When spikes are symmetric, ripples are not: Bilateral spike and wave above 80 Hz in focal and generalized epilepsy

Pizzo, Francesca; Ferrari-Marinho, Taíssa; Amiri, Mina; Frauscher, Birgit; Dubeau, François; Gotman, Jean

doi:10.1016/j.clinph.2015.11.451

Cited by 26 publications

(19 citation statements)

References 37 publications

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“…Nevertheless, all publications seem to show that HFOs localize to the affected hemisphere or lobe. 15,28,[64][65][66] That HFOs are able to mirror disease activity has been shown by various authors (see also the sections HFOs Mirror Disease Activity and Important Aspects of HFOs in Children). Pizzo et al attempted to apply HFO assessment to the differentiation between secondary bilateral synchrony in focal epilepsy and primary bilateral synchrony in idiopathic generalized epilepsy.…”

Section: Scalp Eegmentioning

confidence: 94%

“…They did not, however, help to differentiate between focal and generalized epilepsy. 65 Interestingly, the work of Melani et al 66 showed that rates of HFOs in the scalp EEG clearly depended on the rates of epileptic spikes. Furthermore, scalp interictal epileptiform discharges, when frequently accompanied by HFOs, were shown to be associated with larger cortical metabolic responses and with thalamic involvement lateralized to the side of cortical ripples.…”

Section: Scalp Eegmentioning

confidence: 99%

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High‐frequency oscillations: The state of clinical research

et al. 2017

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Summary Modern electroencephalographic (EEG) technology contributed to the appreciation that the EEG signal outside the classical Berger frequency band contains important information. In epilepsy, research of the past decade focused particularly on interictal high-frequency oscillations (HFOs) > 80 Hz. The first large application of HFOs was in the context of epilepsy surgery. This is now followed by other applications such as assessment of epilepsy severity and monitoring of antiepileptic therapy. This article reviews the evidence on the clinical use of HFOs in epilepsy with an emphasis on the latest developments. It highlights the growing literature on the association between HFOs and post-surgical seizure outcome. A recent meta-analysis confirmed a higher resection ratio for HFOs in seizure-free versus non–seizure-free patients. Residual HFOs in the postoperative electrocorticogram were shown to predict epilepsy surgery outcome better than preoperative HFO rates. The review further discusses the different attempts to separate physiological from epileptic HFOs, as this might increase the specificity of HFOs. As an example, analysis of sleep microstructure demonstrated a different coupling between HFOs inside and outside the epileptogenic zone. Moreover, there is increasing evidence that HFOs are useful to measure disease activity and assess treatment response using noninvasive EEG and magnetoencephalography. This approach is particularly promising in children, because they show high scalp HFO rates. HFO rates in West syndrome decrease after adrenocorticotropic hormone treatment. Presence of HFOs at the time of rolandic spikes correlates with seizure frequency. The time-consuming visual assessment of HFOs, which prevented their clinical application in the past, is now overcome by validated computer-assisted algorithms. HFO research has considerably advanced over the past decade, and use of noninvasive methods will make HFOs accessible to large numbers of patients. Prospective multicenter trials are awaited to gather information over long recording periods in large patient samples.

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Section: Scalp Eegmentioning

confidence: 94%

Section: Scalp Eegmentioning

confidence: 99%

High‐frequency oscillations: The state of clinical research

et al. 2017

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“…On the other hand, scalp HFOs could be more useful in patient with widely distributed spikes. This approach demonstrated the possibility of lateralizing the seizure onset zone in patients with focal epilepsy and secondary bilateral synchrony (Pizzo et al, 2015). Further studies are required to estimate, in larger samples and in the context of clinical practice, the added-value of scalp HFOs in patients with focal epilepsies.…”

Section: High Frequency Oscillationsmentioning

confidence: 99%

“…More recently, it has been demonstrated that HFOs (ripple) can be detected in scalp EEG in patients with focal epilepsies (Andrade-Valenca et al, 2011;Melani et al, 2013;Zelmann et al, 2014;Pizzo et al, 2015;Cuello-Oderiz et al, 2017;Zijlmans et al, 2017). Nevertheless, scalp HFOs analyses require careful methodology to avoid muscular or movement artefact (Zijlmans et al, 2017), and regarding filtering in order to avoid "false-ripple" detection (Bénar et al, 2010) Even although scalp HFOs have better specificity than spikes they are less sensitive (Andrade-Valenca et al, 2011).…”

Section: High Frequency Oscillationsmentioning

confidence: 99%

Focal epilepsies and focal disorders

Lagarde¹,

Bartolomei²

2019

Handbook of Clinical Neurology

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Electroencephalographic (EEG) investigations are crucial in the diagnosis and management of patients with focal epilepsies. EEG may reveal different interictal epileptiform discharges (IED: spikes, sharp waves). The EEG visibility of spike depends on the surface area of cortex involved (>10cm 2) and the brain localisation of cortical generators. Regions generating IED (defining the "irritative zone") are not necessarily equivalent to the seizure onset zone. Focal seizures are dynamic processes originating from one or several brain regions (generating fast oscillations and called "epileptogenic zone") before to spread to other structures (generating lower frequency oscillations and called "propagation zone"). Several factors limit the expression of seizures on scalp EEG, such as area involved, degree of synchronization and depth of the cortical generators. Different scalp EEG seizure onset patterns may be observed: fast discharge, background flattening, rhythmic spikes, sinusoidal discharge, or sharp activity but to a large extent EEG changes are linked to seizure propagation. Finally, in the context of presurgical evaluation, the combination of interictal and ictal EEG features is crucial to provide optimal hypothesis about the epileptogenic zone.

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“…Though the first observations of HFOs were observed in invasive microwire (Bragin et al, 1999) and macroelectrode recordings (Jirsch et al, 2006), recently a small number of groups have also reported several observations of fast oscillations in the ripple range (100–250 Hz) in non-invasive scalp EEG recordings (Kobayashi et al, 2010; Andrade-Valenca et al, 2011; Iwatana et al., 2012; Melani et al, 2013; Pizzo et al, 2016; van Klink et al, 2016; Chu et al, 2017). As expected, these fast oscillations are better observed in scalp EEG recordings with increased spatial and temporal sampling (Chu et al, 2017).…”

mentioning

confidence: 99%

Targeting high frequency oscillations in epilepsy

Chu

2018

Clinical Neurophysiology

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When spikes are symmetric, ripples are not: Bilateral spike and wave above 80 Hz in focal and generalized epilepsy

Cited by 26 publications

References 37 publications

High‐frequency oscillations: The state of clinical research

High‐frequency oscillations: The state of clinical research

Focal epilepsies and focal disorders

Targeting high frequency oscillations in epilepsy

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