Autonomic involvement in Guillain-Barré syndrome: an update

Neuromuscular problems of the critically Ill neonate and child

Acute neuromuscular disorders occasionally occur in the Pediatric Neurologic Intensive Care Unit. Many of these are primary disorders of the motor unit that may present acutely or exacerbate during an intercurrent illness. Additionally, acute neuromuscular disorders may develop during an acute systemic illness requiring intensive care management that predispose the child to another set of acute motor unit disorders. This chapter discusses acute neuromuscular crises in the infant, toddler, and adolescent, as well as neuromuscular disorders resulting from critical illness.

Autoimmune Autonomic Neuropathy: From Pathogenesis to Diagnosis

Autoimmune autonomic ganglionopathy (AAG) is a disease of autonomic failure caused by ganglionic acetylcholine receptor (gAChR) autoantibodies. Although the detection of autoantibodies is important for distinguishing the disease from other neuropathies that present with autonomic dysfunction, other factors are important for accurate diagnosis. Here, we provide a comprehensive review of the clinical features of AAG, highlighting differences in clinical course, clinical presentation, and laboratory findings from other neuropathies presenting with autonomic symptoms. The first step in diagnosing AAG is careful history taking, which should reveal whether the mode of onset is acute or chronic, followed by an examination of the time course of disease progression, including the presentation of autonomic and extra-autonomic symptoms. AAG is a neuropathy that should be differentiated from other neuropathies when the patient presents with autonomic dysfunction. Immune-mediated neuropathies, such as acute autonomic sensory neuropathy, are sometimes difficult to differentiate, and therefore, differences in clinical and laboratory findings should be well understood. Other non-neuropathic conditions, such as postural orthostatic tachycardia syndrome, chronic fatigue syndrome, and long COVID, also present with symptoms similar to those of AAG. Although often challenging, efforts should be made to differentiate among the disease candidates.

Analysis of Post-COVID-19 Guillain-Barré Syndrome over a Period of One Year in the University Hospital of Split (Croatia)

The virus SARS-CoV-2 (Severe Acute Respiratory Syndrome Coronavirus 2) is capable of attacking the nervous system in several ways and leading to neurological diseases such as GBS (Guillain-Barré syndrome) through the resulting neurotropism and immune response. The aim of this study is to show the relationship between Coronavirus disease (COVID-19) and GBS and to better understand the clinical symptoms to prevent poor outcomes. Data from 15 patients were extracted from the Department of Neurology, University Hospital of Split, Croatia, for the year 2021. The age of the patients ranged from 26 to 89 years, of whom 27% were women. Sixty seven percent of all GBS patients recovered from COVID-19 infection, whereas post-vaccinal polyradiculoneuritis was detected in 6%. Forty four percent of the patients who developed GBS had a severe form of COVID-19 infection. Forty percent of patients were treated with intravenous immunoglobulins (IVIG), followed by therapeutic plasma exchange (PLEX) in 27%. After the therapy, improvement was observed in 13 patients, while two patients died. The results suggest that SARS-CoV-2 triggers GBS because it follows a similar pattern of infection as the other viral and bacterial agents that contribute to the onset of GBS. There is no evidence that prior infection with COVID-19 worsens the clinical presentation of GBS.

Guillain-Barré Syndrome

OBJECTIVE

This article summarizes the clinical features, diagnostic criteria, differential diagnosis, pathogenesis, and prognosis of Guillain-Barré syndrome (GBS), with insights into the current and future diagnostic and therapeutic interventions for this neuromuscular syndrome.

LATEST DEVELOPMENTS

GBS is an acute, inflammatory, immune-mediated polyradiculoneuropathy that encompasses many clinical variants and divergent pathogenic mechanisms that lead to axonal, demyelinating, or mixed findings on electrodiagnostic studies. The type of antecedent infection, the development of pathogenic cross-reactive antibodies via molecular mimicry, and the location of the target gangliosides affect the subtype and severity of the illness. The data from the International GBS Outcome Study have highlighted regional variances, provided new and internationally validated prognosis tools that are beneficial for counseling, and introduced a platform for discussion of GBS-related open questions. New research has been undertaken, including research on novel diagnostic and therapeutic biomarkers, which may lead to new therapies.

ESSENTIAL POINTS

GBS is among the most frequent life-threatening neuromuscular emergencies in the world. At least 20% of patients with GBS have a poor prognosis and significant residual deficits despite receiving available treatments. Research is ongoing to further understand the pathogenesis of the disorder, find new biomarkers, and develop more effective and specific treatments.

Neuroprognostication: Guillain-Barré Syndrome

Guillain-Barré syndrome is an immune-mediated disease of the peripheral nerves characterized by rapidly progressing symmetric weakness, areflexia, and albuminocytological dissociation. Most patients reach their nadir within 2 weeks. Disease severity can be mild to severe, with 20% of patients requiring mechanical ventilation. Intravenous immunoglobulin and plasma exchange are equally effective treatments. Monitoring strength, respiratory function, blood pressure, and heart rate, as well as pain management and rehabilitative therapy are important aspects of management. About 20% of patients require assistance to walk at 6 months. Older age, preceding diarrhea, and lower Medical Research Council (MRC) sum scores predict poor outcome. Death from cardiovascular and respiratory complications can occur in the acute or recovery phases of the illness in 3 to 7% of the patients. Risk factors for mortality include advanced age and disease severity at onset. Neuropathic pain, weakness, and fatigue can be residual symptoms; risk factors for these include axonal loss, sensory involvement, and severity of illness.

Encephalopathy with Guillain-Barré syndrome: seek a different cause

A 30-year-old woman developed symptoms, signs and neurophysiology consistent with Guillain-Barré syndrome and was admitted to the neurosciences intensive care unit owing to respiratory compromise. Here, she received a clonidine infusion for agitation, complicated by a minor hypotensive episode, following which she became unconscious. MR scan of the brain showed changes compatible with hypoxic brain injury. Urinary amino acids showed increased urinary α-ketoglutarate. Genetic testing using whole-exome sequencing identified pathogenic variants in the SLC13A3 gene known to be associated with an acute reversible leukoencephalopathy with increased urinary α-ketoglutarate. The case highlights the importance of considering inborn errors of metabolism in cases of unexplained encephalopathy.

[Characteristics of sympathetic skin response in children with Guillain-Barré syndrome]

OBJECTIVES

To explore the value of sympathetic skin response (SSR) in the early diagnosis and prognostic evaluation of Guillain-Barre syndrome (GBS) in children.

