Significance of positive temporal sharp waves in the neonatal electroencephalogram

CARFS7: A guide and proforma for reading a preterm neonate's EEG

OBJECTIVES

The important role of the EEG in preterm and term babies in investigating brain function and seizures, predicting outcomes, evaluating therapeutic interventions and decision-making is being increasingly acknowledged. Development of the brain in the last trimester of pregnancy results in rapid changes in the EEG patterns in this period. Acquiring and interpreting the EEG of a preterm baby can be challenging. The aim of this study was to develop a proforma titled CARFS⁷ (Continuity, Amplitude, Reactivity, Frequency, Synchrony, Symmetry, Sleep, Sharps, Shapes, Size and Seizures) to enable neurologists to read EEGs of premature babies with greater confidence, ease and accuracy and produce a report more easily repeatable and homogenous among operators.

METHODS

The CARFS⁷proforma was developed based on a literature review and the personal experience of the authors. The parameters of the EEG evaluated and scored in the proforma are Continuity, Amplitude, Reactivity/Variability, Frequency, Synchrony, Symmetry, Sleep, Sharps, Shapes/Patterns, Size and Seizures. We also assessed the interrater reliability of the proposed scoring system incorporated in the proforma.

RESULTS

CARFS⁷ proforma incorporates a number of parameters that help evaluate the preterm EEG. The interrater reliability of the proposed scoring system in the CARFS⁷proforma was high.

CONCLUSIONS

CARFS⁷ is a user friendly proforma for reading EEGs in the preterm infant. Interrater reliability using Cohen's k shows high agreement between two child neurologists who independently rated the EEGs of 25 premature babies using this proforma. CARFS⁷ has the potential to provide, accurate, reproducible and valuable information on brain function in the preterm infant in clinical practice.

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.

Significance of background activity and positive sharp waves in neonatal electroencephalogram as prognostic of cerebral palsy

OBJECTIVE

To study the significance of electroencephalographic background activity and positive sharp waves in neonatal electroencephalogram as prognostic of cerebral palsy.

METHOD

We studied prospectively and sequentially 73 newborns who had severe neonatal complications (neonatal anoxia, seizures, respiratory distress, sepsis, and meningitis). Nineteen newborns were excluded and 54 children formed the object of our study and were followed for 2 years. We analyzed gestational age, conceptional age, electroencephalographic background activity and positive sharp waves, which were correlated with cerebral palsy.

RESULTS

There were no statistically significant correlation between gestational age and conceptional age and cerebral palsy; the electroencephalographic background activity was correlated with cerebral palsy as well as the positive sharp waves.

CONCLUSION

Children with electroencephalographic background activity markedly abnormal and accompanied by positive sharp waves were associated with a worse prognosis.

Positive temporal sharp waves in preterm infants with and without brain ultrasound lesions

OBJECTIVE

Clinical significance of neonatal positive temporal sharp waves (PTS) is controversial. The aim of this work is to study (1) PTS incidence in preterm infants with or without major ultrasound lesion (MUL) per gestational age (GA), and (2) the relationship between PTS in both sleep states and other electroencephalographic (EEG) findings with poor prognoses.

METHODS

97 preterm infants of <27-36 weeks GA, and 12 full-term healthy infants were presented. Prospective study included (1) neurodevelopmental assessment at 40-42 weeks conceptional age (CA), (2) serial neurosonography, and (3) EEG recording at postnatal week 1, 2, 4 and at 40-42 weeks CA.

RESULTS

In 50 neonates without MUL, peak PTS was at 31-32 weeks GA. In 47 neonates with MUL, PTS increased significantly from week 2 after birth, descending at the 4th. Neonates of <33 weeks GA with MUL showed significantly increased PTS at term. A significant relationship was found between PTS and other EEG abnormalities with poor neurologic prognoses. PTS incidence varied with sleep states, being predominant in indeterminate sleep in neonates with MUL.

CONCLUSIONS

PTS increased significantly in infants with MUL, mainly at week 2 of postnatal life, persisting high until term CA, and correlated with other abnormal EEG findings.

SIGNIFICANCE

PTS are highly sensitive to MUL.

