Electrophysiological Biomarkers of Epilepsy

Abstract

In patients being evaluated for epilepsy and in animal models of epilepsy, electrophysiological recordings are carried to capture seizures to determine the existence of epilepsy. Electroencephalography recordings from the scalp, or sometimes directly from the brain, are also used to locate brain areas where seizure begins, and in surgical treatment help plan the area for resection. As seizures are unpredictable and can occur infrequently, ictal recordings are not ideal in terms of time, cost, or risk when, for example, determining the efficacy of existing or new anti-seizure drugs, evaluating potential anti-epileptogenic interventions, or for prolonged intracerebral electrode studies. Thus, there is a need to identify and validate other electrophysiological biomarkers of epilepsy that could be used to diagnose, treat, cure, and prevent epilepsy. Electroencephalography recordings in the epileptic brain contain other interictal electrophysiological disturbances that can occur more frequently than seizures, such as interictal spikes (IIS) and sharp waves, and from invasive studies using wide bandwidth recording and small diameter electrodes, the discovery of pathological high-frequency oscillations (HFOs) and microseizures. Of IIS, HFOs, and microseizures, a significant amount of recent research has focused on HFOs in the pathophysiology of epilepsy. Results from studies in animals with epilepsy and presurgical patients have consistently found a strong association between HFOs and epileptogenic brain tissue that suggest HFOs could be a potential biomarker of epileptogenicity and epileptogenesis. Here, we discuss several aspects of HFOs, as well as IIS and microseizures, and the evidence that supports their role as biomarkers of epilepsy.

Advances of Intracranial Electroencephalography in Localizing the Epileptogenic Zone

“…Data suggest that a reduction of summated synchronous inhibitory postsynaptic potentials (IPSPs) mediated by inhibitory interneurons plays a role in the generation of pathological HFOs [33]. Some studies suggest that principal cell firing or inhibitory postsynaptic currents contribute to their generation.…”

High Frequency Neuromagnetic Signals: A New Biomarker for Localizing Epileptic Areas Running Title: High-Frequency Neuromagnetic Signals in Epilepsy

“…Recent reports have shown that HFBS can also record with scalp Electrophotography (EEG) [33][34][35][36][37][38][39][40]. Scalp EEG is a non-invasive procedure as compared with intracranial recordings.…”

High Frequency Neuromagnetic Signals: A New Biomarker for Localizing Epileptic Areas Running Title: High-Frequency Neuromagnetic Signals in Epilepsy

“…Recent reports have shown that HFBS can also record with scalp Electrophotography (EEG) [33][34][35][36][37][38][39][40]. Scalp EEG is a non-invasive procedure as compared with intracranial recordings.…”