METHODS

A retrospective analysis was conducted on the clinical data of 25 children with GBS who were diagnosed from October 2018 to November 2022, and 30 children who were diagnosed with Tourette's syndrome during the same period were selected as the control group. The characteristics of SSR were compared between the two groups, and the association of SSR with autonomic dysfunction (AD), disease severity, and prognosis was analyzed.

RESULTS

The GBS group had a significantly higher abnormal rate of SSR than the control group during the acute phase (P<0.001). SSR combined with early nerve conduction (within 2 weeks after onset) had a sensitivity of 84%, a specificity of 100%, and an accuracy of 93% in the diagnosis of GBS. There were no significant differences in the proportion of AD cases, as well as the Hughes scores during the disease peak, between the abnormal and normal SSR groups (P>0.05). All 7 children with poor short-term prognosis (at 1 month after onset) had abnormal SSR.

CONCLUSIONS

SSR can be used for the early diagnosis of GBS and the monitoring of treatment response in children.

Autonomic nervous system involvement in chronic inflammatory demyelinating polyradiculoneuropathy: a literature review

BACKGROUND AND AIMS

Although dysautonomia is a well-recognized complication of acute demyelinating polyradiculoneuropathy, it is rarely reported and evaluated in chronic demyelinating neuropathies. The purpose of this review is to search and synthesize the current literature on the prevalence and type of autonomic dysfunction (AD) in chronic inflammatory demyelinating polyradiculoneuropathy (CIDP).

METHODS

PubMed and Web of Science were searched for studies reporting AD in CIDP.

RESULTS

Twelve studies, including 346 patients with CIDP, were found eligible for the review. Seven studies used autonomic tests only as an additional component of the comprehensive clinical evaluation, and found that dysautonomia in CIDP may indicate the presence of a comorbid disease (e.g., diabetes) and facilitate the differentiation of CIDP from other neuropathies (e.g., amyloid neuropathy). Five studies performed quantitative assessment of autonomic function in CIDP as a primary goal. Two studies have used the Composite Autonomic Severity Score (CASS) to assess severity and distribution of dysautonomia. The reported prevalence of dysautonomia in CIDP during quantitative assessment of autonomic function ranged from 25 to 89%, depending on the battery of tests used, with CASS not exceeding 4 points. The abnormalities in autonomic tests indicated both sympathetic and parasympathetic dysfunction and did not correlate with the duration, severity and variant of CIDP.

CONCLUSIONS

Clinical or subclinical involvement of the ANS has been shown to be common and relatively mild in CIDP. The impact of autonomic impairment on disability and of its possible response to therapy in CIDP needs to be further investigated.

Prognostic Implications of Early Albuminocytological Dissociation in Guillain-Barré Syndrome

BACKGROUND

Half of Guillain-Barré syndrome (GBS) present elevated cerebrospinal fluid (CSF) protein levels within 1 week since symptom onset and 80% within 2 weeks. Our objective was to determine the clinical and prognostic implication of albuminocytological dissociation in early GBS.

METHODS

An ambispective cohort study was conducted. Good outcome was considered if the patient was able to walk unaided (Guillain-Barré disability score [GDS] ≤ 2 points) at 3-month follow-up. Patients were classified into two groups: with and without albuminocytological dissociation; we compared clinical and paraclinic characteristics between the groups. We analyzed clinical and electrophysiological factors related to presenting early dissociation through a multivariate model.

RESULTS

We included 240 patients who fulfilled Asbury criteria for GBS. On further selection, only 94 patients fulfilled inclusion. Mean age was 45.94 ± 17.1 years and 67% were male. Median time from symptom onset to admission was 5 days (IQR 3-6). Regarding albuminocytological dissociation and electrophysiological variants, we found a significant difference: acute inflammatory demyelinating polyneuropathy (AIDP) [60.6% vs 26.2%, p = 0.002], acute motor axonal neuropathy (AMAN) [21.2% vs 49.1%, p = 0.009] and acute motor sensory axonal neuropathy (AMSAN) [12.1% vs 1.6%, p = 0.05]. We did not observe significant differences in recovery of independent walking in short term between both groups. The presence of conduction block in any variant (OR 3.21, 95% CI 1.12-9.16, p = 0.02) and absence of sural registration (OR 5.69, 95% CI 1.48-21.83, p = 0.011) were independent factors related to early dissociation.

CONCLUSIONS

Early dissociation (<7 days) is not associated with any particular clinical feature or unfavorable outcome. It is more common to see in AIDP rather than axonal variants.

Guillain-Barré Syndrome Associated with SARS-CoV-2 in Two Pediatric Patients

Guillain-Barré syndrome (GBS) is a recognised complication of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). We report two children with GBS associated with SARS-CoV-2 who presented to a tertiary centre in Muscat, Oman in 2021: The first patient was a three-month-old female infant who presented with bradypnea, encephalopathy, and generalised weakness that required mechanical ventilation. Polymerase chain reaction (PCR) testing of the nasopharyngeal swabs (NPS) was positive for SARS-CoV-2. She had axonal variant GBS based on a nerve conduction study, cerebrospinal fluid analysis, and neuroimaging findings. The second patient was a six-year-old girl with fever, vomiting, and diarrhea followed by ascending weakness who presented with quadriplegia and facial weakness. Subsequently, she developed respiratory muscle weakness and required mechanical ventilation. PCR testing of NPS was negative for SARS-Cov-2, however IgG serology analysis was positive. The clinical course of these two patients was rapidly progressive and both of them required mechanical ventilation. The patient with axonal variant GBS made an incomplete recovery.

Sympathetic skin response (SSR) in pediatric Guillain-Barré syndrome

Introduction

In the present study, sympathetic skin response (SSR) characteristics were explored in children with Guillain-Barré syndrome (GBS) and the value of early diagnosis and prognostic evaluation in GBS complicated by autonomic dysfunction (AD) was evaluated.

Methods

A total of 25 children with GBS and 30 healthy controls (HCs) were enrolled in this prospective study. SSR findings for the two groups were compared. SSR and nerve conduction study (NCS) results were compared among patients with GBS, and differences in clinical characteristics between the groups with abnormal and normal SSR were analyzed.

