Status epilepticus (SE) can take various forms in
idiopathic generalized epilepsy (
IGE), some of which forms also occur in symptomatic or
focal epilepsies. Although the clinical semiology of the SE episodes may be similar in these different
epilepsies, the frequency, response to treatment and prognosis differ. (a) Convulsive SE is surprisingly uncommon in
IGE and much less common than in the secondarily generalized or
partial epilepsies. Also, when it does occur, it usually responds rapidly to treatment. (b) Typical absence SE occurs only in patients with
IGE (the subcategories with typical absence
seizures) and also in the syndrome of de novo absence SE of late onset. This form of nonconvulsive SE should be differentiated from atypical absence SE, which occurs in the secondarily
generalized epilepsy encephalopathies, and from complex partial SE which occurs in
focal epilepsy. The clinical symptoms of these three types overlap but the prognosis and response to treatment are different. The mechanisms underlying absence SE are uncertain and may include both genetic and environmental factors. The termination of absence
seizures has been hypothesized to be due to persistent activation of a depolarizing current in thalamocortical neurons that inactivates
T-type calcium channels. SE could thus result from dysfunction of this channel or mechanisms that hyperpolarize thalamocortical neurons-these include decreased cortical inhibition, increased reticular thalamic neuronal activity or increased thalamocortical neuron GABA(B)-receptor activation. (c) Generalized electrographic SE is encountered in
IGE in the syndrome of phantom absence with GTCS. It also occurs in ESES and in the
Landau-Kleffner syndrome. The seizure phenomenology overlaps with the focal SE of temporal or
frontal lobe epilepsy. (d) Myoclonic SE is also uncommon in
IGE but occurs in
juvenile myoclonic epilepsy. It is more commonly encountered in
progressive myoclonic epilepsies,
myoclonic-astatic epilepsy and in the
Dravet syndrome. (e) Autonomic status occurs largely in the
Panayiotopoulos syndrome. It is included here under the rubric of
IGE, although the
epilepsy has focal as well as generalized features and its nosological position is controversial. Fifty percent of
seizures in this syndrome could be classified as
status epilepticus. There is no doubt that convulsive SE can result in cerebral damage. In animal models of focal SE, nonconvulsive forms can also result in cerebral damage, but cerebral damage is not observed in animal models of absence SE. Similarly, cerebral damage seems not to occur in the forms of nonconvulsive SE in human
IGE.