Hyperventilation during routine electroencephalography: are three minutes really necessary?

A Review of Hyperventilation Activation in Diagnosis and Management of Childhood Absence Epilepsy

Childhood absence epilepsy is one of the most prevalent pediatric epilepsy syndromes, but diagnostic delay is common and consequential. Childhood absence epilepsy is diagnosed by history and physical examination including hyperventilation with electroencephalography (EEG) used to confirm the diagnosis. Hyperventilation produces generalized spike-wave discharges on EEG in >90% of patients with childhood absence epilepsy and provokes clinical absence seizures consisting of brief loss of consciousness typically within 90 seconds. Child neurologists report a high volume of referrals for children with "staring spells" that strain already limited health care resources. Resources are further strained by the use of EEG for monitoring antiseizure medication effectiveness with unclear benefit. In this review, we examine the safety and efficacy of hyperventilation activation as a tool for the diagnosis and management of childhood absence seizures.

Hyperventilation Induced Seizures in Focal Epilepsy: Two Cases and a Review of Literature

We report two cases of temporo-perisylvian epilepsy with habitual seizures consistently inducible by hyperventilation (HV). One case was non-lesional, while the other was a lesional temporo-perisylvian epilepsy. Both underwent surgical resection and were seizure-free or nearly seizure-free thereafter. We discuss the pathophysiological changes evoked by HV in healthy brains, and those with generalized and focal epilepsy. We provide a comprehensive and critical review of the literature on the role of HV in focal epilepsy. We suggest HV should be considered an activation method for patients with focal epilepsy during epilepsy monitoring unit admissions and may help in the localization of the epileptogenic network/zone.

Hyperventilation and Seizures: Not a New Sense: A Literature Review

Hyperventilation and seizures have a long association in the clinical literature and were known to have a relationship long before the electroencephalogram (EEG) was used to record changes in brain activity. As the use of EEG recording progressed, hyperventilation was the first activation method used to assist with diagnosis of epilepsy. Along with slowing of brain activity, hyperventilation can activate epileptiform spiking activity in patients with epilepsy. Currently, hyperventilation is used in standard practice to assist with the diagnosis of epilepsy during EEG recording. Hyperventilation activates epileptiform spiking activity more often than seizures but can trigger clinical seizures in up to 50% of patients with generalized epilepsy. It is more likely to trigger events in children with absence seizures than adults, and it acts as a trigger in patients with focal epilepsy far less often. However, while some clinicians suggest that its diagnostic value is limited, especially in adults with focal epilepsies, others suggest that it is simple, safe, and an important diagnostic tool, even in these patients. This review presents the history of hyperventilation and seizures, its use in the clinical practice, and possible mechanisms involved.

High ventilation breathwork practices: An overview of their effects, mechanisms, and considerations for clinical applications

High Ventilation Breathwork (HVB) refers to practices employing specific volitional manipulation of breathing, with a long history of use to relieve various forms of psychological distress. This paper seeks to offer a consolidative insight into potential clinical application of HVB as a treatment of psychiatric disorders. We thus review the characteristic phenomenological and neurophysiological effects of these practices to inform their mechanism of therapeutic action, safety profiles and future clinical applications. Clinical observations and data from neurophysiological studies indicate that HVB is associated with extraordinary changes in subjective experience, as well as with profound effects on central and autonomic nervous systems functions through modulation of neurometabolic parameters and interoceptive sensory systems. This growing evidence base may guide how the phenomenological effects of HVB can be understood, and potentially harnessed in the context of such volitional perturbation of psychophysiological state. Reports of putative beneficial effects for trauma-related, affective, and somatic disorders invite further research to obtain detailed mechanistic knowledge, and rigorous clinical testing of these potential therapeutic uses.

Routine and sleep EEG: Minimum recording standards of the International Federation of Clinical Neurophysiology and the International League Against Epilepsy

This article provides recommendations on the minimum standards for recording routine ("standard") and sleep electroencephalography (EEG). The joint working group of the International Federation of Clinical Neurophysiology (IFCN) and the International League Against Epilepsy (ILAE) developed the standards according to the methodology suggested for epilepsy-related clinical practice guidelines by the Epilepsy Guidelines Working Group. We reviewed the published evidence using the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) statement. The quality of evidence for sleep induction methods was assessed by the Grading of Recommendations, Assessment, Development and Evaluations (GRADE) method. A tool for Quality Assessment of Diagnostic Studies (QUADAS-2) was used to assess the risk of bias in technical and methodological studies. Where high-quality published evidence was lacking, we used modified Delphi technique to reach expert consensus. The GRADE system was used to formulate the recommendations. The quality of evidence was low or moderate. We formulated 16 consensus-based recommendations for minimum standards for recording routine and sleep EEG. The recommendations comprise the following aspects: indications, technical standards, recording duration, sleep induction, and provocative methods.

