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Nonconvulsive SE
Although NCSE in childhood is receiving increasing attention, the classification of NCSE has not yet been fully clarified (6, 21, 27, 28, 46, 49, 56).
NCSE is characterized clinically by subtle manifestations such as clouding of consciousness, pseudodementia, or ataxia, no overt motor (convulsive) manifestations, and electrically continuous or repetitive seizure patterns. It is often difficult to notice, and controversial in its definition and classification (6, 12, 20, 27, 49). Electroencephalographic (EEG) findings have decisive importance, showing continuous or nearly continuous electrographic seizure activity lasting at least 30 minutes (55). The EEG criteria for diagnosing NCSE include discrete electrographic seizures, continuous spike-and-wave activity, or rhythmic recurrent epileptiform activity that usually shows marked improvement with the injection of benzodiazepines. These EEG findings also differentiate generalized from focal-onset NCSE (21).
Generalized NCSE (GNCSE), mainly absence status, is more often observed than partial SE in NCSE occurring in chronic epileptics. In acute symptomatic SE, however, nonconvulsive complex partial SE predominates, and its poor prognosis necessitates intensive emergency treatment (55). Accordingly, it is important to differentiate partial nonconvulsive SE from absence status, which has a better prognosis.
After prolonged generalized convulsive SE (GCSE) or following incomplete treatment, convulsive symptoms become very subtle, and the residual persistent disturbance of consciousness and autonomic symptoms may be confused with transition to NCSE. A careful diagnosis of SE is important and should take into account the results of EEG monitoring (55).
Generalized Nonconvulsive SE
GNCSE is characterized by various degrees of clouding of mental processes, from simple slowing of ideation to complete unconsciousness, and by diffuse bilateral spike-and-wave activity on the EEG.
Absence status
Absence status (AS) is characterized by repetitive absences, either typical or atypical, or prolonged clouding of consciousness, which varies from light to profound stupor or confusion, together with diffuse spike-and-wave activity on the EEG. Complex mental testing may be needed to detect absence status with only mild mental slowing. Blinking, myoclonia of the upper extremities, or automatisms may occasionally occur but are not distinctive features of AS.
This status, however, has terminologic and nosologic problems, being variously called petit mal status, epileptic twilight state, ictal stupor, spike-wave stupor, and minor epileptic status (2, 20, 39, 46). Electrographically, bilaterally synchronous spike-and-wave patterns are repeated at very short intervals or continue without interruption. In atypical ASE and some time after the onset of typical AS, slow spike-and-wave patterns become predominant and somewhat irregular. Atypical AS associated with Lennox-Gastaut syndrome or myoclonic-astatic epilepsy is more often observed in childhood epilepsy (12, 20, 46).
Petit mal status, typical AS, or spike-wave stupor. Formerly, we (39) proposed reserving the term petit mal status for cases with closely repeated 3-Hz spike-and-wave bursts corresponding to a series of petit mal absences and applying the term spike-wave stupor exclusively to those cases with uninterrupted continuous 3-Hz spike-and-wave bursts and prolonged altered consciousness.
Typical ASE rarely occurs in childhood absence epilepsy but is somewhat more frequent in other idiopathic forms of generalized epilepsy and in adults (20).
Minor epileptic status. Reporting findings in 22 children, Brett (7) differentiated minor epiletic status from AS by the presence of myoclonus and less frequent spike-and-wave activity intermingled with slow waves on EEG, and by its poor prognosis. This syndrome is characterized clinically by periodic or fluctuating lowering of awareness and responsiveness and decreased speech, sometimes so severe as to simulate dementia (i.e., pseudodementia), and is often associated with lack of coordination and unsteadiness in walking that resembles ataxia (i.e., pseudoataxia) because of the intrusion of repeated small myoclonic jerks or twiches. Because both negative and positive myoclonus are observed, Brett's cases (7) may include or be combined with some type of ESES syndrome or myoclonic status.
Angelman's syndrome is often accompanied by NCSE, which in most cases may be this kind of minor epileptic status (9, 33, 50). It is mainly observed from late infancy to early childhood.
NCSE with hypsarrhythmia. The most typical continuous and longlasting epileptic EEG abnormality is hypsarrhythmia, observed in West syndrome. Infants with this condition become stuporous and apathetic, and their development stagnates or deteriorates. Thus, the twilight state in hypsarrhythmia may be regarded as a form of NCSE (12, 46).
NCSE in myoclonic-astatic epilepsy and Lennox-Gastaut syndrome. NCSE is reported in 30%–40% of patients with myoclonic-astatic epilepsy in childhood (12). It is characterized by apathy or stupor and slurred or decreased speech, and 2–3 Hz spike-and-wave bursts on the EEG. There is palpable irregular twitching of the facial muscles and the extremities, and astatic seizures and head nodding can appear serially (12). This status of minor seizures may be a mixed type of atypical AS, myoclonic status, or myoclonic-astatic status.
