Review Question - QID 218785

This patient who presents with multiple daily episodes of temporary loss of awareness without associated motor symptoms is most likely experiencing absence seizures. The thalamic T-type calcium channel blocker ethosuximide can be used to treat this form of seizures.

Absence seizures (also known as petit mal seizures) most commonly occur in children and are characterized by multiple brief episodes (~10 seconds) of unresponsiveness. Parents or teachers may report the patient had a blank stare but then recovered quickly with no postictal deficits and automatisms. The characteristic electroencephalogram finding in these patients is generalized 3-4-Hz spike and wave discharges. The treatment for absence seizures is ethosuximide, which functions by blocking thalamic T-type calcium channels. The side effects of this drug include GI distress, fatigue, headache, and rashes such as Stevens-Johnson syndrome.

Ijff et al. studied the cognitive performance of patients with pediatric absence seizures who were treated with ethosuximide. They found that patients with well controlled seizures performed much better but that the drug itself may have mild effects on cognitive slowing. They recommended studying these effects more carefully as children are particularly sensitive to cognitive slowing during their developmental years.

Incorrect Answers:
Answer 2: Gamma-aminobutyric acid agonist describes the mechanism of action for benzodiazepines that can be used in acute treatment for status epilepticus or alcohol withdrawal syndromes. Status epilepticus would present with a seizure that does not terminate and can be fatal if untreated.

Answer 3: Glutamate receptor blocker describes one of the mechanisms of action for lamotrigine, which can be used to treat simple partial, complex partial, and generalized tonic-clonic seizures. These seizures present with rhythmic movements of the extremities associated with loss of consciousness. Lamotrigine can also be used as a second-line agent for absence seizures but is not as effective as ethosuximide.

Answer 4: Sodium channel blocker describes the mechanism of action for valproate, which can be used as a second line agent for absence seizures. It is also used for myoclonic seizures, which would present with spontaneous movements of the extremities.

Answer 5: Synaptic vesicle modulator describes the mechanism of action for levetiracetam, which can be used to treat simple partial, complex partial, and generalized tonic-clonic seizures. These seizures present with rhythmic movements of the extremities associated with loss of consciousness.

Bullet Summary:
The thalamic T-type calcium channel blocker ethosuximide is used to treat childhood absence seizures characterized by transient loss of awareness without associated motor symptoms.