Citations

Purpose of review This review aims to summarize the current literature describing vestibular-autonomic interactions and to describe their putative role in various disorders’ clinical presentations, including orthostatic dizziness and motion sensitivity. Recent findings The vestibular-autonomic reflexes have long been described as they relate to cardiovascular and respiratory function. Although orthostatic dizziness may be in part related to impaired vestibulo-sympathetic reflex (orthostatic hypotension), there are various conditions that may present similarly. A recent clinical classification aims to improve identification of individuals with hemodynamic orthostatic dizziness so that appropriate recommendations and management can be efficiently addressed. Researchers continue to improve understanding of the underlying vestibular-autonomic reflexes with recent studies noting the insular cortex as a cortical site for vestibular sensation and autonomic integration and modulation. Work has further expanded our understanding of the clinical presentation of abnormal vestibular-autonomic interactions that may occur in various conditions, such as aging, peripheral vestibular hypofunction, traumatic brain injury, and motion sensitivity. Summary The vestibular-autonomic reflexes affect various sympathetic and parasympathetic functions. Understanding these relationships will provide improved identification of underlying etiology and drive improved patient management.

Injury of the afferent limb of the baroreflex from neck radiation causes radiation-induced afferent baroreflex failure (R-ABF). Identification and management of R-ABF is challenging. We aimed to investigate the pattern of autonomic dysfunction on standardized autonomic testing in patients with probable R-ABF. We retrospectively analyzed all autonomic reflex screens performed at Mayo Clinic in Rochester, MN, between 2000 and 2020 in patients with probable R-ABF. Additional tests reviewed included ambulatory blood pressure monitoring, plasma norepinephrine, and thermoregulatory sweat test. We identified 90 patients with probable R-ABF. Median total composite autonomic severity score (range, 0–10) was 7 (interquartile range, 6–7). Cardiovascular adrenergic impairment was seen in 85 patients (94.4%), increased blood pressure recovery time after Valsalva maneuver in 71 patients (78.9%; median 17.4 seconds), and orthostatic hypotension in 68 patients (75.6%). Cardiovagal impairment was demonstrated by abnormal heart rate responses to deep breathing (79.5%), Valsalva ratio (87.2%), and vagal baroreflex sensitivity (57.9%). Plasma norepinephrine was elevated and rose appropriately upon standing (722–1207 pg/mL). Ambulatory blood pressure monitoring revealed hypertension, postural hypotension, hypertensive surges, tachycardia, and absence of nocturnal dipping. Blood pressure lability correlated with impaired vagal baroreflex function. Postganglionic sympathetic sudomotor function was normal in most cases; the most frequent thermoregulatory sweat test finding was focal neck anhidrosis (78.9%). Standardized autonomic testing in R-ABF demonstrates cardiovascular adrenergic impairment with orthostatic hypotension, blood pressure lability, and elevated plasma norepinephrine. Cardiovagal impairment is common, while sudomotor deficits are limited to direct radiation effects.

Abstract The aim of this book is to provide the clinician with a comprehensive and clinical relevant survey of emerging concepts on the organization and function of the nervous system and neurologic disease mechanisms, at the molecular, cellular, and system levels. The content of is based on the review of information obtained from recent advances in genetic, molecular, and cell biology techniques; electrophysiological recordings; brain mapping; and mouse models, emphasizing the clinical and possible therapeutic implications. Many chapters of this book contain information that will be relevant not only to clinical neurologists but also to psychiatrists and physical therapists. The scope includes the mechanisms and abnormalities of DNA/RNA metabolism, proteostasis, vesicular biogenesis, and axonal transport and mechanisms of neurodegeneration; the role of the mitochondria in cell function and death mechanisms; ion channels, neurotransmission and mechanisms of channelopathies and synaptopathies; the functions of astrocytes, oligodendrocytes, and microglia and their involvement in disease; the local circuits and synaptic interactions at the level of the cerebral cortex, thalamus, basal ganglia, cerebellum, brainstem, and spinal cord transmission regulating sensory processing, behavioral state, and motor functions; the peripheral and central mechanisms of pain and homeostasis; and networks involved in emotion, memory, language, and executive function.