Prognostic significance of multimodality evoked response testing in high-risk newborns

Evaluation of the Relationship between Pain Exposure and Somatosensory Evoked Potentials in Preterm Infants: A Prospective Cohort Study

BACKGROUND AND AIM

First, to compare somatosensory evoked potentials (SEPs) in preterm newborns without major brain injury studied at term equivalent age (TEA) with a term historical control group. Second, to investigate the impact of pain exposure during the first 28 days after birth on SEPs. Third, to evaluate the association between SEPs and Bayley-III at 2 years corrected age (CA).

METHODS

Infants born at <32 weeks' gestational age (GA) were studied with continuous-SEPs. First, SEP differences between preterm and term infants were analyzed. Second, regression analyses were conducted to explore the association between SEPs and painful procedures, and then between SEPs and neurodevelopment.

RESULTS

86 preterm infants were prospectively enrolled. Preterm infants exhibited prolonged N1 latencies, central conduction times (CCTs), lower N1-P1 amplitudes, and more recurrently abnormal SEPs compared to term infants. Higher pain exposure predicted longer N1 latency and slower CCT (all p < 0.005), adjusting for clinical risk factors. Younger GA and postmenstrual age (PMA) at SEP recording were associated with longer N1 latency and lower N1-P1 amplitude (all p < 0.005). A normal SEP at TEA positively predicted cognitive outcome at 2 years CA (p < 0.005).

CONCLUSION

Pain exposure and prematurity were risk factors for altered SEP parameters at TEA. SEPs predicted cognitive outcome.

Evoked potentials recorded during routine EEG predict outcome after perinatal asphyxia

OBJECTIVE

To evaluate the added value of somatosensory (SEPs) and visual evoked potentials (VEPs) recorded simultaneously with routine EEG in early outcome prediction of newborns with hypoxic-ischemic encephalopathy under modern intensive care.

METHODS

We simultaneously recorded multichannel EEG, median nerve SEPs, and flash VEPs during the first few postnatal days in 50 term newborns with hypoxic-ischemic encephalopathy. EEG background was scored into five grades and the worst two grades were considered to indicate poor cerebral recovery. Evoked potentials were classified as absent or present. Clinical outcome was determined from the medical records at a median age of 21months. Unfavorable outcome included cerebral palsy, severe mental retardation, severe epilepsy, or death.

RESULTS

The accuracy of outcome prediction was 98% with SEPs compared to 90% with EEG. EEG alone always predicted unfavorable outcome when it was inactive (n=9), and favorable outcome when it was normal or only mildly abnormal (n=17). However, newborns with moderate or severe EEG background abnormality could have either favorable or unfavorable outcome, which was correctly predicted by SEP in all but one newborn (accuracy in this subgroup 96%). Absent VEPs were always associated with an inactive EEG, and an unfavorable outcome. However, presence of VEPs did not guarantee a favorable outcome.

CONCLUSIONS

SEPs accurately predict clinical outcomes in newborns with hypoxic-ischemic encephalopathy and improve the EEG-based prediction particularly in those newborns with severely or moderately abnormal EEG findings.

SIGNIFICANCE

SEPs should be added to routine EEG recordings for early bedside assessment of newborns with hypoxic-ischemic encephalopathy.

Value of electroencephalographic monitoring in newborns with hypoxic-ischemic encephalopathy treated with hypothermia

BACKGROUND

The values of electroencephalography (EEG) in neonatal hypoxic-ischemic encephalopathy (HIE) during therapeutic hypothermia (TH) are still uncertain.

AIMS

The aim of this study is to detect EEG background, the prevalence of seizures during cooling, and to determine different EEG patterns that can predict brain injury in magnetic resonance imaging (MRI).

PATIENTS AND METHODS

Thirty-nine newborns with HIE were subjected to TH. Continuous monitoring by video-EEG was carried out throughout cooling and during rewarming. MRI was done for all newborns after rewarming. The predictive value of EEG background for MRI brain injury was evaluated at 6-h intervals during cooling and rewarming.

RESULTS

At all-time intervals, normal EEG was associated with no or mild MRI brain injury. At the beginning of cooling, normal background was more predictive of a favorable MRI outcome than at later time points. After 24 h of monitoring, diffuse burst suppression and depressed patterns had the greatest prognostic value. In most patients, a discontinuous pattern was not associated with poor prognosis. Thirty-one percent developed electrical seizures, and 8% developed status epilepticus. Seizures were subclinical in 42%. There is a significant association between duration of seizure patterns detected on the EEG and severity of brain injury on MRI.

