How is an EEG finding of periodic lateralized epileptiform interpreted?

Updated: Aug 06, 2019
  • Author: Selim R Benbadis, MD; Chief Editor: Helmi L Lutsep, MD  more...
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PLEDS are caused by acute destructive focal lesions and are a transitory phenomenon: they tend to disappear in weeks, even if the causal lesion persists. Over time, the record takes on a less specific focal slow appearance, which is more likely to persist. By far the most common etiology is an acute cerebrovascular event [5] ; second most common is focal encephalitis such as that caused by herpes. In a clinical context suggestive of viral encephalitis, the EEG can be of great value for diagnosis and can guide tissue biopsy. Though most often associated with an acute destructive lesion, PLEDS, like other EEG findings, are not specific as to etiology and have been described in almost all types of structural lesions, including subdural hematoma and chronic lesions, especially in the presence of a superimposed systemic disturbance. [6]

In keeping with their epileptiform morphology, PLEDS have a close association with clinical seizures, and on average about 80% of patients with PLEDS have clinical seizures.

Periodic lateralized epileptiform discharges (PLED 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 (PLED 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.

The transition between PLEDS and a clear ictal seizure pattern is very gradual, illustrating the hypothesis that PLEDS may represent a subclinical ictal pattern. In clinical practice, however, PLEDS usually are managed as interictal discharges (ie, spikes or sharp waves). They indicate a high risk for focal seizures, but usually are not treated with antiepileptic drugs unless clinical evidence for seizures is noted. This position is endorsed by the authors and others. This is somewhat controversial, however, and some advocate antiepileptic treatment in all patients with PLEDS.

Periodic patterns in Creutzfeldt-Jakob disease usually are generalized and bisynchronous but occasionally, especially early in the course, they may be unilateral or markedly asymmetric, and thus take on the appearance of PLEDS.

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