More than two-thirds of patients with Lennox-Gastaut syndrome experience SE (4), which usually consists of clouding of consciousness with or without intermixed serial tonic seizures of short or long duration.
Myoclonic status
Myoclonic status is usually classified as a form of convulsive status (20) and subdivided into idiopathic and symptomatic generalized epilepsies. Rhythmic myoclonic jerks occur in the generalized forms and appear mainly in proximal muscles. The level of consciousness depends on the underlying disorders, and sometimes there is no clouding (20). Diffuse polyspike-and-wave discharges precede the myoclonic jerks.
It may be reasonable to classify this status as NCSE when jerks or twiches are very small and clouding of consciousness is a more prominent feature (20). Myoclonic status in nonprogressive encephalopathies as described by Dalla Bernardina et al. (9) belongs to this kind of NCSE and probably overlaps with atypical ASE, minor epileptic status, or obtunded status. Nonconvulsive myoclonic status is also observed in eyelid myoclonia with absences.
Atonic and akinetic SE
This rare form of SE is peculiar to very young children during hyperthermia and is characterized by immobility (without or with tonus), sometimes with a few minor clonias, and unconsciousness. The EEG shows an epileptic recruiting rhythm progressively mixed with delta activity, forming some spike-and-wave patterns (20).
Partial (Focal) Nonconvulsive SE
Simple partial SE
Nonconvulsive simple partial SE (SPSE) by definition should not be associated with alterations of consciousness, and is more often neocortical and extratemporal in origin (46, 60). Rare cases with somatoinhibitory SE (ictal paralysis), somatosensory SE, visual SE (elementary visual phenomena, amaurotic, visual hallucination), auditory SE, dysphasic/aphasic SE, SE with pure transient amnesia (59), autonomic/vegetative SE, and SE with expression of fear, depression, and anxiety have been reported (46, 60).
Complex partial SE
Complex partial SE (CPSE) often originates from temporal or frontal lobe foci, but on rare occasions it originates from other cortical areas; an example is visual hallucinatory SE (46). Clinically, CPSE is characterized by recurrent or prolonged seizures involving some alteration of contact with the environment, of memory or of consciousness, but it usually stops short of coma. Automatisms may be observed, but not convulsive movement. Its fundamental characteristic, which enables differentiation of CPSE from other twilight states such as AS, is a cyclicity that alternates between total unresponsiveness with stereotyped automatisms and partial unresponsiveness with reactive automatisms (46, 56).
Nonconvulsive SE, Undetermined Whether Partial or Generalized
ESES syndrome
Among the NCSE conditions, ESES (26, 29, 42) is a peculiar pathologic condition that is observed only in childhood epilepsy. Epilepsy with continuous spike waves during slow-wave sleep (CSWS) (8) characterized by ESES has many interesting electroclinical characteristics. However, its pathophysiology and the points of discriminating epilepsy with CSWS from related conditions, such as ESES syndrome (37), are still unclear (2, 10, 18, 19, 58). Some authors prefer to use the term CSWS syndrome (2, 19). ESES syndrome and its developmental aspects are discussed later in the chapter.
Landau-Kleffner syndrome
Active epileptic discharges appearing predominantly from the temporal areas can cause acquired aphasia, mainly due to auditory agnosia, in children ages 2–11 years (2, 48, 53). Epileptic seizures such as generalized tonic-clonic, focal motor seizures, or atypical absences usually appear before or after the onset of decreased speech, but there are no seizures in 17%–30% of cases (2). Intelligence usually is preserved, but behavior disorders are often observed. Epilepsy, aphasia, and epileptic EEG abnormalities disappear by the age of 15.
This is understandable in the context of ESES syndrome (43, 48, 53), as ESES/CSWS is observed, but the spike-wave index during slow-ware sleep is relatively low, about 30% or more.
Obtundation status in severe myoclonic epilepsy in infancy
In this type of status, observed in 30%–40% of cases of Dravet syndrome, patients become obtunded and lose interest in their environment or do not answer (16). They may have erratic, small myoclonias, sometimes associated with increased muscular tone. The EEG shows diffuse dysrhythmia of slow waves, intermixed with focal and diffuse spikes, sharp waves, and spike-and-wave complexes, without correspondence between the spikes and the myoclonias (16). This status may belong to the category of ASE in a broad sense and may overlap minor epileptic status (7). Nearly the same atypical ASE is also observed in Lennox-Gastaut syndrome or myoclonic-astatic epilepsy (2, 4, 12).
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