Magnetic resonance imaging abnormalities as a marker of multiple system atrophy in isolated rapid eye movement sleep behavior disorder

The Pathobiology of Behavioral Changes in Multiple System Atrophy: An Update

While cognitive impairment, which was previously considered a red flag against the clinical diagnosis of multiple system atrophy (MSA), is a common symptom of this rare neurodegenerative disorder, behavioral disorders are reported in 30 to 70% of MSA patients. They include anxiety, apathy, impaired attention, compulsive and REM sleep behavior disorders (RBD), and these conditions, like depression, are early and pervasive features in MSA, which may contribute to disease progression. Despite changing concepts of behavioral changes in this synucleinopathy, the underlying pathophysiological and biochemical mechanisms are poorly understood. While specific neuropathological data are unavailable, neuroimaging studies related anxiety disorders to changes in the cortico-limbic system, apathy (and depression) to dysfunction of prefrontal-subcortical circuits, and compulsive behaviors to impairment of basal ganglia networks and involvement of orbito-frontal circuits. Anxiety has also been related to α-synuclein (αSyn) pathology in the amygdala, RBD to striatal monoaminergic deficit, and compulsive behavior in response to dopamine agonist therapy in MSA, while the basic mechanisms of the other behavioral disorders and their relations to other non-motor dysfunctions in MSA are unknown. In view of the scarcity of functional and biochemical findings in MSA with behavioral symptoms, further neuroimaging and biochemical studies are warranted in order to obtain better insight into their pathogenesis as a basis for the development of diagnostic biomarkers and future adequate treatment modalities of these debilitating comorbidities.

REM sleep and neurodegeneration

Several brainstem, subcortical and cortical areas are involved in the generation of rapid eye movement (REM) sleep. The alteration of these structures as a result of a neurodegenerative process may therefore lead to REM sleep anomalies. REM sleep behaviour disorder is associated with nightmares, dream-enacting behaviours and increased electromyographic activity in REM sleep. Its isolated form is a harbinger of synucleinopathies such as Parkinson's disease or dementia with Lewy bodies, and neuroprotective interventions are advocated. This link might also be present in patients taking antidepressants, with post-traumatic stress disorder, or with a history of repeated traumatic head injury. REM sleep likely contributes to normal memory processes. Its alteration has also been proposed to be part of the neuropathological changes occurring in Alzheimer's disease.

Reduced cardiac 123I-MIBG uptake is a robust biomarker of Lewy body disease in isolated rapid eye movement sleep behaviour disorder

Cardiac 123I-MIBG scintigraphy is used to assess the function of postganglionic presynaptic cardiac sympathetic nerve endings. 123I-MIBG cardiac uptake is markedly reduced in patients with isolated rapid eye movement sleep behaviour disorder, similar to Parkinson's disease and dementia with Lewy bodies. As a result, it can be used as an early biomarker of isolated rapid eye movement sleep behaviour disorder. Most patients with isolated rapid eye movement sleep behaviour disorder develop synucleinopathies: Parkinson's disease, dementia with Lewy bodies or multiple system atrophy. We aimed to investigate whether cardiac postganglionic denervation is present in patients with isolated rapid eye movement sleep behaviour disorder, as well as its possible usefulness as a marker for Lewy body disease status. This retrospective cohort study examined 306 patients (236 men and 70 women; mean age: 68.2 years; age range: 43-87 years) with polysomnography-confirmed isolated rapid eye movement sleep behaviour disorder who were followed for 1-3 months and underwent 123I-MIBG scintigraphy. We retrospectively analysed data from 306 patients with polysomnography-confirmed isolated rapid eye movement sleep behaviour disorder, and their longitudinal outcomes were documented at two centres. Among isolated rapid eye movement sleep behaviour disorder patients, reduced 123I-MIBG uptake was observed in the early and delayed images in 84.4 and 93.4% of patients, respectively, whereas 88.6% of the patients had a high washout rate. This large Japanese two-cohort study (n = 306) found that 91 patients (29.7%) developed an overt synucleinopathy (51 Parkinson's disease, 35 dementia with Lewy bodies, 4 multiple system atrophy, and 1 cerebellar ataxia) during a mean follow-up duration of 4.72 ± 3.94 years, with a conversion risk of 14.5% at 3 years, 25.4% at 5 years, 41.4% at 8 years and 52.5% at 10 years. On the other hand, among patients with heart-to-mediastinum ratio < 2.2 in the delayed images (n = 286), 85 (29.7%) developed Parkinson's disease or dementia with Lewy bodies during a mean follow-up duration of 4.71 ± 3.94 years, with a conversion risk of 14.5% at 3 years, 25.6% at 5 years, 42.0% at 8 years and 51.0% at 10 years. Among the 33 patients who underwent repeat 123I-MIBG scintigraphy, there was a progressive decline in uptake over the next 4.2 years, with patients exhibiting reduced uptake progressing to Parkinson's disease or dementia with Lewy bodies. In contrast, patients without decreased 123I-MIBG uptake progressed to multiple system atrophy. Reduced cardiac 123I-MIBG uptake was detected in over 90% of isolated rapid eye movement sleep behaviour disorder patients, with progression to Parkinson's disease or dementia with Lewy bodies, rather than multiple system atrophy, over time. Reduced 123I-MIBG uptake is a robust maker for Lewy body disease among isolated rapid eye movement sleep behaviour disorder patients.

