Atypical EEG pattern in children with absence seizures

Abstract

SUMMARY -We studied four children with diagnosis of absence seizures (generalized primary epilepsy), and with a generalized delta activity on the EEG during clinical attacks provoked by hyperventilation. The lack of ictal generalized spike-and-wave discharges with a frequency of 3 Hz in our patients, makes this an atypical pattern. All children had complete control of their seizures and disappearance of the EEG changes with valproate. We concluded that generalized delta activity observed on EEG during the hyperventilation in children should not always be considered as a normal finding for age, since it could be an ictal event of an absence seizure.KEY WORDS: epilepsy, absence seizures, EEG, hyperventilation, delta activity. Padrão atípico no EEG de crianças com crises de ausênciaRESUMO -Estudamos quatro crianças com o diagnóstico de crises de ausência (epilepsia generalizada primária) e com atividade delta generalizada no EEG, durante crises provocadas pela hiperpnéia. A ausência de descargas generalizadas por complexos ponta-onda a 3 Hz, durante as crises de nossos pacientes, é achado incomum. Todas as crianças tiveram completo controle de suas crises com o valproato, assim como o desaparecimento das alterações no EEG. Concluimos que a atividade delta generalizada observada no EEG de crianças durante a hiperpnéia nem sempre deve ser vista como achado normal, podendo ser um evento crítico da crise generalizada ausência. PALAVRAS-CHAVE: epilepsia, crises de ausência, EEG, hiperventilação, atividade delta.Childhood absence seizures is a type of generalized epilepsy, and includes characteristic clinical and EEG manifestations. It is characterized by onset of seizures between the age of 3 and 12 years and a peak at 6-7 years, absence seizures and an EEG finding of generalized spike-and-wave complexes with a typical frequency of 3 Hz. It is well known that during hyperventilation in children, delta activity is frequently seen, and is considered reflexion of a normal development finding 2,5 . Lee and Kirby (1988) 7 first reported generalized high amplitude rhythmic delta activity during hyperventilation accompanied by clinical manifestation of staring spells with unresponsiveness.Our aim in this paper is to describe four children, 6-8 year old, who presented generalized delta activity on EEG during hyperventilation and that were accompanied by clinical seizures. REPORT OF CASES• Case 1: CCOS, a 7-year-old girl had onset of absence seizures four months earlier. Pregnancy and delivery were normal, as was the child's early development. Physical and neurological examinations were normal, as well as computed tomography (CT) scan. Their seizures lasts no longer than a few seconds, occurred up to 4 per day, with no postictal changes. During the absences seizures, there was a loss of awareness and responsiveness

Hyperventilation‐induced High‐amplitude Rhythmic Slowing with Altered Awareness: A Video‐EEG Comparison with Absence Seizures

“…Unlike Epstein et al (2), we observed automatisms in all of our 22 patients. Automatisms also were described in most other reports of HIHARS and altered awareness (3–7). Although automatisms were common in both the HIHARS and the absence control group, eye opening and eyelid flutter were seen more frequently in absence seizures.…”

“…Three children were described with “extremely unusual” stereotyped attacks during HV, and the authors considered that these were nonepileptic events. Subsequent reports of episodic, altered awareness during HIHARS speculated on whether these episodes are epileptic seizures (3–5) or nonepileptic phenomena (2,6,7). In a study of 12 children with the EEG criteria for HIHARS, verbal recall and motor responsiveness to an auditory click were normal at baseline and during HV before slowing, but all children exhibited impaired verbal recall, and eight of 12 failed to respond to auditory clicks during an episode of HIHARS (2).…”

“…At times the episodes of HV‐induced high‐amplitude rhythmical slowing (HIHARS) have a relatively abrupt onset. Clinical testing during episodes of HIHARS may demonstrate altered awareness, which prompted speculation that these episodes might be epileptic (3,5). However, the episodes of HIHARS with altered awareness resolve spontaneously in most patients, and it is generally considered that these episodes are not epileptic (2,7).…”

Outcome of children with hyperventilation‐induced high‐amplitude rhythmic slow activity with altered awareness

“…It may also be associated with clinical symptoms such as dizziness and markedly impaired concentration, 4 and in some children HIHARS may be associated with automatisms 5 . This has prompted speculation that these episodes might be epileptic 6,7 . In addition, resolution of blank spells associated with HIHARS has been demonstrated with the use of antiepileptic medications 6,7 .…”

“…This has prompted speculation that these episodes might be epileptic 6,7 . In addition, resolution of blank spells associated with HIHARS has been demonstrated with the use of antiepileptic medications 6,7 . However, the phenomenon of HIHARS does appear to occur in typically developing children with no evidence of epilepsy, 2 and it has been proposed that HIHARS represents one extreme of a spectrum of physiologically mediated altered responsiveness during hyperventilation 5 …”