Cerebral function monitoring: a new scoring system for the evaluation of brain maturation in neonates

Cerebral function monitoring (CFM), using compressed single-channel amplitude-integrated electroencephalogram recorded from 2 biparietal electrodes, has been shown previously to be a simple bedside tool for monitoring neonatal central nervous system (CNS) status. As the pattern of the CFM changes with gestational age, the technique can be used to assess brain maturation in premature infants. We have developed a new scoring system for the interpretation of neonatal CFM recordings. The objective of this study was to evaluate CFM tracings at increasing gestational and postnatal ages to develop a scoring system to quantify CFM pattern changes.

Term and preterm neonates were studied with CFM at 12 to 24 hours of life, 48 to 72 hours of life, and then weekly or biweekly until hospital discharge. Each study comprised 8 to 24 hours of continuous CFM recording. CFM recordings were evaluated using the scoring system for record continuity, presence of cyclic changes in electrical activity, degree of voltage amplitude depression, and bandwidth. Each variable was scored for each recording. All variables were summed to yield a total score (minimum 0, maximum 13). Total scores were correlated with gestational and postconceptional ages.

Thirty infants were studied with gestational ages at birth that ranged from 24 to 39 weeks and birth weights that varied between 450 and 3850 g. A total of 146 CFM tracings were analyzed. With advancing gestational and postconceptional age, scores for each variable as well as total scores progressively increased with CNS maturation. The highest scores were attained at 35 to 36 weeks' postconceptional age, which corresponded to previously reported subjective observations performed by visual description of CFM patterns. Of the 4 component variables that we analyzed, the most sensitive indicators of CNS maturity were 1) the presence of a cycling pattern, 2) the continuity of the record pattern, and 3) the CFM recording bandwidth.

Our proposed scoring system may be a valuable tool to quantify changes during CFM more objectively, reflecting variations in CNS activity in newborn infants and allowing for better statistical comparisons between amplitude-integrated electroencephalogram tracings from different patients as well as from the same patient at different points of time.