Electroencephalography in premature and full-term infants. Developmental features and glossary.

Following the pioneering work of C. Dreyfus-Brisac and N. Monod, research into neonatal electroencephalography (EEG) has developed tremendously in France. French neurophysiologists who had been trained in Paris (France) collaborated on a joint project on the introduction, development, and currently available neonatal EEG recording techniques. They assessed the analytical criteria for the different maturational stages and standardized neonatal EEG terminology on the basis of the large amount of data available in the French and the English literature. The results of their work were presented in 1999. Since the first edition, technology has moved towards the widespread use of digitized recordings. Although the data obtained with analog recordings can be applied to digitized EEG tracings, the present edition, including new published data, is illustrated with digitized recordings. Herein, the reader can find a comprehensive description of EEG features and neonatal behavioural states at different gestational ages, and also a definition of the main aspects and patterns of both pathological and normal EEGs, presented in glossary form. In both sections, numerous illustrations have been provided. This precise neonatal EEG terminology should improve homogeneity in the analysis of neonatal EEG recordings, and facilitate the setting up of multicentric studies on certain aspects of normal EEG recordings and various pathological patterns.

Pathological features of neonatal EEG in preterm babies born before 30 weeks of gestationnal age.

Pathological features on very premature EEG concern background abnormalities and abnormal ictal and nonictal patterns. Positive rolandic sharp waves keep an important place regarding diagnosis and prognosis of white-matter lesions. Background abnormalities, that may be classified as acute-stage or chronic-stage abnormalities, give essential complementary information. These abnormal patterns remain precocious markers of cerebral lesions and are complementary to cerebral imaging. Analysis of these abnormalities has always to take into account medication received by the baby during the recording and that could modify the EEG.

[Pathological patterns in neonatal EEG before 30 weeks of gestational age]. / Les aspects pathologiques de l'EEG du nouveau-né prématuré avant 30 semaines d'âge postmenstruel.

Pathological features on very premature EEG concern background abnormalities and abnormal patterns. Positive rolandic sharp waves keep an important place regarding diagnosis and prognosis. Background abnormalities give essential complementary informations. Unusual patterns (abnormal localisation or morphological aspect, high amplitude) remain early markers of cerebral lesions. Analysis of these pathological features must always take into account treatment given to the baby, which can by itself modify the EEG.

[Indications of electroencephalogram in the newborn]. / Indications de l'électroencéphalogramme en période néonatale. Recommandations du groupe de neurophysiologie clinique de l'enfant.

The electroencephalogram (EEG), an easy-to-use and non invasive cerebral investigation, is a useful tool for diagnosis and early prognosis in newborn babies. In newborn full term babies manifesting abnormal clinical signs, EEG can point focal lesions or specific aetiology. EEG background activity and sleep organization have a high prognostic value. Tracings recorded over long period can detect seizures, with or without clinical manifestations, and differentiate them from paroxysmal non epileptic movements. The EEG should therefore be recorded at the beginning of the first symptoms, and if possible before any seizure treatment. When used as a neonatal prognostic tool, EEG background activity is classified as normal, abnormal (type A and type B discontinuous and hyperactive rapid tracing) or highly abnormal (inactive, paroxysmal, low voltage plus theta tracing). In such cases, the initial recording must be made between 12 and 48 h after birth, and then between 4 and 8 days of life. Severe EEG abnormalities before 12 h of life have no reliable prognostic value but may help in the choice of early neuroprotective treatment of acute cerebral hypoxia-ischemia. During presumed hypoxic-ischemic encephalopathy, unusual EEG patterns may indicate another diagnosis. In premature newborn babies (29-32 w GA) with neurological abnormalities, EEG use is the same as in term newborns. Without any neurological abnormal sign, EEG requirements depend on GA and the mother's or child's risk factors. Before 28 w GA, when looking for positive rolandic sharp waves (PRSW), EEG records are to be acquired systematically at D2-D3, D7-D8, 31-32 and 36 w GA. It is well known that numerous and persistent PRSW are related to periventricular leukomalacia (PVL) and indicate a bad prognosis. In babies born after 32 GA with clinically severe symptoms, an EEG should be performed before D7. Background activity, organization and maturation of the tracing are valuable diagnosis and prognosis indicators. These recommendations are designed (1) to get a maximum of precise informations from a limited number of tracings and (2) to standardize practices and thus facilitate comparisons and multicenter studies.

[Electroencephalography of the premature and term newborn. Maturational aspects and glossary]. / Electroencéphalographie du nouveau-né prématuré et à terme. Aspects maturatifs et glossaire.