Routine and sleep EEG: Minimum recording standards of the International Federation of Clinical Neurophysiology and the International League Against Epilepsy

This article provides recommendations on the minimum standards for recording routine ("standard") and sleep electroencephalography (EEG). The joint working group of the International Federation of Clinical Neurophysiology (IFCN) and the International League Against Epilepsy (ILAE) developed the standards according to the methodology suggested for epilepsy-related clinical practice guidelines by the Epilepsy Guidelines Working Group. We reviewed the published evidence using the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) statement. The quality of evidence for sleep induction methods was assessed by the Grading of Recommendations, Assessment, Development and Evaluations (GRADE) method. A tool for Quality Assessment of Diagnostic Accuracy Studies (QUADAS-2) was used to assess the risk of bias in technical and methodological studies. Where high-quality published evidence was lacking, we used modified Delphi technique to reach expert consensus. The GRADE system was used to formulate the recommendations. The quality of evidence was low or moderate. We formulated 16 consensus-based recommendations for minimum standards for recording routine and sleep EEG. The recommendations comprise the following aspects: indications, technical standards, recording duration, sleep induction, and provocative methods.

Respiratory alkalosis provokes spike-wave discharges in seizure-prone rats

Hyperventilation reliably provokes seizures in patients diagnosed with absence epilepsy. Despite this predictable patient response, the mechanisms that enable hyperventilation to powerfully activate absence seizure-generating circuits remain entirely unknown. By utilizing gas exchange manipulations and optogenetics in the WAG/Rij rat, an established rodent model of absence epilepsy, we demonstrate that absence seizures are highly sensitive to arterial carbon dioxide, suggesting that seizure-generating circuits are sensitive to pH. Moreover, hyperventilation consistently activated neurons within the intralaminar nuclei of the thalamus, a structure implicated in seizure generation. We show that intralaminar thalamus also contains pH-sensitive neurons. Collectively, these observations suggest that hyperventilation activates pH-sensitive neurons of the intralaminar nuclei to provoke absence seizures.

EEG Characteristics to Hyperventilation by Age and Sex in Patients With Various Neurological Disorders

Introduction: Hyperventilation provocation test(s) (HPT) concomitant to electroencephalography (EEG) may detect hidden disorders of the nervous system (CNS). There are various types of abnormal EEG in responses to HPT that provoke different interpretations. However, it is not evident how the onset time of pathological EEG responses to hyperventilation (PERH) reveals dysfunction of the CNS in humans. It is also not clear if age and biological sex affect EEG characteristics in response to HPT. Our previous studies have revealed three types of PERH (disorganization of basic rhythm, paroxysmal discharges, epileptiform activity) concerning the manifestation time of first, second, and third minutes. The current work aims to classify the PERH with regards to age (3–6, 7–12, 13–18, 19–30, 31–50, 50 > year) and the biological sex of the patients.

Methods: This study examined the EEG of 985 outpatients with various functional disorders of the CNS. The patients were assigned to one of three experimental groups based on the time occurrence of PERH in response to the HPT.

Results: The disorganized basic EEG rhythm in the first, second, third minute of HPT was observed across all age and sex groups. All three types of PERH in the first minute were comparable for both sexes. However, some discrepancies between females compared to males were observed in the second and third minutes. All three types of PERH in the first and the second minutes were found only in women. The second type of PERH has revealed at the second minute of PHT in 13–18-year-old five girls.

Conclusion: The three main types of PERH were detected at the first minute in all age groups and sex in patients with various CNS dysfunctions. It is diagnostically informative should be used as a marker during the monitoring of treatment. The specific activity of the brain's response to HPT depends on time, age, sex. The data indicate that taking into account sex differences and age during HPT leads to better results. The sensitivity and severity of the NS reaction toward hypocapnia, stress, and emotion increase in women. Therefore, in such cases should not be recommended to expand functional loads.

