Coon, Elizabeth A.

Abstract Introduction Risk of sudden death in multiple system atrophy (SuD-MSA) is greatest during sleep. Mechanisms underlying SuD-MSA may involve impaired brainstem arousal and cardiovascular responses to hypercapnia in MSA patients. We hypothesized that nocturnal arousal-related tachycardia events are reduced in MSA patients. We analyzed whether nocturnal pulse event frequency was altered in patients with MSA compared to patients with sleep disordered breathing without MSA utilizing portable overnight oximetry. Methods We retrospectively analyzed 46 probable MSA and 46 age-sex matched patients with sleep disordered breathing (SDB) without MSA, excluding patients receiving cardioactive medications. Nocturnal oxyhemoglobin desaturation indices (ODI) and pulse event indices (PEI) were automatically recorded for all patients using portable overnight oximetry. We calculated a PEI/ODI ratio to determine the relationship between probable breathing-related arousals and pulse rate change. Cardiovagal function was assessed by heart rate to deep breathing and Valsalva ratio in patients with MSA and Composite Autonomic Severity Score was assigned. Group comparisons were made with non-parametric tests. Multivariable regression explored relationships between oximetry variables and clinical characteristics. Results Average age at overnight oximetry was 62.9 ± 7.7 years. Total respiratory events between MSA patients compared with OSA controls were similar (95.0 ± 118.6 vs 73.5± 54.2, p=0.61). Total pulse events were lower in MSA than OSA controls without MSA (25.5±44.2 vs 111.6±120.2, p<0.001), as were pulse events per hour (3.1 ± 5.3 vs. 12.8 ± 10.8, p <0.001). The ratio of PEI/ODI was lower in MSA than OSA patients without MSA (p<0.001). Twelve (26%) MSA patients had zero pulse rate events, while all OSA patients without MSA had at least 1 pulse rate event (p<0.001). The number of pulse events was not associated with severity of cardiovagal dysfunction on daytime autonomic function testing. Conclusion Patients with MSA have fewer pulse rate events when compared with SDB patients without MSA, despite similar overall respiratory event frequency. The number of pulse events was not explained by severity of daytime autonomic dysfunction in those with MSA. Whether nocturnal pulse event response to sleep disordered breathing is a marker of disease severity or plays a role in SuD-MSA deserves further study. Support (If Any)

Abstract Study Objectives Multiple system atrophy (MSA) is associated with disturbances in cardiovascular, sleep and respiratory control. The lateral paragigantocellular nucleus (LPGi) in the ventrolateral medulla (VLM) contains GABAergic neurons that participate in control of rapid eye movement (REM) sleep and cardiovagal responses. We sought to determine whether there was loss of putative GABAergic neurons in the LPGi and adjacent regions in MSA. Methods Sections of the medulla were processed for GAD65/67 immunoreactivity in eight subjects with clinical and neuropathological diagnosis of MSA and in six control subjects. These putative GABAergic LPGi neurons were mapped based on their relationship to adjacent monoaminergic VLM groups. Results There were markedly decreased numbers of GAD-immunoreactive neurons in the LPGi and adjacent VLM regions in MSA. Conclusions There is loss of GABAergic neurons in the VLM, including the LPGi in patients with MSA. Whereas these findings provide a possible mechanistic substrate, given the few cases included, further studies are necessary to determine whether they contribute to REM sleep-related cardiovagal and possibly respiratory dysregulation in MSA.

AbstractAutonomic dysfunction is a characteristic feature in the synucleinopathies. Differences in cellular deposition and neuronal populations affected by α-synuclein aggregation influence the manifestations and severity of autonomic failure in the different synucleinopathy disorders. The Lewy body disorders (Parkinson's disease, dementia with Lewy bodies, and pure autonomic failure) have predominantly peripheral involvement, whereas multiple system atrophy chiefly manifests as central autonomic failure. Clinical and laboratory features may be useful in distinguishing the different synucleinopathies based on the pattern and severity of autonomic failure. Treatment recommendations are aimed at the underlying pathophysiology and utilize non-pharmacologic and pharmacologic approaches. This review will focus on pathophysiology, clinical manifestations, and management recommendations for autonomic failure including neurogenic orthostatic hypotension, thermoregulatory dysfunction, genitourinary dysfunction, and gastrointestinal dysfunction in the synucleinopathies.

Abstract Background Multiple system atrophy (MSA) is a neurodegenerative disorder from α‐synuclein aggregation. in vitro studies suggest vitamin B12 may interrupt α‐synuclein‐mediated neurodegeneration. The objective of this study was to determine whether serum vitamin B12 level at MSA diagnosis is associated with survival. Methods One hundred eighty‐two MSA patients evaluated at Mayo Clinic with vitamin B12 testing were studied. We determined the risk of death in relationship to serum vitamin B12 levels at MSA diagnosis, adjusting for predictors of poor survival. Results Predictors of shorter survival included vitamin B12 < 367 ng/L (HR, 1.8; 95% CI, 1.3–2.7), falls within 3 years of MSA diagnosis (HR, 1.6; 95% CI, 1.1–2.3), bladder symptoms (HR, 1.6; 95% CI, 1.0–2.6), urinary catheter requirement (HR, 1.7; 95% CI, 1.0–2.8), male sex (HR, 1.4; 95% CI, 1.0–2.0), and MSA‐P subtype (HR, 1.5; 95% CI, 1.0–2.0). Conclusions Low vitamin B12 levels are associated with shorter survival in MSA. Additional studies to explore this observation and assess the potential role of vitamin B12 as a modifiable survival factor are needed. © 2020 International Parkinson and Movement Disorder Society

Accurate antemortem diagnosis of parkinsonism is primarily based on clinical evaluation with limited biomarkers. We evaluated the diagnostic utility of quantitative rapid eye movement (REM) sleep without atonia analysis in the submentalis and anterior tibialis muscles in parkinsonian patients (53 synucleinopathy, 24 tauopathy). Receiver operating characteristic curves determined REM sleep without atonia cutoffs distinguishing synucleinopathies from tauopathies. Elevated submentalis muscle activity was highly sensitive (70–77%) and specific (95–100%) in distinguishing synucleinopathy from tauopathy. In contrast, anterior tibialis synucleinopathy discrimination was poor. Our results suggest that elevated submentalis REM sleep without atonia appears to be a potentially useful biomarker for presumed synucleinopathy etiologies in parkinsonism. ANN NEUROL 2019;86:969–974