When the Crown has Thorns - Epileptic Spike-Wave Discharges over the Vertex

Epileptiform abnormalities that arise over the midline can sometimes be confused with normal sleep transients, such as vertex sharp waves, because of their location and their activation during sleep. However, epileptiform transients can be distinguished from sleep architecture by their waveform and their occurrence during wakefulness. Here, we report a 24-year-old man with drug-resistant epilepsy whose seizures began with tonic posturing of the left leg before progressing to bilateral tonic-clonic activity. During presurgical scalp video-EEG monitoring, his interictal background showed focal spike-wave discharges maximal over the vertex (phase reversal at Cz), with a more-well-defined field over the right parasagittal region (C4/F4), that were present during both sleep and awake states. The discharges met the IFCN criteria for focal interictal epileptiform discharges (spiky morphology, duration shorter than background activity, asymmetric waveform, after-going slow wave, and physiologic distribution) and appeared to be distinct from the patient's vertex sharp waves. Prior to electroclinical seizures, these discharges would increase in prevalence and appear as repetitive spike-wave discharges. When distinguishing epileptiform from nonepileptiform transients, it is critical to consider both their morphology, especially the degree of background disruption and presence of an after-going slow wave, and their variability with state changes.