Name: Author Spotlight: Advancing Pediatric Epilepsy Surgery in Children Through Novel Biomarkers and Enhanced Localization
Uploaded: 2024-09-20T12:50:00
Duration: 2 min 2 s
Description: For children with drug-resistant epilepsy (DRE), seizure freedom relies on the delineation and resection (or ablation/disconnection) of the epileptogenic ...

Integrating MEG and HD-EEG in Pediatric Epilepsy Localization

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			<td>AIRSTIM unit</td>
			<td>SD Instruments</td>
			<td>N/A</td>
			<td>The SDI AIRSTIM system is an alternative unconditioned stimulus to shock</td>
		</tr>
		<tr>
			<td>Baby Shampoo&#160;</td>
			<td>Johnson&#39;s</td>
			<td>N/A</td>
			<td>Baby Shampoo is as gentle to the eyes as pure water and is specially designed to gently cleanse baby&#8217;s delicate hair and scalp.&#160;</td>
		</tr>
		<tr>
			<td>Control III disinfectant cleaning solution</td>
			<td>Maril Products, Inc.</td>
			<td>http://www.controlthree.com/</td>
			<td>Disinfectant and germicide solution formulated for hospitals</td>
		</tr>
		<tr>
			<td>Elekta Neuromag</td>
			<td>TRIUX</td>
			<td>NM24132A</td>
			<td>Comprehensive bioelectromagnetic measurement system characterized by 306-channel neuromagnetometer for functional brain studies</td>
		</tr>
		<tr>
			<td>FASTRAK</td>
			<td>Polhemus technology</td>
			<td>NS-7806</td>
			<td>Using A/C electromagnetic technology, FASTRAK delivers accurate position and orientation data, with virtually no latency. With a single magnetic source, FASTRAK delivers data for up to four sensors. The source emits an electromagnetic field, sensors within the field of range are tracked in full 6DOF (6 Degrees-Of-Freedom). Setup is simple and intuitive, with no user calibration required.</td>
		</tr>
		<tr>
			<td>Genuine Grass Reusable Cup EEG Electrodes</td>
			<td>Natus Medical, Inc.</td>
			<td>N/A</td>
			<td>Each Genuine Grass EEG Electrode undergoes rigorous mechanical and electrical testing to assure long life for unsurpassed recording clarity and dependability.</td>
		</tr>
		<tr>
			<td>Geodesic Sensor Net</td>
			<td>Electrical Geodesics, Inc.</td>
			<td>S-MAN-200-GSNR-001</td>
			<td>32 to 256 electrodes to place on the human head to aquire dense-array electroencephalography data</td>
		</tr>
		<tr>
			<td>GeoScan Sensor Digitization System</td>
			<td>Electrical Geodesics, Inc.</td>
			<td>8100550-03</td>
			<td>Handheld Scanner and Software for 3D electrode position registration</td>
		</tr>
		<tr>
			<td>Natus Xltek NeuroWorks</td>
			<td>Natus Medical, Inc.</td>
			<td>https://natus.com/</td>
			<td>The Natus NeuroWorks platform simplifies the process of collecting, monitoring and managing data for routine EEG testing, ambulatory EEG, long-term monitoring, ICU monitoring, and research studies.</td>
		</tr>
		<tr>
			<td>Natus NeuroWorks EEG Software</td>
			<td>Natus Medical, Inc.</td>
			<td>https://natus.com/neuro/neuroworks-eeg-software/</td>
			<td>NeuroWorks EEG software simplifies the process of collecting, monitoring, trending and managing EEG testing data, allowing care providers to save time and focus on delivering the best care.</td>
		</tr>
		<tr>
			<td>ROSA ONE Brain</td>
			<td>Zimmer Biomet</td>
			<td>https://www.zimmerbiomet.com/en/products-and-solutions/zb-edge/robotics/rosa-brain.html</td>
			<td>ROSA ONE Brain is a robotic solution to assist surgeons in planning and performing complex neurosurgical procedures through a small drill hole in the skull.&#160;</td>
		</tr>
		<tr>
			<td>Ten20 Conductive Paste</td>
			<td>Weaver and company</td>
			<td>N/A</td>
			<td>Ten20 contains the right balance of adhesiveness and conductivity, enabling the electrodes to remain in place while allowing the transmittance of electrical signals.</td>
		</tr>
	</tbody>
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electromagnetic source imaging in presurgical evaluation of children with drug-resistant epilepsy

