High-Amplitude Delta Waves with Multifocal Spikes: Characteristic EEG Pattern in Angelman Syndrome

Background: Angelman syndrome (AS) is a neurogenetic disorder caused by loss of UBE3A gene function on maternal chromosome 15, characterized by developmental delay, intellectual disability, severe speech impairment, microcephaly, epilepsy, ataxia, and involuntary movements. Early diagnosis is often challenging as typical clinical findings may not be apparent before age 2 years. Current guidelines emphasize the importance of early genetic testing. Case Presentation: We report an eight-month-old female presenting with involuntary movements of the head and extremities. Video-EEG at one year of age showed high-amplitude generalized delta waves (1-4 Hz) with superimposed multifocal spikes and sharp waves, consistent with the characteristic EEG pattern of AS. Importantly, no epileptic spasms were observed, distinguishing this pattern from West syndrome. Following current diagnostic standards, genetic testing revealed a 6.4 Mb deletion on 15q11.2q13.1 by SNP microarray, encompassing 24 OMIM genes including UBE3A, compatible with class I deletion. Conclusion: Recognition of the characteristic EEG pattern using standardized terminology can guide early identification of AS patients and prompt appropriate genetic evaluation. Distinguishing this pattern from West syndrome has important therapeutic implications. Our case demonstrates the integration of proper EEG interpretation with contemporary genetic testing standards for optimal patient care.