EEG Abnormal Waveforms

The electroencephalogram (EEG) is a noninvasive technique for measuring neurophysiological activity. This evaluation modality serves as a valuable tool for analyzing the brain's complex functions by detecting electrical activity. EEG signals reflect the brain’s electrical function and are recorded by placing electrodes on the scalp to measure cortical neuron activity. Hans Berger first used EEG in humans in 1924, publishing his findings in 1929. EEG records voltage fluctuations over time from multiple scalp electrodes arranged in a specific pattern to sample different cortical regions. These signals represent fluctuating dendritic potentials from superficial cortical layers, requiring voltage amplification for proper recording. However, extracranial electrodes do not effectively capture deep brain activity. EEG waveforms result from the summation of excitatory (EPSPs) and inhibitory postsynaptic potentials (IPSPs) in cortical neurons. Some benign EEG variants appear normal but may be mistaken for epileptiform activity. Abnormal EEG waveforms include both epileptiform and nonepileptiform abnormalities. Recognizing the differences requires understanding normal EEG patterns across different physiological states in children and adults. Electroencephalographers must also distinguish artifacts from true abnormalities and identify benign variants. This article reviews abnormal EEG waveforms and their clinical significance.