CONCLUSIONS

Continuous EEG monitoring in newborns with HIE under cooling has a prognostic value about early MRI brain injury and identifies electrographic seizures, approximately 50% of which are subclinical. Treatment of clinical and subclinical seizure results in a reduction of the total duration of seizure pattern supports the hypothesis that subclinical seizures should be treated.

Somatosensory and auditory processing in opioid-exposed newborns with neonatal abstinence syndrome: a magnetoencephalographic approach

OBJECTIVE

Opioid exposure during pregnancy is a potential risk factor for the developing central nervous system of the fetus. We studied evoked responses in buprenorphine-exposed newborns who displayed neonatal abstinence syndrome (NAS) to elucidate the possible alterations in functioning of the somatosensory and auditory systems.

METHODS

We compared somatosensory (SEFs) and auditory evoked magnetic fields (AEFs), recorded with magnetoencephalography (MEG), of 11 prenatally buprenorphine-exposed newborns with those of 12 healthy newborns. Peak latencies, source strength and location of SEFs or AEFs were recorded.

RESULTS

AEFs were present in all buprenorphine-exposed newborns without significant differences from those of healthy newborns. In contrast, though no group level differences in SEFs existed, at individual level the response deviated from the typical neonatal morphology in four buprenorphine-exposed newborns.

CONCLUSIONS

Although buprenorphine exposure during pregnancy does not seem to cause constant deficiencies in somatosensory or auditory processing, in some newborns the typical development of somatosensory networks may be - at least transiently - disrupted.

Neurophysiological measures of nociceptive brain activity in the newborn infant--the next steps

Infants within neonatal intensive care units can receive multiple medically essential painful procedures per day. How they respond to these events, how best to alleviate the negative effects, and the long-term consequences for the infant are all significant questions that have yet to be fully answered. In recent years, several studies have examined cortical responses to noxious stimuli in the neonate through the use of near-infrared spectroscopy (NIRS) and electroencephalography (EEG). These investigations dispel any notion that the newborn infant does not process noxious stimuli at a cortical level and open the way for future research. In this Viewpoint Article, we review these studies and discuss key clinical challenges which may be elucidated with the use of these techniques.

Conclusion

Simultaneously measuring the changes that are evoked in behaviour, physiology and the cortex following noxious events will provide the best approach to understanding the neonate's experience of pain.

Somatosensory evoked potentials are of additional prognostic value in certain patterns of brain injury in term birth asphyxia

OBJECTIVE

(a) To relate MRI patterns of brain injury to somatosensory evoked potentials (SEPs), and (b) to determine the prognostic value of SEPs in addition to continuous EEG monitoring (cEEG) and cerebral imaging, in term asphyxiated newborns.

METHODS

Fifty one consecutive neonates were studied. Survivors were followed for at least 2 years. cEEG, started within 24h, was done for ≥ 24 h and scored. SEPs and MRIs were performed in the first week. Brain injury patterns were classified.

RESULTS

Bilaterally abnormal SEPs had a sensitivity of 90% (28/31) and specificity of 85% (17/20) in predicting a poor outcome, defined as death or severe handicap. SEPs were of particular value in predicting outcome in isolated symmetrical white matter injury and predicting the development of hemiparesis in isolated asymmetrical watershed injury. Binary logistic regression analysis revealed a significant relation to outcome separately for cEEG, deep grey matter injury on MRI and SEPs. SEPs provided additional value when added to cEEG and MRI in the model (p=0.034).

CONCLUSIONS

SEPs are of additional prognostic value after term birth asphyxia.

SIGNIFICANCE

In certain patterns of postasphyxial neonatal brain injury like asymmetrical watershed lesions and symmetrical white matter injury, EPs are complementary to information obtained from cEEG and MRI for prognostication.

Neonatal somatosensory evoked potentials: maturational aspects and prognostic value

The aim of this prospective study was to evaluate the diagnostic role of somatosensory evoked potentials (SEP) during the neonatal period with regard to maturational changes and prognostic value in perinatal hypoxic-ischemic encephalopathy. Median nerve SEP analysis was performed in 31 healthy infants (group A1, 33-35 weeks, n = 10; group A2, 36-37 weeks, n = 11; group A3, 38-41 weeks, n = 10) and in 10 term infants with hypoxic-ischemic encephalopathy (group B). Cortical latency N1 and central conduction time values were analyzed for group A in relation to postconceptional age and postnatal age and for group B in relation to degree of hypoxic-ischemic encephalopathy and neurodevelopmental outcome (at the mean age of 6.6 + or - 1.6 years). Central latencies were correlated with postconceptional age but not postnatal age. Mean N1 latency and central conduction time values did not differ significantly between groups A1 and A2; the most pronounced decrease was between groups A2 and A3 (postconceptional ages 36-37 vs 38-41 weeks). In group B, central latencies were prolonged, compared with controls (P < 0.001), but were not significantly correlated with long-term outcome in patients with moderate hypoxic-ischemic encephalopathy (n = 6). Neonatal SEP analysis thus is an objective and noninvasive method for assessing functional integrity of the somatosensory pathway. In term infants, SEPs are a valuable additional tool for early diagnosis of hypoxic-ischemic encephalopathy, but are not prognostic of neurodevelopmental long-term outcome in moderate hypoxic-ischemic encephalopathy.

