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Electrographic and Clinical Natural History of Lateralized Periodic Discharges

Purpose: The long-term electrographic features of lateralized periodic discharges (LPD) and their impact on clinical management are unclear. The authors investigated routine EEGs (rEEG) to analyze the delayed natural history of LPDs, and studied the clinical care of these patients. Methods: After IRB approval, the prospectively maintained continuous EEG (cEEG) database was searched to identify patients fulfilling the following criteria: LPDs on cEEG, age ≥18 years, no epilepsy history, and rEEG completed within 1 to 12 months of hospital discharge. Their rEEGs were reviewed followed by clinical data extraction. Appropriate statistical tools were used for data analysis. Results: Thirty-nine patients (20 females) with a mean age of 63.3 ± 16.8 years at the time of cEEG fulfilled the study criteria. Thirty-three (85%) had associated electrographic seizures. rEEG was performed 4.7 ± 3.5 months after cEEG. Seven (18%) patients had interictal epileptiform discharges (IEDs) on the rEEG. The LPDs on cEEG of these patients were more often continuous, with an amplitude >2 times their background compared with 10 (26%) patients with normal rEEGs findings. After a mean follow-up of 19.8 ± 9.9 months, 11 (31%) patients developed epilepsy, but only 3 had IEDs on their rEEG. Majority (86%) of patients were on AEDs at the time of last follow-up. Conclusions: LPDs lead to markers of epileptogenicity in around 18% of patients. One-third of the study population developed epilepsy. rEEG findings were not found to be good indicators of epilepsy development in our small, retrospective study limited by its sampling bias. Indiscriminate, long-term use of AEDs in these patients is a concerning finding.