Neonatal seizures and neonatal epileptic syndromes

The neonatal period is defined as the first 28 days of life of a term infant; for premature infants the limit of this period is 44 completed weeks of the infant's conceptional age (CA)-defined as the chronological age plus gestational age (GA) at birth. The clinical and electroencephalographic (EEG) manifestations of seizures during this period are determined primarily by the development features of the immature brain at the time of seizure onset, but are also related to the type and diversity of etiologies and risk-factors for seizures neonates may face early in life. Neonatal seizures may be strikingly different from the clinical and electrical seizures of older children and adults. In addition, findings from basic science investigations suggest that immature animals are more likely to experience seizures in response to injury than more mature animals, although the developing brain is less susceptible to seizure-induced injury.     

Recognizing and classifying epileptic seizures and epileptic syndromes

The appropriate diagnosis of the patient with epilepsy is first dependent on a determination of the type of seizure. When the type of seizure has been determined, consideration must be given to the nature of the epileptic syndrome, including concerns regarding the etiology of the attacks. The gradual evolution of the various classification schemes of epileptic seizures and epileptic syndromes complicates the task of the physician but also affords evidence of the dynamism extant in clinical epilepsy research. Intensive monitoring will assist not only in the diagnosis of the individual patient but also in the long-term re-evaluation and revision of the empirical classifications.     

Hidden focal EEG seizures during prolonged suppressions and high-amplitude bursts in early infantile epileptic encephalopathy.

OBJECTIVE: We report on a 27-month-old female with atypical early infantile epileptic encephalopathy (EIEE), who developed tonic spasms, partial seizures and myoclonic jerks along with episodic bradycardia at 5 days. METHODS: We recorded digital electroencephalography (EEG) using either an 11-channel neonatal montage or 19 channel scalp electrodes, at 200 Hz sampling rate, and a single reference for a minimum of 30 min. RESULTS: At 18 days EEG showed suppression-burst (SB) patterns during wakefulness and sleep. Tonic spasms concomitant with bursts recorded as brief, low-amplitude fast waves. EEG at 8 months showed increased amplitude of bursts to 1 mV and extension of suppression periods to 65 s. By increasing recording sensitivity, we detected focal epileptiform discharges of slow rhythmic sharp and slow waves building to 30 microV during suppression periods. Status epilepticus occurred at 16 months. EEG at 27 months returned to the previous SB pattern with rare partial seizures. CONCLUSIONS: This report is the first to demonstrate clinically silent focal EEG seizures during prolonged suppression periods in atypical EIEE by off-line digital EEG. SIGNIFICANCE: Digital EEG sensitivity can reveal covert electrical activity during suppression periods in epileptic neonates and infants.     

Tonic seizures: their significance for lateralization and frequency in different focal epileptic syndromes

PURPOSE: To determine whether the clinical features of tonic seizures (TSZ) are useful for lateralization of epileptic syndromes and the differential diagnosis of focal epileptic syndromes. METHODS: From a group of 481 patients, 123 patients with TSZ (44 females; mean age, 22.9 years; mean age at onset, 7 years; mean duration of epilepsy, 16 years) were selected. A total of 1595 epileptic seizures, documented during videoelectroencephalographic monitoring, were analyzed. Patients who had had surgery for epilepsy previously were excluded. Seizures were classified using a semiological seizure classification. Epilepsy syndromes were classified using all test data (electroencephalography, magnetic resonance imaging, computed tomography, positron emission tomography, and single-photon emission tomography). Data were compared using chi2 analysis or the Fisher exact test. RESULTS: More patients with TSZ had extratemporal than temporal lobe epilepsies (79% vs. 1.7%; p < 0.0001) among those with an epilepsy localized to one lobe (n = 306). In the 123 patients, TSZ were part of 170 different seizure evolutions. Seizure evolutions began with TSZ as the first seizure type more often in patients with frontal lobe epilepsy (FLE) compared with patients with parieto-occipital lobe epilepsy (POLE) (40% in POLE vs. 67% in FLE; p < 0.05). In contrast, TSZ in POLE were more likely to be preceded by auras (50% in POLE vs. 26% in FLE; p < 0.05). TSZ were bilateral in 129 (76%) and unilateral in 41 (24%) seizure evolutions. Unilateral TSZ correctly lateralized the epilepsy syndrome to the contralateral hemisphere. CONCLUSION: Analysis of seizure semiology and evolution in patients with TSZ is helpful for differentiating between focal epilepsies of temporal, frontal, and parieto-occipital origin. Unilateral TSZ provide useful information for the lateralization of the epileptic syndrome.     

