Intraoperative neuromonitoring utilizing electroencephalography (EEG) is rarely performed during neuroendoscopy. The authors present a case in which this monitoring modality was used for a patient with a colloid cyst in preparation for an open craniotomy should an endoscopic approach fail. In this case, EEG serendipitously captured near-complete cessation of electrocerebral activity that occurred during intraventricular irrigation in response to ventricular collapse and resulted in no postoperative deficits. To the authors' knowledge, this is the first reported case of severe suppression of electrical activity captured by EEG during neuroendoscopy. Although they describe a transient phenomenon that resulted in no residual cognitive or neurological deficits, the importance of cautious introduction of ventricular irrigation, the need to carefully monitor intracranial pressure during neuroendoscopic procedures, and the need to pay close attention to irrigation temperature and composition should not be underestimated. Additional studies regarding the utility of EEG in alerting neurosurgeons to adverse electrical cerebral activity during neuroendoscopy are warranted.