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Juvenile absence epilepsy
Juvenile absence epilepsy (JAE) is a genetic epilepsy with onset occurring around puberty. JAE is characterized by sporadic occurrence of absence seizures, frequently associated with a long-life prevalence of generalized tonic-clonic seizures (GTCS) and sporadic myoclonic jerks.
ORPHA:1941Classification level: Disorder
The incidence of JAE is still unknown but it accounts for approximately 2-3% of patients with adult epilepsy in general, and about 8-10% of patients with genetic generalized epilepsy (GGE). No sex predominance has been observed.
JAE is characterized by sporadic occurrence of absence seizures (only one or a few absences daily; 100% of cases), frequently associated with a long-life prevalence of generalized tonic-clonic seizures (GTCS; 80%) and sporadic myoclonic jerks (20%). The seizures onset is typically between 9 and 13 years of age and it manifests as a ''staring spell'' that can be accompanied by atonic postures such as drooping of the head and/or automatisms such as lip smacking. GTCS and myoclonic seizures often occur 1-10 years after the absence seizure onset. Patients with JAE usually develop normally, although uncontrolled absence seizures may have an impact on their ability to learn at school.
The exact etiology of JAE is still elusive. However, genetic mutations for voltage-gated sodium channels (CACNB4 gene (2q22-q23)), potassium channels (CLCN2 gene (3q27.1)), and EFHC1 (6p12.3) may be involved in a subset of patients. Moreover, different mutations have been found in genes for GABA receptors (ligand ion channels), specifically in the GABRA1 gene (5q34).
Diagnosis relies on the clinical features and on electroencephalogram (EEG) recorded awake and during sleep, that displays a generalized 3-4 Hz spike-and-slow-wave complexes.
Differential diagnosis includes childhood absence epilepsy, juvenile myoclonic epilepsy, Jeavons syndrome (see these terms).
The transmission is still unknown although an increased risk for first degree related parents to develop JME may exist.
Management and treatment
The antiepileptic drugs of choice are valproic acid (VPA) and lamotrigine (LTG). In cases where VPA deals with only partial seizure control, add-on of LTG (GTCS) or ethosuximide (absence seizures) can be beneficial.
Prognosis of JAE is usually favorable with good therapy responsiveness. Generally, seizure freedom can be achieved with antiepileptic medication in 62-84% of all patients with JAE. However, the occurrence of GTCS predicts a worse prognosis.