EEG morphology of partial epileptic seizures

We studied the EEG features of partial seizures in 66 patients. An EEG evolution (morphology and/or frequency change) characterised 79% of attacks: 92% of 48 events with clinical features, but only 44% of 18 subclinical seizures. Aside from attenuation which initiated 7 seizures (11%), 31 (47%) began with sinusoidal waves, 25 (39%) with repetitive epileptiform potentials, and 10 (15%) with both phenomena. Metamorphosis between these forms occurred in about 1/3 of seizures beginning with either form alone. A wave form change occurred in 44% of clinical attacks but only 7% of subclinical seizures. Spikes and sharp waves were the most common repetitive epileptiform potentials encountered. Repetition rate of phenomena at onset usually lay in the theta or delta range except for a few with high frequency sinusoidal waves. Further ictal EEG progression was more likely to occur if a mixed frequency change or frequency increase characterised early evolution.     

Classification criteria of epileptic seizures and syndromes

Care must be exercised not to intermingle with classification of seizures and classification of epilepsies in an inconsistent fashion. Criteria for each class must be defined as clearly as possible, and these criteria must be those which are necessary for classifying any given case. The international classification first proposed by the ILAE in 1970 was an attempt to distinguish seizures from epilepsies; the seizure types defined in the 2001 diagnostic scheme are conceptually akin to the syndromes in the 1989 classification in the sense that they imply etiological, therapeutic, and prognostic significance. However, there exists no room in the new diagnostic scheme to accommodate electro-clinical seizure types, which have been used for more than three decades. The concept of epileptic syndrome in the 1989 classifications seems to have been changed to epileptic seizure type in the 2001 diagnostic scheme, and seizure type of the latter virtually becomes synonymous with epileptic syndrome of the former. In the 2001 diagnostic scheme, seizure type can be used to supplement syndrome, and can stand alone when syndrome diagnosis cannot be made. In other words, seizure types may replace syndromes, or vice versa. We should not return to an era prior to 1970 where no distinction exists between epilepsies and seizures. In a cohort of patients with active epilepsy, to what extent is syndrome classification applicable? In 300 consecutive patients hospitalized in a tertiary center, syndromic diagnosis was applicable to only 61%. Similarly, another 100 consecutive patients, classification of epilepsy was possible but not defined as a syndrome in 32% patients, according to the 1989 classification. The 1989 syndrome classification assigned in each category "other epilepsies not defined as a syndrome." These epilepsies are diagnosed only dichotomously; idiopathic focal or generalized, symptomatic focal or generalized, or undetermined whether focal or generalized. In other words, even if we could complete a list to include all the new syndromes that may exist, it is very unlikely that it would cover all epilepsies.     

Characterization of neonatal seizures by conventional EEG and single-channel EEG.

