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  • Updated 09.10.2016
  • Released 04.26.2001
  • Expires For CME 09.10.2019

Dyscognitive focal status epilepticus

Introduction

This article includes discussion of dyscognitive focal status epilepticus, complex partial status epilepticus, continuous status of partial seizures with complex symptomatology, epileptic twilight states with productive-psychotic signs and symptoms, limbic status epilepticus, psychomotor status epilepticus, and temporal lobe status epilepticus. The foregoing terms may include synonyms, similar disorders, variations in usage, and abbreviations.

Overview

Dyscognitive focal (limbic, psychomotor, or complex partial) status epilepticus represents a most intriguing epileptic condition. Variable confusion and responsiveness, impaired memory of the event, fluctuating and often bizarre behavior—including automatisms—and sometimes lateralizing signs, such as aphasia, are usually present. However, if dyscognitive focal status presents only with subtle signs and symptoms of cognitive and autonomic impairment, it might be difficult to recognize and differentiate from psychiatric conditions. EEG remains essential to diagnose dyscognitive focal status epilepticus and to differentiate it from generalized nonconvulsive status epilepticus (absence status). Causes of dyscognitive focal status epilepticus include acute and chronic focal cerebral injuries, including ischemic stroke, intracranial hemorrhage, abscess, meningoencephalitis, neoplasias, malformations, and a history of epilepsy. Medications and other metabolic and systemic stressors (eg, infections, hypoxemia) may be implicated or superimposed. The list of differential diagnosis includes toxic or metabolic encephalopathy, delirium, psychiatric conditions, limbic encephalitis, and transient global amnesia. Of particular importance are the more recently described syndromes associated with antibodies against synaptic proteins that may occur with or without cancer, including limbic encephalitis with antibodies directed towards the antigens of the voltage-gated potassium channel complex (LGI1, CASPR2, Contactin-2), as well as other antibodies (to NMDA receptors [NMDARs], AMPA receptors [AMPARs], and GABA type B receptors [GABABRs]). In this updated article, the author discusses evidence about diagnosis and treatment of dyscognitive focal status epilepticus.

Key points

• Dyscognitive seizures produce impairment in cognition, including perception, attention, emotion, memory, or the ability to perform complex executive functions. The clinical presentation may not be recognized as a seizure manifestation, and EEG is crucial for diagnosis and management of dyscognitive status epilepticus.

• Dyscognitive status epilepticus, as in other types of status epilepticus, is defined as dyscognitive seizures lasting 30 minutes or longer. However, a clinical operational definition of 5 minutes of continuous seizure provides an appropriate indication for initiating treatment.

• Dyscognitive and other forms of nonconvulsive status epilepticus are often misdiagnosed. A high index of suspicion is necessary in patients who received treatment for convulsive status epilepticus and do not recover, in critically ill patients with acute encephalopathy, and in patients with focal epilepsy with inappropriate behavior of confusional state.

• The treatment of status epilepticus has potential risks, and aggressive treatment with sedation and intubation may not be appropriate for some patients with dyscognitive status epilepticus, in particular for older patients with serious comorbidities. In these situations, treatment with less sedative antiepileptic drugs should be considered.

Historical note and terminology

Status epilepticus was infrequently recorded up to the dissertation of Louis Calmeil, where the expression “etat de mal” is first found, but still in the notion of generalized convulsive status epilepticus only (40). The proceedings of the 10th Marseilles Colloquium of 1962 represent the first book on this subject (113). At the Marseilles Colloquia 1962 and 1964, definitions and classifications of seizures and of status epilepticus were proposed with the obvious notion that there are as many types of status as types of seizures.

Trousseau was probably the first who observed that petit mal seizures might, as with grand mal, occur in such frequency "that one seizure would become confused with the next, simulating a continuous seizure that might persist for 2 or 3 days" (319). But, although Trousseau identified petit mal status, his was not the first description of nonconvulsive status epilepticus. In 1822, Prichard described cases of epileptic fugue and furor as well as "epileptic ecstasy" (247). Bright, as well as Charcot, described fugue states, and Hughlings Jackson described such a condition in temporal lobe epilepsy (34; 46; 305).

In 1954, Penfield and Jasper identified recurrent sensory phenomena (simple partial status epilepticus; aura continua) and found them to be "at least as common as continuing circumscribed movements" (239). In 1945 and 1960, Lennox and Lennox used the term petit mal status for psychiatric conditions associated with continuous bifrontal spike-wave activity and with a duration of hours to days (188; 189).

