Name: a multimodal imaging- and stimulation-based method of evaluating connectivity-related brain excitability in patients with epilepsy
Uploaded: 2016-11-13T14:00:00
Description: Watch this Scientific Journal Video about A Multimodal Imaging- and Stimulation-based Method of Evaluating Connectivity-related Brain Excitability in Patients with Epilepsy at JoVE.com

The authors would like to thank Emily L. Thorn, B.A., for her assistance with the Source estimation of evoked electrical activity Section. MMS was supported by a KL2/Catalyst Medical Research Investigator Training award from Harvard Catalyst/The Harvard Clinical and Translational Science Center (National Center for Research Resources and the National Center for Advancing Translational Sciences, National Institutes of Health Award KL2 TR001100). CJC was supported by a grant from the National Institutes of Health (5K12NS066225). APL was supported in part by grants from the Sidney R. Baer Jr. Foundation, the National Institutes of Health (R01 HD069776, R01 NS073601, R21 MH099196, R21 NS082870, R21 NS085491, R21 HD07616), and Harvard Catalyst/The Harvard Clinical and Translational Science Center (NCRR and the NCATS, NIH UL1 RR025758). BSC was supported by the National Institute of Neurological Disorders and Stroke (R01 NS073601).

The protocol described here was approved by the institutional review boards of the Beth Israel Deaconess Medical Center and the Massachusetts Institute of Technology.
1. Subject Selection
<ol>
	<li>Patient selection for research protocol.
	<ol>
		<li>Identify patients with active epilepsy (seizures within the past year) or a history of remote epilepsy (prior seizures, but with no seizures in the past five years either on or off medication) and periventricular nodular heterotopia on structura...

Resting-state functional connectivity MRI has been used to identify network connectivity in the human brain, and to identify alterations of connectivity that occur in different disease states26,31,32. However, as fMRI functional connectivity is based on identifying correlations in the BOLD signal, and as blood oxygenation changes have a non-trivial relationship with underlying neural activity, the causal significance and physiological relevance of these fMRI connectivity findings is unclear. TMS enables spatia...