From the first publication of C. Dreyfus-Brisac and N. Monod, a strong tradition combined with tremendous development of neonatal EEG has taken place in France. After 3 years of collaborative work, 12 clinical neurophysiologists trained at the Port-Royal medical school in Paris detail in this paper the currently available neonatal EEG recording techniques. They have synthesized the criteria of maturational state analysis and have defined the normal and pathological neonatal EEG patterns, including descriptions already present in the French as well as the English literature. In this review one may find a complete description of neonatal EEG patterns according to the states of vigilance and to gestational age. Furthermore, definitions of all normal and pathological patterns are provided in a glossary. Both chapters are illustrated by numerous figures. This detailed terminology in neonatal EEG should allow a better homogeneity in EEG reports, and could lead to multicentric studies on normal, unusual or pathological patterns, according to etiology. Although based on analogic EEG data, this work can equally be applied to digitized EEG tracings.

Hemifacial spasm or subcortical epilepsy?

A child with Goldenhar's syndrome presented at about one week of age with stereotyped, repetitive paroxysmal episodes of hemifacial contraction, suggestive of partial seizures or hemifacial spasm. Later in life he also developed independent, permanent abnormal eye and chin movements identical in rhythm to those seen in myorhythmias, suggesting involvement of the dentato-olivary pathway. MRI demonstrated a hamartomatous lesion at the level of the pontomedullary junction. We speculate that the nature of the lesion could be responsible for the partial seizures mimicking hemifacial spasm and that because of its location, this same lesion could also be implicated in the genesis of myorhythmias. The presence of a hamartomatous lesion in a region affected by the abnormal development of the first and second branchial arches is not fortuitous.

[Diagnosis of brain death in the newborn and the child]. / Diagnostic de la mort cérébrale chez le nouveau-né et l'enfant.

The purpose of this article was to sum up the problems raised by diagnosis of brain death in the child through a review of the literature. The clinical and paraclinical criteria of the diagnosis are considered in terms of the respective value and complementarity of different examinations. The fact that organ removal has become increasingly frequent in the child requires a rapid and reliable determination of the irreversibility of brain damage. The guidelines set up after conferences in which American authors participated to reach a consensus opinion relate to the child's age, the etiology, of the coma and the results of various paraclinical examinations. The diagnostic value of these examinations is assessed and the limitations of the various approaches are considered, particularly as regards certain etiologies in the newborn. It is suggested that it would be useful to inquire into the different diagnostic means used in France with respect to this difficult problem. Finally, the ethical and moral problems raised by some recent practices such as organ removal in anencephalic patients are discussed.

[Brain abscess in the newborn infant (27 cases: initial electroclinical study, course]. / Abcès cérébraux néo-nataux (27 cas): étude électroclinique initiale, évolution.

The authors studied 27 brain abscesses in neonates. The neonates were divided in two groups: neonates with seizures and neonates without seizures. The authors tested the diagnostic and predictive value of the initial EEG aspect. They noted the absence of correlation between EEG focal abnormalities and localizations shown by the CT scan. They observed a severe electroclinical evolution in more than fifty percent of the cases presented.

[Herpetic encephalitis: prognostic elements in adults and children (49 cases)]. / Encéphalite herpétique: éléments de pronostic chez l'adulte et l'enfant (49 cas).

In 49 cases (26 children, 23 adults) of proven Herpes simplex encephalitis, the authors studied the influence of age, disturbances of consciousness, time of diagnosis and therapy on patients' outcome, as well as the prognostic value of EEG data. Mortality was low in late childhood and young adulthood in spite of the constancy and depth of coma; it was very high in newborns and adults over 40 years of age and it was always correlated with the severeness of initial consciousness disturbances. The onset of periodic complexes (in 65% of the children and 78% of adults on the first EEG) does not systematically imply a poor outcome. Correlations between these EEG patterns and bioptic or surgical data tend to prove that these periodic complexes are already present in a prenecrotic state. Reversibility may be complete. On the other hand, the association between a contralateral focus or diffusion of initial abnormalities and an early coma imply a poor prognosis (12 deaths and 2 major sequellae in 14 cases). The importance of early presumptive diagnosis and therapeutical onset is stressed. The only cases of complete recovery are found among young adults treated early (surgery for older cases) thanks to an initial typical EEG. In young children, first clinical symptoms are often not evocative. Great importance should be attached to the onset of partial seizures and interictal loss of consciousness in a feverish child (24 out of 26 cases). Antiviral therapy should be started as soon as a Herpes simplex encephalitis is suspected, since the new antiviral drugs have a relatively low toxicity and do not interfere with the immunological diagnosis.

[Significance of discontinuous traces in the full-term newborn infant]. / Significations du tracé discontinu chez le nouveau-né à terme.

