Absence Seizures

• Patricio Sebastian Espinosa, M.D., M.P.H.

 Basic Information

Definition

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. Usually the patients are not aware of them 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.

Synonyms

1. Childhood absence epilepsy

2. Seizures, absence

ICD-10CM CODES
G40.309	Generalized idiopathic epilepsy and epileptic syndromes, not intractable, without status epilepticus

Epidemiology & Demographics

Incidence

1 to 10 cases per 100,000 population.

Peak Incidence

6 to 7 yr.

Prevalence

Represents up to 18% of all pediatric epilepsy syndromes.

Predominant Sex and Age

More common in girls than in boys, absences typically begin between 4 and 8 yr.

Physical Findings & Clinical Presentation

1. Patients with absence seizures usually have normal physical and neurologic examinations.

2. During the seizures, the patients are unresponsive and can have motor phenomena (automatisms, eye blinks, mouth and hand movements).

3. Absence seizures are not associated with postictal confusion.

4. They may be triggered by hyperventilation associated with activity.

5. 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.

Etiology

Genetic.

Diagnosis

Differential Diagnosis

1. Juvenile absence epilepsy.

2. Juvenile myoclonic epilepsy.

3. Complex partial seizures.

4. Focal seizures with altered consciousness (Table E1).

5. Nonepileptic spells comprised of staring.

Workup

1. EEG with hyperventilation and photic stimulation is crucial in the diagnosis.

2. Ambulatory EEG and video EEG are recommended for patients with diagnostic uncertainty.

Laboratory Tests

No specific studies needed.

Imaging Studies

1. MRI of the brain 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).

2. CT 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.

Treatment

The medication of choice based on the best current evidence available is ethosuximide, followed by valproic acid and lamotrigine.

Nonpharmacologic Therapy

Not applicable.

General Rx

1. Ethosuximide: initial dose: 10 mg/kg/day; then after 7 days, 20 mg/kg.

2. Divalproex sodium (Depakote): initial dose: 5 to 10 mg/kg/day (divided bid), maximum dose: 60 mg/kg/day.

3. Lamotrigine (Lamictal): dose for patients 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).

Chronic Rx

1. Children with recurrent seizures require chronic treatment.

2. 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.

Complementary & Alternative Medicine

Not applicable.

Disposition

1. Response to treatment is excellent.

2. Absence seizures tend to remit in teenage years.

3. Epilepsy can be considered as resolved once 10 years have elapsed since the last event, including 5 years free from medications.

Referral

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

Pearls & Considerations

Comments

1. Absence seizures can be present in other epilepsy syndromes.

2. Valproate should be avoided in girls and women with childbearing potential due to the risk of teratogenicity.

3. Carbamazepine and phenytoin should be avoided in the treatment of absence seizures, since these medications may worsen seizures and could provoke absence status epilepticus.

4. All women of childbearing age taking antiepileptic drugs should take folic acid supplementation (1-4 mg/day) for the prevention of neural tube defects.

Prevention

Sleep deprivation and alcohol consumption should be avoided.

Patient & Family Education

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

Suggested Reading

• T.A. Glauser, et al.: Ethosuximide, valproic acid, and lamotrigine in childhood absence epilepsy. N Engl J Med. 362 (9):790–799 2010 20200383

Related Content

1. Absence Seizures (Patient Information)