Paroxysmal sympathetic hyperactivity after acquired brain injury: A review of diagnostic criteria

Paroxysmal sympathetic hyperexcitability after brain injury: A clinical analysis of case series

BACKGROUND

Paroxysmal sympathetic hyperexcitability (PSH) is a group of complex syndromes with various etiologies. Previous studies were limited to the description of traumatic brain injury (TBI), and the description of PSH after other types of brain injury was rare. We explored the clinical features, treatment, and prognosis of PSH after various types of brain injuries.

METHODS

Patients admitted to the neurosurgery intensive care unit with PSH after brain injury from July 2019 to December 2022 were included. Demographic data, clinical manifestations, drug therapy, and disease prognosis were retrospectively collected and analyzed.

RESULTS

Fifteen male and 9 female patients with PSH after brain injury were selected. TBI was most likely to cause PSH (66.7%), followed by spontaneous intracerebral hemorrhage (25%). Glasgow coma scale scores of 19 patients (79.2%) were lower than 8 and 14 patients (58.3%) underwent tracheotomy. Electroencephalogram monitoring was performed in 12 individuals, none of which showed epileptic waves. Clinical symptom scale showed mild symptoms in 17 cases (70.8%). Almost all patients were administered a combination of drugs. After follow-up, most patients had a poor prognosis and 2 (8.3%) died after discharge.

CONCLUSION

The etiology of PSH is complex. TBI may be the most common cause of PSH. Non-TBI may also be an important cause of PSH. Therefore, early identification, prevention and diagnosis are helpful for determining the prognosis and outcome of the disease.

Decreased levels of hydrogen sulfide in the hypothalamic paraventricular nucleus contribute to sympathetic hyperactivity induced by cerebral infarction

Paroxysmal sympathetic hyperactivity (PSH) is a common clinical feature secondary to ischemic stroke (IS), but its mechanism is poorly understood. We aimed to investigate the role of H2S in the pathogenesis of PSH. IS patients were divided into malignant (MCI) and non-malignant cerebral infarction (NMCI) group. IS in rats was induced by the right middle cerebral artery occlusion (MCAO). H2S donor (NaHS) or inhibitor (aminooxy-acetic acid, AOAA) were microinjected into the hypothalamic paraventricular nucleus (PVN). Compared with the NMCI group, patients in the MCI group showed PSH, including tachycardia, hypertension, and more plasma norepinephrine (NE) that was positively correlated with levels of creatine kinase, glutamate transaminase, and creatinine respectively. The 1-year survival rate of patients with high plasma NE levels was lower. The hypothalamus of rats with MCAO showed increased activity, especially in the PVN region. The levels of H2S in PVN of the rats with MCAO were reduced, while the blood pressure and renal sympathetic discharge were increased, which could be ameliorated by NaHS and exacerbated by AOAA. NaHS completely reduced the disulfide bond of NMDAR1 in PC12 cells. The inhibition of NMDAR by MK-801 microinjected in PVN of rats with MCAO also could lower blood pressure and renal sympathetic discharge. In conclusion, PSH may be associated with disease progression and survival in patients with IS. Decreased levels of H2S in PVN were involved in regulating sympathetic efferent activity after cerebral infarction. Our results might provide a new strategy and target for the prevention and treatment of PSH.

Paroxysmal Sympathetic Hyperactivity in Stroke

OBJECTIVE

Paroxysmal sympathetic hyperactivity (PSH) is a life-threatening neurological emergency associated with severe brain injury. Stroke-related PSH, particularly post-aneurysmal subarachnoid hemorrhage (aSAH) PSH, has been relatively understudied and is often misdiagnosed as an aSAH-related hyperadrenergic crisis. This study aims to clarify the feature of stroke-related PSH.

METHODS

This study discusses the case of a patient with post-aSAH PSH and identifies 19 articles (25 cases) on stroke-related PSH by searching the PubMed database from 1980 to 2021.

RESULTS

In the total cohort, 15 (60.0%) patients were male and the average age was 40.1 ± 16.6 years. The primary diagnoses included intracranial hemorrhage (13 cases, 52.0%), cerebral infarction (7 cases, 28.0%), subarachnoid hemorrhage (4 cases, 16.0%), and intraventricular hemorrhage (1 case, 4.0%). The sites of stroke damage were predominantly the cerebral lobe (10 cases, 40.0%), basal ganglia (8 cases, 32.0%), and the pons (4 cases, 16.0%). The median time of PSH onset after admission was 5 (1-180) days. Most cases employed combination therapy with sedation drugs, beta-blockers, gabapentin, and clonidine. On the Glasgow Outcome Scale, outcomes included death (4 cases, 21.1%), vegetative state (2 cases, 10.5%), severe disability (7 cases, 36.8%), and in only one case (5.3%) was a good recovery noted.

CONCLUSIONS

The clinical features and treatment of post-aSAH PSH differed from those of aSAH-related hyperadrenergic crises. Early diagnosis and treatment can prevent severe complications. PSH should be acknowledged as a potential complication of aSAH. Differential diagnosis can aid in developing individualized treatment plans and improving patient prognosis.

Effect of propranolol and clonidine after severe traumatic brain injury: a pilot randomized clinical trial

OBJECTIVE

To evaluate the safety, feasibility, and efficacy of combined adrenergic blockade with propranolol and clonidine in patients with severe traumatic brain injury (TBI).

BACKGROUND

Administration of adrenergic blockade after severe TBI is common. To date, no prospective trial has rigorously evaluated this common therapy for benefit.

METHODS

This phase II, single-center, double-blinded, pilot randomized placebo-controlled trial included patients aged 16-64 years with severe TBI (intracranial hemorrhage and Glasgow Coma Scale score ≤ 8) within 24 h of ICU admission. Patients received propranolol and clonidine or double placebo for 7 days. The primary outcome was ventilator-free days (VFDs) at 28 days. Secondary outcomes included catecholamine levels, hospital length of stay, mortality, and long-term functional status. A planned futility assessment was performed mid-study.

RESULTS

Dose compliance was 99%, blinding was intact, and no open-label agents were used. No treatment patient experienced dysrhythmia, myocardial infarction, or cardiac arrest. The study was stopped for futility after enrolling 47 patients (26 placebo, 21 treatment), per a priori stopping rules. There was no significant difference in VFDs between treatment and control groups [0.3 days, 95% CI (- 5.4, 5.8), p = 1.0]. Other than improvement of features related to sympathetic hyperactivity (mean difference in Clinical Features Scale (CFS) 1.7 points, CI (0.4, 2.9), p = 0.012), there were no between-group differences in the secondary outcomes.

