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Childhood absence epilepsy
Childhood absence epilepsy (CAE) is a familial generalized pediatric epilepsy, characterized by very frequent (multiple per day) absence seizures, usually occurring in children between the ages of 4 and 10 years, with, in most cases, a good prognosis.
CAE accounts for 10% to 17% of all cases of epilepsy diagnosed in school-aged children. Incidence has been estimated at 1/50,000-1/12,500 in the United States. Females are usually more affected than males.
CAE usually occurs in children between the ages of 4 and 10 years, with a peak between 5 and 7 years. The disease is characterized by frequent (multiple per day) absence seizures with an abrupt onset and offset. Photosensitivity is reported in 18% of CAE patients. In rare cases, CAE is also associated with an increased rates of adverse behavioral, psychiatric, language, and subtle cognitive comorbidities (including attention problems, anxiety, depression, social isolation and low self-esteem). These cognitive concerns are frequently complicated by attention deficit hyperactivity disorder (ADHD). Intellectual disability may also be observed. Onset of absence seizures under the age of 4 years is observed in a rare subset of CAE patients, a proportion of whom have encephalopathy due to GLUT1 deficiency (see this term).
Although CAE is genetically determined, the precise mode of inheritance and genes involved remain largely unidentified. Mutations in the genes NIPA2 (15q11.2) which encodes a magnesium transporter; CACNA1H (16p13.3) which encodes a T-type calcium channel are reported to be susceptibility genes in Chinese Han population; GABRA1 (5q34), GABRB3 (15q12), GABRG2 (5q34) which encode gamma-aminobutyric acid (GABA) receptors; JRK (8q24.3) which encodes a putative DNA-binding protein; and SLC2A1 (1p34.2) which encodes a facilitated glucose transporter, may be implicated in CAE. Mutations in CLCN2 (3q27.1) which encodes a chloride channel, may be a susceptibility locus in a subset of CAE.
Diagnosis relies on the clinical features and electroencephalographic findings of bilateral, synchronous symmetrical spike waves, usually 3 Hz, on a normal background activity.
Differential diagnosis includes epilepsy with myoclonic absences, Jeavons syndrome, juvenile absence epilepsy, perioral myoclonia with absences, juvenile myoclonic epilepsy, encephalopathy due to GLUT1 deficiency as well as absences associated with chromosomal anomalies (ring chromosome 20, 15q13.3 microdeletion syndrome) (see these terms).
Management and treatment
Treatment of CAE involves the use of antiepileptic drugs such as ethosuximide, valproate, and lamotrigine. However, lack of response is common. Levetiracetam (alternative choice for patients with CAE and photosensitivity) or topiramate are options for refractory absence seizures but may not be successful.
In 56-65% of affected children, a 5-year remission rate off antiepileptic drugs is observed. Terminal remission generally occurs 3-8 years after the onset of CAE. However, in the remaining 30% of children, seizures persist either as absences alone (10-15%), absences with either generalized tonic-clonic or myoclonic seizure (5-15%), or evolution to juvenile myoclonic epilepsy (5-15%).