Technical standards for recording and interpretation of neonatal electroencephalogram in clinical practice

Neonatal electroencephalogram (EEG), though often perceived as being difficult to record and interpret, is relatively easy to study due to the immature nature of the brain, which expresses only a few well-defined set of patterns. The EEG interpreter needs to be aware of the maturational changes as well as the effect of pathological processes and medication on brain activity. It gives valuable information for the treatment and prognostication in encephalopathic neonates. In this group, serial EEGs or EEG monitoring often gives additional information regarding deterioration/improvement of the brain function or occurrence of seizures.

Prediction of neurodevelopmental outcome after preterm birth

Prediction of outcome after preterm birth is critical, but remains difficult, particularly in the early postnatal period. The ability to predict outcome improves parental counseling and selection of infants for early therapeutic strategies aiming at preventing or ameliorating cerebral injury. This review gives an overview of the spectrum and severity of neurodevelopmental, behavioral, and psychosocial outcomes, with discussion of predictors of outcome and, in particular, the clinical, electrophysiological, and imaging predictors. A detailed neurologic examination of infants is a valuable predictive tool in terms of later moderate to severe neurodevelopmental impairments; however, it may be limited in the immediate newborn period. Electrophysiological, neuroimaging, and clinical risk factors for adverse neurodevelopmental outcome have been identified. Good prediction is usually achieved for major functional disabilities in early childhood, but is poorer for moderate or mild long-term outcome. Future research should focus on the long-term quality of life, academic achievement, and the influence of the sociocultural environment. More emphasis should be placed on genetic diversity as a modifying factor for the large variability in outcome.

Does very premature birth affect the functioning of the somatosensory cortex?--A magnetoencephalography study

Increased survival of extremely low birth weight infants has led to a need for new prognostic methods to predict possible future neurological impairment. We investigated the early development of the somatosensory system by recording the somatosensory evoked magnetic fields (SEFs) during natural sleep at fullterm age in 16 very prematurely born infants and 16 healthy newborns born at term. The purpose was to determine possible changes in the function of the somatosensory cortex in the prematurely born infants by comparing the latency, strength, location and morphology of the SEFs with those of healthy fullterm newborns. We recorded reliable SEFs in all patients and controls. The equivalent current dipole (ECD) strength of the first cortical response, M60, was significantly lower in the patients. Otherwise, the general morphology and latency of the SEFs were similar in the two groups of babies. The similar response latencies in the two groups indicate normally developed conduction in the somatosensory system of the prematurely born infants. The attenuated ECD strength may reflect weaker synchrony in firing or a smaller number of the cortical neurons activated by the somatosensory stimulation. At the individual level, in four of the preterm infants, a later M200 response was not present or could not be modeled: all of them had lesions of the underlying hemisphere depicted by ultrasound and magnetic resonance imaging.

Neonatal SEP - back to bedside with basic science

Scalp-recorded somatosensory evoked potentials (SEPs) have been successfully used in neonatal assessment for several decades. The current routine SEP paradigm is markedly predictive for future cerebral palsy (CP) or other neurocognitive sequelae in brain-injured babies. Recent advances in basic science have dramatically increased our knowledge about structural-functional development of SEP-related brain mechanisms. It has thereby become apparent that preterm SEP differs from that in more mature counterparts in that it also comprises responses from transient brain structures, and hence being unique to the preterm period. It is now obvious also that several aspects in the current SEP paradigm, ranging from the type of stimulation to the methods of recording and analysis, are suboptimal for preterm babies. Recent progress in recording and analysis techniques have made it possible to combine SEP studies with EEG recordings, as well as to implement advanced analyses (e.g. time-frequency analysis) into routine practice. This review summarizes literature from relevant areas in basic science, and proposes a novel, integrated approach in neonatal SEP studies in order to significantly increase the fidelity of testing somatosensory system.

