Presurgical evaluation of epilepsy

Rosenow, Felix; Lüders, Hans

doi:10.1093/brain/124.9.1683

Cited by 1,438 publications

(1,179 citation statements)

References 128 publications

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“…A major motivation for much of the work on the relationship between pHFOs and epileptic tissue is to contribute to the identification of the epileptogenic zone (Rosenow and Luders, 2001) to guide epilepsy surgery (Jiruska et al, 2008;Zijlmans et al, 2012). In this context it does not matter if pHFOs are an epiphenomenon, for instance a biomarker for enhanced excitability of a population of neurons.…”

Section: Evidence For Hfos In Experimental and Clinical Epilepsymentioning

confidence: 99%

Mechanisms of physiological and epileptic HFO generation

Jefferys

Prida

Wendling

et al. 2012

Progress in Neurobiology

268

238

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High frequency oscillations (HFO) have a variety of characteristics: band-limited or broad-band, transient burst-like phenomenon or steady-state. HFOs may be encountered under physiological or under pathological conditions (pHFO). Here we review the underlying mechanisms of oscillations, at the level of cells and networks, investigated in a variety of experimental in vitro and in vivo models. Diverse mechanisms are described, from intrinsic membrane oscillations to network processes involving different types of synaptic interactions, gap junctions and ephaptic coupling. HFOs with similar frequency ranges can differ considerably in their physiological mechanisms. The fact that in most cases the combination of intrinsic neuronal membrane oscillations and synaptic circuits are necessary to sustain network oscillations is emphasized. Evidence for pathological HFOs, particularly fast ripples, in experimental models of epilepsy and in human epileptic patients is scrutinized. The underlying mechanisms of fast ripples are examined both in the light of animal observations, in vivo and in vitro, and in epileptic patients, with emphasis on single cell dynamics. Experimental observations and computational modeling have led to hypotheses for these mechanisms, several of which are considered here, namely the role of out-ofphase firing in neuronal clusters, the importance of strong excitatory AMPA-synaptic currents and recurrent inhibitory connectivity in combination with the fast time scales of IPSPs, ephaptic coupling and the contribution of interneuronal coupling through gap junctions. The statistical behaviour of fast ripple events can provide useful information on the underlying mechanism and can help to further improve classification of the diverse forms of HFOs.

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Section: Evidence For Hfos In Experimental and Clinical Epilepsymentioning

confidence: 99%

Mechanisms of physiological and epileptic HFO generation

Jefferys

Prida

Wendling

et al. 2012

Progress in Neurobiology

268

238

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“…The second step is to localize the epileptogenic zone, which is defined as the region, the resection of which is necessary and sufficient to achieve seizure freedom 18 . Although the anatomical extent of the epileptogenic zone cannot be directly measured, it can be assumed using a multimodality approach comprising clinical, EEG, MRI, and neuropsychological evaluations.…”

Section: Minimum Requirements For An Epilepsy Surgery Centermentioning

confidence: 99%

Surgical Treatment for Epilepsy

Engel¹

2008

JAMA

101

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Surgical treatment for epilepsy remains highly underutilized: in the United States, there has been no increase in the number of surgical procedures performed annually since 1990 1 ; for most patients referred, the average duration of epilepsy is 22 years 2 ; and there has been no change in this delay to surgery 3 , despite two randomized controlled trials 4, 5 and an American Academy of Neurology practice parameter that recommended surgery as the treatment of choice for medically refractory temporal lobe epilepsy 6 . This session addressed issues relevant to increasing the availability of epilepsy surgery, particularly in countries with limited resources. Who should be referred for surgical therapy?Two-thirds of patients with epilepsy have epileptic seizures that are easily controlled by antiseizure drugs. Of the remainder, causes of apparent pharmacoresistance include noncompliance, seizures that are not epileptic, misdiagnosis of the type of epilepsy condition, prescription of the wrong antiseizure drug or the wrong regimen and dosage, and lifestyle issues that lower seizure threshold or provoke ictal events.The International League against Epilepsy has proposed that drug-resistant epilepsy should be defined as "failure of adequate drug trials of two tolerated, appropriately chosen and used antiepileptic drugs (whether as monotherapy or in combination) to achieve sustained seizure freedom" 7 . Studies have shown that after failure of two appropriate drug trials, only 3 % of patients eventually become seizure free 8 .It is recommended, therefore, that patients meeting this definition of drug-resistant epilepsy should be referred to an epilepsy center with specialized epileptologists, who can identify specific epilepsy syndromes, distinguish them from psychogenic non-epileptic seizures and other non-epileptic events, diagnose underlying treatable causes, use specialized pharmacologic approaches, address disabling psychosocial problems, and consider alternative treatments such as vagus nerve stimulation, ketogenic diet, behavioral therapies, and surgery. Rather than asking who should be referred for surgical therapy, neurologists

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“…In presurgical diagnostics for patients with epilepsy, the brain areas which generate epileptic spikes are called the irritative zone (Rosenow and Luders, 2001). It is however unclear to what extent the spikes are indicators of the epileptic potential of the underlying cortex.…”

Section: Introductionmentioning

confidence: 99%

High-frequency changes during interictal spikes detected by time-frequency analysis

Jacobs

Kobayashi

Gotman

2011

Clinical Neurophysiology

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Objective-High-frequency (HF) changes were analysed in relation to anatomical origin of spikes, shape and occurrence within the seizure onset zone (SOZ). We evaluated whether HF changes are linked to the SOZ, as established for distinct high-frequency oscillations.Methods-SEEG was filtered at 500 Hz and sampled at 2000 Hz. Spikes were selected by shape (spike/spike-slow wave) and location (SOZ/non-SOZ and neocortex/amygdala/hippocampus) in 15 patients. About 50 spikes were averaged for each set. Changes compared to baseline were quantified with false discovery rate controlled t-statistics using time-frequency spectra. Counts of increased or decreased time-frequency values were compared across spike categories in the 80-250 and 250-500 Hz bands.Results-Seventy-seven spike types were analysed. Differences between spike categories were most prominent between 250 and 500 Hz. HF changes were more frequent and larger in mesial temporal than in neocortical spikes and for spikes with slow waves than spikes alone. HF changes above 250 Hz were more frequent in spikes within than outside the SOZ. Conclusions-HF increases above 250Hz show regional differences and are very prominent in the SOZ. Hippocampal spikes have the strongest HF components.Significance-Analysis of HF changes during spikes may provide information on differing pathophysiological mechanisms of spikes and on epileptogenicity of the tissue.

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Presurgical evaluation of epilepsy

Cited by 1,438 publications

References 128 publications

Mechanisms of physiological and epileptic HFO generation

Mechanisms of physiological and epileptic HFO generation

Surgical Treatment for Epilepsy

High-frequency changes during interictal spikes detected by time-frequency analysis

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