Generalized nonmotor (absence) seizures-What do absence, generalized, and nonmotor mean?

ObjectiveClinical absences are now classified as generalized nonmotor (absence) seizures by the International League Against Epilepsy (ILAE). The aim of this paper is to critically review the concept of absences and to put the accompanying focal and motor symptoms into the context of the emerging pathophysiological knowledge. MethodsFor this narrative review we performed an extensive literature search on the term absence, and analyzed the plethora of symptoms observed in clinical absences. ResultsArising from the localization and the involved cortical networks, motor symptoms may include bilateral mild eyelid fluttering and mild myoclonic jerks of extremities. These motor symptoms may also occur unilaterally, analogous to a focal motor seizure with Jacksonian march. Furthermore, electroencephalography (EEG) abnormalities may exhibit initial frontal focal spikes and consistent asymmetries. Electroclinical characteristics support the cortical focus theory of absence seizures. Simultaneous EEG/functional magnetic resonance imaging (fMRI) measurements document cortical deactivation and thalamic activation. Cortical deactivation is related to slow waves and disturbances of consciousness of varying degrees. Motor symptoms correspond to the spike component of the 3/s spike-and-wave-discharges. Thalamic activation can be interpreted as a response to overcome cortical deactivation. Furthermore, arousal reaction during drowsiness or sleep triggers spikes in an abnormally excitable cortex. An initial disturbance in arousal mechanisms (dyshormia) might be responsible for the start of this abnormal sequence. SignificanceThe classification as generalized nonfocal and nonmotor (absence) seizure does not covey the complex semiology of a patient's clinical events.