Epilepsy is one of the most common and disabling neurological disorders characterized by recurrent and unprovoked seizures that can be either focal or generalized in nature. Despite the availability of several effective pharmacologic therapies (e.g., antiseizure medications [ASMs]), about 20-30% of these patients are unable to control their seizures and suffer from drug-resistant epilepsy (DRE)1. For these patients, epilepsy surgery is the most effective treatment to eliminate seizures; a successful surgery can be achieved through the complete resection (or ablation/disconnection) of the epileptogenic zone (EZ), defined as the minimal area indispensable for the generation of seizures2. Accurate delineation and resection (or ablation/disconnection) of the EZ while preserving the eloquent cortex are crucial factors in ensuring seizure freedom. To establish surgical candidacy, several noninvasive diagnostic tools are used by a multidisciplinary team to define different cortical areas (i.e., irritative zone, seizure onset zone [SOZ], functional deficit zone, and epileptogenic lesion), which serve as indirect approximators of the EZ3. Extra-operative monitoring with intracranial EEG (iEEG) is required when none of these methods unequivocally identify the EZ. The role of iEEG is to define precisely the EZ by localizing the SOZ (i.e., the brain area where clinical seizures generate) and map eloquent brain areas. Yet, it presents serious limitations due to its invasiveness4,5,6, it offers limited spatial coverage, and it needs a clear presurgical localization hypothesis7. As a result, the actual focus and extent of the SOZ may be missed, leading to unsuccessful surgery. Also, its interpretation requires the recording of multiple stereotyped clinical seizures during several days of hospitalization, which increases the chances of complications (e.g., infection and/or bleeding)5. Hence, there is an unmet need to develop reliable and noninvasive localization methods that can provide clinically useful information and overall improve the presurgical evaluation of children with DRE.
Over the last decades, electric and magnetic source imaging (ESI and MSI) have been increasingly utilized in the presurgical evaluation of patients with DRE for the delineation of epileptogenic as well as functional brain areas. Particularly, ESI and MSI allow the reconstruction of neural sources from noninvasive recordings, such as high-density EEG (HD-EEG) and magnetoencephalography (MEG), to help guide surgical planning or iEEG electrode placement. ESI and MSI can be applied for localizing either interictal epileptiform discharges (IEDs), such as spikes and sharp waves, or ictal (seizure) activity. It may further be used for the localization of different functional brain areas involved in sensory, motor, auditory, and cognitive functions. The reconstruction of electrophysiological events, such as IEDs and seizures, allows the identification of the irritative zone (i.e., the brain area where IEDs originate) and the SOZ, respectively, which are considered a valid surrogate for the EZ localization. The localization of the eloquent cortex (i.e., the brain areas indispensable for defined cortical functions)3 allows instead to map the location and extent of eloquent areas with respect to the planned resection and, therefore, reduce in advance potential functional deficits that may be expected from epilepsy surgery8,9,10,11. Several studies investigated the clinical utility of ESI and/or MSI in the presurgical evaluation of epilepsy, and they showed promising findings in the delineation of the EZ12,13,14,15,16,17,18,19. For example, Mouthaan et al.14 performed an extensive meta-analysis using noninvasive data of 11 prospective and retrospective epilepsy studies and reported that these source localization techniques can overall identify the EZ with high sensitivity (82%) and low specificity (53%). Other studies also showed that MSI and ESI can correctly localize the epileptic focus within the resected area in epileptic patients having a normal magnetic resonance imaging (MRI)19,20,21. These localization results are particularly important for those patients who are ineligible for epilepsy surgery due to inconclusive clinical or imaging findings. In summary, ESI and MSI can contribute significantly to the presurgical mapping of epileptogenic as well as functional brain areas in patients with DRE.
