Objective: To assess the value and the limitations of amplitude integrated electroencephalogram (EEG) using the cerebral function monitor (CFM) in comparison with standard EEG in neonates who have hypoxic ischemic encephalopathy or were suspected of having convulsions.
Methods. In 36 neonates with a gestational age ≥36 weeks, CFM and simultaneously recorded EEG traces were analyzed off-line and independently classified. CFM background activity: continuous normal voltage; continuous normal voltage, slightly discontinuous (DNV); burst-suppression (BS); continuous extremely low voltage; flat tracing. CFM epileptiform activity: suspected epileptic activity, single seizure (SS), repetitive seizures (RS), status epilepticus (SE). EEG background activity: normal, depressed, low voltage undifferentiated, excessive discontinuity, BS, no activity. Epileptiform activity: interictal unifocal, interictal multifocal, ictal unifocal, ictal multifocal, SE.
Results. A total of 33 traces were suitable for analysis. Interobserver agreement on background activity was reached in 31 cases (κ = 0.92) for CFM and in 27 cases (κ = 0.74) for EEG. There was full agreement on CFM ictal activity (RS, SS, or SE) and EEG ictal activity. A normal CFM (continuous normal voltage) corresponded with a normal or a depressed EEG in 90% of the cases. The positive predictive value for a severely abnormal CFM (BS, continuous extremely low voltage, flat tracing) to correspond with a severely abnormal EEG (excessive discontinuity, BS, low voltage undifferentiated, no activity) was 100% (negative predictive value, 80%; sensitivity, 76%; specificity, 100%). DNV (10) on CFM corresponded either with depressed (6) or excessive discontinuity (4) on EEG. Ictal activity on EEG corresponded with SS, RS, or SE on CFM in 8 cases (sensitivity, 80%; specificity, 100%; positive predictive value, 100%; negative predictive value, 92%).
Conclusion. CFM is a reliable tool for monitoring both background patterns (especially normal and severely abnormal) and ictal activity. Certain focal, low amplitude, and very short periods of seizure discharges can be missed. We recommend using CFM as a monitoring device and performing intermittent standard EEG whenever there is any doubt about the classification of the CFM (ie, DNV pattern or suspected epileptiform activity).