Results

Within the GBS group, six patients (24%) required mechanical ventilation, 17 patients (66.7%) had AD, 18 patients (72%) had an abnormal SSR, and 13 patients (52%) had AD combined with SSR abnormalities. There was a statistically significant difference in SSR latency in the lower limbs between the GBS group and HCs (P < 0.05). There was no statistically significant difference between SSR and NCS results in the acute phase of GBS (P > 0.05), and there was no significant difference in the rate of AD or in Hughes functional grade at nadir between the groups with abnormal and normal SSR (P>0.05). However, there was a statistically significant difference between the results of SSR and NCS tests during the recovery phase (P = 0.003). Abnormal SSR mainly occurred in cases of the acute inflammatory demyelinating polyradiculoneuropathy (AIDP) subtype. In addition, SSR was abnormal in all pediatric GBS patients with poor prognosis 1 month after onset of symptoms.

Conclusion

Two-thirds of the children with GBS have AD. SSR could be used for early diagnosis and follow-up of GBS and may also be helpful in evaluating disease severity and short-term prognosis.

Takotsubo Cardiomyopathy: A Possible Rare Complication of Guillain-Barré Syndrome

Dysautonomia is a common and severe complication of Guillain-Barré syndrome (GBS), which may manifest as cardiac arrhythmias, labile blood pressure, diaphoresis, and changes in gastrointestinal motility. Takotsubo cardiomyopathy (TCM) is a life-threatening manifestation of dysautonomia in patients with GBS, which is not widely underlined in the literature. The association between GBS and TCM has been well-documented in previous studies; however, there are few reported cases with GBS who developed TCM following their diagnosis with GBS. In this case report, we will discuss our experience treating a 59-year-old female patient who became hemodynamically unstable while recovering from an acute GBS infection. She was diagnosed with TCM after undergoing an echocardiogram and coronary angiogram ruling out thrombotic or obstructive coronary disease and myocarditis.

Guillain-Barré syndrome AMSAN variant in a 90-year-old woman after COVID-19: a case report

BACKGROUND

Guillain-Barré syndrome (GBS) is an inflammatory disease of the peripheral nervous system characterized by rapidly evolving polyneuropathy caused by autoimmune demyelination and/or axonal degeneration. Since SARS-CoV-2 outbreak, several GBS cases following exposure to coronavirus disease-2019 (COVID-19) have been reported in literature, raising the concern of the latter being a potential trigger event for GBS.

CASE PRESENTATION

We report the case of a 90-year-old Caucasian woman who was admitted to our hospital because of fatigue, worsening gait and leg strength, dysphonia, dysarthria and dysphagia, started 3 weeks after being exposed to COVID-19. Based on clinical presentation GBS was suspected, so she performed a lumbar puncture and electromyography, which confirmed the diagnosis of acute motor and sensory axonal neuropathy (AMSAN) variant. We administered high dose of intravenous immunoglobulin with slight neurological improvement. However, after 2 weeks of hospitalization with maximization of care, her physical condition worsen, manifesting severe frailty. The patient was discharged with home support services for managing parenteral nutrition and intense scheduled physiotherapy. A few days later, the patient experienced a further decline in her clinical condition and died at home.

CONCLUSIONS

To the best of our knowledge, we report the oldest woman with GBS AMSAN variant after COVID-19 described in the existing literature. Our case supports further research aimed at improving recognition, characterization and prompt management of neurological diseases related to COVID-19 in older patients.

Dysautonomia and related outcomes in Guillain-Barre syndrome

BACKGROUND

Guillain-Barre syndrome (GBS) presents an annual incidence of 1.2-2.3 per 100,000. Sympathetic and parasympathetic nervous systems' peripheral control of visceral organs is affected by GBS aberrant immune response. Associated cardiovascular, gastrointestinal, sudomotor, pupillary, and other systems disturbances cause significant morbidity and mortality. This study aims to evaluate the dysautonomia spectrum in GBS patients, its relationship with patient outcomes, and compare it with those without autonomic disturbances.

METHODS

We performed an ambispective review study of patients with GBS and dysautonomia admitted to the Institute of Neurology from 2017 to 2021. We recorded demographics, comorbidities, nerve conduction studies, clinical course, hospital complications, and functional outcomes.

RESULTS

We included 214 patients, mean age 46.44 ± 16.49 years, 51 (31 %) presented dysautonomia, hypertension in most of the patients 39 (84.8 %), hypotension 35 (76.1 %), tachycardia 35 (76.1 %), enteric dysmotility 35 (76.1 %), and need for vasopressor 27 (58.7 %) were common characteristics. Twenty (39.2 %) with a demyelinating form and twenty (39.2 %) with an axonal motor form. The bivariate analysis report factors associated with dysautonomia, were lower cranial nerves (VII, IX, X) involvement (p = 0.002), need for mechanical ventilation (p = 0.0001) and intensive care (p = 0.0001), higher mEGOS (p = 0.05), EGRIS (p = 0.004), GBS disability score (p = 0.004), and delirium presence (p = 0.001). Kaplan-Meier survival analysis showed that dysautonomic patients needed more days for the independent walk (p = 0.004). There was no associated mortality.

CONCLUSIONS

Autonomic dysfunction in GBS significantly affects the peripheral nervous system. With consequently worse functional results. Further investigation needs to clarify whether more aggressive treatment is beneficial in this category of GBS.

Paroxysmal Sympathetic Hypertension: An Underdiagnosed Entity or a Diagnostic Difficulty?

How to cite this article: Pratyusha K, Jindal A. Paroxysmal Sympathetic Hypertension: An Underdiagnosed Entity or a Diagnostic Difficulty? Indian J Crit Care Med 2023;27(2):151.

Retrospective evaluation of Guillain-Barre syndrome in children: A single-center experience

BACKGROUND

Although Guillain-Barré syndrome (GBS) is now the most common cause of acute flaccid paralysis in children, information on the long-term follow-up of GBS is still limited. Identification of prognostic factors can play an important role in treatment strategies and the follow-up of patients. This study aimed to evaluate the effectiveness of monitoring the GBS disability score (DS) in predicting morbidity and mortality.

METHODS

The patients were separated into two groups those with DS≥ or <3 on admission. These groups were compared in respect of demographic data, clinical and laboratory findings, and the DS recorded on admission and at first, third, sixth, 12th, and 24th months.

RESULTS

The study included 44 patients (54.5% male, 45.5% female) with a median age of 5 years. The most common involvements during the disease were weakness, ataxia, neuropathic pain, cranial neuropathy, respiratory distress, autonomic dysfunction, and psychiatric symptoms, respectively. In patients with a DS of ≥3, the time from onset of symptoms to hospital admission was shorter, and the length of hospital stay was longer. Children with back pain and autonomic dysfunction had a DS of ≥3. A high 3-month DS was found to be a significant predictor for the development of sequelae.