Brain MRI Biomarkers in Isolated Rapid Eye Movement Sleep Behavior Disorder: Where Are We? A Systematic Review

The increasing number of MRI studies focused on prodromal Parkinson's Disease (PD) demonstrates a strong interest in identifying early biomarkers capable of monitoring neurodegeneration. In this systematic review, we present the latest information regarding the most promising MRI markers of neurodegeneration in relation to the most specific prodromal symptoms of PD, namely isolated rapid eye movement (REM) sleep behavior disorder (iRBD). We reviewed structural, diffusion, functional, iron-sensitive, neuro-melanin-sensitive MRI, and proton magnetic resonance spectroscopy studies conducted between 2000 and 2023, which yielded a total of 77 relevant papers. Among these markers, iron and neuromelanin emerged as the most robust and promising indicators for early neurodegenerative processes in iRBD. Atrophy was observed in several regions, including the frontal and temporal cortices, limbic cortices, and basal ganglia, suggesting that neurodegenerative processes had been underway for some time. Diffusion and functional MRI produced heterogeneous yet intriguing results. Additionally, reduced glymphatic clearance function was reported. Technological advancements, such as the development of ultra-high field MRI, have enabled the exploration of minute anatomical structures and the detection of previously undetectable anomalies. The race to achieve early detection of neurodegeneration is well underway.

Diagnostic and prognostic performance of plasma neurofilament light chain in multiple system atrophy: a cross-sectional and longitudinal study

BACKGROUND

The longitudinal dynamics of neurofilament light chain (NfL) in multiple system atrophy (MSA) were incompletely illuminated. This study aimed to explore whether the plasma NfL (pNfL) could serve as a potential biomarker of clinical diagnosis and disease progression for MSA.

METHODS

We quantified pNfL concentrations in both a large cross-sectional cohort with 214 MSA individuals, 65 PD individuals, and 211 healthy controls (HC), and a longitudinal cohort of 84 MSA patients. Propensity score matching (PSM) was used to balance the age between the three groups. The pNfL levels between groups were compared using Kruskal-Wallis test. Linear mixed models were performed to explore the disease progression-associated factors in longitudinal MSA cohort. Random forest model as a complement to linear models was employed to quantify the importance of predictors.

RESULTS

Before and after matching the age by PSM, the pNfL levels could reliably differentiate MSA from HC and PD groups, but only had mild potential to distinguish PD from HC. By combining linear and nonlinear models, we demonstrated that pNfL levels at baseline, rather than the change rate of pNfL, displayed potential prognostic value for progression of MSA. The combination of baseline pNfL levels and other modifiers, such as subtypes, Hoehn-Yahr stage at baseline, was first shown to improve the diagnosis accuracy.

