Periodic Lateralized Epileptiform Discharges (PLEDs) in Patients With Neurosyphilis and HIV Infection.

Periodic lateralized epileptiform discharges (PLEDs) are an electroencephalographic pattern recorded in the setting of a variety of brain abnormalities. It is best recognized for its association with acute viral encephalitis, stroke, tumor, or latestatus epilepticus. However, there are other conditions that have been recognized as the underlying pathology for PLEDs such as alcohol withdrawal, Creutzfeldt-Jacob disease, anoxic brain injury, and hemiplegic migraine. However, there are only rare case reports of PLEDs in patients with neurosyphilis. Here, we report 2 patients presenting with encephalopathy and seizures with PLEDs, ipsilateral or contralateral to their main brain magnetic resonance imaging abnormalities. Further workup revealed neurosyphilis in both patients, one in association with human immunodeficiency virus (HIV) infection. Given the increasing incidence of neurosyphilis with or without HIV infection, these cases suggest neurosyphilis as a consideration in the differential for patients presenting with PLEDs.

Emergence of dominant initiation sites for interictal spikes in rat neocortex.

Neuronal populations with unbalanced inhibition can generate interictal spikes (ISs), where each IS starts from a small initiation site and then spreads activation across a larger area. We used in vivo voltage-sensitive dye imaging to map the initiation site of ISs in rat visual cortex disinhibited by epidural application of bicuculline methiodide. Immediately after the application of bicuculline, the IS initiation sites were widely distributed over the entire disinhibited area. After ∼ 10 min, a small number of sites became "dominant" and initiated the majority of the ISs throughout the course of imaging. Such domination also occurred in cortical slices, which lack long-range connections between the cortex and subcortical structures. This domination of IS initiation sites may allow timing-related plasticity mechanisms to provide a spatial organization where connections projecting outward from the dominant initiation site become strengthened. Understanding the spatiotemporal organization of IS initiation sites may contribute to our understanding of epileptogenesis in its very early stages, because a dominant IS initiation site with strengthened outward connectivity may ultimately develop into a seizure focus.