CONCLUSION

Despite the safety and feasibility of adrenergic blockade with propranolol and clonidine after severe TBI, the intervention did not alter the VFD outcome. Given the widespread use of these agents in TBI care, a multi-center investigation is warranted to determine whether adrenergic blockade is of therapeutic benefit in patients with severe TBI. Trial Registration Number NCT01322048.

Paroxysmal Sympathetic Hyperactivity in Adult Patients with Brain Injury: A Systematic Review and Meta-Analysis

BACKGROUND

Paroxysmal sympathetic hyperactivity (PSH) is a syndrome of excessive sympathetic activity, mainly occurring in severe traumatic brain injury. However, few studies have reported the frequency of PSH and its related risk factors in adult patients with brain injury.

METHODS

We performed this systematic review and meta-analysis to estimate the combined incidence of PSH and the associated risk factors in adult patients with brain injury. This study was registered with the PROSPERO international prospective register of systematic reviews (https://www.crd.york. ac.uk/PROSPERO/Identifier: CRD 42021260493), and a systematic search was conducted of the scientific databases Embase, PubMed, Web of Science, Cochrane Library, and Google Scholar. All identified observational studies regarding the incidence and risk factors of PSH in adult patients with brain injury were included. Two authors extracted data independently; data were analyzed by STATA version 16.

RESULTS

The search yielded 9 studies involving 1643 adult patients. PSH was detected in 438 patients. The combined incidence of PSH in adult patients with brain injury was 27.4% (95% confidence interval [CI], 0.190-0.358). The risk factors include patients' age (SMD = -0.592; I² = 77.5%; 95% CI, -1.027 to -0.156; P = 0.008), traffic accident (odds ratio [OR], 1.783; I² =18.0%; 95% CI, 1.128-2.820; P = 0.013), admission Glasgow Coma Scale score (SMD = -1.097; I² =28.3%; 95% CI, -1.500 to -0.693; P = 0.000), hydrocephalus (OR, 3.936; I² =67.9%; 95% CI, 1.144-13.540; P = 0.030), and diffuse axonal injury (OR, 4.747; I² =71.1%; 95% CI, 1.221-18.463; P = 0.025) and were significantly associated with the presence of PSH after brain injury.

CONCLUSIONS

PSH occurs in nearly a quarter of adult patients with brain injury. Patient's age, traffic accident, admission Glasgow Coma Scale score, hydrocephalus, and diffuse axonal injury were risk factors for PSH in adult patients with brain injury. These findings may contribute to novel strategies for early diagnosis and interventions that aid in the rehabilitation of patients with brain injury.

Relationship between hyperhidrosis and hypothalamic injury in patients with mild traumatic brain injury

Hyperhidrosis is clinical symptom of various diseases and is an important clinical feature of paroxysmal sympathetic hyperactivity (PSH). Traumatic brain injury (TBI) is known to be most common condition associated with PSH, and PSH has been mainly reported in moderate and severe TBI. However, very little has been reported on PSH or hyperhidrosis in mild TBI patients. In this study, we used diffusion tensor imaging (DTI) to investigate the relationship between hyperhidrosis and hypothalamic injury in patients with mild TBI. Seven patients with hyperhidrosis after mild TBI and 21 healthy control subjects were recruited for this study. The Hyperhidrosis Disease Severity Scale was used for evaluation of sweating at the time of DTI scanning. The fractional anisotropy and apparent diffusion coefficient DTI parameters were measured in the hypothalamus. In the patient group, the fractional anisotropy values for both sides of the hypothalamus were significantly lower than those of the control group (P < .05). By contrast, the apparent diffusion coefficient values for both sides of the hypothalamus were significantly higher in the patient group than in the control group (P < .05). In conclusion, we detected hypothalamic injuries in patients who showed hyperhidrosis after mild TBI. Based on the results, it appears that hyperhidrosis in patients with mild TBI is related to hypothalamic injury.

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.

Paroxysmal sympathetic hyperactivity during traumatic brain injury

Traumatic brain injury (TBI) is one of the leading causes of disability, morbidity, and mortality worldwide. Some of the more common etiologies of TBI include closed head injury, penetrating head injury, or an explosive blast head injury. Neuronal damage in TBI is related to both primary injury (caused by mechanical forces), and secondary injury (caused by the subsequent tissue and cellular damages). Recently, it has been well established that Paroxysmal Sympathetic Hyperactivity (PSH), also known as "Sympathetic Storm", is one of the main causes of secondary neuronal injury in TBI patients. The clinical manifestations of PSH include recurrent episodes of sympathetic hyperactivity characterized by tachycardia, systolic hypertension, hyperthermia, tachypnea with hyperpnea, and frank diaphoresis. Given the diverse manifestations of PSH and its notable impact on the outcome of TBI patients, we have comprehensively reviewed the current evidence and discussed the pathophysiology, clinical manifestations, time of onset and duration of PSH during TBI. This article reviews the different types of head injuries that most commonly lead to PSH, possible approaches to manage and minimize PSH complications in TBI and the current prognosis and outcomes of PSH in TBI patients.

Paroxysmal Sympathetic Hyperactivity in Moderate-to-Severe Traumatic Brain Injury and the Role of Beta-Blockers: A Scoping Review

Introduction

Most cases of paroxysmal sympathetic hyperactivity (PSH) result from traumatic brain injury (TBI). Little is known about its pathophysiology and treatment, and several neuroprotective drugs are used including beta-blockers. The aim of our study is to collate existing evidence of the role of beta-blockers in the treatment of PSH.

Methods

We searched MEDLINE, ResearchGate, and Google Scholar, for keywords related to PSH and the role of beta-blockers in moderate-to-severe TBI on September 23, 2020. Two authors blindly screened the articles found with Rayyan. Both resolved their conflicts by mutual consent. If no solution was found, a third author was consulted. Simple descriptive data analysis was performed and the results were presented both in a narrative and tabular form.

Results

Of the 19 items found, 10 met the criteria for inclusion. 50% were systematic reviews without meta-analysis, 40% were observational studies, and 10% were experimental studies. Propranolol was the main beta-blocker found in 80% of the studies and was the only molecule used in the treatment of paroxysmal sympathetic hyperactivity in 40% of the included studies. Only two studies evaluated and showed a significant association between beta-blockers and mortality rate (5.1% vs. 10.8%; P=0.03), (3% vs. 15%; P=0.002), respectively.

