Bilateral independent periodic discharges are associated with electrographic seizures and poor outcome: A case-control study

Abstract

Objective: To determine the clinical correlates bilateral independent periodic discharges (BIPDs) and their association with electrographic seizures and outcome.

Methods: Retrospective case-control study of patients with BIPDs compared to patients without periodic discharges ("No PDs") and patients with lateralized periodic discharges ("LPDs"), matched for age, etiology and level of alertness.

Results: We included 85 cases and 85 controls in each group. The most frequent etiologies of BIPDs were stroke, CNS infections, and anoxic brain injury. Acute bilateral cerebral injury was more common in the BIPDs group than in the No PDs and LPDs groups (70% vs. 37% vs. 35%). Electrographic seizures were more common with BIPDs than in the absence of PDs (45% vs. 8%), but not than with LPDs (52%). Mortality was higher in the BIPDs group (36%) than in the No PDs group (18%), with fewer patients with BIPDs achieving good outcome (moderate disability or better; 18% vs. 36%), but not than in the LPDs group (24% mortality, 26% good outcome). In multivariate analyses, BIPDs remained associated with mortality (OR: 3.0 [1.4-6.4]) and poor outcome (OR: 2.9 [1.4-6.2]).

Conclusion: BIPDs are caused by bilateral acute brain injury and are associated with a high risk of electrographic seizures and of poor outcome.

Significance: BIPDs are uncommon but their identification in critically ill patients has potential important implications, both in terms of clinical management and prognostication.

Keywords: Bilateral independent periodic discharges; Continuous EEG monitoring; Periodic discharges; Seizures.

Fig. 1.

69-year old stuporous male with multiple pyogenic cerebral abscesses from bacterial endocarditis. The EEG (A) showed bilateral independent periodic discharges that occur at approximately 0.5 per second over each hemisphere, predominantly in the frontotemporal regions (dashed boxes). Low-frequency and high-frequency filters were set at 0.5 and 70 Hz, respectively; notch filter was off. Brain MRI (B-D) demonstrated disseminated ring-enhancing lesions with surrounding edema located at the grey-white matter junction. Several electrographic seizures were recorded, which ceased upon treatment with anti-seizure medications. The patient partially recovered and was discharged to a skilled nursing facility.

Fig. 2.

74-year old comatose female with post-anoxic brain injury after cardiac arrest. The EEG (A) showed bilateral independent periodic discharges that occurred at approximately 0.5 per second over each hemisphere (dashed boxes). Low-frequency and high-frequency filters were set at 0.5 and 70 Hz, respectively; notch filter was off. Brain MR] demonstrated diffuse cortical hyperintense signal changes on fluid-attenuated inversion recovery (B) and diffusion-weighted imaging (C). No clinical or electrographic seizures occurred. The patient did not regain consciousness and died in the hospital.