Absence status epilepticus

C P Panayiotopoulos MD PhD (Dr. Panayiotopoulos of St. Thomas' Hospital has no relevant financial relationships to disclose.)
Jerome Engel Jr MD PhD, editor. (Dr. Engel of the David Geffen School of Medicine at the University of California, Los Angeles, has no relevant financial relationships to disclose.)
Originally released June 30, 1999; last updated January 12, 2017; expires January 12, 2020

This article includes discussion of absence status epilepticus, petit mal status epilepticus, idiopathic (typical) absence status epilepticus, atypical absence status epilepticus, cryptogenic or symptomatic (atypical) absence status epilepticus, absence status epilepticus in comatose or critically ill patients, and situation-related absence status epilepticus. The foregoing terms may include synonyms, similar disorders, variations in usage, and abbreviations.

Overview

Absence status epilepticus is a prolonged, generalized absence seizure that usually lasts for hours and can even last for days. The cardinal symptom is the altered state of consciousness while the patient is usually fully alert and partially responsive. Absence status epilepticus may be typical, occurring in patients with idiopathic generalized epilepsy, or atypical, occurring in patients with neurocognitive impairment as with epileptic encephalopathies. Absence status epilepticus may also appear de novo, mainly in adults without a previous history of epilepsy. Absence status epilepticus is often misdiagnosed as focal status epilepticus or a confusional nonepileptic condition or epileptic prodrome. Frequently, absence status epilepticus occurs because of ill-advised antiepileptic drug treatment, such as with tiagabine or carbamazepine in patients with idiopathic generalized epilepsy.

Key points

 

• Absence status epilepticus is a prolonged, generalized absence seizure that usually lasts for hours and can even last for days.

 

• The cardinal symptom is the altered content of consciousness while the patient is usually fully alert and partly responsive.

 

• Most patients suffer from idiopathic generalized epilepsy, but absence status epilepticus may also appear de novo. Other types of seizure such as absences, myoclonic jerks, and generalized tonic-clonic seizures may predate the first occurrence of absence status epilepticus for many years.

 

• Absence status epilepticus is often misdiagnosed as focal status epilepticus, confusional nonepileptic condition, or epileptic prodrome.

 

• Frequently, absence status epilepticus occurs because of ill-advised antiepileptic drug treatment such as tiagabine, carbamazepine, gabapentin, oxcarbazepine, pregabalin, or vigabatrin.

Historical note and terminology

According to Wolf and colleagues, the first historical case of absence status epilepticus seems to be described on an ex-voto table of 1501 in the parish church of Gmünd in Austria of an ancestor of a family with onset of typical absence seizures in childhood and subsequent generalized tonic-clonic seizures (Wolf et al 2007).

The first unequivocal documentation of absence status epilepticus with EEG was by Putman and Merritt (Putman and Merritt 1941) and Lennox (Lennox 1945). Prolonged episodes of nonconvulsive status epilepticus were described on many occasions before the EEG-era (Shorvon 1994; Shorvon 1995).

Absence status epilepticus is the name proposed by the Commission on Classification and Terminology of the International League Against Epilepsy (Commission on Classification and Terminology of the International League Against Epilepsy 1981; Commission on Classification and Terminology of the International League Against Epilepsy 1989). Absence status is not synonymous with nonconvulsive status epilepticus. Nonconvulsive status epilepticus is a term that rightly has been discarded in the new ILAE diagnostic scheme because it encompasses heterogeneous conditions, which may be focal, such as limbic status epilepticus, or generalized, such as absence status epilepticus (Engel 2001; Engel 2006; Meierkord and Holtkamp 2007; Panayiotopoulos 2010a). According to an expert consensus, "nonconvulsive status epilepticus is a term used to denote a range of conditions in which electrographic seizure activity is prolonged and results in nonconvulsive clinical symptoms” (Walker et al 2005). However, convulsive elements and, particularly, myoclonic jerks are common in generalized nonconvulsive status epilepticus, as in eyelid or perioral status epilepticus. If the term “nonconvulsive” is used, the distinction between “focal nonconvulsive” and “generalized nonconvulsive” should be made for clinical and management purposes (Fernandez-Torre et al 2012; Fernandez-Torre et al 2015). Petit mal status epilepticus and various other synonyms have also been used in the past. Unified EEG terminology and criteria for nonconvulsive status epilepticus have been proposed (Beniczky et al 2013), and its various types, including absence status epilepticus, have been systematically classified (Sutter and Kaplan 2013).

Classification. Considering that absence status epilepticus is a prolonged absence seizure, it is reasonable to adopt for this condition a definition and classification similar to that recognized for epileptic seizures and syndromes manifested with absences (Commission on Classification and Terminology of the International League Against Epilepsy 1989; Panayiotopoulos 1997; Panayiotopoulos 2010a; Engel 2001; Engel 2006; Shorvon and Walker 2005; Walker et al 2005; Koutroumanidis et al 2010).

