Abnormal EEG

A sharp transient is characterized as epileptiform if it meets at least 4 out of 6 criteria proposed by the International Federation of Clinical Neurophysiology (IFCN) to define interictal epileptiform discharges: (1) sharp/spiky, (2) waveform width different from the ongoing background activity, (3) asymmetric, (4) followed by an aftergoing slow wave, (5) disruption of the background, and (6) physiological field. Morphologically, an epileptiform discharge is classified as a sharp wave if its duration falls within the range of 70 to 200 milliseconds.

A sharp transient is characterized as epileptiform if it meets at least 4 out of 6 criteria proposed by the International Federation of Clinical Neurophysiology (IFCN) to define interictal epileptiform discharges: (1) sharp/spiky, (2) waveform width different from the ongoing background activity, (3) asymmetric, (4) followed by an aftergoing slow wave, (5) disruption of the background, and (6) physiological field. Morphologically, an epileptiform discharge is classified as a spike if its duration falls within the range of 20 to 70 milliseconds.

A sharp transient is characterized as epileptiform if it meets at least 4 out of 6 criteria proposed by the International Federation of Clinical Neurophysiology (IFCN) to define interictal epileptiform discharges: (1) spiky, (2) waveform width different from the ongoing background activity, (3) asymmetric, (4) followed by an aftergoing slow wave, (5) disruption of the background, and (6) physiological field with a bifrontal/midline predominance. Morphologically, an epileptiform discharge is classified as polyspikes if it consists of a sequence of more than two consecutive spikes.

Focal seizures, on EEG, are defined as (a) epileptiform discharges averaging >2.5 Hz for ≥10 seconds, or (b) any pattern with definite evolution lasting ≥10 seconds.

Generalized epileptiform discharges, 3 Hz, are characterized by a burst of 3 Hz bilaterally synchronous (generalized) sharp transients that meet the criteria proposed by the International Federation of Clinical Neurophysiology (IFCN) to define interictal epileptiform discharges.

Generalized epileptiform discharges, 3 Hz, polyspike-wave are characterized by a burst of 3 Hz bilaterally synchronous (generalized) sharp transients that meet at least 4 out of 6 criteria proposed by the International Federation of Clinical Neurophysiology (IFCN) to define interictal epileptiform discharges: (1) sharp/spiky, (2) waveform width different from the ongoing background activity, (3) asymmetric, (4) followed by an aftergoing slow wave, (5) disruption of the background, and (6) physiological field. Morphologically, an epileptiform discharge is classified as a polyspike-wave if it consists of a short duration spike (20 to 70 milliseconds) followed by an aftergoing slow wave. Additionally, these spike-wave complexes consist of a sequence of more than two consecutive spikes per complex, meeting the criteria for polyspikes.

Generalized epileptiform discharges, ≤2.5 Hz are characterized by a burst of ≤2.5 Hz rhythmic generalized sharp transients that meet at least 4 out of 6 criteria proposed by the International Federation of Clinical Neurophysiology (IFCN) to define interictal epileptiform discharges. This interictal pattern of generalized slow (≤2.5 Hz) epileptiform (spike-wave) discharges is typically seen in patients with Lennox-Gastaut syndrome (LGS).