Hyperventilation maneuver during EEG in children with epilepsy after the COVID-19 pandemic. Is a routine procedure necessary?

OBJECTIVE

Hyperventilation (HV) is one of the main and basic activation methods during ambulatory electroencephalogram (EEG), unless medical reasons contraindicate it. During the COVID-19 pandemic, with the high risk of human-to-human infection, local guidelines and recommendations have been developed that suggest not to perform the HV maneuver routinely. Our objective was to characterize patients who present positive HV in an epilepsy center.

METHODS

We analyzed retrospectively all the ambulatory EEGs performed during one year in our specialized ambulatory child and adolescent epilepsy center, and describe patients with positive maneuver.

RESULTS

A total of 305 EEGs were performed. Patients under 3 years and 11 months were excluded as well as all patients that did not fill up the criteria for epilepsy diagnosis. From the 252 EEGs that were included in the study, 194 EEGs (77%) were classified as abnormal and 58 (23%) as normal. From these same 252 EEGs, 150 EEG finished correctly the HV maneuver. Physiological slowing response was found in 54 EEGs (36%), no changes (negative) in 83 (55%), and abnormal response (positive) in 13 EEGs (9%). The 13 HV-positive EEGs showed 4 patients with an increase of epileptiform activity, 3 patients experienced an increase of basal preregistered abnormal slowing, and 6 EEGs showed trigger of bilaterally synchronous and symmetric 2-4 Hz spike-and-slow wave discharges and absences. None of these last 6 patients needed more than 3 minutes to elicit the paroxysmal discharge.

SIGNIFICANCE

Based on these findings and according with other studies, the low positivity and high specificity of the HV maneuver support the idea that HV could be excluded during the COVID-19 pandemic situation, and also reevaluate whether it could be changed to a complementary maneuver, restricted only for cases where absence epilepsy is suspected. Larger studies will be needed to reaffirm this proposal.

Diagnosing and managing childhood absence epilepsy by telemedicine

The diagnosis of childhood absence epilepsy (CAE) is typically based on history and description of spells, supported by an office-based positive hyperventilation test and confirmed by routine electroencephalography (EEG). In the current coronavirus disease 2019 (COVID-19) pandemic, many pediatric neurologists have switched to telemedicine visits for nonemergent outpatient evaluations. We present a series of children diagnosed as having CAE on the basis of a positive hyperventilation test performed during remote televisits. Several of these children were begun on treatment for CAE prior to obtaining an EEG, with significant seizure reduction. Our series documents the feasibility of CAE diagnosis and management by telemedicine.

A critical analysis of the purported role of hypoxaemia in the comorbidity of obstructive sleep apnoea and epilepsy

Obstructive sleep apnoea (OSA) is a globally prevalent sleep disorder of significant health concern and confounded with several comorbidities resulting in adverse effect(s) on quality of life in patients afflicted with it. Of particular interest is the enigmatic high comorbidity of OSA with epilepsy, the exact underlying pathophysiology of which remains elusive despite a multitude of research performed in the last four decades. Hypoxaemia, which is an important characteristic feature found in OSA during apnoeic spells, has been implicated in the high comorbidity of OSA with epilepsy, the basis of which rests upon hypoxaemia-mediated brain damage, subcortical release phenomenon, oxidative stress and neuroinflammatory reactions. However, several studies present contradictory evidences that potentially refute the hypoxaemia-based mechanism. Additionally, the role of hypercapnia thatgenerally accompanies hypoxaemia during apnoeic spells, cannot be overlooked and is known to be potentially protective against neuronal hyperexcitability. Thus, hypoxaemia theory implicated in the high comorbidity of OSA and epilepsy appears weak and refutable. This brief paper studies and critically analyses the role of hypoxaemia in conjunction with hypercapnia in the underlying pathophysiology of the comorbidity.