[EEG and ischemic stroke in full-term newborns]

The aims of this study were to describe EEG anomalies in unilateral neonatal ischemic stroke without hypoxic-ischemic encephalopathy, and to determine possible links between these abnormalities and long-term outcome. In 6 full-term newborns without severe fetal distress ischemic stroke was confirmed by computed tomography and/or magnetic resonance imaging. Twenty EEGs were recorded during the neonatal period, 5 in acute stage and 15 later. The duration of the follow-up ranged from 3 to 9 years. All newborns developed unilateral clonic seizures, right-sided (5 cases) or left-sided (1 case); seizures began between 14 and 48 h of life. At follow-up, 3 children were normal at 2 and 6 years of age, while the 3 others had sequelae: epilepsy at 9 years of age in one, and unilateral mild cerebral palsy in the 2 others (3 and 4 years of age), with behavioral problems in one of them. Critical EEG discharges, rhythmic sharp waves and/or slow waves were recorded on the injured side. Abnormalities of interictal activity were excess of alpha or theta rhythms, transitory EEG discontinuity or low voltage. The 2 children with cerebral palsy had numerous unilateral post-ictal positive rolandic slow sharp waves (PRSSWs), which were similar to the positive rolandic sharp waves of premature infants; the child with behavioral problems had numerous positive left-sided temporal fast sharp waves. PRSSWs could be associated with contralateral motor sequelae, while positive left temporal fast sharp waves were associated with long term behavioral problems. These findings may be used for future prospective studies aimed at specifying the relation between EEG abnormalities and long-term outcome.

Polysomnography in neonatal seizures

Seizures are one of the most frequent problems in the neonatal period, and are frequently associated with high mortality and morbidity rates. On the other hand, neonatal seizures may represent a first or even the only sign of central nervous system dysfunction. However, establishing the diagnosis of neonatal seizures poses several problems, and clinical observation is not sufficient in many cases. Neonatal polysomnography is a valuable tool both in the diagnostic and in the prognostic assessment of neonatal seizures. The present text reviews some technical aspects related to neonatal polysomnographies, and its usefulness in the area of suspected neonatal seizures. Moreover, some questions are raised regarding rhythmic discharges and their significance as a possible ictal and interictal epileptic pattern in the neonate.

Electroencephalography in infants with periventricular leukomalacia: prognostic features at preterm and term age

Cystic periventricular leukomalacia represents the most severe white-matter lesion in preterm infants and its occurrence accounts for most cases of neurologic impairment in these subjects. Electroencephalographic (EEG) findings and their prognostic value in relation to motor and cognitive outcome were investigated in a group of preterm infants affected by different degrees of cystic periventricular leukomalacia. EEG recordings were carried out in the early postnatal period (first 2 weeks of life) on 24 infants and at term age on 29. In the early postnatal period, background EEG abnormalities ("dysmaturity") were significantly more apparent in affected infants than in a control group, and, among infants with cystic periventricular leukomalacia, this parameter related to the occurrence of cerebral palsy; moreover, at the same age, the incidence of abnormal EEG transients seemed to show a correlation with cognitive outcome. At term age, these latter abnormalities were significantly more apparent in neonates with cystic periventricular leukomalacia than in control subjects, but they did not show any prognostic value. In conclusion, these data indicate that, during the early postnatal period, the EEG is a useful diagnostic and prognostic tool for preterm infants with white-matter lesions, whereas at term age, the role of EEG tracings appears secondary.

Neonatal EEG: a powerful tool in the assessment of brain damage in preterm infants

Serial EEG recordings beginning immediately after birth are not only of great diagnostic and prognostic value but also useful to elucidate the timing and the mode of brain injuries in the preterm newborn. It is extremely useful to distinguish between acute stage and chronic stage EEG abnormalities. The former is characterized by findings of acute depression such as increased discontinuity, decreased faster frequency activities, and lowered amplitudes. The latter mainly includes dysmature patterns and disorganized patterns. The timing of brain insult can be assessed by considering EEG findings in relation to the time of birth. Different modes of brain injury are associated with different types of EEG abnormalities and different types of neurological outcome. Sudden strong brain insults are usually associated with findings of severe depression followed by disorganized pattern and later cerebral palsy, while persistent mild insults are usually associated with prolonged mild depression followed by dysmature pattern and later mental retardation. Routine serial EEG studies in preterm infants demonstrated that one fourth of cerebral palsies in these infants were of antenatal origin, two thirds of perinatal origin and postnatal injuries played the least role. Periventricular leucomalacia (PVL) manifesting itself on the ultrasound in the late neonatal period and suggesting postnatal origin was often found to be of antenatal origin with an EEG soon after birth. PVL without apparent causes was often associated with abnormal fetal heart rate patterns and early neonatal EEG abnormalities, and considered to have originated in the antepartum period.

A new way of building a database of EEG findings

Whereas computer-based electroencephalography (EEG) is widely applied, the EEG interpretations are usually not stored in a way that favours exploitation of modern computer technology. This paper reports an EEG description system facilitating categorization of EEG data in a computerized database. The system interactively communicates with the digital EEG system and also with the general patient administrative system. The main new quality of this system is the methods for data input and automatic data retrieval from several systems, rather than the establishment of a database of EEG data itself. The EEGs are visually analysed and categorized. Manually marked EEG events are automatically transferred to the database and such events as well as defined electrode positions within these epochs are directly linked to their corresponding descriptions. The database is updated without demand for filling in the events in the database in a second operation. Thereby, the EEG interpreter builds the database while analysing the EEG. This system provides an improved accessibility of EEG data for clinical, normative, educational and scientific use.