CONCLUSIONS

Although progressive muscle weakness and inability to walk are the most common symptoms of GBS, it should be kept in mind that atypical manifestations such as hemiplegia and ophthalmoplegia may also occur. For an objective assessment of clinical improvement during follow-up, the DS for motor functions can be used.

Neurological Emergencies in the Intensive Care Unit

Neurological emergencies carry significant morbidity and mortality, and it is necessary to have a multidisciplinary approach involving the emergency physician, the neurologist, the intensivist, and the critical care nursing staff. These disorders can be broadly divided into noninfectious and infectious etiologies. In this article, we review a few of the neurological emergencies that present to the neurological intensive unit, with emphasis on convulsive status epileptics, myasthenia gravis, Guillain-Barré syndrome, meningitis, encephalitis, and brain abscess.

Cardiovascular Autonomic Assessment in Guillain-Barré Syndrome: A Longitudinal Study

BACKGROUND

Severe dysautonomia is typically seen during acute phase of Guillain-Barré syndrome (GBS).

OBJECTIVE

To investigate the relationship of cardiovascular autonomic dysfunction with motor recovery in GBS.

MATERIALS AND METHODS

Consecutive GBS patients presented to our hospital were recruited. Clinical assessment was evaluated with the Medical Research Council (MRC) sum score and GBS disability score (GDS). All patients had series of autonomic testing on admission and after treatment at 6 and 24 weeks. Both computation-dependent tests (heart rate variability [HRV] and baroreflex sensitivity [BRS]) and autonomic maneuvers were performed. Age- and gender-matched healthy controls (HC) were recruited. The data obtained at admission, 6 weeks and 24 weeks were compared within groups for statistical difference.

RESULTS

Six patients (4 men; mean age 39.5 ± 14.3 years) were recruited over one year. Five had GBS and one Miller Fisher syndrome. The mean MRC sum score and GDS on admission were 52.3 ± 4.3 and 3.5 ± 0.8 respectively. During admission, time-domain average RR interval (AVNN) and BRS were significantly poorer among cases compared to HC. Active standing 30:15 ratio and cold pressor test at admission were also significantly abnormal when compared with HC. All the autonomic parameters had normalized by 6 weeks and these were significant for the high frequency-HRV, BRS, and active standing 30:15 ratio. For MRC and GDS, there were significant improvements in the scoring over a period of 24 weeks.

CONCLUSIONS

Dysautonomia in GBS improved gradually and in keeping with motor and disability recovery.

Clinical Course and Diagnostic Findings of Biopsy Controlled Presumed Immune-Mediated Polyneuropathy in 70 European Cats

There is a paucity of information on the clinical course and outcome of young cats with polyneuropathy. The aim of the study was to describe the clinical features, diagnostic investigations, and outcome of a large cohort of cats with inflammatory polyneuropathy from several European countries. Seventy cats with inflammatory infiltrates in intramuscular nerves and/or peripheral nerve biopsies were retrospectively included. Information from medical records and follow up were acquired via questionnaires filled by veterinary neurologists who had submitted muscle and nerve biopsies (2011–2019). Median age at onset was 10 months (range: 4–120 months). The most common breed was British short hair (25.7%), followed by Domestic short hair (24.3%), Bengal cat (11.4%), Maine Coon (8.6%) and Persian cat (5.7%), and 14 other breeds. Male cats were predominantly affected (64.3%). Clinical signs were weakness (98.6%) and tetraparesis (75.7%) in association with decreased withdrawal reflexes (83.6%) and, less commonly, cranial nerve signs (17.1%), spinal pain/hyperesthesia (12.9%), and micturition/defecation problems (14.3%). Onset was sudden (30.1%) or insidious (69.1%), and an initial progressive phase was reported in 74.3%. Characteristic findings on electrodiagnostic examination were presence of generalized spontaneous electric muscle activity (89.6%), decreased motor nerve conduction velocity (52.3%), abnormal F-wave studies (72.4%), pattern of temporal dispersion (26.1%) and unremarkable sensory tests. The clinical course was mainly described as remittent (49.2%) or remittent-relapsing (34.9%), while stagnation, progressive course or waxing and waning were less frequently reported. Relapses were common and occurred in 35.7% of the cats' population. An overall favorable outcome was reported in 79.4% of patients. In conclusion, young age at the time of diagnosis and sudden onset of clinical signs were significantly associated with recovery (p &lt; 0.05). Clinical and electrodiagnostic features and the remittent-relapsing clinical course resembles juvenile chronic inflammatory demyelinating polyneuropathy (CIDP), as seen in human (children/adolescents), in many aspects.

Advances in Our Clinical Understanding of Autonomic Regulation Therapy Using Vagal Nerve Stimulation in Patients Living With Heart Failure

The ANTHEM-HF, INOVATE-HF, and NECTAR-HF clinical studies of autonomic regulation therapy (ART) using vagus nerve stimulation (VNS) systems have collectively provided dose-ranging information enabling the development of several working hypotheses on how stimulation frequency can be utilized during VNS for tolerability and improving cardiovascular outcomes in patients living with heart failure (HF) and reduced ejection fraction (HFrEF). Changes in heart rate dynamics, comprising reduced heart rate (HR) and increased HR variability, are a biomarker of autonomic nerve system engagement and cardiac control, and appear to be sensitive to VNS that is delivered using a stimulation frequency that is similar to the natural operating frequency of the vagus nerve. Among prior studies, the ANTHEM-HF Pilot Study has provided the clearest evidence of autonomic engagement with VNS that was delivered using a stimulation frequency that was within the operating range of the vagus nerve. Achieving autonomic engagement was accompanied by improvement from baseline in six-minute walk duration (6MWD), health-related quality of life, and left ventricular EF (LVEF), over and above those achieved by concomitant guideline-directed medical therapy (GDMT) administered to counteract harmful neurohormonal activation, with relative freedom from deleterious effects. Autonomic engagement and positive directional changes have persisted over time, and an exploratory analysis suggests that improvement in autonomic tone, symptoms, and physical capacity may be independent of baseline NT-proBNP values. Based upon these encouraging observations, prospective, randomized controlled trials examining the effects on symptoms and cardiac function as well as natural history have been warranted. A multi-national, large-scale, randomized, controlled trial is well underway to determine the outcomes associated with ART using autonomic nervous system engagement as a guide for VNS delivery.