Indications for epilepsy monitoring in pediatric and adolescent health care

Seizures present in childhood with infinite diversity. History alone may suffice for diagnosis in some cases; more often additional evidence is needed to clarify events of concern. Electroencephalography (EEG) is a primary methodology used for seizure identification and management. Pediatric and adolescent health care providers are increasingly asked to make decisions about when and how to refer patients for eventual monitoring and must then be able to confidently interpret any resulting report(s). Comprehensive literature review was undertaken to provide a succinct and up-to-date overview aimed at general and subspecialty non-neurologist pediatric and adolescent health care providers to not only convey a solid general understanding of EEG and what it entails for patients and their families, but also foster a deeper understanding of the indications for monitoring-and how to interpret documented findings. In plain language this resultant guide reviews EEG basics, provides a crash course in the various types of EEG available, discusses broad indications for epilepsy monitoring, guides counseling and management for patients and their families both before and after EEG, and ultimately aids in the interpretation of both findings and prognosis. This review should allow both primary and subspecialty non-neurologic pediatric and adolescent health care providers to better identify when and how to best utilize EEG as part of a larger comprehensive clinical approach, distinguishing and managing both epileptic and nonepileptic disorders of concern while fostering communication across providers to facilitate and coordinate better holistic long-term care of pediatric and adolescent patients.

Absence seizure provocation during routine EEG: Does position of the child during hyperventilation affect the diagnostic yield?

PURPOSE

When performed correctly, hyperventilation (HV) for three minutes provokes absence seizures in virtually all children, a finding suggestive of a diagnosis of childhood absence epilepsy (CAE). Interestingly, some children experience absence seizures while performing HV in the office yet do not experience absences during HV on subsequent routine EEG. In most instances, HV during routine EEG is performed in the supine position, while in the office HV is done with the child sitting-up. Therefore, we hypothesized that the position in which HV is performed may influence its yield in provoking absence seizures.

METHODS

We conducted a randomized multi-center controlled trial among children (4-10 years old) with suspected CAE. During a routine EEG, children were asked to perform HV twice, in the supine and sitting positions.

RESULTS

Twenty children (four males) diagnosed with CAE were included in the analysis. Seventeen of the 20 patients experienced absence seizures while sitting and 13 experienced seizures during supine HV (p = 0.031). All patients that had absence seizures during supine HV also had seizures during sitting HV. Among patients with absences in both positions, seizure duration was significantly shorter during sitting HV (mean 8.69 seconds) than during supine HV (mean 12 seconds) (p = 0.042). An opposite tendency was seen in the younger age group (4-7 years), with shorter seizures in the supine HV group (5.6 seconds supine, 7.57 seconds sitting, p = 0.019).

CONCLUSIONS

HV in the sitting position may increase the yield of provoking absence seizures during routine EEGs, thereby improving its sensitivity in the diagnosis of CAE.

Out of thin air: Hyperventilation-triggered seizures

Voluntary hyperventilation triggers seizures in the vast majority of people with absence epilepsy. The mechanisms that underlie this phenomenon remain unknown. Herein, we review observations - many made long ago - that provide insight into the relationship between breathing and absence seizures.

Hypocapnia and hyperoxia induction using a hyperventilation protocol in electroconvulsive therapy

INTRODUCTION

Hyperventilation in electroconvulsive therapy sessions has been associated with seizure threshold, seizure characteristics, and cognitive effects. There is no consensus on the optimal procedure of applying hyperventilation manoeuvres during electroconvulsive therapy.

MATERIAL AND METHODS

Prospective evaluation of the effects of systematic use of hyperventilation manoeuvres with facial mask and capnography (protocolized hyperventilation [pHV]), on ventilation parameters and on seizures. The study included a sample of 130 sessions (65 performed according to hyperventilation standard practice and 65 successive sessions, with pHV) of 35 patients over a period of 10 weeks.

RESULTS

The pHV manoeuvres reduced exhaled CO₂ and increased O₂ saturation significantly (P<.001). The average CO₂ reduction achieved was 6.52±4.75mmHg (95% CI -7.7 to -5.3). The CO₂ values after pHV correlated significantly with seizure duration and O₂ values, with other electroencephalographic quality indices. In pHV sessions, compared with sessions performed according to hyperventilation standard practice, the average lengthening of the motor and electroencephalographic seizure was 3.86±14.62 and 4.73±13.95s, respectively. No differences were identified in other ictal quality parameters.

CONCLUSIONS

The proposed pHV manoeuvres significantly modify ventilation parameters. The hypocapnia and hyperoxia obtained by applying these manoeuvres lengthen the duration of seizures without worsening the quality of the electroencephalographic trace. The use of pHV is generalisable and might improve electroconvulsive therapy procedure without adding costs.