Diagnosis and management of autonomic failure in neurodegenerative disorders

Central Autonomic Network and heart rate variability in premature neonates

INTRODUCTION

The Central Autonomic Network (CAN) is a hierarchy of brain structures that collectively influence cardiac autonomic input, mediating the majority of brain-heart interactions, but has never been studied in premature neonates. In this study, we use heart rate variability (HRV), which has been described as the "primary output" of the CAN, and resting state functional MRI to characterize brain-heart relationships in premature neonates.

METHODS

We studied premature neonates who underwent resting state functional MRI (rsfMRI) at term, (37-weeks postmenstrual age [PMA] or above) and had HRV data recorded during the same week of their MRI. HRV was derived from continuous electrocardiogram data during the week of the rsfMRI scan. For rsfMRI, a seed-based approach was used to define regions of interest (ROI) pertinent to the CAN, and blood oxygen level-dependent signal was correlated between each ROI as a measure of functional connectivity. HRV was correlated with CAN connectivity (CANconn) for each region, and sub-group analysis was performed based on sex and clinical comorbidities.

RESULTS

Forty-seven premature neonates were included in this study, with a mean gestational age at birth of 28.1 +/- 2.6 weeks. Term CANconn was found to be significantly correlated with HRV in approximately one-fifth of CAN connections. Two distinct patterns emerged among these HRV-CANconn relationships. In the first, increased HRV was associated with stronger CANconn of limbic regions. In the second pattern, stronger CANconn at the precuneus was associated with impaired HRV maturation. These patterns were especially pronounced in male premature neonates.

CONCLUSION

We report for the first time evidence of brain-heart relationships in premature neonates and an emerging CAN, most striking in male neonates, suggesting that the brain-heart axis may be more vulnerable in male premature neonates. Signatures in the heart rate may eventually become an important non-invasive tool to identify premature males at highest risk for neurodevelopmental impairment.

At the heart of the matter: how mental stress and negative emotions affect atrial fibrillation

Atrial fibrillation (AF) is the most common form of cardiac arrhythmia, affecting 2%-3% of the world's population. Mental and emotional stress, as well as some mental health conditions (e.g., depression) have been shown to significantly impact the heart and have been suggested to act both as independent risk factors and triggers in the onset of AF. In this paper, we review the current literature to examine the role that mental and emotional stress have in the onset of AF and summarise the current knowledge on the interaction between the brain and heart, and the cortical and subcortical pathways involved in the response to stress. Review of the evidence suggests that mental and emotional stress negatively affect the cardiac system, potentially increasing the risk for developing and/or triggering AF. Further studies are required to further understand the cortical and sub-cortical structures involved in the mental stress response and how these interact with the cardiac system, which may help in defining new strategies and interventions to prevent the development of, and improve the management of AF.

Do Neurotrophins Connect Neurological Disorders and Heart Diseases?

Neurotrophins (NTs) are one of the most characterized neurotrophic factor family members and consist of four members in mammals. Growing evidence suggests that there is a complex inter- and bi-directional relationship between central nervous system (CNS) disorders and cardiac dysfunction, so-called "brain-heart axis". Recent studies suggest that CNS disorders, including neurodegenerative diseases, stroke, and depression, affect cardiovascular function via various mechanisms, such as hypothalamic-pituitary-adrenal axis augmentation. Although this brain-heart axis has been well studied in humans and mice, the involvement of NT signaling in the axis has not been fully investigated. In the first half of this review, we emphasize the importance of NTs not only in the nervous system, but also in the cardiovascular system from the embryonic stage to the adult state. In the second half, we discuss the involvement of NTs in the pathogenesis of cardiovascular diseases, and then examine whether an alteration in NTs could serve as the mediator between neurological disorders and heart dysfunction. The further investigation we propose herein could contribute to finding direct evidence for the involvement of NTs in the axis and new treatment for cardiovascular diseases.

[Interactions between the brain and heart]

The brain and heart are closely interconnected. Physiologically, the brain influences the way the heart beats. An example for this physiological influence is the control of the heart rate via efferences of the autonomic nervous system. Clinical examples for this direction of interactions include cardiac complications after stroke as well as takotsubo cardiomyopathy; however, the heart and brain are reciprocally connected so that heart activity also influences the brain beyond its function as the generator of bloodflow supplying the brain. Examples for this are the perception of stimuli depending on the time of presentation during the heart cycle. Clinical examples of the direction of this interaction constitute stroke as a thromboembolic complication of atrial fibrillation as well as the correlation of atrial fibrillation and dementia. This review article gives an overview of the bidirectional interactions between the heart and brain, partly including the cardiovascular system, discusses their implications for the clinical routine and gives an outlook on current fields of research.