Transcranial magnetic stimulation (TMS) is a means of noninvasively stimulating regions of cortex via electromagnetic induction. In TMS, a large but spatially restricted magnetic flux is used to induce an electrical field in a target cortical area, and thereby modulate the activity of the underlying neural tissue. TMS to motor cortex results in motor evoked potentials that can be measured peripherally via electromyography (EMG). When applied in pairs or triplets of pulses, TMS can be used to assess the activity of specific intracortical GABAergic and glutaminergic circuits1-3, and thus assess the balance of excitation and inhibition in vivo in human patients. In epilepsy specifically, TMS studies have shown that cortical hyperexcitability is present in patients with epilepsy4,5, and may normalize with successful anti-epileptic drug therapy and thus predict response to medication6. Furthermore, TMS measures of cortical excitability show intermediate values in patients with a single seizure7 and in siblings of patients with both idiopathic generalized and acquired focal epilepsies8. These findings suggest that TMS measures of cortical excitability may allow us to identify endophenotypes for epilepsy. However, the sensitivity and specificity of these measures are limited, likely because TMS-EMG can only be assessed with stimulation of motor cortical circuits, and many patients with epilepsy have seizure foci outside the motor cortex.
Electroencephalography (EEG) provides an opportunity to directly measure the cerebral response to TMS, and can be used to assess cerebral reactivity across wide areas of neocortex. Studies integrating TMS with EEG (TMS-EEG) have shown that TMS produces waves of activity that reverberate throughout the cortex9,10 and that are reproducible and reliable11-13. By evaluating the propagation of evoked activity in different behavioral states and in different tasks, TMS-EEG has been used to causally probe the dynamic effective connectivity of human brain networks10,14-16. TMS-EEG measures have shown significant abnormalities in diseases ranging from schizophrenia17 to ADHD18, and in disorders of consciousness such as persistent vegetative state19. Furthermore, several groups have identified EEG correlates of the paired-pulse TMS-EMG metrics that are abnormal in patients with epilepsy20,21. Of particular relevance, previous studies have also suggested that abnormal stimulation-evoked EEG activity is seen in patients with epilepsy22-25.
Another means of evaluating brain circuits is via resting-state functional connectivity MRI (rs-fcMRI), a technique that evaluates the correlations over time in the blood oxygenation level dependent (BOLD) signal from different brain regions26. Studies using rs-fcMRI have demonstrated that the human brain is organized into distinct networks of interacting regions26-29, that neuropsychiatric diseases may occur within specific large-scale distributed neural networks identified by rs-fcMRI30, and that the brain networks identified via rs-fcMRI are often abnormal in neuropsychiatric disease states31,32. In terms of potential clinical applications, rs-fcMRI has several advantages over conventional task-based fMRI application33, including less reliance on subject cooperation and concern over variable performance. Consequently, there has recently been an explosion of studies exploring rs-fcMRI changes in different disease states. However, one of the limitations of rs-fcMRI is the difficulty in determining whether and how correlations (or anticorrelations) in the BOLD signal relate to the electrophysiological interactions that form the basis of neuronal communication. A related problem is that it is often unclear whether the rs-fcMRI changes seen in various disease states have physiologic significance. In particular with regards to epilepsy, it is unclear whether abnormalities in rs-fcMRI are due solely to interictal epileptiform transients, or exist independently of such electrophysiological abnormalities; simultaneous EEG-fMRI is needed to help evaluate between these possibilities34.
As TMS can be used to produce transient or sustained changes in the activations of different cortical regions, TMS studies provide a means of causally assessing the significance of different resting-state fMRI connectivity patterns. One approach is to use rs-fcMRI to guide therapeutic stimulation efforts in different disease states; it could be expected that TMS targeted to regions that are functionally connected to areas known to be involved in different disease states is more likely to be therapeutically effective than TMS targeted to regions without such functional connectivity, and indeed several studies have found preliminary evidence for this35,36. Another approach would involve using TMS-EEG to causally assess the physiologic significance of different resting-state fcMRI patterns. Specifically, one can test the hypothesis that regions that show abnormal functional connectivity in a specific disease state should show a different response to stimulation in patients than in healthy subjects, and that these physiologic abnormalities are present specifically (or primarily) with stimulation of the abnormally connected region.
To illustrate the above, we provide an example of a recent study in which rs-fcMRI, TMS and EEG were combined to explore cortical hyperexcitability in patients with epilepsy due to the developmental brain abnormality periventricular nodular heterotopia (PNH)37. Patients with PNH present clinically with adolescent- or adult-onset epilepsy, reading disability, and normal intelligence, and have abnormal nodules of gray matter adjacent to the lateral ventricles on neuroimaging38,39. Previous studies have shown that these periventricular nodules of heterotopic gray matter are structurally and functionally connected to discrete foci in the neocortex40,41, and that epileptic seizures may originate from neocortical regions, heterotopic gray matter, or both simultaneously42, suggesting that epileptogenesis in these patients is a circuit phenomenon. By using resting-state fc-MRI to guide TMS-EEG, we demonstrated that patients with active epilepsy due to PNH have evidence of cortical hyperexcitability, and that this hyperexcitability appears to be limited to regions with abnormal functional connectivity to the deep nodules.
The protocol is conducted in two separate sessions. During the first session, structural and resting-state blood-oxygenation level-dependent (BOLD) contrast MRI sequences are acquired (for patients), or just structural MRI sequences (for the healthy controls). Between the first and second sessions, resting-state functional connectivity analysis is used to define the cortical targets for the patients, and the MNI coordinates for these targets are obtained. The equivalent cortical targets (based on MNI coordinates) are then identified for each healthy control subject. In the second session, the TMS-EEG data is obtained.
In the example given in this paper, functional-connectivity MRI analyses were performed using an in-house software toolbox and the MRI software43,44. Neuro-navigated TMS was performed with a transcranial magnetic stimulator with real-time MRI neuronavigation. EEG was recorded with a 60-channel TMS-compatible system, which utilizes a sample-and-hold circuit to avoid amplifier saturation by TMS. EEG data were analyzed using custom scripts and the EEGLAB toolbox45 (version 12.0.2.4b) running in MATLAB R2012b.

<table border="0" cellpadding="0" cellspacing="0" width="573">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">3T MRI scanner</td>
			<td style="width:71px;"></td>
			<td style="width:119px;"></td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">MRI functional connectivity software</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">MRI image viewing software</td>
			<td></td>
			<td></td>
			<td>MRICron</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Transcranial Magnetic Stimulator</td>
			<td>Nexstim</td>
			<td>eXimia Stimulator&#160;</td>
			<td>Can use stimulators from other suppliers e.g. Magventure, Magstim</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">MRI neuronavigation system</td>
			<td>Nexstim</td>
			<td>NBS v3.2.1</td>
			<td>Alternative MRI neuronavigation system e.g. Brainsight, Localite</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">TMS-compatible EEG system</td>
			<td>Nexstim</td>
			<td>Eximia EEG</td>
			<td>Alternatives: Brain Products, Synamps, ANT</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Matlab</td>
			<td>Mathworks</td>
			<td>R2012b</td>
			<td>Alternatives: Octave</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">EEGLab</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr height="21">
			<td colspan="2" height="21" style="height:21px;">Minimum Norm Estimate (MNE) software</td>
			<td></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">FreeSurfer</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

a multimodal imaging- and stimulation-based method of evaluating connectivity-related brain excitability in patients with epilepsy