OBJECTIVE: To perform a detailed, contemporary temporal-spatial characterization of neonatal seizures (NS) and to compare conventional EEG (CEEG) to single-channel EEG for NS detection. METHODS: Digitally recorded CEEGs were reviewed for NS characteristics (quantity, duration, location of onset, peak-to-peak amplitude). The presence and characteristics of each NS were simultaneously noted in a single, derived EEG channel (C3-->C4). RESULTS: Eight hundred fifty-one seizures from 125 CEEGs recorded were analyzed. Mean seizure rate was 7.0 NS/h (range: 0.5-21). Mean seizure burden (percent time CEEG showed NS at any location) was 24.8% (range: 0.7-86.9). Seizure rate was only moderately correlated with seizure burden (Spearman coefficient=0.58). Eighty-one percent of NS originated from central-temporal or midline vertex electrodes. Seventy-eight percent of NS appeared in the C3-->C4 channel. CONCLUSIONS: Accurate measurement of NS burden requires detailed temporal-spatial characterization. The theoretical ceiling of sensitivity for NS detection in the single EEG channel C3-->C4 is high. However, further processing the raw EEG in limited electrode arrays may reduce the sensitivity of NS detection. SIGNIFICANCE: CEEG is the gold standard for NS detection. However, reduced montage EEG techniques are increasingly available. This detailed contemporary temporal-spatial characterization of NS evaluates the potential limitations of reduced montage techniques.     

Automatic recognition of epileptic seizures in the EEG

During prolonged EEG monitoring of epileptic patients, the continuous EEG tracing may be replaced by a selective recording of ictal and interictal epileptic activity. We have described previously methods for the EEG recording of seizures with overt clinical manifestations and for the automatic detection of spikes. This paper describes a method for the automatic detection of seizures in the EEG, independently of the presence of clinical signs; it is based on the decomposition of the EEG into elementary waves and the detection of paroxysmal bursts of rhythmic activity having a frequency between 3 and 20 c/sec. Simple procedures are used to measure the amplitude of waves relative to the background, their duration and rhythmicity. The evaluation of the method on 24 surface recordings (average duration 12.4 h) and 44 recordings from intracerebral electrodes (average duration 18.7 h) indicated that it was capable of recognizing numerous types of seizures. False detections due to non-epileptiform rhythmic EEG bursts and to artefacts were quite frequent but were not a serious problem because they did not unduly lengthen the EEG tracing and they could be easily identified by the electroencephalographer. The program can perform on-line and simultaneously the automatic recognition of spikes and of seizures in 16 channels.     

Vomiting as an ictal manifestation of epileptic seizures and syndromes.

Twenty-four out of 900 adult and children patients with epilepsy, were found to have vomiting during an ictus. All the 24 patients were children before puberty with a similar clinical pattern consisting of partial seizures which were mainly nocturnal. Ictal vomiting was always concurrent with other epileptic manifestations, more often deviation of the eyes and impairment of consciousness. The initial part of the ictus was short or prolonged for hours with frequent "marching" to hemi-convulsions and generalised seizures. Seventeen of the 24 children suffered from benign childhood epilepsies (BCE) with complete remission in long follow-up. A significantly higher association was found between ictal vomiting and the syndrome of BCE with occipital spikes (p less than 0.001) but not with centro-temporal spikes (p less than 0.2). The recognition of this association may have important theoretical implications. On clinical grounds, it may prevent unnecessary investigations and undue concern.     

International classification of epileptic seizures, epilepsies, and epileptic syndromes]

Epilepsy is one of the common diseases in neurology. Its correct diagnosis and classification are important for choosing the most appropriate treatment. Currently, Classification of Epileptic Seizures in 1981 and Classification of Epilepsies and Epileptic Syndromes in 1989, both were proposed by International League Against Epilepsy (ILAE), are available. As for Classification of Epilepsies and Epileptic Syndromes, two divisions continue to be widely used to shape the major classes: The first separates epilepsies with generalized seizures (generalized epilepsy) from epilepsies with partial or focal seizures (localization-related, partial or focal epilepsies). The other separates epilepsies of known etiology (symptomatic or secondary epilepsies) from those that are idiopathic (primary) and those that are cryptogenic. In 2001, ILAE Task Force proposed a new classification. However, its daily use has yet been limited. Simple and useful classification will lead to better understanding and more appropriate management of epilepsy.     