A case of parasympathetic hyperactivity and associated Parry-Romberg syndrome

This case report describes a 46-year-old female with a history of multiple endocrine neoplasia type 1 syndrome status post-parathyroidectomy, thymectomy via robotic video-assisted thoracoscopic surgery, and pituitary adenoma resection presenting with parasympathetic hyperactivity and Parry-Romberg syndrome. Parry-Romberg syndrome is a rare disorder that manifests as facial hemiatrophy. Reported symptoms include cognitive dysfunction, olfactory hallucinations, and parasympathetic hyperactivity: miosis of the right eye, anhidrosis, diarrhea, urinary incontinence, bowel incontinence, and orthostatic hypotension. Previous reports have noted associations between Parry-Romberg syndrome and sympathetic hyperactivity and dysregulation. This case report focuses on an association between Parry-Romberg syndrome and unopposed parasympathetic activity.

Heart-Brain Axis: Effects of Neurologic Injury on Cardiovascular Function

A complex interaction exists between the nervous and cardiovascular systems. A large network of cortical and subcortical brain regions control cardiovascular function via the sympathetic and parasympathetic outflow. A dysfunction in one system may lead to changes in the function of the other. The effects of cardiovascular disease on the nervous system have been widely studied; however, our understanding of the effects of neurological disorders on the cardiovascular system has only expanded in the past 2 decades. Various pathologies of the nervous system can lead to a wide range of alterations in function and structure of the cardiovascular system ranging from transient and benign electrographic changes to myocardial injury, cardiomyopathy, and even cardiac death. In this article, we first review the anatomy and physiology of the central and autonomic nervous systems in regard to control of the cardiovascular function. The effects of neurological injury on cardiac function and structure will be summarized, and finally, we review neurological disorders commonly associated with cardiovascular manifestations.

Brain-heart interactions: physiology and clinical implications

The brain controls the heart directly through the sympathetic and parasympathetic branches of the autonomic nervous system, which consists of multi-synaptic pathways from myocardial cells back to peripheral ganglionic neurons and further to central preganglionic and premotor neurons. Cardiac function can be profoundly altered by the reflex activation of cardiac autonomic nerves in response to inputs from baro-, chemo-, nasopharyngeal and other receptors as well as by central autonomic commands, including those associated with stress, physical activity, arousal and sleep. In the clinical setting, slowly progressive autonomic failure frequently results from neurodegenerative disorders, whereas autonomic hyperactivity may result from vascular, inflammatory or traumatic lesions of the autonomic nervous system, adverse effects of drugs and chronic neurological disorders. Both acute and chronic manifestations of an imbalanced brain-heart interaction have a negative impact on health. Simple, widely available and reliable cardiovascular markers of the sympathetic tone and of the sympathetic-parasympathetic balance are lacking. A deeper understanding of the connections between autonomic cardiac control and brain dynamics through advanced signal and neuroimage processing may lead to invaluable tools for the early detection and treatment of pathological changes in the brain-heart interaction.

Pharmacodynamics of a low subacute levodopa dose helps distinguish between multiple system atrophy with predominant Parkinsonism and Parkinson's disease

The differential diagnosis between multiple system atrophy with predominant parkinsonism (MSA-P) and Parkinson's disease (PD) may be challenging at disease onset. Levodopa responsiveness helps distinguish the two groups, but studies evaluating this issue using objective standardized tests are scanty. We retrospectively examined the extent of levodopa response by an objective kinetic-dynamic test in a series of patients prospectively followed up for a parkinsonian syndrome and eventually diagnosed as MSA-P or PD. Sixteen MSA-P and 31 PD patients under chronic levodopa therapy received a first morning fasting dose of levodopa/benserazide (100/25 mg) or levodopa/carbidopa (125/12.5 or 100/25 mg) and underwent simultaneous serial assessments of plasma levodopa concentration and alternate finger tapping frequency up to 3 h post dosing. The main levodopa pharmacodynamic variables were the maximum percentage increase in tapping frequency over baseline values (ΔTapmax %) and the area under the tapping effect-time curve (AUCTap). Levodopa pharmacokinetics did not show significant differences between MSA-P and PD, whereas both the magnitude and overall extent of levodopa tapping effect were markedly reduced in the MSA-P group (p < 0.001). The combined use of specific cut-off values for both the main pharmacodynamic variables, ΔTapmax % <20% and AUCTap <1900 [(tapping/min)·min], correctly discriminated 15 out of 16 MSA-P patients from PD patients. A combined estimation of these pharmacodynamic variables after a subacute low levodopa dose may be a simple and practical clinical tool to aid the differential diagnosis between MSA-P and PD.