Table 1. Classification of Absence Status Epilepticus

Typical absence status epilepticus

 

I. Idiopathic (typical) absence status epilepticus in order of prevalence:

   

• Simple absence status epilepticus (mainly in idiopathic generalized epilepsy with phantom absences and juvenile absence epilepsy)

   

• Perioral myoclonic absence status epilepticus (of perioral myoclonia with absences)

   

• Eyelid myoclonic absence status epilepticus (of eyelid myoclonia with absences)

   

• Myoclonic absence status epilepticus (of juvenile myoclonic epilepsy)

   

• Other types of simple or complex absence status epilepticus (fixation-off-sensitive idiopathic generalized epilepsy with mainly catamenial absence status epilepticus; photosensitive idiopathic generalized epilepsy with absences; other unrecognized or unclassified syndromes of idiopathic generalized epilepsy)

 

II. Cryptogenic or symptomatic (typical) absence status epilepticus of cryptogenic/symptomatic generalized epilepsy with typical absence seizures:

   

• fixation-off-sensitive cryptogenic/symptomatic generalized epilepsy with mainly catamenial absence status epilepticus

   

• frontal lobe typical absence status epilepticus

Cryptogenic or symptomatic (atypical) absence status epilepticus of:

 

I. Lennox-Gastaut syndrome

 

II. Other cryptogenic/symptomatic generalized epilepsies mainly of childhood

Situation-related absence status epilepticus due to:

 

I. Drugs such as major neuroleptics but mainly due to benzodiazepine withdrawal

 

II. Electrolyte and other metabolic disturbances

 

III. GABA-B agonist-induced absence status epilepticus in patients with epileptic seizures (tiagabine or vigabatrin)

 

IV. Severe brain anoxia. Comatose or critically ill patients

Absence seizures are broadly divided into: (1) typical absences of mainly idiopathic generalized epilepsy with generalized, greater than 2.5 Hz spike or polyspike-and-slow waves, and (1) atypical absences of symptomatic or cryptogenic epilepsies with slower, less than 2.5 Hz generalized discharges (Commission on Classification and Terminology of the International League Against Epilepsy 1981). Similarly, absence status epilepticus is divided into typical absence status epilepticus of mainly idiopathic generalized epilepsy and atypical absence status epilepticus of symptomatic and cryptogenic generalized epilepsies.

Image: Typical absence status epilepticus in idiopathic generalized epilepsy with phantom absences (1)
Image: Atypical absence status in symptomatic generalized epilepsy
Video: Absence status epilepticus and absences (patient description)
Furthermore, to comply with seizure and syndrome classification, absence status epilepticus may be situation-related and caused by the introduction or withdrawal of certain drugs, intoxication, or electrolyte or metabolic disturbances. Symptomatic absence status may also be caused by severe brain anoxia or other brain damage.

ILAE Task Force classification. The ILAE Task Force report (Engel 2006) classifies absence status epilepticus as:

(A) Typical and atypical absence status epilepticus. When absence status epilepticus occurs in the idiopathic epilepsies, it has features similar to atypical absence and can be terminated by antiepileptic drugs. In the generalized symptomatic epilepsies, there is overlap with focal status epilepticus due to lesions of certain frontal lobe areas. The absence status epilepticus occurring in elderly patients without a prior history of epilepsy, as well as drug-induced and drug-withdrawal absence status epilepticus, have been characterized and most likely represent similar mechanisms; however, there may be several types of typical and atypical absence status epilepticus.

(B) Myoclonic absence status epilepticus. Myoclonic absence status epilepticus consists of proximal, predominantly upper extremity myoclonic jerks corresponding with 3 Hz spike-wave discharges in the EEG. It can last hours or even days and is usually resistant to therapy.

The 2010 ILAE proposal has not dealt with status epilepticus (Berg et al 2010). However, the ILAE Task Force on the Classification of Status Epilepticus has now published its report on “a definition and classification of status epilepticus” that encompasses all types of status epilepticus and takes into consideration current knowledge regarding its pathophysiology and the need to address clinical treatment decision making time points, as well as the conduct of epidemiologic and clinical studies (Trinka et al 2015). Accordingly, status epilepticus is a condition resulting either from the failure of the mechanisms responsible for seizure termination or from the initiation of mechanisms that lead to abnormally prolonged seizures (after time point t1). It is a condition that can have long-term consequences (after time point t2), including neuronal death, neuronal injury, and alteration of neuronal networks, depending on the type and duration of seizures. This definition is conceptual, with 2 operational dimensions: the first is the length of the seizure and the time point (t1) at which the seizure should be regarded as an “abnormally prolonged seizure,” and the second time point (t2) is the time of ongoing seizure activity beyond which there is a risk of long-term consequences. In the case of convulsive (tonic-clonic) status epilepticus, both time points are based on animal experiments and clinical research. This evidence is incomplete; furthermore, there is considerable variation so these time points should be considered as the best estimates currently available. Data are not yet available for other forms of status epilepticus, but as knowledge and understanding increases, time points can be defined for specific forms of status epilepticus based on scientific evidence and can be incorporated into the definition, without changing the underlying concepts. The division into 2 time points has clear clinical implications: the time point of operational dimension 1 determines the time at which treatment should be considered or started, whereas the time point of operational dimension 2 determines how aggressively treatment should be implemented to prevent long-term consequences. The time domain may vary considerably between different forms of status epilepticus. There is limited information to define t1 and t2 in focal status epilepticus and no information for absence status epilepticus. T1 for absence status epilepticus has been arbitrarily estimated as between 10 to 15 minutes (Trinka et al 2015).

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