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Two types of febrile seizure: anoxic (syncopal) and epileptic mechanisms differentiated by oculocardiac reflex
Insights
Cardiac asystole induced by ocular compression was significantly longer in children with anoxic febrile convulsions (FCs) compared to epileptic FCs. This suggests vagal-mediated cerebral ischemia plays a role in certain FC types.
Area of Science:
- Pediatric Neurology
- Cardiology
- Neurophysiology
Background:
- Febrile convulsions (FCs) are common in children.
- The underlying mechanisms of FCs are not fully understood, with both epileptic and anoxic origins proposed.
- Ocular compression can induce cardiac asystole, reflecting autonomic nervous system activity.
Purpose of the Study:
- To investigate the role of vagal-mediated cerebral ischemia in febrile convulsions.
- To differentiate mechanisms of FCs based on induced cardiac asystole duration.
- To explore the implications for understanding FCs, epilepsy, and related conditions.
Main Methods:
- Measured cardiac asystole duration induced by ocular compression in 100 children post-febrile convulsions.
- Classified children into anoxic FCs, epileptic FCs, and unclassified groups based on clinical presentation and EEG.
- Analyzed the correlation between FC type and induced asystole duration.
Main Results:
- Abnormal asystole (≥4 seconds) was induced in 50% of the anoxic FC group, 16% of the unclassified group, and 0% of the epileptic FC group.
- A statistically significant difference (P=0.005) in asystole duration was observed across the three groups.
- Results support the hypothesis of vagal-mediated cerebral ischemic anoxia in FC genesis.
Conclusions:
- Vagal-mediated cerebral ischemic anoxia is implicated in the genesis of FCs resembling anoxic seizures.
- A substantial number of FCs without an obvious epileptic mechanism may also involve this pathway.
- The findings necessitate a re-examination of FC significance, genetics, management, and prognosis.
Abstract:
The duration of cardiac asystole induced by ocular compression was measured in 100 consecutive children referred for electroencephalographic examination after one or more febrile convulsions (FC). The children were classified into three groups-namely, those with anoxic FCs, those with epileptic FCs, and "others"-according to the appearances of the FC and the electroencephalogram (EEG). In 14 children the description of the FC suggested non-epileptic anoxic cerebral seizures such as are seen after prolonged syncope or breath-holding. In 35 children the FCs were assumed to be epileptic in mechanism on the basis of unilateral (hemiclonic) twitching, known cerebral disease, a family history of epilepsy, or spikes on the EEG. In the 51 "others" the FCs could not be classified. Definitely abnormal asystole (four seconds or over) was induced by ocular compression in half the anoxic group, in 16% of the "others," but in none of the epileptic group. The differences between the degree of asystole induced in each of the three groups was highly significant (P=0.005).These results support the hypothesis that vagal-mediated cerebral ischaemic anoxia is implicated in the genesis of FCs that resemble anoxic seizures and in a substantial number of those without an obvious epileptic mechanism. The significance, genetics, management, and prognosis of FCs must now be re-examined in this light.