Conclusion

Propranolol is the beta-blocker that has been shown to be effective in reducing the length of stay and mortality rate in moderate-severe traumatic brain injury patients with PSH. However, further studies are needed to precisely define the terms and conditions of its use.

Effectiveness of Pharmacological Agents and Validation of Diagnostic Scales for the Management of Paroxysmal Sympathetic Hyperactivity in Hispanics

The identification and treatment of paroxysmal sympathetic hyperactivity (PSH) still present a significant challenge. We assessed the efficacy of pharmacological agents in treating PSH symptoms and the validity of the diagnostic scales in a cohort of Hispanic patients. A retrospective chart review of cases from a single hospital was conducted in 464 records. Exclusion criteria included underlying conditions such as severe infection. Only nine patients remained in the cohort after examining their clinical records, corresponding to the following diagnoses: traumatic brain injury, subdural hemorrhage, anoxic or ischemic encephalopathy, pneumocephalus, and cerebral palsy. Using the PSH likelihood scale, six of the nine patients were identified with a score of 17 or higher, corresponding to a "probable" PSH, and three patients obtained a score between 8 and 16, corresponding to a "possible" PSH diagnosis. The top three classes of medications used were beta-blockers, antipyretics, and opioids. Benzodiazepines and neuromodulators were also frequently used in patients with trauma, but not in the ones with non-traumatic injuries. Interestingly, 75% of the patients have prescribed levothyroxine as a home medication after the PSH presentation. Medication administration did not follow a specific pattern, suggesting high variability in the management of PSH within our setting, requiring further research. Our results suggest that the pituitary axis might be involved in the progression of PSH. Establishing a specific medical code (e.g., ICD-10) describing PSH as a single entity is essential for appropriate identification and management.

Paroxysmal Sympathetic Hyperactivity

Paroxysmal sympathetic hyperactivity (PSH) is a relatively common, but often unrecognized, complication of acute diffuse or multifocal brain diseases, most frequently encountered in young comatose patients with severe traumatic brain injury. It is presumed to be caused by loss of cortical inhibitory modulation of diencephalic and brain stem centers and possible additional maladaptive changes in the spinal cord that combine to produce exaggerated sympathetic responses to stimulation. The syndrome consists of repeated sudden episodes of tachycardia, tachypnea, hypertension, sweating, and sometimes fever and dystonic posturing. The diagnosis is clinical. Treatment includes reducing any external stimulation that can trigger the episodes, and starting abortive (e.g., intravenous morphine) and preventive medications (e.g., gabapentin, propranolol, clonidine). Prompt and adequate treatment of PSH may reduce the likelihood of secondary complications, such as dehydration, weight loss and malnutrition, and muscle contractures.

Organic features of autonomic dysregulation in paediatric brain injury - Clinical and research implications for the management of patients with Rett syndrome

Rett Syndrome (RTT) is a complex neurodevelopmental disorder with autonomic nervous system dysfunction. The understanding of this autonomic dysregulation remains incomplete and treatment recommendations are lacking. By searching literature regarding childhood brain injury, we wanted to see whether understanding autonomic dysregulation following childhood brain injury as a prototype can help us better understand the autonomic dysregulation in RTT. Thirty-one (31) articles were identified and following thematic analysis the three main themes that emerged were (A) Recognition of Autonomic Dysregulation, (B) Possible Mechanisms & Assessment of Autonomic Dysregulation and (C) Treatment of Autonomic Dysregulation. We conclude that in patients with RTT (I) anatomically, thalamic and hypothalamic function should be explored, (II) sensory issues and medication induced side effects that can worsen autonomic function should be considered, and (III) diaphoresis and dystonia ought to be better managed. Our synthesis of data from autonomic dysregulation in paediatric brain injury has led to increased knowledge and a better understanding of its underpinnings, leading to the development of application protocols in children with RTT.

Alcohol Withdrawal Syndrome in Neurocritical Care Unit: Assessment and Treatment Challenges

Alcohol withdrawal syndrome (AWS) can range from mild jittery movements, nausea, sweating to more severe symptoms such as seizure and death. Severe AWS can worsen cognitive function, increase hospital length of stay, and in-hospital mortality and morbidity. Due to a lack of reliable history of present illness in many patients with neurological injury as well as similarities in clinical presentation of AWS and some commonly encountered neurological syndromes, the true incidence of AWS in neurocritical care patients remains unknown. This review discusses challenges in the assessment and treatment of AWS in patients with neurological injury, including the utility of different scoring systems such as the Clinical Institute Withdrawal Assessment and the Minnesota Detoxification Scale as well as the reliability of admission alcohol levels in predicting AWS. Treatment strategies such as symptom-based versus fixed dose benzodiazepine therapy and alternative agents such as baclofen, carbamazepine, dexmedetomidine, gabapentin, phenobarbital, ketamine, propofol, and valproic acid are also discussed. Finally, a treatment algorithm considering the neurocritical care patient is proposed to help guide therapy in this setting.

Efficacy of trazodone for treating paroxysmal sympathetic hyperactivity presenting after left temporal subcortical hemorrhage

Paroxysmal sympathetic hyperactivity (PSH) is a clinical condition characterized by abnormal paroxysmal surges in sympathetic nervous system activity. PSH is known to occur after severe head injury and hypoxic encephalopathy. Cases of PSH that develop after stroke have been reported worldwide; however, PSH is not commonly reported in the field of stroke research in Japan. Some studies have suggested that gabapentin may improve the symptoms of PSH. To our knowledge, this is the first case report demonstrating the efficacy of trazodone for the treatment of PSH that developed after temporal subcortical hemorrhage. A 49-year-old woman presented to our clinic with mild confusion and sensory aphasia after experiencing left temporal subcortical hemorrhage; a conservative treatment was initiated at our hospital. Immediately upon hospitalization, she developed prolonged consciousness disorder, high fever, tachycardia, malignant hypertension, tachypnea, constipation, and overactive bladder. The patient's symptoms improved after the administration of trazodone. She was diagnosed with PSH after intracranial hemorrhage and was subsequently transferred to a recovery and rehabilitation hospital unit where the oral administration of trazodone continued. Prolonged PSH contributes significantly to the impairment of daily activities in patients with stroke; therefore, early diagnosis and treatment are critical. Here, we report on the efficacy of trazodone as an effective treatment option for improving clinical outcomes and reducing the stay in the stroke care unit.

