PO 238 Preservation of the posterior dominant rhythm/alpha rhythm in paediatric congenital bilateral anophthalmia, with proposed neural dynamic mechanisms: A case review

Abstract

Introduction/Background: Congenital blindness is associated with reduced or absent alpha activity. Additional increase of the faster frequencies in the gamma range was more recently described. Moreover, the deafferentation of the visual cortex was reported to be associated with the presence of needle spikes in this patient group. Method(s): We present an unusual case of a paediatric patient with congenital bilateral anophthalmia, where electroencephalographic (EEG) trace recordings demonstrate the persistence and reactivity of posterior dominant rhythm (PDR)/alpha rhythm and other background cortical activities, irrespective of the absence of ocular structures. Multiple trace studies were performed and later analysed retrospectively to ascertain these findings, revealing consistently reproducible and an unexpectedly reactive PDR. Result(s): In the absence of globes and optic nerves, traditional mechanisms of PDR generation, as outlined in the current existing literature, appear to be bypassed in this novel case. This observation likely indicates the presence of intact visual cortex but it also prompts the re-consideration of the mechanisms underlying alpha rhythm (PDR) generation. We review the suggested pathways for PDR generation and the possible processes which may indirectly influence thalamic and cortical oscillations, which then propagate to the occipital cortex, where scalp EEG then detects the rhythmic patterns associated with visual inhibition during relaxed wakefulness. Conclusion(s): This case reviews and questions the established theories on EEG patterns, highlighting the complexity and multi-modal contributions of neural pathways. The findings underscore the need for further investigation into the neuronic dynamics underlying PDR and other EEG waveforms across various cognitive states, particularly in medical conditions that deviate from the orthodox anatomical and physiological paradigms. Copyright © 2025