Leveraging Continuous Vital Sign Measurements for Real-Time Assessment of Autonomic Nervous System Dysfunction After Brain Injury: A Narrative Review of Current and Future Applications

Subtle and profound changes in autonomic nervous system (ANS) function affecting sympathetic and parasympathetic homeostasis occur as a result of critical illness. Changes in ANS function are particularly salient in neurocritical illness, when direct structural and functional perturbations to autonomic network pathways occur and may herald impending clinical deterioration or intervenable evolving mechanisms of secondary injury. Sympathetic and parasympathetic balance can be measured quantitatively at the bedside using multiple methods, most readily by extracting data from electrocardiographic or photoplethysmography waveforms. Work from our group and others has demonstrated that data-analytic techniques can identify quantitative physiologic changes that precede clinical detection of meaningful events, and therefore may provide an important window for time-sensitive therapies. Here, we review data-analytic approaches to measuring ANS dysfunction from routine bedside physiologic data streams and integrating this data into multimodal machine learning-based model development to better understand phenotypical expression of pathophysiologic mechanisms and perhaps even serve as early detection signals. Attention will be given to examples from our work in acute traumatic brain injury on detection and monitoring of paroxysmal sympathetic hyperactivity and prediction of neurologic deterioration, and in large hemispheric infarction on prediction of malignant cerebral edema. We also discuss future clinical applications and data-analytic challenges and future directions.

Severe bradycardia in a teenager as the initial manifestation for Guillain Barré syndrome: a case report

BACKGROUND

Guillain-Barré syndrome is the most common cause of flaccid paralysis, with multiple known clinical variants. Autonomic dysfunction, although frequently reported in the clinical course, is often overlooked in the pediatric population and is usually not the initial presenting symptom in this age group CASE PRESENTATION: We present the case of a previously healthy 17-year-old who arrived at the Emergency Department complaining of gastrointestinal symptoms associated with lipothymia. An initial electrocardiogram (ECG) showed sustained sinus bradycardia subsequently associated with arterial hypertension. Structural and inflammatory cardiac pathology were ruled out, as well as auriculoventricular conduction block and posterior reversible encephalopathy syndrome. On the ninth day after initial symptoms, the patient presented sensory and motor nerve disturbances with the cerebrospinal fluid analysis showing a clear albumin-cytologic dissociation, consistent with an atypical presentation of GBS with autonomic dysfunction. Immunoglobulin therapy was administered, developing subsequent aseptic meningitis, that required discontinuation of previous therapy and treatment with plasmapheresis. Clinical improvement was achieved with full motor function recovery.

CONCLUSION

This case illustrates a Guillain-Barré syndrome variant in which autonomic dysfunction preceded neurologic deficit, a finding uncommon in children, emphasizing this as an important differential diagnosis for severe bradycardia in pediatric patients.

The Omnipresence of Autonomic Modulation in Health and Disease

The Autonomic Nervous System (ANS) is a critical part of the homeostatic machinery with both central and peripheral components. However, little is known about the integration of these components and their joint role in the maintenance of health and in allostatic derailments leading to somatic and/or neuropsychiatric (co)morbidity. Based on a comprehensive literature search on the ANS neuroanatomy we dissect the complex integration of the ANS: (1) First we summarize Stress and Homeostatic Equilibrium - elucidating the responsivity of the ANS to stressors; (2) Second we describe the overall process of how the ANS is involved in Adaptation and Maladaptation to Stress; (3) In the third section the ANS is hierarchically partitioned into the peripheral/spinal, brainstem, subcortical and cortical components of the nervous system. We utilize this anatomical basis to define a model of autonomic integration. (4) Finally, we deploy the model to describe human ANS involvement in (a) Hypofunctional and (b) Hyperfunctional states providing examples in the healthy state and in clinical conditions.

Pearls & Oy-sters: Delayed Diagnosis of Acute Motor Axonal Neuropathy With Cardiac Arrest

We present the case of a 53-year-old female who presented with right lower extremity weakness with preceding systemic symptoms including fever and chest pain. She developed rapid quadriparesis over 24 hours and had ventricular fibrillation with cardiac arrest. Examination demonstrated tetraplegia, facial diplegia with spared extra-ocular movements and areflexia. Electrodiagnostic studies including nerve conduction studies and electromyography were consistent with Acute Motor Axonal Neuropathy (AMAN). This case highlights an atypical asymmetric presentation with initially preserved reflexes, rapid progression and cardiac dysfunction that can occur independent of dysautonomia. Treatment options include intravenous immunoglobulin (IVIg) or plasmapheresis as well as supportive care and long term multidisciplinary rehabilitation and communication strategies.

Postprandial cerebral infarction

Some neurological diseases are accompanied by autonomic dysfunction. Postprandial hypotension (PPH) is one disorder accompanied by autonomic dysfunction. Although the major symptoms of PPH are fall and syncope, PPH is sometimes overlooked because of its non-specific symptoms, such as dizziness, nausea, and light-headedness. Because PPH could result in decreased cerebral perfusion pressure accompanied by a decrease in blood pressure, PPH may be linked to the risk of hemodynamic stroke or transient ischemic events, especially in patients with chronic cerebral large vessel occlusion/stenosis. Whether chronic cerebral large vessel occlusion or stenosis causes symptomatic ischemic events depends on the patient's compensatory collateral circulation and cerebral vasoreactivity. Therefore, we hypothesized that cerebral blood flow assessment could be essential for stratifying patients at high risk of postprandial cerebral infarction. However, there have been few reports on the association between cerebral blood flow and the occurrence of postprandial cerebral infarction. In a literature review, we identified seven cases of postprandial cerebral infarction. Postprandial cerebral infarction occurs in patients with chronic cerebral large vessel occlusion/stenosis accompanied by cerebral blood flow reduction. Non-pharmacotherapeutic and pharmacotherapeutic approaches could improve postprandial cerebral infarction; however, one patient with poor compensatory collateral circulation and reduced cerebral vasoreactivity experienced recurrent symptomatic episodes even with sufficient medical treatment and needed extracranial-intracranial bypass surgery. Physicians should be aware of PPH as it can complicate neurological disorders. Long-term blood pressure monitoring for the detection of PPH and cerebral blood flow assessment is needed in patients with cerebral large vessel occlusion/stenosis to prevent postprandial cerebral infarction.

Association Between the Rate of Treatment Response and Short-Term Outcomes in Childhood Guillain-Barré Syndrome

Introduction: Few studies have examined the association between the rate of treatment response and the outcome of pediatric Guillain-Barré syndrome (GBS). Therefore, our study aimed to identify treatment response in relation to the short-term outcomes of GBS. Further, we investigated its potential predictive value for prognosis.