Identification and Management of Paroxysmal Sympathetic Hyperactivity After Traumatic Brain Injury

Paroxysmal sympathetic hyperactivity (PSH) has predominantly been described after traumatic brain injury (TBI), which is associated with hyperthermia, hypertension, tachycardia, tachypnea, diaphoresis, dystonia (hypertonia or spasticity), and even motor features such as extensor/flexion posturing. Despite the pathophysiology of PSH not being completely understood, most researchers gradually agree that PSH is driven by the loss of the inhibition of excitation in the sympathetic nervous system without parasympathetic involvement. Recently, advances in the clinical and diagnostic features of PSH in TBI patients have reached a broad clinical consensus in many neurology departments. These advances should provide a more unanimous foundation for the systematic research on this clinical syndrome and its clear management. Clinically, a great deal of attention has been paid to the definition and diagnostic criteria, epidemiology and pathophysiology, symptomatic treatment, and prevention and control of secondary brain injury of PSH in TBI patients. Potential benefits of treatment for PSH may result from the three main goals: eliminating predisposing causes, mitigating excessive sympathetic outflow, and supportive therapy. However, individual pathophysiological differences, therapeutic responses and outcomes, and precision medicine approaches to PSH management are varied and inconsistent between studies. Further, many potential therapeutic drugs might suppress manifestations of PSH in the process of TBI treatment. The purpose of this review is to present current and comprehensive studies of the identification of PSH after TBI in the early stage and provide a framework for symptomatic management of TBI patients with PSH.

Efficacy of trazodone for treating paroxysmal sympathetic hyperactivity presenting after thalamic hemorrhage: A case report

Paroxysmal sympathetic hyperactivity (PSH) is a clinical condition characterized by abnormal paroxysmal surges in sympathetic nervous system activity. PSH is known to occur after severe head injury and hypoxic encephalopathy. Cases of PSH that develop after stroke have been reported worldwide; however, PSH is not commonly reported in the field of stroke research in Japan. Some studies have suggested that gabapentin may improve the symptoms of PSH. To our knowledge, this is the first case report demonstrating the efficacy of trazodone for the treatment of PSH that developed after thalamic hemorrhage. A 45-year-old woman presented to our clinic with headache and paralysis of the left side of her body after experiencing right thalamic hemorrhage; a conservative treatment was initiated at our hospital. Immediately upon hospitalization, she developed high fever, tachycardia, tachypnea, constipation, and overactive bladder and had breathing difficulties. Blood sampling revealed elevated levels of myocardial escape enzymes; however, coronary angiography did not show any significant stenosis or occlusion. The patient's symptoms improved after the administration of trazodone. She was diagnosed with catecholamine cardiomyopathy associated with PSH after intracranial hemorrhage and was subsequently transferred to a recovery and rehabilitation hospital unit where the oral administration of trazodone continued. Prolonged PSH contributes significantly to the impairment of daily activities in patients with stroke; therefore, early diagnosis and treatment are critical. Here, we report on the efficacy of trazodone as an effective treatment option for improving clinical outcomes and reducing the stay in the stroke care unit.

Influence of paroxysmal sympathetic hyperactivity (PSH) on the functional outcome of neurological early rehabilitation patients: a case control study

Background

Paroxysmal Sympathetic Hyperactivity (PSH) is a frequently observed condition among critically ill patients on intensive care units. According to different studies, PSH is associated with worse recovery and increased mortality in acute-care facilities. In this monocentric, retrospective case-control study, we investigated whether this association also applies to post-acute neurological early rehabilitation.

Methods

The study included n = 387 patients, admitted to an intensive care or intermediate care unit within 1 year (2016). Among these, 97 patients showed clinical signs of PSH. For each patient with PSH, a patient without PSH was identified, controlling for age, gender, functional and respiratory status upon admission. However, for 25 patients with PSH, there was no suitable control patient fulfilling all defined matching criteria. Primary outcome was type of discharge, dichotomized into favorable (follow-up rehabilitation) and unfavorable outcome (all others). Secondary outcome measures were functional and respiratory status, number of secondary diagnoses, duration of treatment interruptions and length of stay at discharge.

Results

About 25% of neurological early rehabilitation patients showed clinical signs of PSH. A young age (OR = 0.94; CI = 0.91–0.97) and less severe PSH symptoms (OR = 0.79; CI = 0.69–0.90) were independent predictors of a favorable outcome. In addition, severity of PSH symptoms was associated with weaning duration, while the occurrence of PSH symptoms alone had no influence on most secondary outcome variables. The treatment on intermediate care units proved to be longer for patients with PSH symptoms, only.

Conclusions

Patients with PSH represent a large group of neurological early rehabilitation patients. Overall, we did not find PSH-related differences in most of the examined outcome measures. However, severe PSH symptoms seem to be associated with poorer outcome and longer treatment on intermediate care units, in order to prevent possible complications.

A study into the feasibility of using HRV variables to guide treatment in patients with paroxystic sympathetic hyperactivity in a neurointensive step-down unit

BACKGROUND

Patients suffering brain injury may experience paroxystic sympathetic hyperactivity, presenting diagnostic and therapeutic challenges in neurointensive rehabilitation. The syndrome has been modelled as peripheral and central excitatory:inhibitory ratios of autonomous nervous activity. Another model represents the symptoms as oscillations of the two components of the autonomous nervous system. In therapeutic framework, the syndrome is perceived as the patient misconstruing sensory input relating to body positioning.

OBJECTIVE

To investigate whether changes in frequency domain of heart rate variability reflect pharmacological and/or therapeutic measures in rehabilitation.

METHODS

ECG was recorded before and after pharmacological and therapeutic interventions in eight patients with high probability of the syndrome in a neurointensive step-down unit. Recordings were analysed off-line in frequency parameters. Appropriate statistical methods were applied.

RESULTS

Low, high frequency and the LF/HF ratio changed significantly following therapeutic as well as pharmacological interventions.

DISCUSSION

The cohort was small, the setting the immediate postictal period of intensive care with multidisciplinary rehabilitation. Still, changes in frequency domain were detected following therapeutic efforts. This opens up the venue of on-line monitoring of the intended therapeutic effect.

