Abstract Introduction Cochlear implants (CIs) generate electrical stimulation that can be detected by scalp electrodes, producing rhythmic waveforms that may resemble cerebral activity. While CI artifacts are known in EEG, their implications for polysomnography (PSG) are underrecognized. As more CI users undergo sleep testing, these device-dependent waveforms may be misinterpreted as alpha, theta, arousals, or epileptiform activity. We present a bilateral CI artifact identified during EEG monitoring and discuss its relevance for PSG interpretation. Report of case(s) A 42-year-old woman with congenital bilateral sensorineural hearing loss and bilateral cochlear implants underwent video-EEG monitoring for evaluation of brief behavioral arrest episodes. EEG demonstrated continuous rhythmic, sharply contoured activity over T7/T8, extending to P7/P8, with frequencies of 5–11 Hz and amplitudes of 50–150 μV. The morphology was fixed, non-evolving, symmetric, and lacked physiologic field distribution. The pattern persisted across wakefulness and drowsiness without clinical correlation. Because of her bilateral CIs, artifact was suspected. Sequential deactivation of the CI processors led to immediate disappearance of the rhythmic activity, while reactivation reinstated unilateral or bilateral artifact depending on which device was powered. These reproducible on/off transitions confirmed a device-generated origin. Relevance to Polysomnography Although detected during EEG monitoring, the identical waveform would appear on PSG EEG channels, particularly temporal and mastoid leads. On PSG, CI artifact may mimic: • posterior alpha rhythm during wakefulness • rhythmic theta in N1/N2 • alpha intrusions or arousal-like bursts • temporal epileptiform discharges Misinterpretation may lead to incorrect sleep staging, inflated arousal indices, or unnecessary neurologic evaluation. Conclusion Cochlear implants can produce persistent alpha–theta rhythmic artifacts that resemble physiologic or epileptiform EEG patterns. Sleep physicians and technologists should recognize these device-dependent waveforms, which will appear on PSG, to avoid misinterpretation and unwarranted interventions. Support (if any) McLaughlin M, Lu J, Dimitrijevic A. Cochlear implant artifact characterization on scalp EEG. Clin Neurophysiol. 2012;123(8):1505–1511. Gilley PM, Sharma A, Dorman MF. Cortical activity and cochlear implants: EEG considerations. J Am Acad Audiol. 2008;19(8):539–550. Castellanos NP, Díaz F. Artifact sources in EEG and strategies for their mitigation. Int J Psychophysiol. 2018;134:10–26. AASM Manual for the Scoring of Sleep and Associated Events, Version 2.6. American Academy of Sleep Medicine; 2020.
VAIDYA et al. (Fri,) studied this question.