[Electroencephalography of the premature and term newborn. Maturational aspects and glossary]

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.

[Indications for emergency EEG in perinatal pain]

EEG is a basic tool in neurological evaluation of fullterm or premature newborn. An emergency recording (in hours following birth) is required in two circumstances: a suspicion of seizure (especially before starting specific therapy), and a major behavioral disorder. The main cause is, in fullterm newborn, hypoxic-ischemic encephalopathy. More precise informations are provided by recording between 10 and 48 hours after birth. In premature, emergency EEG may be recorded between 24 and 48 hours after birth. Some particular EEG features suggest specific causes such as metabolic or infectious diseases and focal lesions. In some cases, especially during seizures, conventional EEG can be completed by continuous monitoring.

[Intraventricular hemorrhage and parenchymatous ischemia in the newborn at term. Report of five cases]

Although intraventricular hemorrhage associated with cerebral ischemia without severe perinatal asphyxia is rare in full-term newborns, it can be severe, have early or late onset depending on the etiology and be of poor prognosis. Five full-term neonates (37 to 41 weeks of gestational age) without criteria of severe perinatal asphyxia were admitted to the intensive care unit for seizures: four were between seven and 11 days of age and one was only 12 h old. Clinical or electroclinical seizures recorded by continuous EEG monitoring were numerous, leading to status epilepticus in three babies. They were unilateral (at the level of the left hemisphere) in one infant and have not been recorded in the fourth case. Past-ictal EEG abnormalities were numerous rolandic or temporal slow or fast sharp waves of variable polarity. Cranial CT scans showed uni- or bilateral intraventricular hemorrhage with dilatation and subcortical or periventricular ischemic lesions with hemorrhage. Four out of the five infants died during the neonatal period.

Prognostic value of abnormal EEG transients in preterm and full-term neonates

The prognostic value of abnormal EEG transients was investigated in 362 subjects submitted to EEG recording during the neonatal age and followed-up at least until the 12th month of corrected age. The incidence of negative and positive spikes and sharp waves, of rhythmic sharp theta and delta activities and of alpha discharges were evaluated by means of a quantitative score. These abnormal EEG transients appeared to be generally rare and even absent in a large number of subjects. In infants with normal outcome their incidence tends to increase from low postmenstrual ages towards term period. Full-term newborns with abnormal neurological outcome presented a significantly higher incidence of these transients. Preterm infants with unfavourable evolution showed a higher incidence only when submitted to EEG recording at around term age. However, no difference between subjects with normal and abnormal outcome was detected in preterm infants when evaluated at low postmenstrual ages. The hypothesis that at low postmenstrual ages brain damage might, on the one hand, give rise to abnormal transients and, on the other, alter the "capability' of manifesting them (together with other EEG maturational aspects), might explain these results.

Positive temporal sharp waves in electroencephalograms of the premature newborn

Positive temporal sharp waves (PTS) were studied in electroencephalograms (EEG) of 92 premature infants born either at 31 and 32 weeks of gestational age, recorded during the first week of life. The infants were assigned either to a reference group (asymptomatic) or to one of three pathologic groups (neonatal asphyxia, hypoglycemia or hypocalcemia, or periventricular leukomalacia with rolandic positive sharp waves). Regardless of the group, no significant differences in PTS criteria (morphology, frequency, amplitude, duration and lateralization) were found between 31- and 32-week infants. The PTS observed in 55% of the asymptomatic infants were characterized by low frequency (0.13 +/- 0.12/min), a mean amplitude of 109.8 +/- 25.8 microV and a mean duration of 148.7 +/- 35.4 ms. For PTS recorded in 72 to 75% of pathologic infants, mean duration and amplitude were significantly greater in all groups than in asymptomatic infants, whereas frequency was significantly greater only in the group presenting with asphyxia. Discriminant analysis based on the three PTS criteria (frequency, amplitude and duration) allowed correct classification for only 30 to 54% of infants in the four groups. The frequency of PTS decreased rapidly during the second week of life in asymptomatic infants, but persisted in a larger number of infants in the pathologic groups. This study shows that PTS have no negative significance when they are few in number, short in duration, moderate in amplitude and rapidly regressive, thus probably reflecting the vulnerability of the temporal lobe during the traumatic period of birth. However, they require attention when they are abundant and/or slow, ample or tend to persist. They may thus constitute a nonspecific response to injury to an immature brain.

