Atypical absence seizures:
Occur only in the context of mainly severe symptomatic or cryptogenic epilepsies of children with learning difficulties who also have frequent seizures of other types, such as atonic, tonic and myoclonic. Have slower onset and termination and changes in tone are more pronounced. Have particular ictal characteristics: EEG is of slow (less than 2.5 Hz) spike and slow wave. The discharge is heterogeneous, often asymmetrical and may include irregular spike and slow wave complexes, fast and other paroxysmal activity. Background interictal EEG is usually abnormal. Syndromes
Absence seizure syndromes are childhood absence epilepsy, epilepsy with myoclonic absences, juvenile absence epilepsy and juvenile myoclonic epilepsy. Other proposed syndromes are Jeavons syndrome (eyelid myoclonia with absences), and genetic generalised epilepsy with phantom absences. Absence seizures are also known to occur to patients with porphyria and can be triggered by stress or other porphyrin-inducing factors. Treatment
Treatment of patients with absence seizures only is mainly with ethosuximide or valproic acid, which are of equal efficacy controlling absences in around 75% of patients. Lamotrigine monotherapy is less effective, controlling absences in around 50% of patients. This summary has been recently confirmed by Glauser et al. (2010), who studied the effects of ethosuximide, valproic acid, and lamotrigine in children with newly diagnosed childhood absence epilepsy. Drug dosages were incrementally increased until the child was free of seizures, the maximal allowable dose was reached, or a criterion indicating treatment failure was met. The primary outcome was freedom from treatment failure after 16 weeks of therapy; the secondary outcome was attentional dysfunction.
Absence seizures are one of several kinds of generalized seizures. These seizures are sometimes referred to as petit mal seizures (from the French for "little illness", a term dating from the late 18th century). Absence seizures are characterized by a brief loss and return of consciousness, generally not followed by a period of lethargy (i.e. without a notable postictal state). Absence seizure is very common in children. It affects both sides of the brain. Epidemiology
Absence seizures affect between 0.7 and 4.6 per 100,000 in the general population and 6% to 8% in children younger than 15 years. Childhood absence seizures account for 10% to 17% of all absence seizures. Onset is between 4 and 10 years and peaks at 5 to 7 years. It is more common in girls than in boys. Etiology
An absence seizure is specifically caused by multifactorial inheritance. The voltage-gated T-type calcium channel is regulated by GABRG2, GABRG3, and CACNA1A2 genes. Inheritance of these genes is involved in etiology of absence seizure. The factors that trigger an absence seizure are lack of sleep and compliance, drinking alcohol, and benzodiazepine withdrawal, and use of medication that reduces the threshold of seizure such as Isoniazid, antipsychotics. Signs and symptoms
The clinical manifestations of absence seizures vary significantly among patients. Impairment of consciousness is the essential symptom, and may be the only clinical symptom, but this can be combined with other manifestations.