Autonomic Dysfunction and Associations with Functional and Neurophysiological Outcome in Moderate/Severe Traumatic Brain Injury: A Scoping Review

The quantification and objective documentation of autonomic dysfunction in traumatic brain injury (TBI) is neither well studied nor extensively validated. Most of the descriptions of autonomic dysfunction in the literature are in the form of vague non-specific clinical manifestations. Few studies propose the use of objective measures of assessing the extent of autonomic dysfunction to link them to the outcome of TBI. Our goal was to perform a scoping systematic review of the literature on the objective documentation of autonomic dysfunction in terms of functional and physiological variables to be linked to outcome of TBI. PubMed/MEDLINE^®, BIOSIS, Scopus, Embase, Cochrane Libraries, and Global Health databases were searched. Two reviewers independently screened the results. Full texts for citations passing this initial screen were obtained. Inclusion and exclusion criteria were applied to each article to obtain final articles for review. The initial search yielded 2619 citations. Of 69 articles selected for final review, 14 were chosen based on the inclusion and exclusion criteria and are included in the results of this article. 9 of these articles assessed autonomic dysfunction using functional variables and 7 assessed autonomic dysfunction using physiological variables. Some studies included both functional and physiological variables. Of the nine studies linking autonomic dysfunction to functional variables, nine included heart rate variability (HRV), three included baroreflex sensitivity (BRS), and two included blood pressure variability (BPV). A total of 2714 adult patients were studied. Although the nature of association between autonomic dysfunction and outcome is unclear, the objective quantification of autonomic dysfunction seems to be associated with global patient outcome and other neurophysiological measures. Further studies are needed to validate its use and explore the underlying molecular mechanisms of the described associations.

Management of Traumatic Brain Injury: An Update

The care of patients with traumatic brain injury can be one of the most challenging and rewarding aspects of clinical neurocritical care. This article reviews the approach to unique aspects specific to the care of this patient population. These aspects include appropriate use of sedation and analgesia, and the principles and the clinical use of intracranial monitors. Common clinical challenges encountered in these patients are also discussed, including the treatment of intracranial hypertension, temperature management, and control of sympathetic hyperactivity.

Early Fever As a Predictor of Paroxysmal Sympathetic Hyperactivity in Traumatic Brain Injury

OBJECTIVE

Paroxysmal sympathetic hyperactivity (PSH) is characterized by episodic, hyperadrenergic alterations in vital signs after traumatic brain injury (TBI). We sought to apply an objective scale to the vital sign alterations of PSH in order to determine whether 1 element might be predictive of developing PSH.

SETTING/PARTICIPANTS/DESIGN

We conducted an observational study of consecutive TBI patients (Glasgow Coma Scale score ≤12) and monitored the cohort for clinical evidence of PSH. PSH was defined as a paroxysm of 3 or more of the following characteristics: (1) tachycardia, (2) tachypnea, (3) hypertension, (4) fever, (5) dystonia (rigidity or decerebrate posturing), and (6) diaphoresis, with no other obvious causation (ie, alcohol withdrawal, sepsis).

MAIN MEASURES

The Modified Clinical Feature Severity Scale (mCFSS) was applied to each participant once daily for the first 5 days of hospitalization.

RESULTS

Nineteen (11%) of the 167 patients met criteria for PSH. Patients with PSH had a higher 5-day cumulative mCFSS score than those without PSH (median [interquartile range] = 36 [29-42] vs 29 [22-35], P = .01). Of the 4 components of the mCFSS, elevated temperature appeared to be most predictive of the development of PSH, especially during the first 24 hours (odds ratio = 1.95; 95% confidence interval, 1.12-3.40).

CONCLUSION

Early fever after TBI may signal impending autonomic dysfunction.

Paroxysmal sympathetic hyperactivity: An entity to keep in mind

Paroxysmal sympathetic hyperactivity (PSH) is a potentially life-threatening neurological emergency secondary to multiple acute acquired brain injuries. It is clinically characterized by the cyclic and simultaneous appearance of signs and symptoms secondary to exacerbated sympathetic discharge. The diagnosis is based on the clinical findings, and high alert rates are required. No widely available and validated homogeneous diagnostic criteria have been established to date. There have been recent consensus attempts to shed light on this obscure phenomenon. Its physiopathology is complex and has not been fully clarified. However, the excitation-inhibition model is the theory that best explains the different aspects of this condition, including the response to treatment with the available drugs. The key therapeutic references are the early recognition of the disorder, avoiding secondary injuries and the triggering of paroxysms. Once sympathetic crises occur, they must peremptorily aborted and prevented. of the later the syndrome is recognized, the poorer the patient outcome.

Paroxysmal sympathetic hyperactivity: the storm after acute brain injury

A substantial minority of patients who survive an acquired brain injury develop a state of sympathetic hyperactivity that can persist for weeks or months, consisting of periodic episodes of increased heart rate and blood pressure, sweating, hyperthermia, and motor posturing, often in response to external stimuli. The unifying term for the syndrome-paroxysmal sympathetic hyperactivity (PSH)-and clear diagnostic criteria defined by expert consensus were only recently established. PSH has predominantly been described after traumatic brain injury (TBI), in which it is associated with worse outcomes. The pathophysiology of the condition is not completely understood, although most researchers consider it to be a disconnection syndrome with paroxysms driven by a loss of inhibitory control over excitatory autonomic centres. Although therapeutic strategies to alleviate sympathetic outbursts have been proposed, their effects on PSH are inconsistent between patients and their influence on outcome is unknown. Combinations of drugs are frequently used and are chosen on the basis of local custom, rather than on objective evidence. New rigorous tools for diagnosis could allow better characterisation of PSH to enable stratification of patients for future therapeutic trials.

Management of Traumatic Brain Injury: An Update

The care of patients with traumatic brain injury can be one of the most challenging and rewarding aspects of clinical neurocritical care. This article reviews the approach to unique aspects specific to the care of this patient population. These aspects include appropriate use of sedation and analgesia, and the principles and the clinical use of intracranial monitors. Common clinical challenges encountered in these patients are also discussed, including the treatment of intracranial hypertension, temperature management, and control of sympathetic hyperactivity.