Methods: Our retrospective study included children diagnosed with GBS in the Pediatric Neurology Department of the Children's Hospital of Hebei Province from 2016 to 2020. According to the rate of response from the standard intravenous immunoglobulin (IVIg) treatment, patients were divided into two groups: rapid-response GBS (initial response within 7 days) and slow-response (initial response within 8–30 days). The GBS disability score (Hughes Functional Grading Scale) was used to assess the children's functional disability at nadir, 1 month, and 6 months after onset.

Results: Among the 36 children included in the study, 18 (50%) and 18 (50%) were rapid and slow responders, respectively. Time from IVIg treatment to the initial response was significantly shorter in the rapid-response group (5 [3–6.25] days vs. 10.5[8.75–15] days in slow-response GBS, p < 0.001). Hughes score at 1 month was worse than the rapid responders (Fisher's exact test, p = 0.006). Survival analysis (Kaplan–Meier) with respect to regaining the ability to walk independently (Hughes Functional Grading Scale of 2) within 1 month after onset was significantly different among the two groups (log-rank test for trend, p = 0.024). The abnormal levels of cerebral spinal fluid proteins and autonomic dysfunction were more frequent in the slow-response group than those in the rapid group (p < 0.05).

Conclusion: The rate of response to IVIg treatment was correlated with short-term outcomes in children with GBS and had predictive value for prognosis. The role of patient's initial responses to treatment could be significantly valuable in developing more effective and efficient treatment options.

Takotsubo Cardiomyopathy as a Manifestation of Dysautonomia in Guillain-Barré Syndrome: A Case Series and Review of the Literature

Guillain-Barré syndrome (GBS) is an inflammatory polyneuropathy that classically presents with low back pain, sensory paresthesias, and rapidly progressive weakness. Patients with GBS can develop dysautonomia, and Takotsubo cardiomyopathy (TCM) is a rare potential manifestation of this dysautonomia. This association has been reported only 12 times in the literature so far, which we review here. We present two cases of GBS associated with TCM, to increase awareness with regard to this comorbid relationship, which would encourage prompt initiation of proper supportive care to avoid morbidity and mortality.

We report the case of two patients - a 58-year-old man and a 79-year-old woman - who developed TCM in the setting of axonal variants of GBS. Electrodiagnostic results, cerebrospinal fluid profiles, and echocardiogram findings were consistent with these diagnoses. Both patients were treated with intravenous immunoglobulin (IVIG) in an intensive care unit (ICU) setting. Echocardiogram findings were reversible.

TCM should be recognized as a potential complication of GBS in patients with dysautonomia. This case series adds to the sparse body of literature describing the association between these two conditions. It is not clear if patients with axonal variants of GBS are more predisposed to developing TCM; further, larger case series in the future may help identify the risk factors associated with it. We hope to shed more light on this possible association to expedite the diagnosis and management of this condition.

Posterior reversible encephalopathy syndrome following Miller-Fisher syndrome

A 71-year-old woman presented to the emergency room with dysphonia, diplopia, dysphagia and generalised weakness since that day. Neurological examination revealed eye adduction limitation, ptosis, hypoactive reflexes and gait ataxia. Blood and cerebrospinal fluid analysis and brain CT were normal. Electromyography revealed a sensory axonal polyneuropathy. She was diagnosed with Miller-Fisher syndrome (MFS) and started on intravenous immunoglobulin. Two days after intravenous immunoglobulin treatment was completed, she developed a sustained hypertensive profile and presented a generalised tonic-clonic seizure. Brain MRI was suggestive of posterior reversible encephalopathy syndrome (PRES) and supportive treatment was implemented with progressive improvement. PRES may be a possible complication of MFS not only due to autonomic and inflammatory dysfunctions, but also as a consequence of its treatment. Patients with MFS should be maintained under close surveillance, especially in the first days and preferably in intermediate care units.

Dysautonomia in Guillain-Barré Syndrome: Prevalence, Clinical Spectrum, and Outcomes

BACKGROUND

Guillain-Barré syndrome (GBS), when severe, involves the autonomic nervous system; our objective was to assess the spectrum and predictors of dysautonomia, and how it may impact functional outcomes.

METHODS

A retrospective review of patients admitted to the Mayo Clinic in Rochester, MN between January 1, 2000, and December 31, 2017, with GBS and dysautonomia was performed. Demographics, comorbidities, parameters of dysautonomia, clinical course, GBS disability score, and Erasmus GBS Outcome Score (EGOS) at discharge were recorded.

RESULTS

One hundred eighty seven patients were included with 71 (38%) noted to have at least one manifestation of dysautonomia. There are 72% of patients with a demyelinating form of GBS and 36% of patients with demyelination had dysautonomia. Ileus (42%), hypertension (39%), hypotension (37%), fever (29%), tachycardia or bradycardia (27%), and urinary retention (24%) were the most common features. Quadriparesis, bulbar and neck flexor weakness, and mechanical ventilation were associated with autonomic dysfunction. Patients with dysautonomia more commonly had cardiogenic complications, syndrome of inappropriate antidiuretic hormone, posterior reversible encephalopathy syndrome, and higher GBS disability score and EGOS. Mortality was 6% in patients with dysautonomia versus 2% in the entire cohort (P = 0.02).

CONCLUSIONS

Dysautonomia in GBS is a manifestation of more severe involvement of the peripheral nervous system. Accordingly, mortality and functional outcomes are worse. There is a need to investigate if more aggressive treatment is warranted in this category of GBS.

Effects of acute neurologic disease on the heart

Patients with acute neurologic disease often also have evidence of cardiac dysfunction. The cardiac dysfunction may result in a number of clinical signs including abnormal EKG changes, variations in blood pressure, development of cardiac arrhythmias, release of cardiac biomarkers, and reduced ventricular function. Although typically reversible, these cardiac complications are important to recognize as they are associated with increased morbidity and mortality. In this chapter, we discuss the suspected pathophysiology, clinical presentation, and management of the cardiac dysfunction that occur as a consequence of different types of acute neurologic illness.

Self-reported autonomic dysfunction in a recovery phase of Guillain-Barré syndrome

OBJECTIVE

Autonomic dysfunction occurs in approximately two-thirds of Guillain-Barré syndrome (GBS) patients in the acute phase of the disease. Although improving over time, subclinical autonomic involvement may be present for 3-8 years after the GBS episode. The aim of this study was to determine the frequency of self-reported autonomic disorders in GBS patients three and six months after disease onset compared to healthy controls (HCs).