The questions of whether psychomotor seizures (referred to the temporal lobe) also could occur as a status epilepticus and whether such status activity could be the underlying cause for prolonged twilight states were, however, for a long time controversially discussed (184; 111).

The most important early literature dealing with psychomotor status epilepticus has been focused on the phenomenological description of this condition, distinguishing the discontinuous form, characterized by the occurrence of psychomotor attacks that follow each other at 2 to 10 minute intervals, from the continuous form (149; 363).

Major reviews on status epilepticus were the Santa Monica, California Conference (130) and the Seventeenth Annual Merritt-Putnam in Boston, which was published as a supplement to Epilepsia (70; 201). In the same year, 5 position papers on nonconvulsive status epilepticus were published in the Journal of Clinical Neurophysiology (155). Comprehensive reviews on the behavioral manifestations, presentation, evaluation, and treatment followed (82; 156; 170).

The London Innsbruck Colloquia on Status Epilepticus have discussed and reviewed current advances on molecular and basic science, as well as clinical and therapeutic aspects of status epilepticus (281; 281), and a new proposal for definition and classification of status epilepticus was proposed by a ILAE task force (316).

Definition and problems with definition.

Status epilepticus. The term status was used "whenever a seizure persists for sufficient length of time (subsequently defined as at least 30 to 60 minutes) or is repeated frequently enough to produce a fixed or enduring epileptic condition.” This definition is enshrined into the World Health Organization dictionary of epilepsy as well as the Handbook of clinical neurology and Handbook of electroencephalography and clinical neurophysiology (110; 257; 114). Today, a widely accepted operational definition of status epilepticus is that of a "condition in which epileptic activity persists for 30 minutes or more, causing a wide spectrum of clinical symptoms, and with a highly variable pathophysiological, anatomical and aetiological basis.” It is important to note that this definition implies that status is not simply a rapid repetition of seizures (in fact the word "seizure" is no longer retained) and, as such, an iterative version of ordinary epilepsy, but a condition (or group of conditions) in its own right with distinctive pathophysiological features.

It is estimated that there are between 65,000 and 150,000 cases of status epilepticus in the United States each year, and that approximately 25% are nonconvulsive (41; 148; 311; 163). At least 10% of epileptic patients suffer a status epilepticus during the course of their disease, and 50% of status epilepticus appears in patients with no known history of epilepsy (268). Status epilepticus is more frequent in symptomatic epilepsies, particularly those arising from trauma, tumor, or infection involving the frontal lobe. Both acute and remote cerebral insults can cause status epilepticus, as can severe systemic disease that causes status epilepticus secondary to a toxic-metabolic encephalopathy. Status epilepticus is present in nearly all epileptic syndromes, even idiopathic ones, although it is more frequent in cryptogenic and symptomatic forms. Whereas tonic-clonic status epilepticus is the best known type and its diagnosis is simple, partial status epilepticus, above psychomotor status epilepticus, presents a diagnostic challenge. Particularly difficult clinically is the differential diagnosis of dyscognitive focal status epilepticus, absence status epilepticus, and above all, the form termed "late-onset de novo absence status epilepticus,” which may present as confusional syndrome in the elderly (268; 31; 171; 276).

Nonconvulsive confusional status epilepticus. Nonconvulsive confusional status epilepticus has been categorized into groups having focal or generalized EEG epileptic activity and by etiology and level of consciousness, which predict outcome (157; 282). Based on ictal EEG, a classical separation is: (1) absence status and (2) psychomotor (complex partial) status epilepticus. The differential diagnosis is difficult on the basis of clinical semiology alone. Absence status (or “petit mal” status) can complicate many epileptic syndromes and is the most frequently encountered form of nonconvulsive status epilepticus. It is characterized by confusion of varying intensity and associated in 50% of cases with bilateral myoclonia (307). The EEG shows ictal generalized paroxysmal activity; normalization is obtained after benzodiazepine injection. In absence status, there is nosographic heterogeneity. Four groups can be distinguished: (a) “typical” absence status in patients with generalized idiopathic epilepsies; (b) “atypical” in patients with symptomatic or cryptogenic generalized epilepsies; (c) “de novo” absence status of late onset characterized by toxic or metabolic precipitating factors in middle-aged subjects with no previous history of epilepsy; and (d) absence status with focal characteristics in subjects with a preexisting or newly diagnosed partial epilepsy, mostly of extratemporal origin. “Transitional” forms between these 4 groups exist.

