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

Does Hyperventilation Increase the Diagnostic Yield of the Routine Electroencephalogram: A Retrospective Analysis of Adult and Pediatric Cohorts

PURPOSE

While hyperventilation (HV) increases the diagnostic yield of EEG in children, there is conflicting evidence to support its application in adults. For the first time in history, a large cohort of patients has undergone EEGs without HV during the COVID-19 pandemic. Utilizing this opportunity, we sought to investigate whether HV increases the diagnostic yield of EEG in children compared with adults.

METHODS

Patients aged six years and above who had routine EEGs at Monash Health between January 2019 and December 2020 were studied. The cohort was divided into two, pediatric (younger than 18 years) and adult (18 years or older). Epileptiform abnormalities (ictal and interictal) were the outcomes investigated. The effect of HV was examined with logistic regression to determine odds ratios with 95% confidence intervals.

RESULTS

In total, we studied 3,273 patients (pediatric = 830, adult = 2,443). In the pediatric cohort, HV significantly increased the diagnostic yield of absence seizures ( p = 0.01, odds ratios 2.44, 95% confidence intervals 1.21-4.93). In adults, HV did not increase the yield of absence seizures ( p = 0.34, odds ratios 0.36, 95% confidence intervals 0.05-2.88). Interictal epileptiform discharges during HV were significantly more frequent in children compared with adults ( p < 0.001, odds ratios 3.81, 95% confidence intervals 2.51-5.77).

CONCLUSIONS

Hyperventilation is useful to increase the yield of interictal epileptiform discharges and absence seizures in pediatric patients but not in adults. Hence, routine EEG may be recorded in adults without HV when it is unsafe to perform.

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.

Childhood Absence Epilepsy- Electroclinical Profile and Prevalence of Attention-Deficit/Hyperactivity Disorder Among a Cohort of 47 Children

BACKGROUND

We aimed to find the proportion of attention-deficit/hyperactivity disorder (ADHD) among children with childhood absence epilepsy (CAE) and to describe their electroclinical features.

METHODS

Video electroencephalography (EEG) was performed on 47 children who fulfilled International League Against Epilepsy criteria for CAE. These children were also assessed for the presence of ADHD.

RESULTS

Of the 47 children, 27 (57%) met criteria for the diagnosis of ADHD. Majority (74%) of them had inattentive type of ADHD. Age at onset of absences ranged from three to 12 years (mean 7.2 ± 2.47). We analyzed 219 seizures (154 electroclinical and 65 electrographic). The average seizure duration was 7.1 seconds (range 1 to 38 [S.D. 5.81]). Of the 154 clinical absences, ictal discharges were less than or equal to two seconds in nine of 154 (5.8%); greater than two to less than or equal to four seconds in 33 of 154 (21.4%), and longer than 20 seconds in 11 of 154 (7%). The longest duration of ictal discharge recorded was 38 seconds, and the shortest duration was one second. The onset of ictal discharge had a "lead in" focus in 81% (177 of 219).

CONCLUSIONS

The proportion of ADHD among children with CAE is high. A "lead in" focus of the generalized ictal discharges was observed frequently, lending support to the theory that the origin of seizure discharges in CAE is indeed cortical. The shortest ictal discharge recorded was one second.

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.

ILAE definition of the Idiopathic Generalized Epilepsy Syndromes: Position statement by the ILAE Task Force on Nosology and Definitions

In 2017, the International League Against Epilepsy (ILAE) Classification of Epilepsies described the "genetic generalized epilepsies" (GGEs), which contained the "idiopathic generalized epilepsies" (IGEs). The goal of this paper is to delineate the four syndromes comprising the IGEs, namely childhood absence epilepsy, juvenile absence epilepsy, juvenile myoclonic epilepsy, and epilepsy with generalized tonic-clonic seizures alone. We provide updated diagnostic criteria for these IGE syndromes determined by the expert consensus opinion of the ILAE's Task Force on Nosology and Definitions (2017-2021) and international external experts outside our Task Force. We incorporate current knowledge from recent advances in genetic, imaging, and electroencephalographic studies, together with current terminology and classification of seizures and epilepsies. Patients that do not fulfill criteria for one of these syndromes, but that have one, or a combination, of the following generalized seizure types: absence, myoclonic, tonic-clonic and myoclonic-tonic-clonic seizures, with 2.5-5.5 Hz generalized spike-wave should be classified as having GGE. Recognizing these four IGE syndromes as a special grouping among the GGEs is helpful, as they carry prognostic and therapeutic implications.