Prognostic value of periodic electroencephalographic discharges for neurological patients with profound disturbances of consciousness

ObjectiveTo examine if periodic EEG discharges (PDs) predict poor outcome and development of epilepsy in patients with acute brain illnesses irrespective of underlying cerebral pathology.MethodsIn case-control study we retrospectively analyzed outcome of 102 patients with PDs and 102 age-, gender- and etiology matched controls without PDs.ResultsOf cases, 46.1% had lateralized PDs (LPDs), 3.9% bilateral PDs (BIPDs), 15.7% generalized PDs (GPDs) and 34.3% had combinations thereof. Etiology: Stroke was most common cause of LPDs (53%), cardiac arrest of GPDs (10.5%), previous stroke, CNS infection, anoxia and metabolic encephalopathy all caused 1 case of BIPDs. Outcome: Mortality rate and acquired disability was significantly higher in patients with PDs than in controls, odds ratio (OR) 2.5, 95% CI 1.43–4.40 (p = 0.001). Patients with PDs without superimposed EEG activity had worse outcome than patients with superimposed EEG activity. Tardive epilepsy: Patients with LPDs associated with fast superimposed EEG activity (LPDs-plus) had higher risk for tardive epilepsy than patients with LPDs alone (p = 0.034).ConclusionPDs predicted poor functional outcome and patients with LPDs-plus had higher risk for later development of epilepsy.SignificanceDetailed evaluation of PDs provided valuable prognostic information in neurological patients with disturbed consciousness.

► Periodic discharges on EEG may be independent marker for poor clinical outcome. ► In our case control study, significantly more patients developed epilepsy if they had periodic discharges on previous EEG recording. ► Assessment of persistence, duration and frequency of the periodic discharges provided supplementary information regarding outcome and development of epilepsy.