Magnetoencephalography of the newborn brain

This paper reviews the use of event-related magnetic fields (ERFs) in infants; ERFs can be derived from magnetoencephalography by means of averaging. Basic perceptive skills are important prerequisites for the infant's later development. The automatic cortical processes related to processing auditory, somatosensory and visual stimuli can be addressed by using responses recorded directly from the brain. The traditional method, the event-related potential (ERP), has recently been accompanied by ERFs. Similarly to ERPs, higher processes related to short-term memory, stimulus comparisons, and attention allocation can also be studied with ERFs. Further, since addressing the neonatal higher cognitive and social capabilities is challenging using only behavioural means, ERFs provide information on these important functions at a very early stage immediately after birth or in some cases even before birth. The main advantage of ERFs, compared to ERPs, is detection of the signals with high accuracy both with respect to the noise level and estimation of the spatial location.

Somatosensory processing in healthy newborns

Attempting to understand more about somatosensory processing in newborns, we give an overview of somatosensory potential studies in preterm and term healthy newborns conducted during the past few decades. In addition, we present some of our recent data from somatosensory studies conducted with magnetoencephalography (MEG). The reviewed studies show maturational patterns of cortical responses to median and tibial nerve stimulation within the preterm-term period. In this era, maturation is reflected mainly as shortening of the latencies and increase in the amplitude of especially the early responses. However, the actual somatosensory processing beyond the latency and amplitude analysis has not been the goal in these studies. Although the somatosensory pathways and cortex are mature enough to produce the evoked responses, difficulties in measuring the neonatal responses with similar parameters as used for adults is suggested to reflect the special characteristics of newborn processing. Possible factors behind the inconsistencies between different newborn studies are discussed.

Prediction of outcome at school age in neonatal intensive care unit graduates using neonatal neurologic tools

Prediction of outcome for neonatal intensive care unit graduates is clinically useful to counsel families effectively and target those who may benefit from early interventions. Evoked potentials have proven prognostic value of neurologic outcomes in early childhood; however, their long-term predictive validity remains to be determined. The objective of this prospective study was to determine the long-term predictive value of three neonatal neurologic assessments: brainstem auditory evoked potentials, somatosensory evoked potentials, and the Einstein Neonatal Neurobehavioral Assessment Scale. Seventy-eight high-risk newborns and 28 healthy controls were recruited and were assessed in the newborn period using these tests. At 8 to 9 years of age, 42 subjects and 13 controls were re-evaluated for developmental progress using a range of psychologic, sensorimotor, and neurologic measures. Findings indicated that the somatosensory evoked potential was most accurate at predicting outcome at school age, with high specificity (83-100%) across all domains tested and good sensitivity (80-100%) for intellectual performance and sensorimotor abilities. The brainstem auditory evoked potential was limited by false-negatives, whereas the neonatal neurobehavioral assessment yielded many false-positives. This study provides new evidence that associations between neonatal somatosensory evoked potentials and developmental sequelae continue to be significant at school age.

The role of cortical evoked responses in predicting neuromotor outcome in very preterm infants

To explore the role of posterior tibial somatosensory evoked potentials (SSEP) and flash visual evoked potentials (VEP) in the early prediction of functional brain injury, 93 infants of less than 32 weeks gestation at birth were studied. Neuromotor outcome was defined by clinical examination at the age of 2 years. SSEP, VEP and cerebral ultrasound were compared as predictors of neuromotor outcome. Posterior tibial SSEP were the most accurate single method of predicting neuromotor abnormalities with a 83% positive predictive power for cerebral palsy and a 100% predictive power for abnormal neurology, compared to 17% and 40% for cerebral ultrasound and 38% and 85% for VEP respectively. When SSEP and VEP results were concordant, the positive predictive power for cerebral palsy and abnormal neurology was 100%. Our results suggest that posterior tibial SSEP and VEP are accurate tools in the prediction of outcome in very preterm infants.

Selection of babies for intervention after birth asphyxia

Based on animal experiments, the therapeutic window for neonates with signs of perinatal hypoxia-ischaemia is probably less than 6 h, and early selection of patients is of utmost importance. In term neonates, fetal heart rate and blood flow patterns, the Apgar score, and other clinical scoring systems are insufficient to select patients for intervention, whereas umbilical artery pH<7.0 combined with umbilical arteriovenous differences in PCO(2), lactate/pyruvate ratios in cord blood, and CSF interleukin-1beta have a better predictive value. At present, neurophysiological methods such as (amplitude-integrated) EEG and evoked potentials have the best predictive value. In preterm neonates, lactate/pyruvate and uric acid measurements in cord blood, as well as neurophysiology appear to be helpful to predict brain injury, and might be used to select patients for intervention.