Classification of epileptic seizures and syndromes: new proposals

In the decade of 1980 the International League Against Epilepsy (ILAE) developed a classification system of epileptic seizures and syndromes. These classifications were established progressively and are presently used in all the world. In the following years, video-EEG monitoring became widely available and provided direct information about seizure semiology and ictal EEG that had not been so well understood during the development of the ILAE classifications. This new information demonstrated certain limitations of the old classification of epileptic seizures. In addition, improvements in brain imaging techniques and research in genetics added further information on the pathophysiology of epilepsies and epileptic syndromes. In order to integrate these advances into the practical management of epilepsies, new classification proposals have been developed. This article reviews the clinical implications of these new classifications.     

EEG findings in shunted hydrocephalic patients with epileptic seizures

The EEG findings in 40 shunted hydrocephalic patients tested after the onset of epileptic seizures are assessed. The salient point to emerge from the study is the higher frequency of anomalies, both specific (spikes, slow spikes, spike and wave complexes) and nonspecific (monomorphic and polymorphic slow waves) on the shunted hemisphere (19 cases) than on the unshunted side (8 cases). The lateralization of EEG anomalies on the shunted side in patients with no neurological deficits and no focal damage to the substance of the brain suggests that the EEG focus is in some way related to the presence of the shunt. Without denying the importance of the hydrocephalus etiology as a cause of epilepsy in shunted patients, we do think that, in some cases at least, epilepsy is to be regarded as a surgical complication.

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Sommario Sono stati valutati i reperti EEG di 40 pazienti idrocefalici portatori di derivazione liquorale extratecale controllati in seguito all'insorgenza di manifestazioni convulsive.Il dato principale emergente dallo studio è rappresentato da una prevalenza di anomalie sia specifiche (punte, punte lente, punte onda) sia non specifiche (onde lente mono e polimorfe) sull'emisfero derivato (19 volte) rispetto a quello non derivato (8 volte).La lateralizzazione delle anomalie EEG sull'emisfero ove è presente il catetere di derivazione in casi nei quali l'esame neurologico è normale e non sono presenti danni parenchimali focali fa ritenere che il focolaio EEG sia in qualche modo correlabile con la presenza della derivazione.Senza negare l'importanza dell'etiologia come causa di Epilessia nei pazienti idrocefalici gli AA. ritengono che, almeno in una parte dei casi, l'Epilessia debba essere considerata come una complicanza chirurgica.

     

Interictal sharp EEG transients in neonatal seizures

This study describes the differences between several quantifiable variables that characterize interictal sharp EEG transients (SETS) recorded from neurologically ill neonates with proven electrographic seizures and a comparison group of apparently neurologically well babies with no known seizures. The abundance (number of sharp EEG transients per ten minutes), waveform morphology, repetitive behavior, and spatial distribution of SETS provide interpretive guidelines that help discriminate between these two patient populations.     

Epilepsies and epileptic syndromes starting in the neonatal period

As seizures in the neonatal period have generally been identified only by direct clinical observation, there is frequently a lack of objectivity as to whether seizures are categorized as epilepsies or non-epilepsies. A major characteristic of neonatal seizures is electro-clinical dissociation and some electro-graphic seizures do not produce clinical symptoms. It is difficult to correctly identify real epilepsies or epileptic syndromes in the neonatal period without ictal electroencephalogram (EEG). Some epileptic syndromes starting in the neonatal period such as early myoclonic encephalopathy, Ohtahara syndrome, or migrating partial seizures in infancy are categorized as malignant epilepsies. A suppression-burst EEG pattern (SBP) is usually seen in neonates with serious brain damage, malignant epileptic syndromes or other neurological conditions. However SBP has not been consistently defined in the literature. We review malignant epilepsies and benign familial and non-familial neonatal seizures starting in the neonatal period and propose the characteristics of SBP in Ohtahara syndrome. Epileptic encephalopathies with SBP in the neonatal period are known to evolve into relatively few types of epileptic syndromes. We emphasize the importance of ictal EEG for diagnosis and treatment of malignant epilepsies and epileptic syndromes in the neonatal period.