CONCLUSIONS

Our study contributed to a better understanding of longitudinal dynamics of pNfL in MSA, and validated the values of pNfL as a non-invasive sensitive biomarker for the diagnosis and progression. The combination of pNfL and other factors is recommended for better monitoring and prediction of MSA progression.

The "Hot Cross Bun Sign" in Spinocerebellar Ataxia Types 2 and 7-Case Reports and Review of Literature

Background

The "hot cross bun" sign is a cruciform hyperintensity is seen on T2 weighted imaging within the pons. The sign is considered to be pathognomic for Multiple system atrophy type C. The clinical and radiological features of Multiple system atrophy type C overlap with the autosomal dominant inherited ataxias. We present a case series of 3 African patients with genetically proven Spinocerebellar Ataxia presenting with the Hot cross bun sign and a scoping review of similar studies.

Cases

We described the phenotypic and radiological presentation of genetically confirmed SCA-2 in two, and SCA-7 in one patient, with the "hot cross bun" sign.

Literature Review

We performed a scoping review on the Hot Cross Bun Sign.A total of 66 articles were retrieved. We describe the diverse aetiologies of the sign and associated phenotypic and radiological features. We review the Spinocerebellar Ataxias described with a Hot cross bun sign and make comparisons to Multiple System Atrophy Type C [Ref. 1,2].

Conclusions

To our knowledge this is the first description of an African cohort presenting with the Hot Cross Bun Sign. We expand the differential diagnosis of the Hot Cross Bun Sign.

Multiple system atrophy

Multiple system atrophy (MSA) is a rare neurodegenerative disease that is characterized by neuronal loss and gliosis in multiple areas of the central nervous system including striatonigral, olivopontocerebellar and central autonomic structures. Oligodendroglial cytoplasmic inclusions containing misfolded and aggregated α-synuclein are the histopathological hallmark of MSA. A firm clinical diagnosis requires the presence of autonomic dysfunction in combination with parkinsonism that responds poorly to levodopa and/or cerebellar ataxia. Clinical diagnostic accuracy is suboptimal in early disease because of phenotypic overlaps with Parkinson disease or other types of degenerative parkinsonism as well as with other cerebellar disorders. The symptomatic management of MSA requires a complex multimodal approach to compensate for autonomic failure, alleviate parkinsonism and cerebellar ataxia and associated disabilities. None of the available treatments significantly slows the aggressive course of MSA. Despite several failed trials in the past, a robust pipeline of putative disease-modifying agents, along with progress towards early diagnosis and the development of sensitive diagnostic and progression biomarkers for MSA, offer new hope for patients.

Odor identification predicts the transition of patients with isolated RBD: A retrospective study

Introduction

To determine if the severity of olfactory dysfunction in isolated REM sleep behavior disorder (IRBD) predicts conversion to Parkinson's disease (PD) or dementia with Lewy bodies (DLB).

Methods

Olfaction was tested using the Japanese version of the University of Pennsylvania Smell Identification Test (UPSIT‐J) in 155 consecutive patients with polysomnography‐confirmed IRBD and 34 healthy controls. IRBD patients were followed up for 5.8 ± 3.2 (range 0.2–11) years. Thirty‐eight patients underwent repeat UPSIT‐J evaluation at 2.7 ± 1.3 years after the baseline test.

Results

UPSIT‐J score was lower in IRBD patients than in age‐ and sex‐matched controls. The receiver operating characteristic curve analysis showed that the optimal cutoff score of 22.5 in UPSIT‐J discriminated between IRBD patients and controls with a sensitivity of 94.3% and specificity of 81.8%. Anosmia (UPSIT‐J score < 19) was present in 54.2% of IRBD patients. In total, 42 patients developed a neurodegenerative disease, of whom 17 had PD, 22 DLB, and 3 MSA. Kaplan–Meier analysis showed that the short‐term risk of Lewy body disease (LBD) was higher in patients with anosmia than in those without anosmia. At baseline, the UPSIT‐J score was similar between patients who developed PD and DLB (p = 0.136). All three IRBD patients (100%) who developed MSA did not have anosmia.