This article is devoted to a consideration of the clinical prognostic significance of "tracé discontinu". The authors first distinguish "tracé discontinu" from the "tracé paroxystique" and tracé alternant" patterns in the newborn. The distinction is very important. The bad prognosis of the "tracé paroxystique" is well known, but prognosis of the "tracé discontinu" seems to be different. If the "tracé discontinu" is permanent, there was a 50% favourable outcome in our 22 newborn babies brought to the reanimation department. If some continuous activity can be observed: beginning of sleep organisation, then the prognosis seems to be better: 61% of our cases. As blood levels of anticonvulsants are rarely measured it seems difficult, given our present knowledge, to appreciate anticonvulsive drug effects on EEG recordings. Thus 3 aims should be pointed out: --Measurements of anticonvulsant blood level each time a "tracé discontinu" is observed in a treated newborn. --Early EEG recordings of sufficient duration to obtain eventually some continuous tracing. --Correct differentiation between "tracé paroxystique" and "tracé discontinu" for the clinician: "tracé discontinu" in a full-term newborn should never allow the paediatrician to stop treatment.

[Fast rhythms in metabolic diseases in children]. / Les rythmes rapides dans les maladies métaboliques chez l'enfant.

The authors study fast EEG rhythms in amino acidopathies of the newborn and in progressive encephalopathy of the central nervous system in children, when an inborn error of metabolism has either been found or is suspected. In the first group: amino acidopathies (including phenylketonuria), fast rhythms on the EEG of the neonates are of low amplitude, spindle-like bursts of 7-13 Hz and usually located in rolandic areas. This activity progressively disappears. Later, fast rhythms of beta-frequency and low voltage are spread on the whole scalp with a normal EEG organisation. They are seen in the favourable or rather favourable development of children receiving a diet. In the second group: progressive encephalopathy of the central nervous system, fast rhythms of 14-24 Hz appearing at a rather late stage of the disease, while the normal background activity completely disappears. In neuro-axonal dystrophy, where they are considered as 'specific,' they are of very high voltage, i.e., 50-200 microV. The authors insist on the importance of EEG fast rhythms both in amino acidopathies of the newborn, as a contributive factor to diagnosis and prognosis, and in progressive encephalopathies of the central nervous system, as a valuable tool in the diagnosis of numerous affections.

[Convulsive seizures in the neonatal metabolic diseases (author's transl)]. / Les crises convulsives dans les maladies metaboliques a revelation neo-natale.

Of 61 newborns with disorders in amino acid metabolism, 20 had seizures; 15 of them have been recorded. Clinically, seizures are mostly partial clonic jerks. There seems to be some homogeneity of EEG features in relation to causal amino acidopathy. In every case where seizures, either electroclinical or only infraclinical, occurred the evolution was very poor, even in those diseases that would have had a good prognosis. Therefore the EEG in the newborns is especially interesting, both as an aid to diagnosis by interictal recording and as a prognostic tool by registration of seizures.

[The E.E.G. in non-ketotic hyperglycinaemia (author's transl)]. / l'E.E.G. dans les hyperglycinémies sans cétose.

12 cases of non-ketotic hyperglycinemia in neonates diagnosed at a time of neurological distress were studied. A characteristic tracing was observed permitting correct diagnosis in 6 cases. It consisted of a burst suppression characterized by high voltage complexes separated by low amplitude sequences. This appearance remained until the 15th day, with no electroclinical changes. In cases followed the trace closely resembled hypsarrhythmia.

[E.E.G. appearances in hyperphenylalaninaemia (author's transl)]. / Aspects évoluties de l'E.E.G. dans les hyperphénylalaninémies.

Since 1973 the authors have studied the EEG appearances in hyperphenylalaninaemia : 82 children were studied, comprising : 68 children with phenylketonuria, 33 of whom had been treated within the first 3 months of life, whilst 35 had only started therapy after 9 months; 14 patients with hyperphenylalaninaemia. The morphological appearances seen commonly were compared with those described in the literature: the abnormalities and maturational changes were observed, including background rhythm changes, characteristic appearance of high amplitude, sharp spindles and percentages of generalised fast rhythms. Incidence of re-evaluation tests was also studied. Serial changes represented the most important aspect of this study, correlations being possible between the tracings and the child's development. The effects of correct dietary management, nonadherence to treatment, and the changes occurring on stopping treatment were also assessed. An assessment of the value of the EEG in following these cases could thus be made.

[The E.E.G. in methylmalonic acidaemia (author's transl)]. / l'E.E.G. dans les acidémies méthylmaloniques.

The EEG study was carried out on 8 cases of methylmalonic acidaemia, in the neonatal period (3 cases), developing later with a ketotic coma, hyperglycinemia, hyperammonaemia, leucopenia and thrombocytopenia (3 cases) and detected before birth (2 cases). The tracings of the neonates in the first group had a periodic appearance. The 2 children detected pre-natally had essentially normal EEGs bar a slightly faster rhythm. The tracings of the children in ketotic coma were similar to those seen in metabolic coma of other cause. The value of this study was, besides characterizing the EEC pattern which resembled that seen in other metabolic illnesses in the neonatal period, to study the changes in the EEG trace and their improvement during dialysis treatment. In one case recordings were made throughout the duration of dialysis.