User:Karmattol/Childhood absence epilepsy

Childhood absence epilepsy (CAE), also known as pyknolepsy, is an idiopathic generalized epilepsy which occurs in otherwise normal children. The age of onset is between 4-10 years with peak age between 5-7 years. Children have absence seizures which although brief (~4-20 seconds), they occur frequently, sometimes in the hundreds per day. The absence seizures of CAE involve abrupt and severe impairment of consciousness. Mild automatisms are frequent, but major motor involvement early in the course excludes this diagnosis. The EEG demonstrates characteristic "typical 3Hz spike-wave" discharges. Prognosis is excellent in well-defined cases of CAE with most patients "growing out" of their epilepsy

Epidemiology
Childhood absence epilepsy is a fairly common disorder with a prevalence of 1 in 1000 people.

Causes and mechanisms
Genetics: CAE is a complex polygenic disorder. A limitation in describing the inheritance of CAE is that studies differ in definitions of CAE. Twice as many girls as boys have CAE. When only first degree relatives are considered, 17-20% of patients with CAE have parents or siblings with epilepsy. Recent studies identify chromosomal loci that are associated with some groups or families with CAE or with other epilepsies that feature childhood-onset absence seizures. A variety of mutations in of the calcium channel CACNA1H gene have been found in patients with CAE. Mutations in the gene encoding a GABAA receptor γ subunit have been identified in a large family with CAE and febrile seizures.

Electrophysiology: The characteristic absence seizures of CAE on scalp EEG consist of bursts of generalized 3Hz spike-wave discharges (Figure). There are several historically important theories on how these discharges are generated, but the most current concept is that seizures arise because of abnormalities of T-type calcium channels of neurons located in the reticular nucleus of the thalamus. These channels, in turn, may be associated with some of the genetic defects noted above. xxx .

Diagnosis
Proper diagnosis requires indentification of the appropriate factors of age of onset, normal neurological exam, presence of characteristic absence seizures, and a scalp EEG demonstrating the 3Hz spike-wave discharges. XX% of patients with CAE can have seizures triggered by hyperventilation, a useful test in the clinic and often performed routinely during EEG. Between xx-xx% of patients with CAE will also have occipital intermittent rhythmic delta activity (OIRDA), a pattern of slowing in the back of the scalp EEG. The EEG of patients with CAE should otherwise be normal.

Treatment/Management

 * For the main article on epilepsy treatment, see main epilepsy article.
 * For the treatment specific to Absence seizures, see treatment of absence seizures.

Prognosis
Patients with typical CAE have excellent prognosis with spontaneous remission of seizures. Patients with EEG findings other than typical 3Hz spike-wave discharges or ORIDA (such as polyspike-wave discharges) have greater risks of experiencing generalized tonic-clonic seizures or having seizures that continue past childhood.