutic target of cotinine to prevent cognitive symptoms and transition to dementia in PD.

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.