What is the “L” in LPDs? Localized as well as lateralized
Currently, periodic discharges (PDs) are defined as either periodic lateralized epileptiform discharges (LPDs) or generalized discharges.1 The latter typically occurs in encephalopathy of various etiologies. LPDs, in contrast, are most common in patients with acute cerebral lesions such as herpes encephalitis or stroke, and are typically self‐limiting. Reports on LPDs without underlying lesion are rare. The discussion, whether LPDs reflect an interictal or ictal EEG phenomenon, or whether they are an “ictal‐interictal continuum” is ongoing. However, a colocalizing increased regional cerebral blood flow in SPECT studies and descriptions of acute seizure onset concurrent with LPD appearance in EEG are suggestive for the ictal characteristic of LPDs.4
We here present a paradigmatic case series of three non‐lesional adult patients in whom ictal EEG recordings revealed PDs, which were non‐lateralized but localized to the midline region. These discharges can currently not be adequately classified as they are not generalized and not lateralized.
We, thus, want to emphasize to include the localized non‐lateralized PDs in the term LPDs as they can also be recorded in the midline region. This study is not supposed to evaluate the frequency of this phenomenon or its relation to different etiologies or syndromes, but to raise awareness for this EEG finding and the current gap for adequate classification.