Ictal high-frequency oscillations at 80-200 Hz coupled with delta phase in epileptic spasms

Abstract

Summary Previous studies of epileptic spasms reported that ictal events were associated with high-frequency oscillations (HFOs) or delta waves involving widespread regions. We determined whether ictal HFOs at 80–200 Hz were coupled with a phase of slow-wave, whether ictal slow-waves were diffusely or locally synchronous signals, and whether the mode of coupling between HFOs and slow-wave phases differed between ictal and interictal states. We studied 11 children who underwent extraoperative electrocorticography (ECoG) recording. The phases and amplitudes of slow-waves were measured at the peak of ictal and interictal HFOs in the seizure-onset sites. Ictal HFOs were locked tightly to the phase of slow-wave at ≤1 Hz. Ictal slow-waves propagated from the seizure-onset site to other regions. In contrast, interictal HFOs in the seizure-onset site were loosely locked to the phase of slow-wave at ≤1 Hz but tightly to that of ≥3-Hz. Ictal slow-waves coupled with HFOs can be explained as near-field and locally synchronized potentials generated by the neocortex rather than far-field potentials generated by subcortical structures. Ictal slow-waves in epileptic spasms may be generated by a mechanism different from what generates interictal HFOs–slow-wave complexes.

Vigabatrin therapy implicates neocortical high frequency oscillations in an animal model of infantile spasms

“…The neurobiological basis for these brief seizures is unknown but results from clinical studies have implicated a possible interaction between abnormal neocortical and subcortical circuits in their generation (Chugani et al , 1992, Dulac et al , 2002, Lado and Moshe, 2002, Hrachovy and Frost, 2003). A neocortical contribution of abnormal HFOs to spasm generation is supported by recent recordings in both humans and animals (Frost et al , 2011, Nariai et al , 2011a, Nariai et al , 2011b, Frost et al , 2012). …”

“…Neurophysiological studies of epileptic spasms in humans and an animal model have reported the presence of abnormal HFOs in EEG recordings (Panzica et al , 2007, Frost et al , 2011, Nariai et al , 2011a, Nariai et al , 2011b, Frost et al , 2012). Infantile spasms is the most common form of epileptic spasms.…”

Ictal propagation of high frequency activity is recapitulated in interictal recordings: Effective connectivity of epileptogenic networks recorded with intracranial EEG

“…There are increasing numbers of studies pointing to the importance of high frequency activity - HFA (Jiruska and Bragin, 2011; Jiruska et al, 2010; Jouny et al, 2007b; Rodin et al, 2009), or high frequency oscillations (HFOs) (Burns et al, 2012; Firpi et al, 2007; Jacobs et al, 2008; Jacobs et al, 2010; Jirsch et al, 2006; Nariai et al, 2011a; Ochi et al, 2007; Rampp and Stefan, 2006; Worrell et al, 2008; Worrell et al, 2004), for localizing the seizure onset zone. Recent studies have reported increased postsurgical seizure-free outcomes after resection of brain regions revealing ictal HFOs (Fujiwara et al, 2012; Jacobs et al, 2012; Jacobs et al, 2010; Modur et al, 2011; Nariai et al, 2011b; Ochi et al, 2007; Zijlmans et al, 2012).…”

Neocortical pathological high-frequency oscillations are associated with frequency-dependent alterations in functional network topology

“…Cotic and colleagues have previously shown that epileptic regions that demonstrate local cross-frequency interactions are also areas of increased interelectrode coherence (Cotic et al 2011), and Nariai and colleagues have demonstrated a tight coupling between the phase of slow waves (defined as Յ1 Hz in their study) during epileptic spasms and ictal pHFOs (Ͼ80 Hz) (Nariai et al 2011). Our present finding of elevated interregional slow frequency connectivity within the SOZ during seizure initiation and propagation adds additional emphasis on the role of slow oscillations during seizures.…”