'Weight of Evidence' analysis of neonatal sensory evoked potentials

Abnormalities in neonatal sensory evoked potentials (EPs) may indicate a poor developmental prognosis, but such EPs are highly variable, changing with development, and requiring subjective analysis. 'Weight of Evidence' (W), the logarithm of the ratio of the probability that a response has occurred to the probability that it has not, and 'Response Entropy' (S), the spread of the response over time and frequency bands, might provide objective and quantitative measures of EP abnormalities and developmental changes, based on information processing characteristics. W and S were calculated from visual and somatosensory EPs recorded in 72 premature newborns over 2 sessions, separated by 6-9 weeks. Group 1 had normal brain ultrasound images at the time of recording, and a normal developmental outcome at age 2 years. Group 2 had abnormal brain ultrasound images but normal outcome. Group 3 had abnormal brain imaging and abnormal outcome.W values were lowest in Group 3 (visual p<0.001: somatosensory p<0.04). Entropy diminished between sessions (visual p<0.001: somatosensory p<0.015): it was highest in Group 2 (visual p<0.03). The low W in Group 3 implies a lower signal/noise ratio, reducing information capacity. Decreasing entropy suggests more efficient information encoding with maturation.