Resting-state functional connectivity MRI (rs-fcMRI) is a technique that identifies connectivity between different brain regions based on correlations over time in the blood-oxygenation level dependent signal. rs-fcMRI has been applied extensively to identify abnormalities in brain connectivity in different neurologic and psychiatric diseases. However, the relationship among rs-fcMRI connectivity abnormalities, brain electrophysiology and disease state is unknown, in part because the causal significance of alterations in functional connectivity in disease pathophysiology has not been established. Transcranial Magnetic Stimulation (TMS) is a technique that uses electromagnetic induction to noninvasively produce focal changes in cortical activity. When combined with electroencephalography (EEG), TMS can be used to assess the brain's response to external perturbations. Here we provide a protocol for combining rs-fcMRI, TMS and EEG to assess the physiologic significance of alterations in functional connectivity in patients with neuropsychiatric disease. We provide representative results from a previously published study in which rs-fcMRI was used to identify regions with abnormal connectivity in patients with epilepsy due to a malformation of cortical development, periventricular nodular heterotopia (PNH). Stimulation in patients with epilepsy resulted in abnormal TMS-evoked EEG activity relative to stimulation of the same sites in matched healthy control patients, with an abnormal increase in the late component of the TMS-evoked potential, consistent with cortical hyperexcitability. This abnormality was specific to regions with abnormal resting-state functional connectivity. Electrical source analysis in a subject with previously recorded seizures demonstrated that the origin of the abnormal TMS-evoked activity co-localized with the seizure-onset zone, suggesting the presence of an epileptogenic circuit. These results demonstrate how rs-fcMRI, TMS and EEG can be utilized together to identify and understand the physiological significance of abnormal brain connectivity in human diseases.

Resting-state functional connectivity fMRI can be used to identify regions of cortex that demonstrate high functional connectivity with the heterotopic periventricular gray matter nodules (Figure 1), and control regions without such connectivity. To determine whether such abnormal functional connectivity has physiologic significance, the cortical region with correlated resting-state activity can be chosen as the &#34;connected&#34; target sites for neuronavigated TMS, and...

Watch this Scientific Journal Video about A Multimodal Imaging- and Stimulation-based Method of Evaluating Connectivity-related Brain Excitability in Patients with Epilepsy at JoVE.com

A Multimodal Imaging- and Stimulation-based Method of Evaluating Connectivity-related Brain Excitability in Patients with Epilepsy

Resting-state functional-connectivity MRI has identified abnormalities in patients with a wide range of neuropsychiatric disorders, including epilepsy due to malformations of cortical development. Transcranial Magnetic Stimulation in combination with EEG can demonstrate that patients with epilepsy have cortical hyperexcitability in regions with abnormal connectivity.

Resting-state functional connectivity MRI (rs-fcMRI) is a technique that identifies connectivity between different brain regions based on correlations ...