Monitoring the central nervous system in children with congenital heart defects: clinical neurophysiological techniques

The neurological sequelae following surgery for complex cardiac malformations is being increasingly recognized. The electroencephalogram (EEG) and evoked potentials may be used as monitors of neurological integrity. Criteria for a successful intensive care unit monitoring system have been proposed. EEG findings in the preoperative, perioperative, and postoperative periods are reviewed and may aid in the prediction of neurological sequelae. Recent advances in the development of a computerized neurophysiological monitor at the Montreal Children's Hospital are reviewed. Evoked potentials, auditory, somatosensory, and visual can be used to monitor children with complex cardiac lesions and evaluate them for potential neurological sequelae.

Hypoxemic resuscitation in newborn piglets: recovery of somatosensory evoked potentials, hypoxanthine, and acid-base balance

We tested the hypothesis that hypoxic newborn piglets can be successfully resuscitated with lower O2 concentrations than 21%. Severely hypoxic, 2-4-d-old, anesthetized piglets were randomly divided into five resuscitation groups: 21% O2 (n = 10), 18% O2 (n = 9), 15% O2 (n = 9), 12% O2 (n = 8), all normoventilated, and a hypoventilated 21% O2 group (PaCO2; 7.0-8.0 kPa, n = 9). Base excess (BE) reached -20 +/- 1 mmol/L at the end of hypoxia. After 3 h of resuscitation, BE had risen to -4 +/- 1 mmol/L in the 21% O2, 18% O2, and hypoventilated groups, but was -10 +/- 2 mmol/L in the 15% O2 group (p < 0.05 versus 21% O2 group) and -22 +/- 2 mmol/L in the 12% O2 group (p < 0.05 versus 21% O2 group). Four animals died during resuscitation, all allocated to the 12% O2 group (p < 0.05 versus 21% O2 group). Somatosensory evoked potentials (SEPs) recovered in 39 of 45 piglets, and remained present during resuscitation in all except the 12% O2 group. SEP recovered initially even in six of eight animals in the 12% O2 group, but disappeared again in all later during resuscitation. The SEP amplitude recovered to levels not significantly different from the 21% O2 group in all groups except the 12% O2 group. Plasma hypoxanthine concentrations and extracellular hypoxanthine concentrations in the striatum decreased during resuscitation to levels not significantly different from the 21% O2 group in all but the 12% O2 group (p < 0.05 versus 21% O2 group). In conclusion, severely hypoxic newborn piglets were resuscitated as efficiently with both hypoventilation and 18% O2 as with 21% O2.

Multimodality evoked potentials as a prognostic tool in term asphyxiated newborns

Hypoxic-ischemic (HI) events may cause permanent brain damage, and it is difficult to predict the long-term neurological outcome of survivors. Multimodality evoked potentials (MEPs), using flash visual (fVEPs), somatosensory (SEPs), and brain-stem auditory evoked potentials (BAEPs) may assess the cerebral function in term neonates. MEPs were recorded in 40 hypoxic-ischemic term or near-term neonates during the first week of life in order to predict the neurological outcome. A 3 point grading system registered either mild, moderate, or severe abnormalities. At 24 months of corrected age, the infants were assessed with a blind protocol to determine neurological development. Grade 0 fVEPs and SEPs were associated with a normal neurological status with 100% (P < 0.001) of the infants. Abnormal SEPs or total grade (VEPs + SEPs) > I were not associated with normal outcomes (P < 0.0001). Normal BAEPs did not predict a normal outcome, but severely abnormal BAEPs did predict an abnormal outcome. A significant correlation was found between EP (VEPs + SEPs) grade (r = 0.9, P < 0.0001), Sarnat stage (r = 0.6, P < 0.001), and clinical outcome. This study confirmed that both fVEPs and SEPs are more accurate as prognostic indicators for term neonates. EPs (VEPs + SEPs) also are more accurate in predicting the ultimate neurological outcome compared with the Sarnat scoring.

Sensitivity and specificity of the neonatal brain-stem auditory evoked potential for hearing and language deficits in survivors of extracorporeal membrane oxygenation

OBJECTIVE

We determined the sensitivity and specificity of neonatal brain-stem auditory evoked potentials (BAEP) as markers for subsequent hearing impairment and for developmental problems found later in infancy and childhood.

METHODS

BAEP studies were performed before discharge in infants treated with extracorporeal membrane oxygenation (ECMO), and two specific abnormalities were analyzed: elevated threshold and delayed central auditory conduction. Behavioral audiometry was repeated during periodic follow-up until reliable responses were obtained for all frequencies, and standardized developmental testing was also conducted. The sensitivity and specificity of an elevated threshold on the neonatal BAEP for detecting subsequent hearing loss, and the relationship of any neonatal BAEP abnormality to language or developmental disorders in infancy, were calculated.

