Absence seizures are a type of generalized seizure characterized by brief episodes of staring with impairment of consciousness (absence). They usually last no more than 20 to 30 sec. The onset and the end of the seizures are sudden. Patients are typically unaware of the seizure and resume the activity they were performing before the seizure. The electroencephalogram signature of absence seizures consists of a generalized 3-Hz spike and slow wave discharges.

• Childhood absence epilepsy
• Seizures, absence

• Patients with absence seizures usually have normal physical and neurologic examinations. However, attention deficit hyperactivity disorder (ADHD), anxiety, mood disorders, and learning disorders are common comorbidities in children with absence seizures.
• During the seizures, the patients are unresponsive and can have motor phenomena (automatisms, eye blinks, mouth and hand movements).
• Typical seizure duration is 4 to 20 sec.
• Absence seizures are not associated with post-ictal confusion.
• They may be triggered by hyperventilation associated with activity.
• Tonic clonic seizures are not usually a feature of this syndrome. If the patient also experiences tonic clonic seizures, other etiologies should be investigated, such as juvenile absence epilepsy, juvenile myoclonic epilepsy, complex partial seizures, etc.

Genetic

It is important to distinguish between focal onset impaired awareness seizures (previously called complex partial seizures) and absence seizures (Tables E1 and E2).

• Juvenile absence epilepsy
• Juvenile myoclonic epilepsy
• Complex partial seizures
• Focal seizures with altered consciousness
• Nonepileptic spells comprised of staring
• GLUT1 deficiency syndrome
• Epilepsy with eyelid myoclonia
• Epilepsy with myoclonic absences
• Atypical absence seizures

• Electroencephalogram (EEG) with hyperventilation and photic stimulation is crucial in the diagnosis (Fig. E1).
• Ambulatory EEG and video EEG are recommended for patients with diagnostic uncertainty.

No specific studies needed

• MRI of the brain with and without contrast should be performed in all epilepsy patients, especially if the EEG does not show the typical characteristic of absence seizures (3-Hz spike and slow wave discharges).
• Computed tomography scans of the head should be avoided in children due to unnecessary exposure to radiation and low yield of the test except when MRI cannot be obtained.

Not applicable

• Ethosuximide: Initial dose: 5 to 10 mg/kg/day divided into two doses for children <6 yr and 250 mg/kg twice daily for children 6 yr and older; then after 7 days, the usual maintenance dose is 15 to 40 mg/kg/day in divided doses; goal therapeutic concentration is 40 to 100 micrograms/ml.
• Divalproex sodium (Depakote): Initial dose: 15 mg/kg/day (divided od, bid, or tid); dose is increased by 5 to 10 mg/kg per day at weekly intervals until seizures controlled or side effects prevent further increases; maximum/maintenance dose: 30 to 60 mg/kg/day (divided bid or tid); therapeutic concentration is 50 to 125 micrograms/ml.
• Lamotrigine (Lamictal): Dose for patients age 2.5 to 13 yr on no other antiepileptic drugs. Wk 1 and 2: 0.3 mg/kg/day. Wk 3 and 4: 0.6 mg/kg/day. Wk 5 onward: Increase every 1 to 2 wk by 0.6 mg/kg/day. Maintenance: 4.5 to 7.5 mg/kg/day. Warning: Should be used with caution due to the potential for toxicity and Stevens-Johnson syndrome. Patients on other antiepileptic drugs can also have severe adverse reactions (e.g., valproate can cause increased levels of lamotrigine, and lamotrigine must be titrated much more slowly in patients on valproate therapy).

• Children with recurrent seizures require chronic treatment.
• If children are seizure-free for a period of 1 to 2 yr, a trial on no medications should be considered; children typically outgrow childhood absence seizures.

• Response to treatment is excellent.
• Absence seizures tend to remit in teenage years.
• Epilepsy can be considered as resolved once 10 yr have elapsed since the last event, including 5 yr free from medications.

Not applicable

Patients with epilepsy should be referred for a consultation by a child neurologist, preferably one specializing in epilepsy.

• Absence seizures can be present in other epilepsy syndromes.
• Valproate should be avoided in girls and women with childbearing potential due to the risk of teratogenicity.
• Carbamazepine and phenytoin should be avoided in the treatment of absence seizures since these medications may worsen seizures and provoke absence status epilepticus.
• All women of childbearing age taking antiepileptic drugs should take folic acid supplementation (1 to 4 mg/day) for the prevention of neural tube defects.

Sleep deprivation and alcohol consumption should be avoided.

Patients with ongoing seizures are forbidden to drive; check state regulations and laws regarding driving and epilepsy.

• Absence Seizures (Patient Information)