Review articleNeonatal EEG: a powerful tool in the assessment of brain damage in preterm infants☆
Introduction
The recent increase in the survival rate of very preterm infants has resulted in an increasing incidence of neurological sequelae in these infants. The major neuropathological lesions in such infants are periventricular leucomalacia (PVL) and periventricular hemorrhagic infarction, which later manifest clinically as spastic diplegia and hemiparesis, respectively. Periventricular hemorrhage (PVH) is another neurological complication. Cognitive dysfunction is another important neurological sequlela in these infants. The elucidation of the pathogenesis and the timing of brain injuries in these preterm infants is of the utmost importance to prevent them. Neonatal EEG is a powerful, non-invasive tool for the diagnosis and the assessment of prognosis of brain injuries in the preterm infant. Serial EEG recordings beginning immediately after birth are particularly useful to assess the timing and the mode of brain injuries and to elucidate their pathogenesis in young preterm infants. Various computer analyses have been applied to neonatal EEGs and have proved useful to investigate normal and abnormal developmental neurophysiology of the immature brain, but this review deals with findings obtained mainly with conventional EEG recordings, because they are easily performed and more useful in the assessment of brain injuries in an individual infant.
Section snippets
Normal EEGs of preterm infants
The development of the brain in the last trimester of pregnancy is reflected in the rapid evolutionary changes of EEG patterns in this period. The EEG changes with behavioral state cycles, which also show an increasing organization with advancing conceptional age (CA). For the proper assessment of neonatal EEGs, therefore, it is mandatory to record at least EEGs of active sleep and quiet sleep. In infants under 30 weeks of CA spending most of their time in indeterminate sleep, a record of
Abnormal EEGs of preterm infants
Various classification systems have been reported for abnormal EEGs of the preterm infant [5], [22], [23], [24], [25], [26]. Holmes and Lombroso (1993) [27] divided background EEG abnormalities of the newborn into those of amplitude, continuity, frequency, synchrony, maturation, sleep state and wave form morphology, but a clear distinction between some categories may be difficult and there is often an overlap between categories. The classification of abnormal EEGs of the preterm infant must
Assessment of the timing
Preterm infants are prone to suffer various kinds of brain injury at varying times during development. EEGs may undergo various changes according to the severity and the timing of brain insult (Fig. 6). If brain insult is mild and of short duration, the brain recovers completely without residual damage and the EEG is normalized. But if an insult is severe enough, the brain does not recover completely and the EEG shows chronic stage abnormalities. If an insult is mild but persists for long
The assessment of the mode of brain insults
Brain insults may be sudden and strong, mild and prolonged, or repeated, which can be distinguished with serial EEGs [54]. Repeated or prolonged strong insults may not be compatible with life. Mild degrees of brain insults may result in neurological sequelae if they occur repeatedly. In such cases, it is useful to note the presence of chronic EEG abnormalities in records obtained in late neonatal periods or around term. In preterm infants, brain insults may occur not only repeatedly but also
EEG features for prognostic purpose
It is generally accepted that the background EEG is a good prognostic tool in preterm infants as well as term infants [27]. EEG features used for prognostic purposes are different between authors. Usually various features are grouped into different severity grades and correlated with outcome. Some authors used some selected features such as discontinuity measures [55], [56], maturational features [37], [38], or sharp wave transients [57], [58], [59]. The use of a single feature such as
References (59)
- et al.
The EEG of the early premature
Electroenceph clin Neurophysiol
(1985) - et al.
Interburst interval measurements in the EEGs of premature infants with normal neurological outcome
Electroenceph clin Neurophysiol
(1989) - et al.
Long-term EEG monitoring in the early premature: developmental and chronobiological aspects
Electroenceph clin Neurophysiol
(1991) - et al.
Background EEG activity in preterm infants: correlation of outcome with selected maturational features
Electroenceph clin Neurophysiol
(1994) - et al.
Premature temporal theta (PT theta)
Electroenceph clin Neurophysiol
(1987) - et al.
Physiological significance of sharp wave transients on EEG recordings of healthy pre-term and full-term neonates
Electroenceph clin Neurophysiol
(1994) - et al.
Positive temporal sharp waves on EEG recordings of healthy neonates: a benign pattern of dysmaturity in pre-term infants at post-conceptional term ages
Electroenceph clin Neurophysiol
(1994) - et al.
Positive temporal sharp waves in electroencephalograms of the premature newborn
Neurophysiol Clin
(1996) - et al.
Cerebral lesions in early prematurity: EEG prognostic value in the neonatal period
Brain Dev
(1987) - et al.
The dysmature EEG pattern in infants with bronchopulmonary dysplasia and its prognostic implications
Electroenceph clin Neurophysiol
(1990)
Dysmature EEG pattern in EEGs of preterm infants with cognitive impairment: maturation arrest caused by prolonged mild CNS depression
Brain Dev
The early diagnosis of periventricular leukomalacia in premature infants with positive rolandic sharp waves on serial electroencephalography
J Pediatr
Timing of brain injury in periventricular leucomalacia (PVL) studied with serial neonatal EEGs
Pediatr Neurol
Timing of periventricular leukomalacia using neonatal electroencephalography
Int J Gynecol Obstet
Prognostic value of abnormal EEG transients in preterm and full-term neonates
Electroenceph clin Neurophysiol
Prognostic value of neonatal electroencephalography in premature newborns less than 33 weeks of gestational age
Electroenceph clin Neurophysiol
Neonatal polygraphy in full-term and premature infants: a review of normal and abnormal findings
J Clin Neurophysiol
Electroencephalography in the newborn
Electrophysiological brain maturation in premature infants: an historical perspective
J Clin Neurophysiol
Atlas of neonatal electroencephalography
The neonatal electroencephalogram and sleep cycle patterns
Neonatal Electroencephalogram (I) Normal EEG in early preterm infants (in Japanese)
Rinsho Noha (Osaka)
A semiquantitative analysis of EEG of extremely premature newborn infants (in Japanese)
No to Hattatsu (Tokyo)
Quantification of changes in normal neonatal EEGs with gestation from continuous five-day recordings
Dev Med Child Neurol
Sequential changes in electroencephalogram continuity in very premature infants
Electroenceph clin Neurophysiol
The sharp theta rhythm on the occipital areas of prematures (STOP): a newly described waveform
Clin Electroenceph
Rhythmic alpha/theta bursts in the electroencephalogram of early premature infants: (1)
The features in normal early premature infants (in Japanese), No to Hattatsu (Tokyo)
Continuous four-channel EEG monitoring in the evaluation of echodense ultrasound lesions and cystic leucomalacia
Arch Dis Childh
Significance of positive temporal sharp waves in the neonatal electroencephalogram
Electroenceph clin Neurophysiol
Cited by (0)
- ☆
Presented in part at a satellite meeting to the Eighth International Child Neurology Congress, Diagnostic Procedures and Techniques in Child neurology, San Servolo, Venice, September 11–12, 1998.