Transient dysautonomia in an acute phase of encephalopathy with biphasic seizures and late reduced diffusion

Paroxysmal sympathetic hyperactivity (PSH) is a dysautonomic condition that is associated with various types of acquired brain injuries. Traumatic brain lesions have been documented as the leading cause of PSH. However, detailed clinical features of pediatric PSH caused by intrinsic brain lesions remain to be elusive. We present a 3-year-old boy, who had been diagnosed as having cerebral palsy, developmental delay and epilepsy after perinatal hypoxia-induced brain injury. He developed status epilepticus with fever on the third day of respiratory infection. Whereas the seizure was terminated by systemic infusion of midazolam, consciousness remained disturbed for the next 48h. Serial magnetic resonance imaging studies revealed that acute encephalopathy with biphasic seizures and late reduced diffusion (AESD) evolved on 3days after the seizure. Therapeutic hypothermia was immediately introduced, however, the brain lesion extended to the whole subcortical white matters on day 8. The intermittent bilateral dilation of pupils with increased blood pressure and tachycardia were observed until day 12. Real-time monitoring of electroencephalograms ruled out the recurrent attacks of seizures. The abnormal signs of autonomic nervous system gradually ceased and never relapsed after recovery from the hypothermia. PSH or a transient condition of dysautonomia may emerge and persist during the acute phase of AESD.

[High blood pressure during the autonomic crises in children in intensive care unit: Etiologic circumstances and modality therapeutic]

The dysautonomic (DC) or neurovegetative crisis remains an imperfectly known entity; it associates in a paroxysmal manner a reaction of sympathetic hyperreactivity that can lead to the prognosis. Our objective is to specify the etiological circumstances (DC) and their modality of treatment in pediatric intensive care unit.

MATERIALS-METHODS

Descriptive study on files of children admitted in the intensive care unit of 2010-2015 who presented a DC acquired during their hospitalization.

RESULTS

In total, 41 patients included with an average age of 56.92 months presented DC. Among the etiological circumstances Guillain-Barré syndrome and head trauma are noted. Observed symptoms occur on average at one week of admission; they are related to the consequences of DC. The manifestations are polymorphic: a systolic hypertension is present in all cases with an average PAS of 141.24±13.48mmHg, an average PAD of 86.80±11.01mmHg, a vasomotor disorder, a hyperthermia are noted. Cerebral anoxia post cardiac arrest in 4 patients preceded the onset of DC. Apart from the etiologic treatment, 39 patients were intubated with mechanical ventilation, sedated with morphinomimetic and benzodiazepine±lioresal (baclofen). Treatment of hypertension resulted in the administration of a central antihypertensive. Evolution is good in addition to 5 deaths related to neurovegetative disorders.

CONCLUSION

DC is a poorly understood situation in pediatric intensive care unit, and the circumstances of the disease are variable. The diagnosis must be made with careful consideration because the prognosis may be fatal.

The preventive effect of dexmedetomidine on paroxysmal sympathetic hyperactivity in severe traumatic brain injury patients who have undergone surgery: a retrospective study

Background

Paroxysmal sympathetic hyperactivity (PSH) results and aggravates in secondary brain injury, which seriously affects the prognosis of severe traumatic brain injury patients. Although several studies have focused on the treatment of PSH, few have concentrated on its prevention.

Methods

Ninety post-operation (post-op) severe traumatic brain injury (sTBI) patients admitted from October 2014 to April 2016 were chosen to participate in this study. Fifty of the post-op sTBI patients were sedated with dexmedetomidine and were referred as the “dexmedetomidine group” (admitted from May 2015 to April 2016). The other 40 patients (admitted from October 2014 to May 2015) received other sedations and were referred as the “control group.” The two groups were then compared based on their PSH scores and the scores and ratios of those patients who met the criteria of “probable,” “possible” and “unlikely” using the PSH assessment measure (PSH-AM) designed by Baguley et al. (2014). The durations of the neurosurgery intensive care unit (NICU) and hospital stays and the Glasgow outcome scale (GOS) values for the two groups were also compared to evaluate the therapeutic effects and the patients’ prognosis.

Results

The overall PSH score for the dexmedetomidine group was 5.26 ± 4.66, compared with 8.58 ± 8.09 for the control group. The difference between the two groups’ PSH scores was significant (P = 0.017). The score of the patients who met the criterion of “probable” was 18.33 ± 1.53 in the dexmedetomidine group and 22.63 ± 2.97 in the control group, and the difference was statistically significant (P = 0.045). The ratio of patients who were classified as “unlikely” between the two groups was statistically significant (P = 0.028); that is, 42 (84%) in the dexmedetomidine group and 25 (62.5%) in the control group. The differences in NICU, hospital stays and GOS values between the two groups were not significant.

Conclusion

Dexmedetomidine has a preventive effect on PSH in sTBI patients who have undergone surgery.

Paroxysmal sympathetic hyperactivity in severe traumatic brain injury

BACKGROUND

Paroxysmal sympathetic hyperactivity (PSH) is a less-known complication of traumatic brain injury (TBI). This study was done to assess the clinical features and outcome of patients who develop PSH following severe TBI.

METHODS

A prospective observational study was done on patients, admitted in the intensive care unit, for treatment of severe TBI. The clinical characteristics and outcome of patients, with and without PSH, was compared. At the time of discharge, patients were assessed with the Disability Rating Scale (DRS), and at 6 months with the Glasgow Outcome Score Extended (GOSE).

RESULTS

The incidence of PSH was 8 % (29/343). Tachycardia, hypertension, and sweating were seen in all of the patients. Tachypnea was seen in 24 (82.8 %), hyperthermia in 28 (96.6 %), and posturing in 13 (44.8 %) patients. Thirteen (44.8 %) patients had all six symptoms of PSH. Follow-up data were available for 23 (79.3 %) patients. At the end of 6 months, 14 (60.9 %) patients had died, seven (30.4 %) were severely disabled, and two (8.7 %) were moderately disabled. There was a significant correlation of GOSE with the number of symptoms of PSH (Spearman's rho = 0.502, p = 0.015). The patients with PSH had significantly higher DRS scores at discharge, 25.3 vs. 19.9, p < 0.001; higher mortality at 6 months 60.9 vs. 30.4 %, p < 0.001; and higher proportions with unfavorable outcome.

CONCLUSIONS

Presence of PSH in patients with severe TBI was associated with prolonged hospital stay, poorer DRS at discharge, more deaths, and unfavorable outcome. The number of symptoms of PSH had a significant effect on outcome at 6 months.

