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

Objective: To examine if periodic EEG discharges (PDs) predict poor outcome and development of epilepsy in patients with acute brain illnesses irrespective of underlying cerebral pathology.

Methods: In case-control study we retrospectively analyzed outcome of 102 patients with PDs and 102 age-, gender- and etiology matched controls without PDs.

Results: Of 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).

Conclusion: PDs predicted poor functional outcome and patients with LPDs-plus had higher risk for later development of epilepsy.

Significance: Detailed evaluation of PDs provided valuable prognostic information in neurological patients with disturbed consciousness.