abnormal nervous system electrophysiology abnormal brain wave pattern any anomaly in the standard pattern of rhythmic and rapid fluctuation of electrical potential between parts of the brain, often visualized on an electroencephalogram (EEG); the pattern is often measured to diagnose neurological conditions such as seizure disorders (epilepsy) abnormal ECoG pattern abnormal EEG pattern MPheno.ontology MP:0004994 abnormal electrocorticogram pattern