Secondary Generalization of Focal Onset Seizures

Introduction

Secondary generalization is a phenomenon in which the seizure starts focally and ends with bilateral motor activity. Clinically, it may start with confusion, a somatosensory aura, or focal twitching and proceed at varying rates and with varying symptoms to a convulsion that may be tonic, clonic, or both. The neurological implication is that the seizure starts in part of the brain and over time recruits other regions and increases in intensity. Although the clinical phenomenon is well recognized, the pathophysiology is not yet understood. Intracranial recordings of seizures have shown that there is a progressive recruitment of more areas of the brain (but not necessarily the entire brain) over the course of the seizure, and, as the convulsion begins, there is an increase in the frequency of the discharge. A step-by-step guide to the process of secondary generalization is not offered in this chapter as it is still largely speculative. The chapter, by necessity, speaks more...