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Pseudoseizures caused by hyperventilation resembling absence epilepsy
K N North1, R A Ouvrier, M Nugent
1Department of Neurology, Children's Hospital, Camperdown, Sydney, Australia.
Insights
Recurrent "absences" in children were found to be pseudoseizures triggered by hyperventilation, not epilepsy. These episodes resolved spontaneously in most cases, suggesting a link to cerebrovascular factors.
Area of Science:
- Neurology
- Pediatrics
- Psychology
Background:
- Childhood absence epilepsy is a common neurological disorder.
- Hyperventilation can trigger various neurological symptoms.
- Differentiating absence seizures from other conditions is crucial for accurate diagnosis and treatment.
Observation:
- 18 pediatric patients presented with absence-like episodes and normal neurological examinations.
- Electroencephalogram (EEG) showed normal background activity but paroxysmal slow-wave activity during hyperventilation.
- These hyperventilation-induced episodes mimicked absence seizures but lacked epileptic activity.
Findings:
- The study identified "pseudoseizures caused by hyperventilation resembling absence epilepsy" in children.
- Environmental stress was a factor in 13 of 18 cases.
- Follow-up revealed spontaneous resolution in most patients, with only two continuing to experience absences linked to emotional distress.
Implications:
- Hyperventilation-induced pseudoseizures should be considered in the differential diagnosis of absence epilepsy.
- Cerebrovascular immaturity and excessive vasoconstrictor responses may underlie these episodes.
- Understanding these pseudoseizures can prevent misdiagnosis and unnecessary anti-epileptic treatment.
Abstract:
During the 4-year period, 1982-1986, 18 patients presented to the Children's Hospital, Camperdown, Sydney, with the following features: (1) Recurrent "absences" clinically indistinguishable from childhood absence epilepsy, (2) Normal clinical examination, (3) Electroencephalogram (EEG) demonstrating normal waking background and sleep activity. On hyperventilation, "absences" occurred, characterized on EEG by a marked build-up of paroxysmal slow-wave activity unassociated with evidence of epileptic activity. We designate these attacks "pseudoseizures caused by hyperventilation resembling absence epilepsy." Individual cases demonstrated a variety of other symptoms consistent with the hyperventilation syndrome. There was an identifiable environmental stress in 13 of the 18 cases. Follow-up of 13 patients after a mean period of 20 months revealed that only two children continued to have occasional absences, associated with a clear history of breathing up when upset. Treatment did not influence outcome. On repeat hyperventilation with EEG and respiratory monitoring, five of the 13 had pseudoseizures. There was no indication that susceptibility to these episodes was associated with an abnormal CO2 response. It is postulated that the occurrence of pseudoseizures is related to cerebrovascular immaturity and an excessive vasoconstrictor response to a given level of CO2.