The overall goal of this experiment is to evaluate regional cortical hyperexcitability in patients with epilepsy using resting-state functional connectivity, MRI-guided, transcranial magnetic stimulation in combination with simultaneous EEG recording. This method can help answer key questions in the field of epilepsy and neurophysiology, such as whether patients with epilepsy have evidence of hyperexcitability in regions that are believed to be part of the epileptogenic network. The main advantage of this technique is that it can be used to assess differences in cerebral excitability as a function of connectivity and can be used to assess cortical reactivity across a variety of different brain regions.This technique has implications for the diagnosis and treatment of epilepsy, as cortical hyperexcitability can be identified even when the routine EEG is normal, and epileptogenic circuits can be targeted therapeutically. Demonstrating the procedure will be Tamara Gedankian, a research assistant in my laboratory. Prior to testing, determine the two TMS target regions by superimposing each subject's functional connectivity map onto each subject's structural image.To begin the experimental session, bring the subject into the testing room and have them sit in the chair. Measure the subject's head, and select an Electroencephalography, or EEG, cap, of appropriate size to enable low electrode impedances. Next, thoroughly clean the skin under each electrode using a cotton tip applicator and alcohol.Add conductive gel to each electrode, and press down on the electrode to ensure good contact between the scalp, gel, and electrode. To minimize charging artifacts, ensure that the gel does not spread outside of the electrode holder. Place the reference and ground electrodes on the forehead, and as far from the stimulation coil as possible, to minimize the possibility of a TMS-induced electrode artifact contaminating the entire recording.Place these electrodes within a few centimeters of each other to minimize common-mode noise. Then press the measure impedances button on the EEG system. Check electrode impedances by plugging the EEG output cables into the impedance jack of the EEG recording system.Ensure that the electrode impedance is not greater than five kilomes. Next, prepare the electromyography electrodes on the contralateral hand. Give the subject earplugs to minimize risk of hearing loss and tinnitus.Then place the infrared detectors on the subject's head, ensuring that the detectors are placed in a way to minimized risk of movement during the experimental session. Coregister the subject's head with the MRI images by identifying the location of the preselected, external anatomic fiducial markers on the subject using the pointer that is included with the neuronavigation equipment. Familiarize the subject with stimulation by applying a pulse elsewhere or by applying a low-intensity stimulation pulse to the scalp.Determine the resting motor threshold by locating the subject's motor cortex on the hemisphere ipsilateral to the functional connectivity-base targets. Angle the coil perpendicular to the gyrus with the handle pointing occipitally, and begin stimulation at an intensity that is expected to be sub-threshold. Then increase stimulation intensity in steps of 5%max stimulator output until TMS consistently evokes motor-evoked potentials with amplitudes greater than 50 microvolts in each trial.Decrease stimulation intensity in steps of 1%max stimulator output until less than five positive responses out of 10 are recorded. Finally, set the TMS intensity to the desired value. Apply single pulses of TMS to each of the target regions using the neuronavigation software, with variable intervals between pulses to minimize cortical plasticity and subject expectancy effects.Begin by performing an initial round of an Independent Component Analysis, or ICA, and remove the one to two components representing the large TMS-induced, initial muscle activation. To do this, run ICA using the fast ICA method with the symmetric approach, and the 10 contrast function, using the command shown here. Identify components consistent with the TMS artifact by selecting Tools, Reject data using ICA, and remove components by map, which will plot topographic maps of all the ICA components.Then click on the number for each component to plot component details. Next, delete the artifactual components by selecting Tools, Remove components, and entering the relevant component numbers in the field for Component(s)to remove from data. In the confirmation box that pops up, press Plot ERPs to review the event-related potentials, or ERPs, that result from deletion of the selected components.To review single trial effects, press Plot single trials. After reviewing the ERP, as in single trials, press the Accept button to delete the selected components. Perform a second round of ICA and remove components corresponding to artifacts of decay, blinks, muscle, and electrode noise.To do this, run ICA using the fast ICA method with the symmetric approach and the tan contrast function just as done for the first round of ICA. Likewise, evaluate component properties just as done with the topographic map in the first round of ICA. Then mark components consistent with residual TMS decay artifacts, blink artifacts, and muscle artifacts.Additionally, mark components consistent with channel noise based on spatial and temporal distribution. Finally, remove marked components, just as done in the first round of ICA, by selecting Tools, Remove components, and entering the relevant component numbers in the field for Component(s)to remove from data. Resting-state functional connectivity MRI is used to identify regions on the cortical surface with connectivity to the regions of heterotopia.TMS to these regions produces abnormally increased delayed activity relative to regions that do not have abnormal connectivity and relative to the same sights in healthy controls. Here, source localization of the abnormal late peaks in the TMS-evoked potentials in patients with epilepsy can identify brain regions from which the abnormal activity arises. It may spatially colocalize with the patient's seizure-focus.After watching this video, you should have a good understanding of how to use resting-state functional connectivity, MRI-guided, TMS EEG to evaluate brain excitability in different regions in patients with epilepsy and other neuropsychiatric disorders. Following this procedure, other methods, like repetitive TMS, can be performed to determine if decreasing the cortical excitability in brain regions that are part of the pathogenic network can modify disease activity.

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Research

JoVE Journal

Medicine

In vivo Near Infrared Fluorescence (NIRF) Intravascular Molecular Imaging of Inflammatory Plaque, a Multimodal Approach to Imaging of Atherosclerosis

