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Biomedical subjects

H E Whyte

Publications and source records attributed to H E Whyte.

6 recordsLinked to original sources
PubMed1992

Prognostic reliability of somatosensory and visual evoked potentials of asphyxiated term infants.

The purpose of this study was to determine whether SEPs would improve the predictive power of VEPs for the prognosis of asphyxiated infants. 57 term infants had SEPs and VEPs recorded during the first three days of life, during the first week and at follow-up visits. All survivors have been followed for 18 to 24 months. 34 had a normal outcome, 12 had severe neurological sequelae and 11 died. The SEPs had both high sensitivity (96 per cent) and negative predictive power (97 per cent); normal SEPs virtually guaranteed normal outcome. The VEPs had both a specificity and positive predictive power of 100 per cent; abnormal VEPs guaranteed abnormal outcome. Both together had a higher predictive power than either alone. The combination of VEPs and SEPs yields a powerful means of prognostication for term asphyxiated infants; the results suggest that both be included in the assessment of this population.

Asphyxia Neonatorum↗
PubMed1991

Visual evoked potentials and visual prognosis following perinatal asphyxia.

Twenty-five children born at term with perinatal asphyxia were studied at age 2.5 to 4.5 years to evaluate visual function and to determine the prognostic value of postnatal assessments of visual outcome. Postnatal assessments included several visual evoked potentials and electroretinograms in the first week of life. Follow-up assessments included flash and pattern visual evoked potentials, visual evoked potential threshold measurements, and clinical eye examinations. Nineteen children had normal visual function, three were visually impaired, and three remained blind. A strong association was found between normal, abnormal, or absent visual evoked potentials in the early postnatal period and long-term visual outcome (P less than .0001). Other perinatal indicators of asphyxia, including neurologic status, Apgar scores, and arterial pH values, were poor predictors of visual outcome. The risk of visual impairment was limited to those survivors with neurodevelopmental deficits.

Asphyxia Neonatorum↗
PubMed1987

Changes in the VEP in preterm neonates with arousal states, as assessed by EEG monitoring.

The effect of sleep state on the visual evoked potentials (VEPs) in neonates was investigated in 7 preterm infants. Polygraphic monitoring including EEG, EOG, ECG, respirogram and submental EMG for the purpose of sleep staging was carried out on all infants simultaneously with VEP testing. Awake-sleep stages were classified into 4 states: awake, transitional or atypical, quiet sleep and active sleep. VEPs were recorded from Oz, referenced to Fz, in response to binocular stimulation with light-emitting diode goggles. Polygraphic and EEG data were analyzed separately. Reproducible VEPs that were appropriate for their ages were seen in all infants in the awake state. The N300 was the most reliable component across sleep states but there was a significant decrease in amplitude with quiet sleep. There were no significant differences among awake, atypical or active sleep states. The other two VEP components followed the same trends as the N300. The P200, present in the older infants, disappeared in both active and quiet sleep states; the P400 was typically variable but reliably present in the awake or atypical states. When a distinction is made between quiet sleep and other arousal states, consistent and significant differences emerge. Our results emphasize the need to test infants in the same arousal states in studies of VEPs in order to make valid comparisons of latency or amplitude changes, particularly with longitudinal or follow-up studies.

Arousal↗
PubMed1987

VEPs in normal full-term and premature neonates: longitudinal versus cross-sectional data.

VEPs have been shown to change with CNS maturation in children, yet few studies had documented maturational changes in the premature infant. Using LED goggles, VEPs were studied in 75 neurologically normal infants of 22-42 weeks gestational age (GA) within the first 3 days of life. Twenty of these (22-32 weeks GA) were also followed longitudinally. The 22-23 week GA neonates had no identifiable waves. In all infants greater than 24 weeks a large negative wave is seen with a latency around 300 msec (N300). After 27 weeks GA a late positive wave was present (P400), but with more variable latency and morphology. Between 30 and 35 weeks GA a small positive wave (P200) was seen in over one-third of the neonates; this component was present in all infants greater than 36 weeks GA. The consistency of the N300 across the ages studied suggests that it might arise from the basilar dendrites in the visual cortex, which are well developed by 24 weeks GA and undergo relatively little further development between 24 weeks and term. The P200 is suggested to arise from the apical dendrites which develop in the last trimester, explaining the emergence of P200 after 30 weeks GA. The infants followed longitudinally showed the same components, emerging in the same order, but with more rapid development (particularly of P200) compared to the cross-sectional studies. These data suggest that there are differences in the maturation of the visual system in the extrauterine versus intrauterine environment.

Evoked Potentials, Visual↗
PubMedDate not supplied

Serial visual evoked potentials and outcome in term birth asphyxia.

Birth asphyxia is a major cause of neonatal mortality and morbidity. It remains difficult to predict accurately neurologic outcome among survivors, particularly infants with moderate hypoxic-ischemic encephalopathy. Visual evoked potential (VEP) is a reproducible measure of cortical function and reflects acute changes in central nervous system status secondary to asphyxial insult. We performed serial VEPs on 36 term infants with documented birth asphyxia to investigate the relationship between VEPs and neurodevelopmental outcome at 18 months of age. Fourteen infants were neurologically intact at subsequent examination; all had normal VEPs during the first week of life. Twenty-two infants had died or were significantly handicapped at 18 months of age; 20 had abnormal VEPs persisting beyond day 7 of life. Abnormal VEPs accurately predicted abnormal outcome (100%) and were both sensitive (91%) and specific (100%). In 20 infants who were classified as moderately asphyxiated according to the criteria of Sarnat and Sarnat, even greater accuracy, sensitivity, and specificity (all 100%) were observed. VEPs demonstrate good correlation with neurodevelopmental outcome in term infants with birth asphyxia and provide accurate prognostic information useful in the clinical management of these infants.

Apgar Score↗