What are periodic lateralized epileptiform discharges on EEG of focal lesions?

Answer

Described in 1964 by Chatrian et al, periodic lateralized epileptiform discharges (PLEDS) are a special type of focal abnormality.^{[2, 3]}As implied by their name, they are periodic, lateralized, and epileptiform. Periodicity is the most characteristic feature, and the one that sets PLEDS apart from other focal abnormalities. Periodicity refers to a relatively constant interval between discharges, which varies between 0.5 and 3 seconds and most often is around 1 second. The epileptiform morphology of the discharges is not invariable, as PLEDS are often closer to slow waves than to sharp waves in morphology.

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Media Gallery

Continuous slow, lateralized right hemisphere. While "spilling over" to the left frontal region, the polymorphic delta activity is clearly predominant over the right hemisphere. This type of slowing almost invariably is associated with a structural hemispheric lesion. This patient had a large right middle cerebral artery infarct.
Continuous slow, lateralized left hemisphere. This polymorphic delta activity was continuous throughout the record. This patient had a left hemisphere neoplasm.
Continuous slow, regional right temporal. This polymorphic delta activity is somewhat more focal than that shown in the first image above, with a maximum in the temporal chain. Little such activity is evident in the central chain, but enough to exclude a T4 electrode artifact. The slowing shows phase reversals at T4, indicating a maximum at that electrode.
Continuous slow, regional left temporal. This polymorphic delta activity is somewhat more focal than that in the second image above, with a maximum in the temporal chain. The phase reversals at T3 indicate a maximum at that electrode.
Intermittent slow, lateralized left hemisphere. This brief burst of delta activity is seen in the temporal and central areas. This is a much "weaker" finding than continuous slowing, and much less reliably associated with a structural lesion. This is indicative of mild dysfunction in that region.
Asymmetry, increased beta, regional right frontocentral. The beta activity is increased in amplitude in the right frontocentral region. This is a "breach rhythm" and is caused most often by a skull defect (in this case a burr hole).
Periodic lateralized epileptiform discharges (PLEDS), regional left centrotemporal. The repetitive discharges occur with a periodicity of about 1 second. Polymorphic delta activity is seen over the left hemisphere, but the classification as PLEDS already implies severe focal dysfunction. In addition, it indicates an acute destructive process and very high (80%) risk of seizures.
Periodic lateralized epileptiform discharges (PLEDS), lateralized right hemisphere. The repetitive discharges occur with a periodicity of 2-4 seconds. PLEDS are associated with severe focal dysfunction and with acute destructive processes and very high (80%) risk of seizures.

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Author

Selim R Benbadis, MD Professor, Director of Comprehensive Epilepsy Program, Departments of Neurology and Neurosurgery, Tampa General Hospital, University of South Florida Morsani College of Medicine

Selim R Benbadis, MD is a member of the following medical societies: American Academy of Neurology, American Academy of Sleep Medicine, American Clinical Neurophysiology Society, American Epilepsy Society, American Medical Association

Disclosure: Serve(d) as a director, officer, partner, employee, advisor, consultant or trustee for: Ceribell, Eisai, Greenwich, Growhealthy, LivaNova, Neuropace, SK biopharmaceuticals, Sunovion<br/>Serve(d) as a speaker or a member of a speakers bureau for: Eisai, Greenwich, LivaNova, Sunovion<br/>Received research grant from: Cavion, LivaNova, Greenwich, Sunovion, SK biopharmaceuticals, Takeda, UCB.

Coauthor(s)

Diego Antonio Rielo, MD Staff Physician, Department of Neurology, Memorial Hospital West, Memorial Healthcare

Diego Antonio Rielo, MD is a member of the following medical societies: American Academy of Neurology

Disclosure: Nothing to disclose.

Specialty Editor Board

Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Received salary from Medscape for employment. for: Medscape.

Norberto Alvarez, MD Assistant Professor, Department of Neurology, Harvard Medical School; Consulting Staff, Department of Neurology, Boston Children's Hospital; Medical Director, Wrentham Developmental Center

Norberto Alvarez, MD is a member of the following medical societies: American Academy of Neurology, American Epilepsy Society, Child Neurology Society

Disclosure: Nothing to disclose.

Chief Editor

Helmi L Lutsep, MD Professor and Vice Chair, Department of Neurology, Oregon Health and Science University School of Medicine; Associate Director, OHSU Stroke Center

Helmi L Lutsep, MD is a member of the following medical societies: American Academy of Neurology, American Stroke Association

Disclosure: Medscape Neurology Editorial Advisory Board for: Stroke Adjudication Committee, CREST2; Physician Advisory Board for Coherex Medical; National Leader and Steering Committee Clinical Trial, Bristol Myers Squibb; Consultant, Abbott Vascular, Inc. .

What are periodic lateralized epileptiform discharges on EEG of focal lesions?

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