RESULTS

Test results for 46 ECMO-treated infants (57.5%) were normal, and those for 34 infants (42.5%) were abnormal, with either elevated wave V threshold, prolonged wave I-V interval, or both on neonatal BAEP recordings. Most significantly, 7 (58%) of the 12 children with subsequent sensorineural hearing loss had left the hospital after showing normal results on threshold tests. There was no significant difference in the frequency of hearing loss between subjects with abnormal (5/21, or 24%) and those with normal BAEP thresholds (7/59, or 12%; Fisher Exact Test, p = 0.28). Therefore the sensitivity of neonatal BAEP testing for predicting subsequent hearing loss was only 42%. Neonatal BAEP specificity for excluding subsequent hearing loss was 76%. In contrast, on language development testing, 19 children demonstrated receptive language delay. Of these children, 12 (63%) had abnormal neonatal BAEP recordings and 7 (37%) had a normal BAEP threshold, normal central auditory conduction test results, or both (p = 0.04).

CONCLUSIONS

Neonatal BAEP threshold recordings were of limited value for predicting subsequent hearing loss common in ECMO-treated survivors. However, an abnormal neonatal BAEP significantly increased the probability of finding a receptive language delay during early childhood, even in those with subsequently normal audiometry findings. Because neonatal ECMO is associated with a high risk of hearing and receptive language disorders, parents should be counseled that audiologic and developmental follow-up evaluations in surviving children are essential regardless of the results of neonatal BAEP testing.

The predictive value of cranial ultrasound and of somatosensory evoked potentials after nerve stimulation for adverse neurological outcome in preterm infants

Thirty-nine preterm infants were studied to compare the predictive value of somatosensory evoked responses (SEPs) following median-nerve and posterior tibial-nerve stimulation with the predictive value of cranial ultrasound. With regard to the SEP, a normal median-nerve response was by no means a guarantee of a normal outcome. A normal posterior tibial-nerve response, however, almost guaranteed a normal outcome, but the test was very time consuming and the number of false positive responses was high (sensitivity 95.6%, specificity 50%). The presence of parenchymal involvement, either due to a haemorrhage or cystic leukomalacia predicted cerebral palsy with a sensitivity of 95.6% and specificity of 68.5%. The combination of an abnormal posterior tibial response and the presence of parenchymal brain lesions had the best predictive value with a sensitivity of 91.3% and a specificity of 81.2%. These results show that, although posterior tibial-nerve responses have a better predictive value than median-nerve responses, these values were lower than that of cranial ultrasound. The best prediction was obtained when a combination of posterior-tibial responses and cranial ultrasound was used.

Neurological assessment of the preterm infant

Coinciding with improved overall management of the very preterm infant, more techniques have become available to assess the neurological well-being of these high-risk infants. An overview is given of the different techniques which are now used in many neonatal intensive care units, and their value in predicting neurodevelopmental outcome is discussed. Attention is mainly focused on cranial ultrasound, electroencephalography and the different evoked potential modalities.

Evoked potentials as predictors of outcome in neonatal intensive care unit survivors: review of the literature

Neonatal intensive care unit survivors are at substantial risk for a range of neurodevelopmental sequelae, and therefore a variety of clinical diagnostic techniques have been evaluated as predictors of outcome. We summarize the prognostic value of evoked potentials in newborns at risk. A review of the literature reveals that brainstem conduction abnormalities in auditory brainstem evoked potentials are associated with neuromotor impairment; however, there are many false negative studies. Visual evoked potentials are highly accurate in predicting neurologic deficits in early childhood in asphyxiated term neonates. Sensitivity and specificity are consistently high for somatosensory evoked potentials in term newborns; however, correlations with outcome in premature infants is controversial. Several studies have compared neonatal findings on neuroimaging studies and evoked potentials, and concordant results between these two tests are highly predictive. However, neurologic sequelae often can most accurately be predicted by visual or somatosensory evoked potentials. Evoked potentials may therefore be a useful adjunct to the clinical investigation and prognostication of outcome in the high risk newborn.

Prediction of outcome at school entry in neonatal intensive care unit survivors, with use of clinical and electrophysiologic techniques

OBJECTIVE

To determine the predictive value of multimodality evoked potentials as well as the neonatal neurobehavioral assessment in neonatal intensive care unit survivors at school entry.

