Abstract
The VEP as a measure of brain dysfunction was evaluated in 52 infants <35 weeks gestation. The test was done daily on day 1, 2, 3 and 4 and weekly until discharge using a CA1000 Nicolet machine with flash stimulus (Rate 1.3/sec, repetitions 50). The latency of the most prominent positive wave (P2) is reported. IVH was documented by daily cranial sonograms, intracranial pressure (ICP) and clinical evaluation. 21 of the 52 infants had IVH; 31 did not. IVH infants had significantly lower birthweight, gestation, neurological score and higher ICP. 6 infants had IVH on the day of birth, 13 within 4 days and 2 at 3 wks. In non-IVH infants the mean ± 2SD P2 latency decreases with increasing gestational age from 0.309±.04 msec at ≤30 wks to 0.298±.02 at ≥37 wks. Considering the maturational factor the P2 latency of IVH infants was within 2SD for the mean prior to the bleed. Following a grade III or IV bleed the VEP was absent bilateraly regardless of the site of bleed but was again elicitable by the second week. The P2 remained normal in grade I and II bleeds and was prolonged by 3-4 wks if ventriculomegaly occurred. 4 infants with apnea in the non-IVH group had VEP loss. It appears that VEP is affected by multiple factors that probably interfere with cerebral circulation and oxygenation. Along with sonograms that document anatomical disruption, the evoked responses that indicate functional disruption provide some insight into brain injury in its acute phase.
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