The use of the EEG to predict outcome in premature infants with positive sharp waves

The goal of this study was to investigate the factors that could predict prognosis in 51 premature infants with positive sharp waves on their EEGs (gestational age 23-36 wks) with 114 tracings. Follow-up clinical examinations were conducted, up to 10 yrs later. Death occurred in 18%, from a non-CNS cause, either sepsis or a congenital cardiac or pulmonary defect. A severe outcome was seen in 8% and was related to maternal i.v. drug abuse (IVDA) and the presence of many positive sharp waves. A moderate outcome, noted in 29%, was associated with a Grade III-IV intracerebral hemorrhage (ICH) or periventricular leukomalacia (PVL) and maternal IVDA. A mild outcome seen in 20% was related to infrequent positive sharp waves, vaginal delivery and an improving EEG over time, while a normal outcome (26%) was also related to infrequent discharges, a normalized EEG over time, a normal sonogram and the absence of clinical seizures. The addition of negative sharp waves to the positive ones and the addition of central to temporal positive sharp waves were associated less often with a normal outcome. The general conclusion of this study was that various aspects of positive sharp waves in premature infants, in addition to other factors, can be used to predict outcome in these neonates.

Background EEG activity in preterm infants: correlation of outcome with selected maturational features

The aim of this study is to identify normal EEG patterns of preterm infants, characteristic of early postmenstrual ages (PMAs). Quantitative features of EEG background activity have been examined in records from 83 preterm infants within the first 2 weeks of life at a PMA of 27-34 weeks. These subjects presented different cranial ultrasound findings and different outcomes. EEG quantitative data have been compared to the subsequent neurological evolution. We supposed that the features of EEG background activity which were associated with a favourable outcome should be considered as indexes of "normality" of the tracing for that specific PMA. At 27-30 weeks of PMA a high incidence of "temporal sawtooth," a particular rhythmic theta activity detectable in temporal regions, relates to a favourable evolution, therefore it can be assumed that this activity is a normal feature of EEG tracings at this age. On the contrary, a significant correlation between a high incidence of "temporal sawtooth" and an abnormal outcome is observable at 33-34 weeks and leads us to deduce that this pattern should disappear at this time. After 31 weeks other parameters (such as the incidence of 8-20 Hz activities, the length of the intervals and burst duration) show a significant correlation with the outcome.

Positive temporal sharp waves on EEG recordings of healthy neonates: a benign pattern of dysmaturity in pre-term infants at post-conceptional term ages

One complete sleep cycle was selected in each of ninety-four 3 h EEG recordings on 52 healthy neonates from 29 to 43 weeks CA (28 pre-term (PT)/24 full-term (FT)); 51 who are neurodevelopmentally normal up to at least 18 months of age. Each recording was reviewed to identify positive temporal sharp waves (PTS). This wave form was compared to another commonly occurring wave form, temporal theta of prematurity (PT theta). 588 PTS and 626 PT theta observations were tabulated in terms of frequency, amplitude, morphology, left:right predominance, and sleep state at 6 post-conceptional age ranges up to term. Mean PTS for FT, PT and pre-term at post-conceptional term age (PTT) infants, respectively, were 1.5 +/- 0.85, 2.8 +/- 2.5, 2.0 +/- 1.6 per sleep cycle. PTS amplitudes (microV) were 59.7 +/- 23.5, 38.2 +/- 17.8, and 51.8 +/- 29.3. The peak incidence of PTS occurs at older post-conceptional ages than PT theta (r = 0.21, P = 0.0001). PTT infants had more PTS (chi 2 = 32.5, P = 0.001) than FT infants. Similar numbers and descriptions of PT theta were noted between neonatal groups at post-conceptional term ages. While pathological PTS waves have been described in FT neonates and infants (Chung and Clancy: Electroenceph. clin. Neurophysiol., 1991, 79: 256-263), benign PTS waves are also present on recordings of healthy pre-term and full-term neonates. PTS are electrographically similar to PT theta, but are more abundant at older post-conceptional ages in pre-term infants than full-term infants.(ABSTRACT TRUNCATED AT 250 WORDS)

[Maturation and neurological distress in the newborn]

In the newborn, structural and functional cerebral abnormalities are described as well as clinical manifestations of neurological distress, change with gestational age, and therefore with the degree of central nervous system maturation. The different maturational stages of the cerebral structure, their vascularization and myelinization from the gestational age of 24-25 weeks to the full-term neonate are briefly reported. The cerebral lesions and mechanisms of hypoxoischemic encephalopathy in the full-term neonate are summarized; an analysis of the various clinical symptoms and additional investigations (in particular the electroencephalogram) allows a precise prognosis to be made. In the premature newborn, there are 2 types of cerebral lesions: intraventricular hemorrhage and periventricular leukomalacia. The latter is primarily responsible for neurological sequelae. Clinical manifestations are poor and atypical; data based on complementary procedures (imaging and electroencephalography) allow an accurate evaluation to be made of the damage and neurological prognosis.