Neurogenic Fever

Fever is a relatively common occurrence among patients in the intensive care setting. Although the most obvious and concerning etiology is sepsis, drug reactions, venous thromboembolism, and postsurgical fevers are all on the differential diagnosis. There is abundant evidence that fever is detrimental in acute neurologic injury. Worse outcomes are reported in acute stroke, subarachnoid hemorrhage, and traumatic brain injury. In addition to the various etiologies of fever in the intensive care setting, neurologic illness is a risk factor for neurogenic fevers. This primarily occurs in subarachnoid hemorrhage and traumatic brain injury, with hypothalamic injury being the proposed mechanism. Paroxysmal sympathetic hyperactivity is another source of hyperthermia commonly seen in the population with traumatic brain injury. This review focuses on the detrimental effects of fever on the neurologically injured as well as the risk factors and diagnosis of neurogenic fever.

Paroxysmal Sympathetic Hyperactivity in a Child with Tuberculous Meningitis A Case Study and Review of Related Literature

A one-year old boy was admitted to hospital for lethargy and vomiting over three days. Neurological examination revealed abnormalities. Cerebrospinal fluid examination showed evidence of meningitis. A purified protein derivative (PPD) test, T-SPOT.TB and radiological examination indicated tuberculous meningitis. During treatment, the child developed hypertension, sinus tachycardia, tachypnoea, dystonia and high fever. These episodes improved after administration of propranolol, artane and clonazepam. Paroxysmal sympathetic hyperactivity is a rare manifestation of tuberculous meningitis. Early detection is very important as it can avoid diagnostic errors and overtreatment.

Refractory paroxysmal sympathetic hyperactivity following brain injury in a pregnant woman that dramatically improved after delivery

Case

A 16-year-old primiparous girl in the 11th week of gestation presented to our hospital with a traumatic brain injury suffered during a motorcycle accident. She was comatose on arrival to the hospital and was admitted to the intensive care unit. From day 2, she developed intermittent episodes of tachycardia with tachypnea, fever, profuse sweating, and extensor posturing. She was diagnosed with paroxysmal sympathetic hyperactivity (PSH) and treated with morphine. However, paroxysmal sympathetic hyperactivity could not be controlled and her general condition deteriorated. Intrauterine fetal death was confirmed in the 16th week of gestation, on day 37 of hospitalization. P paroxysmal sympathetic hyperactivity increased each day until delivery and dramatically improved after delivery.

Outcome

The patient gradually regained consciousness and was discharged to a rehabilitation hospital on day 117 after hospitalization.

Conclusion

Pregnancy is a risk factor for paroxysmal sympathetic hyperactivity exacerbation, and delivery can result in resolution of the condition.

Interrelation between Neuroendocrine Disturbances and Medical Complications Encountered during Rehabilitation after TBI

Traumatic brain injury is not a discrete event but an unfolding sequence of damage to the central nervous system. Not only the acute phase but also the subacute and chronic period after injury, i.e., during inpatient rehabilitation, is characterized by multiple neurotransmitter alterations, cellular dysfunction, and medical complications causing additional secondary injury. Neuroendocrine disturbances also influence neurological outcome and are easily overlooked as they often present with diffuse symptoms such as fatigue, depression, poor concentration, or a decline in overall cognitive function; these are also typical sequelae of traumatic brain injury. Furthermore, neurological complications such as hydrocephalus, epilepsy, fatigue, disorders of consciousness, paroxysmal sympathetic hyperactivity, or psychiatric-behavioural symptoms may mask and/or complicate the diagnosis of neuroendocrine disturbances, delay appropriate treatment and impede neurorehabilitation. The present review seeks to examine the interrelation between neuroendocrine disturbances with neurological complications frequently encountered after moderate to severe TBI during rehabilitation. Common neuroendocrine disturbances and medical complications and their clinical implications are discussed.

Morphine: An Effective Abortive Therapy for Pediatric Paroxysmal Sympathetic Hyperactivity After Hypoxic Brain Injury

Paroxysmal sympathetic hyperactivity (PSH) is a life-threatening condition characterized by hyperadrenergic activity and autonomic dysfunction. Also termed autonomic storms, PSH can occur after a variety of cerebral insults, most commonly traumatic brain injury. Limited pediatric literature is available, especially in patients with brain injury from hypoxia. No consensus exists for the terminology, diagnostic criteria, or treatment algorithm for PSH. Thus, the optimal management, including medication selection and dosing, remains unclear. We present the detailed treatment of a 9-year-old, African American male with hypoxic brain injury after pulseless arrest following status asthmaticus, who subsequently developed PSH. The patient began to experience episodes of tachycardia, hypertension, tachypnea, diaphoresis, rigidity, and dystonic posturing on hospital day 5. After ruling out other potential causes, a diagnosis of PSH was made. Episodes of PSH failed to respond to lorazepam or labetalol but were aborted successfully with morphine. Management of PSH after hypoxic brain injury required medications for acute treatment as well as for prevention of PSH. Morphine was found to be highly effective and safe for aborting the autonomic crises. Other agents more commonly described in the literature did not result in an adequate response and were associated with significant adverse effects. A combination of clonazepam, baclofen, and either propranolol or clonidine aided in reducing the frequency of episodes of PSH. We suggest using morphine for aborting severe episodes of PSH that do not respond to antihypertensive agents or benzodiazepines.

Subacute complications during recovery from severe traumatic brain injury: frequency and associations with outcome

BACKGROUND

Medical complications after severe traumatic brain injury (S-TBI) may delay or prevent transfer to rehabilitation units and impact on long-term outcome.

OBJECTIVE

Mapping of medical complications in the subacute period after S-TBI and the impact of these complications on 1-year outcome to inform healthcare planning and discussion of prognosis with relatives.

SETTING

Prospective multicentre observational study. Recruitment from 6 neurosurgical centres in Sweden and Iceland.

PARTICIPANTS AND ASSESSMENTS

Patients aged 18-65 years with S-TBI and acute Glasgow Coma Scale 3-8, who were admitted to neurointensive care. Assessment of medical complications 3 weeks and 3 months after injury. Follow-up to 1 year. 114 patients recruited with follow-up at 1 year as follows: 100 assessed, 7 dead and 7 dropped out.

OUTCOME MEASURE

Glasgow Outcome Scale Extended.