Despite these encouraging findings, such techniques are currently performed in only a few tertiary epilepsy centers on a regular basis and are often underutilized in pediatric populations. Moreover, HD-EEG and MEG are rarely recorded simultaneously, although they provide both confirmatory and complementary information. MEG is sensitive to detect superficial sources with tangential orientation but is blind to radially oriented sources located at the gyri or deeper areas of the brain22,23,24,25,26. Furthermore, MEG provides better spatial resolution (millimeters) compared to EEG16,22,25. Unlike EEG signals, MEG signals are reference-free and are essentially unaffected by different conductivities of brain tissues (i.e., meninges, cerebrospinal fluid, skull, and scalp)25,27 providing undistorted measurements of the magnetic fields produced by the brain. On the other hand, EEG can detect sources of all orientations, but it offers lower spatial resolution than MEG and is more susceptible to artifacts26,28. Due to these complementary sensitivities to source orientation and depth, approximately 30% of the epileptiform activity (e.g., IEDs) can only be recorded on MEG but not on EEG, and vice versa26,29,30,31,32. Contrary to EEG, which allows prolonged recordings, capturing clinical seizures with MEG is challenging due to the restricted recording time that is usually insufficient to record ictal events in most patients. Furthermore, artifacts caused by seizure-related head movements can often interfere with the quality of MEG recordings29,33,34,35. On the other hand, MEG recordings are faster and easier compared to EEG, especially in children since there is no need to attach sensors over the children&#39;s head35.
Advances in hardware have made it possible to record simultaneously MEG and HD-EEG data with a high number of sensors (over 550 sensors) covering the whole head. Moreover, modern developments in EEG technologies have minimized the preparation time for HD-EEG to less than a quarter of an hour36. This is particularly important for pediatric populations with challenging behaviors who are unable to stay still for prolonged periods. Furthermore, advancements in software technologies have allowed the combination of ESI and MSI into a single solution, namely electromagnetic source imaging (EMSI), performed on simultaneous HD-EEG and MEG recordings. Several theoretical and empirical studies reported higher source localization accuracy with EMSI than either modality alone13,30,31,37,38,39,40,41. Using different source localization approaches to reconstruct the activity in response to sensory stimuli, Sharon et al.37 found that EMSI had consistently better localization results than either ESI or MSI alone compared to functional MRI&#160;(fMRI), which serves as noninvasive benchmark of precise localization accuracy. The authors suggested that this improved localization is due to the increased number of sensors for solving the inverse solution and the different sensitivity patterns of the two imaging modalities37. Similarly, Yoshinaga et al.31 performed dipole analysis on simultaneous EEG and MEG data of patients with intractable localization-related epilepsy and showed that EMSI provided information that would be not obtainable by using only one modality alone and led to successful localization for epilepsy surgery in one of the patients analyzed. In a prospective blinded study, Duez et al.13 showed that EMSI achieved a significantly higher odds ratio (i.e., probability of becoming seizure-free) compared to ESI and MSI, a localization accuracy &#8805;52%, and a concordance &#8805;53% and &#8805;36% with the irritative and SOZ, respectively. A more recent study from our group42 has shown that EMSI provided superior localization estimates and better outcome prediction performance than either ESI or MSI alone, with localization errors from resection and SOZ of ~8 mm and ~15 mm, respectively. Despite these promising findings, there is a lack of studies that provide the methodological framework regarding EMSI in children with DRE.
This study illustrates the experimental setup for performing simultaneous MEG and HD-EEG recordings as well as the methodological framework for analyzing these data aiming to localize the irritative zone, SOZ, and eloquent brain areas in children with DRE. More specifically, the experimental setups are presented for (i) recording and localizing interictal and ictal epileptiform activity during sleep and (ii) recording visual-, motor-, auditory-, and somatosensory-evoked responses and mapping relevant eloquent brain areas (i.e., visual, motor, auditory, and somatosensory) during a visuomotor task, as well as auditory and somatosensory stimulations. Detailed steps of the data analysis pipeline are further presented for performing EMSI as well as individual ESI and MSI using equivalent current dipole (ECD) and dynamic statistical parametric mapping (dSPM).

Author Spotlight: Advancing Pediatric Epilepsy Surgery in Children Through Novel Biomarkers and Enhanced Localization

Elektromagnetisk kildeavbildning i prekirurgisk evaluering av barn med medikamentresistent epilepsi

For children with drug-resistant epilepsy (DRE), seizure freedom relies on the delineation and resection (or ablation/disconnection) of the epileptogenic ...