The vascular response to injury is a well-orchestrated inflammatory response triggered by the accumulation of macrophages within the vessel wall leading to an accumulation of lipid-laden intra-luminal plaque, smooth muscle cell proliferation and progressive narrowing of the vessel lumen. The formation of such vulnerable plaques prone to rupture underlies the majority of cases of acute myocardial infarction. The complex molecular and cellular inflammatory cascade is orchestrated by the recruitment of T lymphocytes and macrophages and their paracrine effects on endothelial and smooth muscle cells.1
Molecular imaging in atherosclerosis has evolved into an important clinical and research tool that allows in vivo visualization of inflammation and other biological processes. Several recent examples demonstrate the ability to detect high-risk plaques in patients, and assess the effects of pharmacotherapeutics in atherosclerosis.4 While a number of molecular imaging approaches (in particular MRI and PET) can image biological aspects of large vessels such as the carotid arteries, scant options exist for imaging of coronary arteries.2 The advent of high-resolution optical imaging strategies, in particular near-infrared fluorescence (NIRF), coupled with activatable fluorescent probes, have enhanced sensitivity and led to the development of new intravascular strategies to improve biological imaging of human coronary atherosclerosis.
Near infrared fluorescence (NIRF) molecular imaging utilizes excitation light with a defined band width (650-900 nm) as a source of photons that, when delivered to an optical contrast agent or fluorescent probe, emits fluorescence in the NIR window that can be detected using an appropriate emission filter and a high sensitivity charge-coupled camera. As opposed to visible light, NIR light penetrates deeply into tissue, is markedly less attenuated by endogenous photon absorbers such as hemoglobin, lipid and water, and enables high target-to-background ratios due to reduced autofluorescence in the NIR window. Imaging within the NIR 'window' can substantially improve the potential for in vivo imaging.2,5
Inflammatory cysteine proteases have been well studied using activatable NIRF probes10, and play important roles in atherogenesis. Via degradation of the extracellular matrix, cysteine proteases contribute importantly to the progression and complications of atherosclerosis8. In particular, the cysteine protease, cathepsin B, is highly expressed and colocalizes with macrophages in experimental murine, rabbit, and human atheromata.3,6,7 In addition, cathepsin B activity in plaques can be sensed in vivo utilizing a previously described 1-D intravascular near-infrared fluorescence technology6, in conjunction with an injectable nanosensor agent that consists of a poly-lysine polymer backbone derivatized with multiple NIR fluorochromes (VM110/Prosense750, ex/em 750/780nm, VisEn Medical, Woburn, MA) that results in strong intramolecular quenching at baseline.10 Following targeted enzymatic cleavage by cysteine proteases such as cathepsin B (known to colocalize with plaque macrophages), the fluorochromes separate, resulting in substantial amplification of the NIRF signal. Intravascular detection of NIR fluorescence signal by the utilized novel 2D intravascular NIRF catheter now enables high-resolution, geometrically accurate in vivo detection of cathepsin B activity in inflamed plaque.
In vivo molecular imaging of atherosclerosis using catheter-based 2D NIRF imaging, as opposed to a prior 1-D spectroscopic approach,6 is a novel and promising tool that utilizes augmented protease activity in macrophage-rich plaque to detect vascular inflammation.11,12 The following research protocol describes the use of an intravascular 2-dimensional NIRF catheter to image and characterize plaque structure utilizing key aspects of plaque biology. It is a translatable platform that when integrated with existing clinical imaging technologies including angiography and intravascular ultrasound (IVUS), offers a unique and novel integrated multimodal molecular imaging technique that distinguishes inflammatory atheromata, and allows detection of intravascular NIRF signals in human-sized coronary arteries.

In vivo Near Infrared Fluorescence NIRF Intravascular Molecular Imaging of Inflammatory Plaque, a Multimodal Approach to Imaging of Atherosclerosis

We detail a new near-infrared fluorescence (NIRF) catheter for 2-dimensional intravascular molecular imaging of plaque biology in vivo. The NIRF catheter can visualize key biological processes such as inflammation by reporting on the presence of plaque-avid activatable and targeted NIR fluorochromes. The catheter utilizes clinical engineering and power requirements and is targeted for application in human coronary arteries. The following research study describes a multimodal imaging strategy that utilizes a novel in vivo intravascular NIRF catheter to image and quantify inflammatory plaque in proteolytically active inflamed rabbit atheromata.

The vascular response to injury is a well-orchestrated inflammatory response triggered by the accumulation of macrophages within the vessel wall leading ...

Driving Simulation in the Clinic: Testing Visual Exploratory Behavior in Daily Life Activities in Patients with Visual Field Defects

Patients suffering from homonymous hemianopia after infarction of the posterior cerebral artery (PCA) report different degrees of constraint in daily life, despite similar visual deficits. We assume this could be due to variable development of compensatory strategies such as altered visual scanning behavior. Scanning compensatory therapy (SCT) is studied as part of the visual training after infarction next to vision restoration therapy. SCT consists of learning to make larger eye movements into the blind field enlarging the visual field of search, which has been proven to be the most useful strategy1, not only in natural search tasks but also in mastering daily life activities2. Nevertheless, in clinical routine it is difficult to identify individual levels and training effects of compensatory behavior, since it requires measurement of eye movements in a head unrestrained condition. Studies demonstrated that unrestrained head movements alter the visual exploratory behavior compared to a head-restrained laboratory condition3. Martin et al.4 and Hayhoe et al.5 showed that behavior demonstrated in a laboratory setting cannot be assigned easily to a natural condition. Hence, our goal was to develop a study set-up which uncovers different compensatory oculomotor strategies quickly in a realistic testing situation: Patients are tested in the clinical environment in a driving simulator. SILAB software (Wuerzburg Institute for Traffic Sciences GmbH (WIVW)) was used to program driving scenarios of varying complexity and recording the driver's performance. The software was combined with a head mounted infrared video pupil tracker, recording head- and eye-movements (EyeSeeCam, University of Munich Hospital, Clinical Neurosciences).
The positioning of the patient in the driving simulator and the positioning, adjustment and calibration of the camera is demonstrated. Typical performances of a patient with and without compensatory strategy and a healthy control are illustrated in this pilot study. Different oculomotor behaviors (frequency and amplitude of eye- and head-movements) are evaluated very quickly during the drive itself by dynamic overlay pictures indicating where the subjects gaze is located on the screen, and by analyzing the data. Compensatory gaze behavior in a patient leads to a driving performance comparable to a healthy control, while the performance of a patient without compensatory behavior is significantly worse. The data of eye- and head-movement-behavior as well as driving performance are discussed with respect to different oculomotor strategies and in a broader context with respect to possible training effects throughout the testing session and implications on rehabilitation potential.