STUDY DESIGN

In this prospective study, healthy (n = 24) and high-risk newborn infants (n = 78) were assessed in the newborn period with auditory brain-stem responses (ABRs) and somatosensory evoked potentials (SEPs), as well as the Einstein Neonatal Neurobehavioral Assessment Scale (ENNAS). Healthy and high-risk newborn infants were assessed in a blind fashion at 1, 3, and 5 years of age by a psychologist and a pediatric neurologist. Of those healthy (all 24) and high-risk newborn infants (72/78) with a neonatal ABR, SEP, or both, 62.5% were assessed at 5 years of age with the Wechsler Preschool and Primary Scale of intelligence, the Beery-Buktenica Test of Visual-Motor Integration, the Griffiths Locomotor Subscale, and neurologic examination. Chi-square analyses were carried out on neonatal and outcome measures, and sensitivity, specificity, and predictive values for each of the neonatal tests were ascertained.

RESULTS

The ENNAS and the ABR had good negative predictive value for cognitive (85.7% to 93.3%), locomotor (83.3%), and visual-motor (91.4% to 100%) performance. The ABR had good specificity, whereas the ENNAS was more sensitive. The SEP was an excellent prognostic tool, with high sensitivity (100%) and specificity (80% to 81.3%) for motor as well as cognitive domains. All infants with normal SEPs had favorable outcomes, whereas those with absent potentials did poorly. The SEP abnormalities were associated with findings on neurologic examination in all cases.

CONCLUSIONS

Normal neonatal evoked potentials and ENNAS are associated with favorable outcomes. The SEP most accurately predicts neurodevelopmental status at school entry.

Somatosensory evoked potentials predict neurologic outcome in full-term neonates with asphyxia

OBJECTIVE

To investigate the ability of somatosensory evoked potentials (SSEP) to predict neurologic outcome in term neonates with birth asphyxia.

METHODOLOGY

Upper limb SSEP were performed on nine infants of 1-7 weeks of age who had perinatal asphyxia and an encephalopathy still present at 7 days of age. Comparison was made between the cranial ultrasound, electroencephalogram (EEG), SSEP and neurologic outcome at 9-36 months.

RESULTS

Normal SSEP were found in four infants, all of whom were normal on neurologic follow up at 9-12 months. Neonatal EEG performed on two out of four of these infants were also normal, while cerebral oedema was seen on cranial ultrasound in three of the four studies. No SSEP response was seen initially in three infants, all of whom had adverse outcomes (one death, two with spastic diplegia). In contrast, their neonatal EEG had shown normal background rhythms, while two of the three cranial ultrasounds revealed oedema. For two infants the initial SSEP was absent over one hemisphere and just present over the other. Both children were abnormal on follow up at 10-12 months but did not have a hemiparesis.

CONCLUSIONS

Upper limb SSEP appear more sensitive than EEG or cranial ultrasounds in predicting the short term neurologic outcome of neonates with asphyxia.

Median nerve somatosensory evoked potentials in children receiving ECMO

Somatosensory evoked potentials (SEPs) were recorded from 11 patients receiving venoarterial extracorporeal membrane oxygenation (ECMO). Cortical responses recorded from the right and left hemispheres were compared to those from 2 other groups of children who were not receiving ECMO. One group consisted of 99 brain-injured patients, while the other consisted of a group of 17 neurologically normal controls. SEP responses from each hemisphere were categorized into 3 grades based on the N20 component--normal latency, abnormal (latency increased > 3 S.D.), or absent. For ECMO patients, 15% of tests disclosed a disagreement between the right and left hemispheres, while 27% of tests from the control group revealed a disagreement between the right and left hemispheres. SEPs were normal over the right hemisphere in 9 patients. Central conduction times obtained from the right and left hemispheres were similar in ECMO patients and were not different from those recorded from a group of patients suffering hypoxic-ischemic injuries and a group of normal controls who did not receive ECMO. The results of this pilot study suggest that SEPs may be employed to evaluate ECMO patients as they are in other brain-injured patients.

Multimodality evoked responses in the neurological assessment of the newborn

In recent years increased attention has been devoted to evoked potentials (EP) in newborns. This paper reviews the literature and data from our research group in an attempt to assess the diagnostic and prognostic value of evoked responses in the first weeks of life and their use in different age-specific clinical conditions. The results show that EP are a very sensitive measure of the integrity of the sensory pathways. They make it possible to follow normal physiological maturation and the abnormalities of development resulting from neurological lesions. Repeated measurements of visual evoked potentials and somatosensorial evoked potential are prognostically useful in term infants, but seem much more limited in preterm newborns in predicting neurodevelopmental outcome.