METHODS

Our study included adult patients diagnosed with GBS from May 2017 until May 2018 in seven healthcare centers (67.6 % with demyelinating and 13.6 % with axonal syubtype). Functional disability was assessed by the Guillain-Barré syndrome disability scale (GDS). Each subject filled in the Serbian version of the SCOPA-Aut questionnaire. Using GDS and SCOPA-Aut, patients were tested at month 3 (M3) (n = 71) and month 6 (M6) (n = 70) from symptom onset.

RESULTS

Dysautonomia was more common in patients with GBS compared to HCs at M3 (p < 0.01), while there was no difference at M6 (p > 0.05). Among autonomic disorders, constipation, complications to pass stool, and orthostatic hypotension were the most frequently reported. Patients with axonal variants had worse total SCOPA-Aut scores at M3 in comparison to AIDP patients (11.7 ± 10.1 vs. 6.1 ± 5.1, p < 0.05). GDS score correlated with the total SCOPA-Aut score.

CONCLUSION

Autonomic symptoms are common in GBS patients during the recovery phase. They are more pronounced in patients with axonal forms of GBS and those with a higher degree of functional disability.

Autonomic Hyperactivity

PURPOSE OF REVIEW

Autonomic hyperactivity is a relatively common consequence of severe acute brain injury and can also be seen with spinal cord and peripheral nerve disorders. This article reviews basic pathophysiologic concepts regarding autonomic hyperactivity, its various forms of clinical presentation, and practical management considerations.

RECENT FINDINGS

Paroxysmal sympathetic hyperactivity is most common after traumatic brain injury but can also occur after other forms of severe acute diffuse or multifocal brain injury. Formal criteria for the diagnosis and severity grading of paroxysmal sympathetic hyperactivity have now been proposed. A growing body of literature is beginning to elucidate the mechanisms underlying this disorder, but treatment remains based on observational data. Our mechanistic understanding of other distinct forms of autonomic hyperactivity, such as autonomic dysreflexia after traumatic spinal cord injury and dysautonomia after Guillain-Barré syndrome, remains rudimentary, yet clinical experience shows that their appropriate management can minimize the risk of serious complications.

SUMMARY

Syndromes of autonomic hyperactivity can result from injury at all levels of the neuraxis. Much more research is needed to refine our understanding of these disorders and guide optimal management decisions.

Mechanical ventilation in Guillain-Barré syndrome

Introduction: Up to 30% of patients with Guillain-Barré syndrome (GBS) develop respiratory failure requiring intensive care unit (ICU) admission and mechanical ventilation. Progressive weakness of the respiratory muscles is the leading cause of acute respiratory distress and respiratory failure with hypoxia and/or hypercarbia. Bulbar weakness may compromise airway patency and predispose patients to aspiration pneumonia. Areas covered: Clinical questions related to the use of mechanical ventilation include but are not limited to: When to start? Invasive or noninvasive? When to wean from mechanical ventilation? When to perform tracheostomy? How to manage complications of GBS in the ICU including nosocomial infection, ventilator-associated pneumonia, and ICU-acquired weakness? In this narrative review, the authors summarize the up-to-date knowledge of the incidence, pathophysiology, evaluation, and general management of respiratory failure in GBS. Expert opinion: Respiratory failure in GBS merits more attention from caregivers. Emergency intubation may lead to life-threatening complications. Appropriate methods and time point of intubation and weaning, an early tracheostomy, and predictive prophylaxis of complications benefit patients' long-term prognosis.

Altered mental status in "Guillain-Barré syndrome" -a noteworthy clinical clue

Guillain‐Barré syndrome (GBS) is widely regarded as a “pure” peripheral nervous system disorder. However, this simplistic interpretation belies the fact that central nervous system involvement, often manifesting as derangements in mental status can occur as a complication of the “pure” form of the disorder, as part of GBS variants, as well as in a number of mimic disorders. Despite being common in clinical practice, there is no guidance in the literature as to how to approach such scenarios. Herein, we detail our approach to these cases.

Autonomic neuropathies

Autonomic neuropathies represent a complex group of disorders that preferentially target autonomic fibers and can be classified as either acute/subacute or chronic in onset. Acute-onset autonomic neuropathies manifest with such conditions as paraneoplastic syndromes, Guillain-Barre syndrome, Sjögren syndrome, infection, or toxins/chemotherapy. When the presentation is acute, immune-mediated, and without a secondary cause, autoimmune autonomic ganglionopathy is likely, and should be considered for immunotherapy. Of the chronic-onset forms, diabetes is the most widespread and disabling, with autonomic impairment portending increased mortality and cardiac wall remodeling risk. Acquired light chain (AL) and transthyretin (TTR) amyloidosis represent two other key etiologies, with TTR amyloidosis now amenable to newly-approved gene-modifying therapies. The COMPASS-31 questionnaire is a validated outcome measure that can be used to monitor autonomic severity and track treatment response. Symptomatic treatments targeting orthostatic hypotension, among other symptoms, should be individualized and complement disease-modifying therapy, when possible.

Electrophysiological subtypes and associated prognosis factors of Mexican adults diagnosed with Guillain-Barré syndrome, a single center experience

BACKGROUND

The clinical characteristics of electrophysiological subtypes and prognostic factors of Mexican adults diagnosed with Guillain-Barré Syndrome (GBS) have not been described.

MATERIALS AND METHODS

A single center, ambispective, cohort study was performed (2015-2019). GBS was defined following the Asbury and Cornblath criteria. Electrodiagnosis was made according to Hadden criteria. Clinical, biochemical and electrodiagnostic parameters were described, compared and analyzed using a multivariate model. Only patients who completed a 3-month follow-up were included.

RESULTS

137 GBS patients (92 males; mean age 46.6 ± 16.6).132 (96.3%) underwent an electrodiagnostic assessment.68 (51.5%) were classified as axonal GBS, with further classified into two groups: acute motor axonal neuropathy (AMAN) 45.4%, and acute motor and sensory axonal neuropathy (AMSAN) 8,6%. The following characteristics were lower in the AMAN group: Medical Research Counsel sumscore (MRC) 30.1 ± 16.3 vs 36.4 ± 14.4, unilateral facial palsy 10% vs 25.9% and albuminocytologic dissociation 41.3% vs. 71.7%.Multivariate analysis found AMAN as an independent predictor of an unfavorable outcome OR: 3.34 (p = 0.03) CONCLUSIONS: AMAN subtype is the most frequent presentation of GBS in Mexican adult patients and an independent predictor of inability to walk independently at 3 months after discharge.

