Title : Stimulus-induced pseudo–burst suppression in Powassan encephalitis presenting as NORSE: An unusual EEG finding
Abstract:
Background: Burst suppression is an EEG pattern commonly targeted during treatment of refractory status epilepticus with anesthetic agents, characterized by brief bursts of cerebral activity interspersed with 10-second periods of suppression. In true pharmacologic burst suppression, painful stimulation typically evokes cortical activation, including high-amplitude negative waves, bursts with superimposed 10-Hz activity, or thalamic spindles. Paradoxical increases in suppression following stimulation termed pseudo–burst suppression are extremely rare and not well described, raising the potential for misinterpretation.
Case Discussion: A 21-year-old male presented with fever, altered mental status, and generalized tonic–clonic seizures requiring intubation. Despite broad antimicrobial therapy, multiple antiseizure medications, anesthetic agents, and immunotherapies, he progressed to NORSE. MRI revealed bilateral thalamic and basal ganglia abnormalities. Extensive infectious testing was initially unrevealing; CDC reference testing confirmed Powassan virus encephalitis. Continuous EEG showed persistent generalized periodic discharges at 1–3 Hz without discrete seizures. Painful stimulation and repositioning reproducibly induced transient increases in background suppression with concurrent attenuation of discharges. This stimulus-dependent pattern occurred independently of anesthetic dosing and resolved with cessation of stimulation, distinguishing it from pharmacologic burst suppression.
Conclusions: This case represents, to our knowledge, the first report of reproducible stimulus-responsive pseudo–burst suppression in NORSE due to Powassan encephalitis. Unlike true burst suppression, it is paradoxical, transient, and non–dose-dependent, reflecting a reversal of expected cortical reactivity. Recognition of this unique EEG response is critical to avoid misinterpretation of seizure control and inappropriate therapeutic decisions in refractory status epilepticus.
