A 30-year-old woman with spastic hemiparesis after arteriovenous malformation resection in early childhood, managed with an intrathecal baclofen pump, with subsequent drug-resistant epilepsy, presented with recurrent discrete episodes of hypersomnolence and confusion progressing to obtundation for 24-48 hours. Brain magnetic resonance imaging showed no acute intracranial abnormalities and electroencephalogram (EEG) during the episodes showed diffuse delta activity, left frontal interictal epileptiform discharges (IEDs), and triphasic waves, but no seizures. Antiseizure medication was escalated for presumed postictal episodes.  Although the IEDs on EEG initially improved, frequent episodic hypersomnolence persisted.  Mental status between episodes was normal. Prolonged video-EEG monitoring showed no seizures but one episode of progressively deepening sleep, then diffuse slowing and generalized triphasic waves over 24 hours.  Side port study, roller study, and pump interrogation of her baclofen pump were all normal. Cerebrospinal fluid and autoimmune encephalitis panel were unremarkable. Despite multiple negative functional studies, baclofen toxicity from her baclofen pump was suspected based on the EEG pattern. Her baclofen pump was replaced and her episodes of hypersomnolence resolved.