The most recent classification of seizure types by the International League Against Epilepsy (ILAE) proposed to eliminate the terms dyscognitive, simple partial, complex partial, psychic, and secondarily generalized seizures (99). The term focal seizures with impaired awareness substituted that of complex partial seizures (99). However, this position paper of the ILAE commission for classification and terminology did not consider “dyscognitive” as a synonym for “complex partial” (99).
In this article, the term dyscognitive seizures follows the description by Lüders and colleagues as seizures causing “interference of high cognitive functions essential for fully intact consciousness, including alterations of praxis (apraxia), language (aphasia), and the patient's ability to form memories (amnesia). These alterations of consciousness do not affect the arousal system or postural muscle tone, and the patient remains aware of the external and internal environment, even if the alterations of cognition may interfere somewhat with its perception. Dyscognitive seizures are best identified by listing the specific cognitive disturbance (apraxic seizures, aphasic seizures, amnestic seizures, and so on)” (198). Thus, dyscognitive seizures could be translated as focal seizures with impaired awareness that do not affect the arousal system or postural muscle tone. However, most of the studies discussed herein do not differentiate dyscognitive status from focal status epilepticus with impaired awareness that affect the arousal system or postural muscle tone.
Dyscognitive focal 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.
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• 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.
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• Dyscognitive status epilepticus, as in other types of status epilepticus, is defined as dyscognitive seizures lasting 10 minutes or longer. However, a clinical operational definition of 5 minutes of continuous seizure provides an appropriate indication for initiating treatment.
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• 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.
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• 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 (39). The proceedings of the 10th Marseilles Colloquium of 1962 represent the first book on this subject (112). 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" (245). Bright, as well as Charcot, described fugue states, and Hughlings Jackson described such a condition in temporal lobe epilepsy (34; 45; 304).
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" (237). 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 (186; 187).
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 (182; 110).
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 (148; 363).
Major reviews on status epilepticus were the Santa Monica, California Conference (128) and the Seventeenth Annual Merritt-Putnam in Boston, which was published as a supplement to Epilepsia (69; 200). In the same year, 5 position papers on nonconvulsive status epilepticus were published in the Journal of Clinical Neurophysiology (154). Comprehensive reviews on the behavioral manifestations, presentation, evaluation, and treatment followed (80; 155; 168).
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 (279; 279), and a new proposal for definition and classification of status epilepticus was proposed by a ILAE task force (314).
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 (109; 255; 113). A widely accepted operational definition of status epilepticus was that of a condition in which epileptic activity persists for 30 minutes or more (299). The ILAE Task Force on Classification of Status Epilepticus proposed a new definition of status epilepticus to account for the heterogeneous etiology, phenomenology, and prognosis of nonconvulsive status epilepticus (314). This definition incorporates elements of time (termed T1 and T2) and 4 additional axes (semiology, etiology, EEG correlate, and age). T1 indicates when seizures need to be acutely treated (eg, 10 minutes for focal status epilepticus with impaired awareness and 10 to 15 minutes for absence status epilepticus). T2 indicates the time at which the likelihood of permanent neuronal injury increases, and more aggressive therapy may be justified (more than 60 minutes for focal status epilepticus with impaired awareness and unknown for absence status epilepticus) (314).
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 (40; 147; 310; 161). At least 10% of patients with epilepsy suffer a status epilepticus during the course of their disease, and 50% of status epilepticus appears in patients with no known history of epilepsy (266). Status epilepticus is more frequent in developmental and epileptic encephalopathies and epilepsies with structural etiologies, 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 types and syndromes. Tonic-clonic status epilepticus is the best-known type, and its diagnosis is simple, but focal 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 (266; 31; 169; 274).
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 (156; 280). Based on ictal EEG, a classical separation is: (1) absence status and (2) focal status epilepticus with impaired awareness. The differential diagnosis is difficult on the basis of clinical semiology alone. Absence status can complicate many epileptic syndromes; it is characterized by confusion of varying intensity and is associated in 50% of cases with bilateral myoclonia (306). The EEG shows ictal generalized paroxysmal activity; normalization is obtained after benzodiazepine injection.
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 as, for example, lateralized periodic discharges (LPDs) or periodic lateralized epileptiform discharges (PLEDs) in the EEG (46; 224; 188). LPDs are a matter of controversy, and many authors believe that this EEG pattern reflects severe cerebral dysfunction rather than epileptic activity (144; 317; 188). However, when LPDs occur in a comatose patient after a generalized tonic-clonic status epilepticus, the diagnosis of subtle status epilepticus should be considered. By contrast, LPDs or continuous EEG abnormalities in the context of acute cerebral damage, such as stroke or anoxic or traumatic brain damage, are more difficult to interpret (297; 144; 188). However, ictal EEG patterns with a typical spatiotemporal evolution faster than 2.5 Hz in a comatose patient reflect nonconvulsive seizures or nonconvulsive status epilepticus and should be treated (317).
The 2006 proposal of the ILAE Classification Core Group (86), 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" (86).
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 (314). 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 (314).