Periodic lateralized epileptiform discharges (PLEDs), an EEG pattern that is highly correlated with seizures, may represent an ictal pattern in some patients, but in other patients PLEDs persist despite the absence of seizures or after seizures have been controlled by anti-epileptic drugs. The tenacity of PLEDs was illustrated by continuous EEG recording in a 95-year-old woman with multiple old cerebral infarctions who had been admitted to the hospital because of seizures. The EEG showed PLEDs that were maximal in the left central region. These sometimes evolved into EEG seizure patterns, which were correlated with facial twitching. The seizures were controlled by anti-epileptic drugs (AEDs), but the PLEDs continued. The patient subsequently expired, with EEG monitoring still in progress. The PLEDs persisted as the patient developed agonal respirations. The interval between the epileptiform complexes gradually increased, and they stopped 40 seconds before disappearance of the other EEG background rhythms; cardiac arrest ensued less than 1 minute later. The resistance of the PLEDs to hypoxia reflects the robustness of the mechanisms that produced them, which may also account for their persistence in the face of AED treatment that stopped the seizures.
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