Patients with visual deficits after stroke report about different constraints in daily life most likely due to variable compensatory strategies, which are difficult to differentiate in clinical routine. We present a clinical set-up which allows measurement of different compensatory head- and eye-movement-strategies and evaluating their effects on driving performance.

Patients suffering from homonymous hemianopia after infarction of the posterior cerebral artery (PCA) report different degrees of constraint in daily ...

Computerized Dynamic Posturography for Postural Control Assessment in Patients with Intermittent Claudication

Computerized dynamic posturography with the EquiTest is an objective technique for measuring postural strategies under challenging static and dynamic conditions. As part of a diagnostic assessment, the early detection of postural deficits is important so that appropriate and targeted interventions can be prescribed. The Sensory Organization Test (SOT) on the EquiTest determines an individual&#39;s use of the sensory systems (somatosensory, visual, and vestibular) that are responsible for postural control. Somatosensory and visual input are altered by the calibrated sway-referenced support surface and visual surround, which move in the anterior-posterior direction in response to the individual&#39;s postural sway. This creates a conflicting sensory experience. The Motor Control Test (MCT) challenges postural control by creating unexpected postural disturbances in the form of backwards and forwards translations. The translations are graded in magnitude and the time to recover from the perturbation is computed.
Intermittent claudication, the most common symptom of peripheral arterial disease, is characterized by a cramping pain in the lower limbs and caused by muscle ischemia secondary to reduced blood flow to working muscles during physical exertion. Claudicants often display poor balance, making them susceptible to falls and activity avoidance. The Ankle Brachial Pressure Index (ABPI) is a noninvasive method for indicating the presence of peripheral arterial disease and intermittent claudication, a common symptom in the lower extremities. ABPI is measured as the highest systolic pressure from either the dorsalis pedis or posterior tibial artery divided by the highest brachial artery systolic pressure from either arm. This paper will focus on the use of computerized dynamic posturography in the assessment of balance in claudicants.

Individuals with intermittent claudication exhibit poor balance compared to healthy controls. Computerized dynamic posturography is an objective method for measuring an individual's postural responses to balance disturbances. This provides an objective reflection of the person&#x2019;s ability to respond to situations under which sensory stimuli are altered and unexpected perturbations occur.

Computerized dynamic posturography with the EquiTest is an objective technique for measuring postural strategies under challenging static and dynamic ...

Brain Source Imaging in Preclinical Rat Models of Focal Epilepsy using High-Resolution EEG Recordings

Electroencephalogram (EEG) has been traditionally used to determine which brain regions are the most likely candidates for resection in patients with focal epilepsy. This methodology relies on the assumption that seizures originate from the same regions of the brain from which interictal epileptiform discharges (IEDs) emerge. Preclinical models are very useful to find correlates between IED locations and the actual regions underlying seizure initiation in focal epilepsy. Rats have been commonly used in preclinical studies of epilepsy1; hence, there exist a large variety of models for focal epilepsy in this particular species. However, it is challenging to record multichannel EEG and to perform brain source imaging in such a small animal. To overcome this issue, we combine a patented-technology to obtain 32-channel EEG recordings from rodents2 and an MRI probabilistic atlas for brain anatomical structures in Wistar rats to perform brain source imaging. In this video, we introduce the procedures to acquire multichannel EEG from Wistar rats with focal cortical dysplasia, and describe the steps both to define the volume conductor model from the MRI atlas and to uniquely determine the IEDs. Finally, we validate the whole methodology by obtaining brain source images of IEDs and compare them with those obtained at different time frames during the seizure onset.

This video introduces the preparation, recording, and source analysis procedures of high-resolution EEG on sedated rats with a particular preclinical model of focal epilepsy under noninvasive conditions.

Electroencephalogram (EEG) has been traditionally used to determine which brain regions are the most likely candidates for resection in patients with ...

A Pipeline for 3D Multimodality Image Integration and Computer-assisted Planning in Epilepsy Surgery

Epilepsy surgery is challenging and the use of 3D multimodality image integration (3DMMI) to aid presurgical planning is well-established. Multimodality image integration can be technically demanding, and is underutilised in clinical practice. We have developed a single software platform for image integration, 3D visualization and surgical planning. Here, our pipeline is described in step-by-step fashion, starting with image acquisition, proceeding through image co-registration, manual segmentation, brain and vessel extraction, 3D visualization and manual planning of stereoEEG (SEEG) implantations. With dissemination of the software this pipeline can be reproduced in other centres, allowing other groups to benefit from 3DMMI. We also describe the use of an automated, multi-trajectory planner to generate stereoEEG implantation plans. Preliminary studies suggest this is a rapid, safe and efficacious adjunct for planning SEEG implantations. Finally, a simple solution for the export of plans and models to commercial neuronavigation systems for implementation of plans in the operating theater is described. This software is a valuable tool that can support clinical decision making throughout the epilepsy surgery pathway.