Conclusions

In IRBD patients, anosmia predicts a higher short‐term risk of transition to LBD but cannot distinguish between PD and DLB. At baseline, preserved odor identification may occur in latent MSA. Future IRBD neuroprotective trials should evaluate anosmia as a marker of prodromal LBD.

Biomarkers of conversion to α-synucleinopathy in isolated rapid-eye-movement sleep behaviour disorder

Patients with isolated rapid-eye-movement sleep behaviour disorder (RBD) are commonly regarded as being in the early stages of a progressive neurodegenerative disease involving α-synuclein pathology, such as Parkinson's disease, dementia with Lewy bodies, or multiple system atrophy. Abnormal α-synuclein deposition occurs early in the neurodegenerative process across the central and peripheral nervous systems and might precede the appearance of motor symptoms and cognitive decline by several decades. These findings provide the rationale to develop reliable biomarkers that can better predict conversion to clinically manifest α-synucleinopathies. In addition, biomarkers of disease progression will be essential to monitor treatment response once disease-modifying therapies become available, and biomarkers of disease subtype will be essential to enable prediction of which subtype of α-synucleinopathy patients with isolated RBD might develop.

Update on neuroimaging for categorization of Parkinson's disease and atypical parkinsonism

PURPOSE OF REVIEW

Differential diagnosis of Parkinsonism may be difficult. The objective of this review is to present the work of the last three years in the field of imaging for diagnostic categorization of parkinsonian syndromes focusing on progressive supranuclear palsy (PSP) and multiple system atrophy (MSA).

RECENT FINDINGS

Two main complementary approaches are being pursued. The first seeks to develop and validate manual qualitative or semi-quantitative imaging markers that can be easily used in clinical practice. The second is based on quantitative measurements of magnetic resonance imaging abnormalities integrated in a multimodal approach and in automatic categorization machine learning tools.

SUMMARY

These two complementary approaches obtained high diagnostic around 90% and above in the classical Richardson form of PSP and probable MSA. Future work will determine if these techniques can improve diagnosis in other PSP variants and early forms of the diseases when all clinical criteria are not fully met.

Significance of hyposmia in isolated REM sleep behavior disorder

OBJECTIVE

To determine if hyposmia in isolated REM sleep behavior disorder (IRBD) predicts short-term conversion to any α-synucleinopathy and declines with time.

METHODS

Olfaction was tested using the University of Pennsylvania Smell Identification Test (UPSIT-40) in 140 consecutive patients with polysomnography-confirmed IRBD and in 77 matched controls. Patients were followed-up during 5.6 ± 3.9 (range 0.2-13) years. Twenty-one patients underwent serial UPSIT-40 evaluations at 1-3 and 4-6 years after baseline.

RESULTS

UPSIT-40 score was lower in patients than in controls (20.2 ± 6.5 vs. 28.6 ± 5.0; p < 0.001). Hyposmia (UPSIT-40 score < 19 points) occurred in 42.9% patients. Forty-three (30.7%) patients developed Parkinson disease (PD = 27), dementia with Lewy bodies (DLB = 13) and multiple system atrophy (MSA = 3). Kaplan-Meier analysis showed that hyposmics had higher risk than normosmics to develop a synucleinopathy at the short term (p = 0.030). UPSIT-40 score was similar between patients who developed PD and DLB (p = 0.136). Normal smell occurred in all three (100%) IRBD patients who developed MSA, 12 of 27 (44%) who developed PD, and 4 of 13 (31%) that developed DLB. Serial UPSIT-40 evaluations showed no changes with time (p = 0.518).

CONCLUSION

In IRBD, hyposmia is a short-term risk for synucleinopathies but cannot distinguish underlying PD from DLB. Normosmia not only occurs in latent MSA but also in latent PD and DLB. In future IRBD neuroprotective trails, individuals at entry could be enriched for hyposmia, whereas serial evaluation of smell would not be useful to monitor the efficacy of a therapeutic intervention.