RESULTS

68 patients had ≥1 complication 3 weeks after injury. 3 weeks after injury, factors associated with unfavourable outcome at 1 year were: tracheostomy, assisted ventilation, on-going infection, epilepsy and nutrition via nasogastric tube or percutaneous endoscopic gastroscopy (PEG) tube (univariate logistic regression analyses). Multivariate analysis demonstrated that tracheostomy and epilepsy retained significance even after incorporating acute injury severity into the model. 3 months after injury, factors associated with unfavourable outcome were tracheostomy and heterotopic ossification (Fisher's test), infection, hydrocephalus, autonomic instability, PEG feeding and weight loss (univariate logistic regression). PEG feeding and weight loss at 3 months were retained in a multivariate model.

CONCLUSIONS

Subacute complications occurred in two-thirds of patients. Presence of a tracheostomy or epilepsy at 3 weeks, and of PEG feeding and weight loss at 3 months, had robust associations with unfavourable outcome that were incompletely explained by acute injury severity.

Critical Care for the Patient With Multiple Trauma

Trauma remains the leading cause of death worldwide and the leading cause of death in those less than 44 years old in the United States. Admission to a verified trauma center has been shown to decrease mortality following a major injury. This decrease in mortality has been a direct result of improvements in the initial evaluation and resuscitation from injury as well as continued advances in critical care. As such, it is vital that intensive care practitioners be familiar with various types of injuries and their associated treatment strategies as well as their potential complications in order to minimize the morbidity and mortality frequently seen in this patient population.

Early diagnosis of paroxysmal sympathetic hyperactivity in the ICU

BACKGROUND

Paroxysmal sympathetic hyperactivity (PSH) is a complication of acquired brain injury manifesting with episodic tachycardia, tachypnea, hypertension, diaphoresis, hypertonia, and posturing. No universally accepted diagnostic criteria exist and diagnosis is often delayed until the rehabilitation phase.

METHODS

Electronic records were screened to identify consecutive cases of PSH diagnosed in an intensive care unit (ICU) between 1/2006 and 8/2012 and assess the validity of early clinical diagnosis against formal diagnostic criteria. Data collected included patient demographics, brain injury etiology, symptoms noted by the clinician to support the diagnosis of PSH, PSH manifestations, therapeutic interventions, relevant brain imaging, and investigations to exclude alternative diagnoses. An operational set of diagnostic criteria based on previous literature was used for comparison.

RESULTS

Fifty-three consecutive patients with PSH were identified. Mean age was 33.6 ± 14.5 years (range 16-67). Traumatic brain injury was the most common etiology (30 patients, 56.6 %) but causes were diverse. Mean time to diagnosis was 8.3 ± 11.0 days; 31 patients (59 %) were diagnosed within 7 days and 20 patients (38 %) within 3 days of admission. Tachycardia was almost uniformly present, and diaphoresis, fever, hypertension, and tachypnea were also present in most cases. Dystonia and posturing were present in less than half of patients. 89 % of clinically diagnosed cases met formal diagnostic criteria.

CONCLUSIONS

Paroxysmal sympathetic hyperactivity can be diagnosed early in the ICU. Strict diagnostic criteria supported the clinician's diagnosis in the majority of cases. Diagnosis should not be rejected because of any particular sign's absence, especially dystonia and posturing.

Treatment Progress of Paroxysmal Sympathetic Hyperactivity after Acquired Brain Injury

Paroxysmal sympathetic hyperactivity (PSH) is a common complication of various acquired brain injuries such as traumatic brain injury, subarachnoid hemorrhage, anoxic brain injury, intracerebral hemorrhage, and others. It is manifested by tachycardia, hypertension, tachypnea, diaphoresis, and dystonic posturing. The development of PSH can prolong hospitalization and lead to secondary brain injury and even death. Despite the awareness of the serious clinical impact, there is no consensus on diagnostic criteria. Thus, misdiagnosis and delayed recognition is very common. Most of the current treatment programs come from case reports and small case series; there are very few large-scale randomized controlled trials. Generally accepted medications are opioids, β-blockers and gabapentin (usually used in combination). However, the efficacy of these drugs has not been systematically assessed. The purpose of this review is to determine the treatment strategies and drugs commonly used for PSH at the overall level.

Systemic manifestations of traumatic brain injury

Traumatic brain injury (TBI) affects functioning of various organ systems in the absence of concomitant non-neurologic organ injury or systemic infection. The systemic manifestations of TBI can be mild or severe and can present in the acute phase or during the recovery phase. Non-neurologic organ dysfunction can manifest following mild TBI or severe TBI. The pathophysiology of systemic manifestations following TBI is multifactorial and involves an effect on the autonomic nervous system, involvement of the hypothalamic-pituitary axis, release of inflammatory mediators, and treatment modalities used for TBI. Endocrine dysfunction, electrolyte imbalance, and respiratory manifestations are common following TBI. The influence of TBI on systemic immune response, coagulation cascade, cardiovascular system, gastrointestinal system, and other systems is becoming more evident through animal studies and clinical trials. Systemic manifestations can independently act as risk factors for mortality and morbidity following TBI. Some conditions like neurogenic pulmonary edema and disseminated intravascular coagulation can adversely affect the outcome. Early recognition and treatment of systemic manifestations may improve the clinical outcome following TBI. Further studies are required especially in the field of neuroimmunology to establish the role of various biochemical cascades, not only in the pathophysiology of TBI but also in its systemic manifestations and outcome.

Autonomic dysfunction syndromes after acute brain injury

The central autonomic nervous system (CAN) is a multifaceted, richly connected neural network incorporating the hypothalamus, its descending tracts through the brainstem, the insular cortex and down into the spinal cord. All levels of the CAN are susceptible to injury following traumatic brain injury (TBI), whether from focal or diffuse injury. Focal injuries would be expected to produce localized damage to CAN control centers, whereas the effects of diffuse injuries are presumed to be more diverse and/or widely distributed. As the combination of focal and diffuse injury following TBI can vary widely from one individual to the next, the impact of focal injuries is best understood with reference to the focal ischemic stroke literature. Subarachnoid hemorrhage (SAH), a common complication following TBI, also has predictable effects on autonomic control that can be understood with reference to spontaneous SAH literature. Finally, paroxysmal sympathetic hyperactivity (PSH), a syndrome incorporating episodes of heightened sympathetic drive and motor overactivity following minor stimulation, is discussed as an example of what happens when central inhibitory control of spinal cord autonomics is impaired.