Reliability of parental recall of developmental milestones

The developmental history is a key element of the pediatric evaluation. Precise determination of a child's milestones depends on the parent's recollection of developmental events. As part of a prospective study examining neonatal predictors of outcome, healthy and high-risk newborns were assessed by a neurologist at 1, 3, and 5 years of age. The consistency of a parent's recall of two milestones (i.e., first steps and first meaningful word) was examined at 3 and 5 years. The answers provided by the parent(s) at the first visit (mean/S.D.: 12.67/1.19 months) provided the comparison standard. Twenty-five healthy and 50 high-risk infants had acquired 1 or both developmental skills by the first visit. Of 75, 63 were reexamined at 3 and/or 5 years by the same neurologist. For first steps, excellent correlations were obtained at 3 years (r = 0.74) and modest correlations were determined at 5 years (r = 0.41). The mean difference in age reported between 1 and 3 years was 0.36 +/- 1.81 months, and 0.33 +/- 2.46 months between 1 and 5 years. For first word, correlations were poor at 3 and 5 years (r = 0.27 and r = -0.11, respectively), with mean discrepancies in recall of 2.43 +/- 4.37 months (3-year visit) and 2.74 +/- 5.56 months (5-year visit). Twenty percent (n = 13) of parents reported discrepancies of 6 or more months (mean: 9.4; range: 6-25 months). Furthermore, this error in reporting of first word was later than the correct age in all patients.(ABSTRACT TRUNCATED AT 250 WORDS)

The clinical role of near infrared spectroscopy

Near infrared spectroscopy is a non-invasive bedside technique which allows cotside observation of cerebral haemodynamics and oxygenation in sick newborn infants. Methods have been described for measurement of cerebral blood flow and volume, as well as other tests of the cerebral circulation. The techniques is still under intensive development and further advances and refinements can be expected, but a present it is essentially a technique for research and investigations rather than a clinical tool.

Functional interhemispheric asymmetries at birth as demonstrated by somatosensory evoked potentials

Functional cerebral hemispheric asymmetries detectable at birth have been suggested by a number of neuroanatomic, neuroradiologic, and clinical neurophysiologic modalities. The aim of this study was to determine whether functional interhemispheric asymmetries can be identified using electrophysiologic measures. As part of a prospective study, somatosensory evoked potentials following median nerve stimulation were recorded in nine healthy full-term newborns on day 2 or 3 of life, and somatosensory evoked potentials were repeated at 2 and 6 months of age. These children were subsequently examined at 1 and 3 years of age by a pediatric neurologist and all had normal examinations. Handedness was determined at 3 years by questioning the parent and by clinical observation. Three of nine were left-handers. All three left-handers had clearly identifiable neonatal N19 parietal potentials over the right hemisphere. Following right median nerve stimulation, contralateral parietal potentials were absent on two of the three and questionable in the third. Asymmetries were not clearly present in right-handers although only one showed an increased maturation of the right hemisphere relative to the left. At 2 months of age, interhemispheric differences were no longer clearly evident. This data suggests that preferential hemispheric asymmetries are masked by 2 months of age. This differential rate of development demonstrated by neonatal somatosensory evoked potentials may be an early indicator of ultimate handedness.

Prediction of neurodevelopmental outcome in the preterm infant: short latency cortical somatosensory evoked potentials compared with cranial ultrasound

One hundred and twenty six preterm infants, with a gestational age of 34 weeks or less, were studied to compare the predictive value of somatosensory evoked potentials (SEPs) with that of cranial ultrasound. A normal N1 latency was no guarantee of a normal outcome, nor did a persistently delayed N1 latency always correlate with a poor outcome. As a predictor of cerebral palsy, SEPs had a sensitivity of 44% and a specificity of 92%. The presence of a large haemorrhage (grade IIb/III) or cystic leukomalacia on cranial ultrasound predicted cerebral palsy with a sensitivity of 73.6% and a specificity of 83.1%. These results demonstrate that the role of SEPs recorded after median nerve stimulation is limited in preterm infants.

A comparison of neurobehavioral performance of healthy term and low-risk preterm infants at term

The neurobehavioral performance of a group of low-risk preterm and healthy term infants was assessed at term using the standardized Einstein Neonatal Neurobehavioral Assessment Scale. There was greater similarity than dissimilarity between the two groups; however, preterm infants demonstrated less consistent following to face and voice, and less sustained rooting and grasp reflexes. Preterm infants were more likely to have a more sustained asymmetric tonic neck reflex, a greater popliteal angle and evidence of tremor. These results support the view that processing capability appears to mature on an intrinsically programmed time- and environment-independent pathway, with environmental exposure challenging this adaptive capacity and modifying performance--predominantly with respect to reflexive elements.