We describe the steps to use our custom designed software for image integration, visualization and planning in epilepsy surgery.

Epilepsy surgery is challenging and the use of 3D multimodality image integration (3DMMI) to aid presurgical planning is well-established. Multimodality ...

Multimodal Quantitative Phase Imaging with Digital Holographic Microscopy Accurately Assesses Intestinal Inflammation and Epithelial Wound Healing

The incidence of inflammatory bowel disease, i.e., Crohn&#39;s disease and Ulcerative colitis, has significantly increased over the last decade. The etiology of IBD remains unknown and current therapeutic strategies are based on the unspecific suppression of the immune system. The development of treatments that specifically target intestinal inflammation and epithelial wound healing could significantly improve management of IBD, however this requires accurate detection of inflammatory changes. Currently, potential drug candidates are usually evaluated using animal models in vivo or with cell culture based techniques in vitro. Histological examination usually requires the cells or tissues of interest to be stained, which may alter the sample characteristics and furthermore, the interpretation of findings can vary by investigator expertise. Digital holographic microscopy (DHM), based on the detection of optical path length delay, allows stain-free quantitative phase contrast imaging. This allows the results to be directly correlated with absolute biophysical parameters. We demonstrate how measurement of changes in tissue density with DHM, based on refractive index measurement, can quantify inflammatory alterations, without staining, in different layers of colonic tissue specimens from mice and humans with colitis. Additionally, we demonstrate continuous multimodal label-free monitoring of epithelial wound healing in vitro, possible using DHM through the simple automated determination of the wounded area and simultaneous determination of morphological parameters such as dry mass and layer thickness of migrating cells. In conclusion, DHM represents a valuable, novel and quantitative tool for the assessment of intestinal inflammation with absolute values for parameters possible, simplified quantification of epithelial wound healing in vitro and therefore has high potential for translational diagnostic use.

Accurate assessment of anti-inflammatory effects is of utmost importance for the evaluation of potential new drugs for the treatment of inflammatory bowel disease. Digital holographic microscopy provides assessment of inflammation in murine and human colonic tissue samples as well as automated multimodal evaluation of epithelial wound healing in vitro.

The incidence of inflammatory bowel disease, i.e., Crohn&#39;s disease and Ulcerative colitis, has significantly increased over the last decade. The ...

Network Analysis of Foramen Ovale Electrode Recordings in Drug-resistant Temporal Lobe Epilepsy Patients

Approximately 30% of epilepsy patients are refractory to antiepileptic drugs. In these cases, surgery is the only alternative to eliminate/control seizures. However, a significant minority of patients continues to exhibit post-operative seizures, even in those cases in which the suspected source of seizures has been correctly localized and resected. The protocol presented here combines a clinical procedure routinely employed during the pre-operative evaluation of temporal lobe epilepsy (TLE) patients with a novel technique for network analysis. The method allows for the evaluation of the temporal evolution of mesial network parameters. The bilateral insertion of foramen ovale electrodes (FOE) into the ambient cistern simultaneously records electrocortical activity at several mesial areas in the temporal lobe. Furthermore, network methodology applied to the recorded time series tracks the temporal evolution of the mesial networks both interictally and during the seizures. In this way, the presented protocol offers a unique way to visualize and quantify measures that considers the relationships between several mesial areas instead of a single area.

This protocol describes a procedure to track the evolution of mesial network measures in temporal lobe epilepsy (TLE) patients. It is based on the combination of intracranial recordings with a novel numerical technique for data analysis. Specifically, we present a protocol for network analyses of foramen ovale recordings.

Approximately 30% of epilepsy patients are refractory to antiepileptic drugs. In these cases, surgery is the only alternative to eliminate/control ...

Interictal High Frequency Oscillations Detected with Simultaneous Magnetoencephalography and Electroencephalography as Biomarker of Pediatric Epilepsy

