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Clinical and Electrographic Correlates of Bilateral Independent Periodic Discharges

Freund, Brin*; Gugger, James, J.*; Reynolds, Alexandra; Tatum, William, O.; Claassen, Jan; Kaplan, Peter, W.*

Journal of Clinical Neurophysiology: May 2018 - Volume 35 - Issue 3 - p 234–241
doi: 10.1097/WNP.0000000000000472
Original Research

Purpose: Periodic discharges (PDs) are EEG patterns denoting brain dysfunction and ictal tendency. Their exact meaning regarding etiology and outcomes is not well known. In particular, bilateral independent PDs (BIPDs) are poorly described.

Methods: We performed a retrospective, multicenter study evaluating neuroimaging, epileptic, clinical, and EEG correlates of BIPDs.

Results: Twenty-five patients studied with a mean Glasgow Coma Scale 6.5 and modified Rankin scale 3.9 who underwent EEG monitoring, mean duration 287 hours (range 0.75–3,216). Most common causes of BIPDs were cardiac arrest, Central Nervous System infections, and acute/chronic ischemic/hemorrhagic stroke. Most had subcortical and cortical injuries on neuroimaging. Most of the PDs ranged from 0.5 to 2 Hz in frequency, were of multiple phase types, and localized to the frontal head regions. Eighteen of 25 patients had clinical or electrographic seizures. There was a trend toward seizures in those with BIPDs with a history of epilepsy (P = 0.08) and acute metabolic dysfunction (P = 0.08), particularly with coincident acute structural lesions (P = 0.05). Seizures were predicted by bilaterally symmetric frequencies (P = 0.02) and trended toward higher likelihood with PD frequency <2 Hz (P = 0.08). Two of 25 patients survived past discharge with modified Rankin scale <3. Cardiac arrest was associated with withdrawal of life-sustaining therapy (P < 0.001).

Conclusions: BIPDs arise from acute and chronic neurologic injuries, often associated with metabolic dysfunction. Outcomes are poor in this population. Seizures are common, particularly in patients with PDs that are of a lower frequency or are symmetric in frequency. Further study is warranted to evaluate the association between BIPDs and seizures, as well as functional and longer term outcomes.

*Department of Neurology, Johns Hopkins Bayview Medical Center, Baltimore, Maryland, U.S.A.;

Department of Neurology, Columbia University, New York, New York, U.S.A.; and

Department of Neurology, Mayo Clinic, Jacksonville, Florida, U.S.A.

Address correspondence and reprint requests to Brin Freund, MD, Department of Neurology, Johns Hopkins Hospital, 600 N. Wolfe St, Zayed Tower, Room 6005, Baltimore, MD 21287, U.S.A.; e-mail:

The authors have no funding or conflicts of interest to disclose.

© 2018 by the American Clinical Neurophysiology Society