Absence epilepsy is a type of primary generalized epilepsy in children, and usually presents as staring spells.
Clinical Presentation of Absence Epilepsy
Childhood absence epilepsy develops in children, with a peak onset of 6 years old. Development of these seizures at an age of 10-12 is more consistent with the juvenile subtype or juvenile myoclonic epilepsy rather than the typical childhood absence. Seizures have a sudden onset and abrupt termination of unresponsiveness. The seizures consist of staring spells, often associated with repetitive eyelid movements or oral automatisms. The events last for seconds at a time, typical around 10 seconds. The seizures can be triggered by hyperventilation, and in the pediatrician’s office seizures can provoked by having the child blow into a pinwheel or blow a tissue.
3 Hz Spike and Wave Discharges on EEG
The classic EEG finding in absence seizures is an ictal pattern consisting of 3-Hz generalized spike-wave discharges. An example of this pattern is shown below.
Pathology and Genetics of Absence Epilepsy
Multiple genetic mutations have been associated with this disorder, although not all genetic mutations have been identified. The best described mutations are in calcium channels, chloride channels, GABA-A receptors, and GABA-B receptors. The 3 Hz spike and wave discharges are thought to reflect a synchronized thalamocortical network. T-type calcium channels in the thalamus are thought to be an important component in the epileptic circuit.
Treatment of Absence Seizures
The first-line therapy for absence seizures is ethosuximide. If ineffective, valproic acid, lamotrigine and levetiracetam can be tried. Several anti-seizure medications are thought to worsen absence seizures, and should be avoided. These include carbamazepine, vigabatrin, tiagabine and phenytoin.
The majority of children with absence epilepsy have spontaneous remission of the seizures by the early teenage years. However, the ~1/3 of patients who do not enter remission typically progress to have Juvenile Myoclonic Epilepsy (JME).
Petit mal seizures
The term “petit mal” is often used to describe staring seizures without convulsions, but this term is no longer considered an official descriptor of absence seizures.