EEG Biomarkers of Epileptogenesis

Excerpt

Insults to the brain (e.g., stroke, head trauma, infection, status epilepticus) can precipitate the development of epilepsy—months or even years after the initial insult. While not all patients with such injuries will go on to develop epilepsy, in a subgroup of individuals the injury will trigger epileptogenesis—a complex chain of events that transforms a nonepileptic brain into one that is prone to generating spontaneous seizures. To date, there are no clinically available tools capable of predicting which individuals are at high risk of post-insult epilepsy. A growing number of studies attempt to bridge this gap, by evaluating the utility of different diagnostic modalities (e.g., neuroimaging, molecular testing, electroencephalogram [EEG] analysis) in capturing changes reflective of the epileptogenic process. EEG holds particular promise as a modality for reflecting epileptogenic changes, due to its high temporal resolution and subsequent ability to capture a wide variety of brain-activity signatures. With the added advantages of portability, relative ease of use, safety, and low cost, a successful EEG-based biomarker is likely to become widely accessible in clinical settings. This chapter will discuss the most promising EEG signatures of epileptogenesis (interictal spikes, high-frequency oscillations, theta dynamics, and nonlinear dynamics), and the challenges of translating these biomarkers into clinically applicable tools. We conclude by highlighting the potential value of biomarker paradigms that (1) combine several signatures and (2) examine dynamic changes in these signatures over time.