Absence status epilepticus

Jonathan M Gursky MD (

Dr. Gursky of Montefiore Medical Center/Albert Einstein College of Medicine has no relevant financial relationships to disclose.

)
Solomon L Moshé MD, editor. (

Dr. Moshé of Albert Einstein College of Medicine received consulting fees from Pfizer and UCB.

)
Originally released June 30, 1999; last updated October 25, 2020; expires October 25, 2023

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 developmental and 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 in the setting of medication nonadherence or 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.

 

• Medication nonadherence is a common trigger for the occurrence of absence status epilepticus.

 

• 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, most of which may have been of focal origin (temporal lobe) (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 absence 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; Fisher et al 2017a; Fisher et al 2017b).

Table 1. Classification of Absence Status Epilepticus

Typical absence status epilepticus

 

(Typical) absence status epilepticus in order of prevalence:

 

• Simple absence status epilepticus (mainly in idiopathic generalized epilepsy and juvenile absence epilepsy)
• Perioral myoclonic absence status epilepticus
• Eyelid myoclonic absence status epilepticus
• Myoclonic absence status epilepticus
• 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

Absence status epilepticus of developmental or epileptic encephalopathies including Lennox-Gastaut syndrome

Situation-related absence status epilepticus due to:

 

I. Benzodiazepine withdrawal
II. Electrolyte and other metabolic disturbances
III. GABA agonist-induced absence status epilepticus in patients with epileptic seizures (tiagabine or vigabatrin)
IV. Severe brain anoxia in 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 in developmental and epileptic encephalopathies with slower, less than 2.5 Hz generalized discharges (Commission on Classification and Terminology of the International League Against Epilepsy 1981; Scheffer et al 2017). The ILAE classification of seizure types classifies all absences as “nonmotor seizures of generalized onset” as follows: typical, atypical, myoclonic, and eyelid myoclonia absences (Fisher et al 2017a; Fisher et al 2017b).

Similarly, absence status epilepticus is divided into typical absence status epilepticus of mainly idiopathic generalized epilepsy and atypical absence status epilepticus of developmental or epileptic encephalopathies.

Typical absence status epilepticus in idiopathic generalized epilepsy with phantom absences Image: Absence status epilepticus in idiopathic generalized epilepsy (1)
Atypical absence status in symptomatic generalized epilepsy Image: Atypical absence status in developmental or epileptic encephalopathy
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 developmental and epileptic encephalopathies, 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.

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