Guillain-Barré syndrome and posterior reversible leukoencephalopathy syndrome: a rare association

A 69-year-old woman presented with headaches and visual disturbance in the context of marked hypertension secondary to non-compliance with antihypertensive medications. She developed seizures and hyperreflexia, and MRI brain showed changes consistent with posterior reversible encephalopathy syndrome (PRES). She was treated with antihypertensives with the resolution of symptoms. Over the following week, she developed progressive distal sensory loss, weakness and areflexia. The cerebrospinal fluid examination demonstrated albuminocytologic dissociation, and electrophysiological findings were in keeping with a diagnosis of Guillain-Barré syndrome (GBS). She was treated with intravenous immunoglobulin with gradual recovery. The co-occurrence of PRES and GBS has only been described in a handful of cases. In the majority of these, the dysautonomia of GBS leads to profound hypertension and subsequently PRES. This is a rare case of PRES preceding and possibly even triggering the onset of GBS. In this report, we review the literature and discuss the potential pathogenic mechanisms for this unusual association.

Posterior reversible encephalopathy syndrome associated with Guillain-Barré syndrome: Case report and clinical management considerations

Around half of the patients with Guillain-Barré syndrome (GBS) present autonomic dysfunction requiring admission to intensive care unit in up to a quarter of patients. Treatment of GBS consists of plasma exchange (PE) and intravenous immunoglobulins (IVIG). Posterior reversible encephalopathy syndrome (PRES) consists in a reversible subcortical vasogenic brain edema caused by endothelial damage triggered by abrupt blood pressure changes. We report on a woman who presented with PRES in the course of GBS treated first with IVIG, and then with PE. The present report underlines the challenge that the clinicians face when these two rare syndromes concur. The literature is not helpful considering that both blood pressure fluctuations and IVIG are reported to be involved in the pathogenesis of PRES. In the present letter, both pathogenic mechanisms and clinical management considerations are discussed.

Guillain-Barré syndrome in a heart transplantation recipient

ABSTRACT

A rare case of a heart transplantation recipient with Guillain-Barré syndrome occurred, which was associated with peripheral nervous system damage. Based on a review of epidemiological research, the symptom development process, and diagnostic tools, the authors highlight the extreme rarity of this postinfectious immune disease. After diagnosis, plasma exchange and immunoregulatory therapy should be performed because they result in rapid recovery. If there is delayed diagnosis and treatment, there is a high risk of disability or death. When patients experience acute limb paralysis as the main symptom, nurse practitioners (NPs) should focus on the patient's history, particularly with regard to infectious agents. Closely monitoring the patient to detect respiratory failure and the need for early respiratory intervention can help the patient to avoid the severe complication of permanent brain injury. For NPs, performance of early differential diagnosis is important, especially among patients who have immunosuppressive dependence after transplantation.

Guillain-Barré syndrome complicated by takotsubo cardiomyopathy: an under-recognised association

A 41-year-old woman was admitted with progressive paraesthesia and weakness and was diagnosed with Guillain-Barré syndrome. Following an initial period of recovery with intravenous immunoglobulin treatment, she developed acute chest pain associated with electrocardiographic changes. Investigations excluded acute coronary syndrome and instead confirmed a diagnosis of takotsubo cardiomyopathy, which was treated medically. The patient made an excellent neurological and cardiac recovery. Here we discuss the rarely described association between these two conditions and suggest that patients admitted with Guillain-Barré syndrome may benefit from routine screening with echocardiography.

Acute Neuromuscular Disorders in the Pediatric Intensive Care Unit

BACKGROUND

The neuromuscular disorders encountered in the pediatric intensive care unit (PICU) encompass a broad spectrum of pathologies. These include acute disorders (eg, Guillain-Barre syndrome), acute-on-chronic disorders (eg, myasthenia gravis), progressive disorders (eg, muscular dystrophy), and disorders that develop in the PICU (eg, critical illness myopathy/polyneuropathy). Familiarity with the presenting features of these disorders is of paramount importance in facilitating timely diagnosis.

METHODS

We conducted a retrospective review of the medical records of patients admitted to the PICU or Intermediate Care Program (ICP) at a single tertiary children's hospital from 2006 to 2017 with an acute or acute-on-chronic neuromuscular disorder. We did not include patients with a known progressive neuromuscular disorder or critical illness myopathy/polyneuropathy.

RESULTS

Twenty-four patients were admitted to the PICU/ICP with acute or acute-on-chronic neuromuscular disorders. Diagnosis and indication for ICU/ICP admission were Guillain-Barre syndrome (n = 6; respiratory failure: 3, respiratory monitoring: 2, autonomic instability: 1), myasthenia gravis (n = 5; airway clearance: 3, respiratory failure: 2), acute flaccid myelitis (n = 3; respiratory failure: 2, respiratory monitoring: 1), periodic paralysis (n = 3; intravenous potassium replacement), rhabdomyolysis (n = 3; monitoring for electrolyte derangements), infant botulism (n = 2; respiratory failure), chronic demyelinating polyneuropathy (n = 1; respiratory failure), and congenital myasthenic syndrome (n = 1; apnea). No patients were admitted to the PICU/ICP with a diagnosis of tick paralysis, acute intermittent porphyria, or inflammatory myopathy.

CONCLUSIONS

Although acute and acute-on-chronic neuromuscular disorders are encountered relatively rarely in the PICU, familiarity with the presenting features of these disorders is important in facilitating timely diagnosis. This, in turn, enables the institution of effective management strategies, thereby avoiding complications associated with diagnostic delays.

Autonomic dysfunction: Diagnosis and management

The autonomic nervous system is designed to maintain physiologic homeostasis. Its widespread connections make it vulnerable to disruption by many disease processes including primary etiologies such as Parkinson's disease, multiple system atrophy, dementia with Lewy bodies, and pure autonomic failure and secondary etiologies such as diabetes mellitus, amyloidosis, and immune-mediated illnesses. The result is numerous symptoms involving the cardiovascular, gastrointestinal, and urogenital systems. Patients with autonomic dysfunction (AUD) often have peripheral and/or cardiac denervation leading to impairment of the baroreflex, which is known to play a major role in determining hemodynamic outcome during orthostatic stress and low cardiac output states. Heart rate and plasma norepinephrine responses to orthostatic stress are helpful in diagnosing impairment of the baroreflex in patients with orthostatic hypotension (OH) and suspected AUD. Similarly, cardiac sympathetic denervation diagnosed with MIBG scintigraphy or ¹⁸F-DA PET scanning has also been shown to be helpful in distinguishing preganglionic from postganglionic involvement and in diagnosing early stages of neurodegenerative diseases. In this chapter, we review the causes of AUD, the pathophysiology and resulting cardiovascular manifestations with emphasis on the diagnosis and treatment of OH.