Dyscognitive focal (in the old terminology psychomotor, complex partial, temporal lobe, or limbic) status epilepticus. Psychomotor status epilepticus is characterized by continuous or rapidly recurring psychomotor (complex partial) seizure activity that may involve temporal or extratemporal - most often limbic - regions. Cyclic disturbance of consciousness is characteristic of psychomotor status epilepticus of temporal lobe origin. The diagnosis of complex partial status epilepticus of frontal lobe origin remains a challenge (190; 158). In one third of cases, a frontal lesion is revealed (307).

The former conventional classification of status epilepticus was designed to parallel the seizure type classification scheme (58; 59). It has been questioned with regard to its appropriateness to adequately describe the plurality of the clinical forms of status. The first International Classification of Seizure Type and its revision divided partial seizures, and consequently partial status epilepticus, into "simple" and "complex" according to whether or not consciousness is retained or lost (Gastaut 1969; 109; 58). Therefore, the older term psychomotor status or temporal lobe status was replaced by complex partial status epilepticus (CPSE) and simple partial status epilepticus (SPSE). The following classification of epilepsies and epileptic syndromes include a few syndromes that might conform to the widened definition of status, eg, epilepsia partialis continua, electrical status epilepticus during slow-wave sleep (now called continuous spike-wave discharges during sleep), or Landau-Kleffner syndrome; otherwise, it is lacking a synoptic view (238; 59; 218). In 1994, Shorvon proposed a new scheme in his monograph, grouped by age, and tried to encompass the various nonconvulsive and myoclonic forms that fit uneasily into the "seizure type approach” (280).

The search for a new classification scheme for status is justified by the fact that there are types of status in which no overt "seizure" occurs, including epileptic confusional states. Moreover, there are other borderline or boundary conditions. One, for example, is periodic lateralized epileptiform discharge (PLED) in the EEG (47; 225). PLEDs are a matter of controversy, and many authors believe that this EEG pattern reflects severe cerebral dysfunction rather than epileptic activity. However, when PLED occurs in a comatose patient after a generalized tonic-clonic status epilepticus, the diagnosis of subtle status epilepticus should be considered. By contrast, PLED or continuous EEG abnormalities in the context of acute cerebral damage, such as anoxic or traumatic brain damage, are more difficult to interpret (299).

Because limbic status epilepticus implies seizure discharges in the limbic system, it is not surprising that without intracranial recording from the core structures of the limbic system, such as hippocampal formation and amygdala, limbic status epilepticus is often not detectable. This might be one reason that limbic status epilepticus is rarely reported in literature in comparison to generalized convulsive status epilepticus and absence status epilepticus.

The 2006 proposal of the ILAE Classification Core Group (87), an attempt to complete the earlier work of the Task Force on Classification and Terminology, differentiates "self-limited epileptic seizure types" from "Status epilepticus". Under "Status epilepticus," this report lists 9 headings: (I) epilepsia partialis continua of Kojevnikov, (II) supplementary motor area (SMA) status epilepticus, (III) aura continua, (IV) dyscognitive focal (psychomotor, complex partial) status epilepticus, (V) tonic-clonic status epilepticus, (VI) absence status epilepticus, (VII) myoclonic status epilepticus, (VIII) tonic status epilepticus, and (IX) subtle status epilepticus.

The category (IV) dyscognitive focal (psychomotor, complex partial) is divided into (A) mesial temporal and (B) neocortical. The explanatory text for these 2 subtypes is as follows: "Mesial temporal: Focal status epilepticus, predominantly involving mesial limbic structures, consists of serial dyscognitive focal ictal events without return of clear consciousness in between. Onset can be limited to one side, or can alternate between hemispheres,” and "Neocortical: Focal status epilepticus originating in various neocortical regions can present with a wide variety of unpredictable clinical patterns. Status epilepticus from some frontal foci can resemble absence status or generalized tonic-clonic status. It can present as repetitive discrete behavioral seizures. To some extent, this type of status epilepticus can reflect the neocortical region of origin. For example, occipital status epilepticus might present with unexplained blindness, whereas dysphasia or aphasia could represent focal status in language cortex" (87).

The 2015 report of the ILAE Task Force on Classification of Status Epilepticus proposes the following 4 axes for defining subtypes of status epilepticus: 1) semiology; 2) etiology; 3) EEG correlates; and 4) age (316). Ideally, every patient should be categorized according to each of these 4 axes; however, they acknowledge that this will not always be possible. Axis 1 (semiology) refers to the clinical presentation and is, therefore, the backbone of this classification. The 2 main taxonomic criteria are the presence or absence of prominent motor symptoms and the degree (qualitative or quantitative) of impaired consciousness. Those forms with prominent motor symptoms and impairment of consciousness may be summarized as convulsive as opposed to the nonconvulsive forms of status epilepticus (NCSE) (316).

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