Crucial to the success of epilepsy surgery is the availability of a robust biomarker that identifies the Epileptogenic Zone (EZ). High Frequency Oscillations (HFOs) have emerged as potential presurgical biomarkers for the identification of the EZ in addition to Interictal Epileptiform Discharges (IEDs) and ictal activity. Although they are promising to localize the EZ, they are not yet suited for the diagnosis or monitoring of epilepsy in clinical practice. Primary barriers remain: the lack of a formal and global definition for HFOs; the consequent heterogeneity of methodological approaches used for their study; and the practical difficulties to detect and localize them noninvasively from scalp recordings. Here, we present a methodology for the recording, detection, and localization of interictal HFOs from pediatric patients with refractory epilepsy. We report representative data of HFOs detected noninvasively from interictal scalp EEG and MEG from two children undergoing surgery.
The underlying generators of HFOs were localized by solving the inverse problem and their localization was compared to the Seizure Onset Zone (SOZ) as this was defined by the epileptologists. For both patients, Interictal Epileptogenic Discharges (IEDs) and HFOs were localized with source imaging at concordant locations. For one patient, intracranial EEG (iEEG) data were also available. For this patient, we found that the HFOs localization was concordant between noninvasive and invasive methods. The comparison of iEEG with the results from scalp recordings served to validate these findings. To our best knowledge, this is the first study that presents the source localization of scalp HFOs from simultaneous EEG and MEG recordings comparing the results with invasive recordings. These findings suggest that HFOs can be reliably detected and localized noninvasively with scalp EEG and MEG. We conclude that the noninvasive localization of interictal HFOs could significantly improve the presurgical evaluation for pediatric patients with epilepsy.

High Frequency Oscillations (HFOs) have emerged as presurgical biomarkers for the identification of the epileptogenic zone in pediatric patients with medically refractory epilepsy. A methodology for the noninvasive recording, detection, and localization of HFOs with simultaneous scalp electroencephalography (EEG) and magnetoencephalography (MEG) is presented.

Crucial to the success of epilepsy surgery is the availability of a robust biomarker that identifies the Epileptogenic Zone (EZ). High Frequency ...

Whole-brain Segmentation and Change-point Analysis of Anatomical Brain MRI&#8212;Application in Premanifest Huntington's Disease

Recent advances in MRI offer a variety of useful markers to identify neurodegenerative diseases. In Huntington&#39;s disease (HD), regional brain atrophy begins many years prior to the motor onset (during the &#34;premanifest&#34; period), but the spatiotemporal pattern of regional atrophy across the brain has not been fully characterized. Here we demonstrate an online cloud-computing platform, &#34;MRICloud&#34;, which provides atlas-based whole-brain segmentation of T1-weighted images at multiple granularity levels, and thereby, enables us to access the regional features of brain anatomy. We then describe a regression model that detects statistically significant inflection points, at which regional brain atrophy starts to be noticeable, i.e. the &#34;change-point&#34;, with respect to a disease progression index. We used the CAG-age product (CAP) score to index the disease progression in HD patients. Change-point analysis of the volumetric measurements from the segmentation pipeline, therefore, provides important information of the order and pattern of structural atrophy across the brain. The paper illustrates the use of these techniques on T1-weighted MRI data of premanifest HD subjects from a large multicenter PREDICT-HD study. This design potentially has wide applications in a range of neurodegenerative diseases to investigate the dynamic changes of brain anatomy.

This paper describes a statistical model for volumetric MRI data analysis, which identifies the &#34;change-point&#34; when brain atrophy begins in premanifest Huntington&#39;s disease. Whole-brain mapping of the change-points is achieved based on brain volumes obtained using an atlas-based segmentation pipeline of T1-weighted images.

Recent advances in MRI offer a variety of useful markers to identify neurodegenerative diseases. In Huntington&#39;s disease (HD), regional brain atrophy ...

Semi-quantitative Assessment Using [18F]FDG Tracer in Patients with Severe Brain Injury

Patients with severe traumatic brain injury (sTBI) have difficulty knowing whether they are accurately expressing their thoughts and emotions because of disorders of consciousness, disrupted higher brain function, and verbal disturbances. As a consequence of an insufficient ability to communicate, objective evaluations are needed from family members, medical staff, and caregivers. One such evaluation is the assessment of functioning brain areas. Recently, multimodal brain imaging has been used to explore the function of damaged brain areas. [18F]-fluorodeoxyglucose positron emission tomography-computed tomography ([18F]FDG-PET/CT) is a successful tool for examining brain function. However, the assessment of brain glucose metabolism based on [18F]FDG-PET/CT is not standardized and depends on several varying parameters, as well as the patient&#39;s condition. Here, we describe a series of semiquantitative assessment protocols for a region-of-interest (ROI) image analysis using self-produced [18F]FDG tracers in patients with sTBI. The protocol focuses on screening the participants, preparing the [18F]FDG tracer in the hot lab, scheduling the acquisition of [18F]FDG-PET/CT brain images, and measuring glucose metabolism using the ROI analysis from a targeted brain area.

Semi-quantitative Assessment Using [18F]FDG Tracer in Patients with Severe Brain Injury

[18F]-fluorodeoxyglucose (FDG) positron emission tomography-computed tomography is useful for studying glucose metabolism related to brain function. Here, we present a protocol for an [18F]FDG tracer set-up and semiquantitative assessment of the region-of-interest analysis for targeted brain areas associated with clinical manifestations in patients with severe traumatic brain injury.

Patients with severe traumatic brain injury (sTBI) have difficulty knowing whether they are accurately expressing their thoughts and emotions because of ...