Key Points
- A new conceptual definition of status epilepticus with two operational dimensions (t1 and t2) is proposed
- Time point t1 indicates when treatment should be initiated, and time point t2 indicates when long-term consequences may appear
- The Task Force also proposes a new classification of SE that will provide a framework for clinical diagnosis and therapeutic approaches for each patient
SE is a condition resulting either from the failure of the mechanisms responsible for seizure termination or from the initiation of mechanisms which 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
Classification of Status Epilepticus For classification of SE we propose the following four axes:
1 Semiology
2 Etiology
3 EEG correlates
4 Age
Ideally, every patient should be categorized according to each of the four axes. However, it is acknowledged that this will not always be possible. At initial presentation, the approximate age of the patient and the semiology will be immediately assessable. The etiology will be apparent less frequently and may take time to identify. It is also recognized that EEG recordings will not be available in many settings, particularly at presentation. However, the EEG will affect choice and aggressiveness of treatment, prognosis, and clinical approaches, so an EEG should be sought where possible and as early as possible. In fact, some forms of SE may only be reliably diagnosed by EEG.23 Like in other acute neurologic conditions, the semiology (symptoms and signs) and the EEG pattern in SE are highly dynamic and may change over short time periods in a given patient. Thus, repeated neurologic examinations and EEG investigations in a patient with SE may lead to a different classification. For example, SE may start with focal motor symptoms evolving into bilateral convulsive SE (A.1.b) and may present a few hours later as nonconvulsive SE (NCSE) with coma and minor motor phenomena resembling so called “subtle status” (B.1). Likewise, the EEG may show lateralized periodic discharges at the beginning and a bilateral synchronous pattern at the second investigation.
Axis 1: Semiology
This axis refers to the clinical presentation of SE and is therefore the backbone of this classification. The two main taxonomic criteria are: 1. The presence or absence of prominent motor symptoms 2 The degree (qualitative or quantitative) of impaired consciousness Those forms with prominent motor symptoms and impairment of consciousness may be summarized as convulsive SE as opposed to the nonconvulsive forms of SE (NCSE). Although the term convulsion is sometimes disregarded as a lay term, it reflects the clinician0 s ordinary language. In fact “status epilepticus” is also a lay term, as it is the English translation of etat de mal, which was used in the 19th century by patients in the Salp^etriere.24 Thus, it was decided to keep the well-accepted term “convulsive.” It designates “episodes of excessive abnormal muscle contractions, usually bilateral, which may be sustained, or interrupted”25
Axis 2: Etiology
underlying cause (etiology) of SE is categorized in a manner that is consistent with the concepts of the ILAE Commission for Classification proposal 2010,5 but acknowledges the well-established terms that are used by epileptologists, emergency doctors, neurologists, pediatric neurologists, neurosurgeons, family doctors, and other clinicians looking after patients with SE (Table 3). The term “known” or “symptomatic” is used—consistent with the common neurologic terminology—for SE caused by a known disorder, which can be structural, metabolic, inflammatory, infectious, toxic, or genetic. Based on its temporal relationship, the subdivisions acute, remote, and progressive can be applied. The term “idiopathic” or “genetic” is not applicable to the underlying etiology of SE. In idiopathic or genetic epilepsy syndromes, the cause of status is not the same as for the disease, but some metabolic, toxic, or intrinsic factors (like sleep deprivation) may trigger SE in these syndromes. Therefore, the term “idiopathic” 28 or “genetic” 5 is not used here. SE in a patient with juvenile myoclonic epilepsy (which itself is “idiopathic” or “genetic”) can be symptomatic, due to inappropriate antiepileptic drug (AED) treatment, abrupt drug withdrawal, or drug intoxication. The term “unknown” or “cryptogenic” (Greek: jqύpsοϛ, hidden or unknown, so cέmοϛ, family, class, descent, origin) is used in its strict original meaning: unknown cause. The assumption that it is “presumably” symptomatic or genetic is inappropriate. Synonymously and consistent with the proposal 2010,5 the term “unknown” or appropriate translations in different languages can be used). SE in its varied forms has a plethora of causes; a list is attached The list will be updated periodically and will provide a database for clinicians.
Axis 3:
Electroencephalographic correlates
None of the ictal EEG patterns of any type of SE is specific. Epileptiform discharges are regarded as the hallmark, but with increasing duration of SE, the EEG changes and rhythmic nonepileptiform patterns may prevail. Similar EEG patterns, such as triphasic waves, can be recorded in various pathologic conditions, leading to substantial confusion in the literature. Although the EEG is overloaded with movement and muscle artifact in the convulsive forms of SE and thus of limited clinical value, it is indispensable in the diagnosis of NCSE, as the clinical signs (if any) are often subtle and nonspecific.23,29 Advances in electrophysiologic techniques may provide us with increased capability to utilize EEG in the emergency setting and allow better delineation of the highly dynamic changes of EEG patterns in the near future. Currently there are no evidence-based EEG criteria for SE. Based on large descriptive series and consensus panels,26,27,30–32 we propose the following terminology to describe EEG patterns in SE: 1 Location: generalized (including bilateral synchronous patterns), lateralized, bilateral independent, multifocal. 2 Name of the pattern: Periodic discharges, rhythmic delta activity or spike-and-wave/sharp-and-wave plus subtypes. 3 Morphology: sharpness, number of phases (e.g., triphasic morphology), absolute and relative amplitude, polarity.
Time-related features: prevalence, frequency, duration, daily pattern duration and index, onset (sudden vs. gradual), and dynamics (evolving, fluctuating, or static). 5 Modulation: stimulus-induced vs. spontaneous. 6 Effect of intervention (medication) on EEG.
Axis 4: Age
1 Neonatal (0 to 30 days). 2 Infancy (1 month to 2 years). 3 Childhood (> 2 to 12 years). 4 Adolescence and adulthood (> 12 to 59 years). 5 Elderly (≥ 60 years).
. SE in neonates may be subtle and difficult to recognize. Some forms of SE are seen as an integral part of the electroclinical syndrome; others can occur in patients within a certain electroclinical syndrome, or when trigger factors or precipitating causes are present, such as sleep deprivation, intoxication, or inappropriate medication. Examples are phenytoin in some forms of progressive myoclonic epilepsies,33 carbamazepine in juvenile myoclonic epilepsy,34,35 or absence epilepsies.36
REFERENCE:ILAE OCT 15 UPDATE
Superintendent, ICH.