Publications by authors named "David A Steven"

52 Publications

Epilepsy surgery in stroke-related epilepsy.

Seizure 2021 May 5;88:116-124. Epub 2021 Apr 5.

Epilepsy Program, Department of Clinical Neurological Sciences, Schulich School of Medicine and Dentistry, Western University, 339 Windermere Rd. London, Ontario, Canada, N6A 5A5; Department of Epidemiology and Biostatistics, Schulich School of Medicine and Dentistry, Western University, 339 Windermere Rd. London, Ontario, Canada, N6A 5A5; Neuro-Epidemiology Unit, Schulich School of Medicine and Dentistry, Western University, 339 Windermere Rd. London, Ontario, Canada, N6A 5A5. Electronic address:

Purpose: To provide a descriptive analysis on the presurgical evaluation and surgical management of a cohort of patients with stroke related epilepsy (SRE).

Methods: We retrospectively examined the clinical characteristics, results of non-invasive and invasive presurgical evaluation, surgical management and outcome of consecutive patients with drug-resistant SRE in our institution from January 1, 2013 to January 1, 2020.

Results: Twenty-one of 420 patients (5%) who underwent intracranial EEG (iEEG), resective epilepsy surgery and/or vagus nerve stimulation (VNS) placement, had SRE. Of 13 patients who had iEEG, the ictal onset (IO) was exclusively within the stroke lesion in only one patient. In five patients the IO was extra-lesional and in the remaining seven patients it included the stroke lesion as well as extra-lesional structures. The IO included the mesial temporal region in 11 of the 13 patients (85%). The posterior margin of the stroke lesion was always involved. Five patients underwent surgery without iEEG. In total, 10 patients underwent resective surgery, four VNS placement and two had both corpus callosotomy and VNS placement. Of the patients who had resective surgery, nine were Engel I or II at last follow up.

Conclusion: We found that seizures in patients with drug resistant SRE were more frequently originated in the mesial temporal region than in the stroke lesion itself. Despite the complex epileptic network underlying drug-resistant SRE, a thorough presurgical assessment and adequate use of surgical options can lead to excellent surgical outcomes.
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http://dx.doi.org/10.1016/j.seizure.2021.04.002DOI Listing
May 2021

Acute Hemorrhagic Encephalitis Related to COVID-19.

Neurol Clin Pract 2021 Apr;11(2):e147-e151

Department of Clinical Neurological Sciences (AC, RBJ, CJ, DBD, DAS), Schulich School of Medicine and Dentistry, Western University; Department of Physical Medicine and Rehabilitation (CSB), Schulich School of Medicine and Dentistry, Western University; Department of Medical Imaging (MSM), Schulich School of Medicine and Dentistry, Western University; Department of Medicine (KJB), Schulich School of Medicine and Dentistry, Western University; and Department of Epidemiology and Biostatistics (DAS), Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada.

Purpose Of Review: The novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the most critical public health challenge in recent history. In this report, we present a case of suspected acute hemorrhagic encephalitis with bilateral intracranial hemorrhages associated with coronavirus disease 2019 (COVID-19) infection.

Recent Findings: A 48-year-old female COVID-19-positive patient developed acute changes in her neurologic status. A head CT with CT angiography demonstrated extensive bilateral parietal and occipital intraparenchymal hemorrhage with intraventricular extension and acute hydrocephalus. The patient was treated with an external ventricular drain, and a CSF sample was tested for SARS-CoV-2 but was found to be negative.

Summary: The underlying mechanism for developing acute hemorrhagic encephalitis in viral illnesses may be autoimmune in nature and warrants further investigation. The initial neurologic presentation of COVID-19-related hemorrhagic encephalitis is altered level of consciousness, which may prompt further neurologic examination and imaging to exclude this feature.
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http://dx.doi.org/10.1212/CPJ.0000000000000900DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8032421PMC
April 2021

An evaluation of the diagnostic equivalence of F-FDG-PET between hybrid PET/MRI and PET/CT in drug-resistant epilepsy: A pilot study.

Epilepsy Res 2021 May 16;172:106583. Epub 2021 Feb 16.

Lawson Imaging, Lawson Health Research Institute, London, ON, Canada; Department of Medical Biophysics, Schulich School of Medicine and Dentistry, Western University, London, ON, Canada; Department of Medical Imaging, Schulich School of Medicine and Dentistry, Western University, London, ON, Canada.

Objective: Hybrid PET/MRI may improve detection of seizure-onset zone (SOZ) in drug-resistant epilepsy (DRE), however, concerns over PET bias from MRI-based attenuation correction (MRAC) have limited clinical adoption of PET/MRI. This study evaluated the diagnostic equivalency and potential clinical value of PET/MRI against PET/CT in DRE.

Materials And Methods: MRI, FDG-PET and CT images (n = 18) were acquired using a hybrid PET/MRI and a CT scanner. To assess diagnostic equivalency, PET was reconstructed using MRAC (RESOLUTE) and CT-based attenuation correction (CTAC) to generate PET/MRI and PET/CT images, respectively. PET/MRI and PET/CT images were compared qualitatively through visual assessment and quantitatively through regional standardized uptake value (SUV) and z-score assessment. Diagnostic accuracy and sensitivity of PET/MRI and PET/CT for SOZ detection were calculated through comparison to reference standards (clinical hypothesis and histopathology, respectively).

Results: Inter-reader agreement in visual assessment of PET/MRI and PET/CT images was 78 % and 81 %, respectively. PET/MRI and PET/CT were strongly correlated in mean SUV (r = 0.99, p < 0.001) and z-scores (r = 0.92, p < 0.001) across all brain regions. MRAC SUV bias was <5% in most brain regions except the inferior temporal gyrus, temporal pole, and cerebellum. Diagnostic accuracy and sensitivity were similar between PET/MRI and PET/CT (87 % vs. 85 % and 83 % vs. 83 %, respectively).

Conclusion: We demonstrate here that PET/MRI with optimal MRAC can yield similar diagnostic performance as PET/CT. Nevertheless, further exploration of the potential added value of PET/MRI is necessary before clinical adoption of PET/MRI for epilepsy imaging.
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http://dx.doi.org/10.1016/j.eplepsyres.2021.106583DOI Listing
May 2021

All that glitters: Contribution of stereo-EEG in patients with lesional epilepsy.

Epilepsy Res 2021 Feb 2;170:106546. Epub 2021 Jan 2.

Department of Clinical Neurological Sciences, Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada; Department of Epidemiology and Biostatistics, Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada; Neuro-Epidemiology Unit, Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada. Electronic address:

Objective: To determine the contribution of stereo-EEG for localization purpose in patients with a visible lesion on MRI.

Background: Intracranial EEG is often used to localize the epileptogenic focus in patients with non-lesional focal epilepsy. Its role in cases where a lesion is visible on MRI can be even more complex and the relationship between the lesion and the seizure onset has rarely been addressed.

Methods: All consecutive patients between February 2013 and May 2018 who underwent stereo-EEG and had a lesion visible on MRI were included. We assessed the localization of the seizure onset and its relationship with the lesion. Clinical, radiological, and electrographic analyses were performed.

Results: Stereo-EEG revealed a seizure onset with either partial or no overlap with the lesion seen on MRI in 42 (56 %) of the 75 lesions included. Mesial temporal sclerosis was the only lesion type associated with an exclusively lesional seizure onset (p = 0.003).

Conclusion: Epilepsy surgery in MRI-positive cases should rely not only the results of lesions seen on MRI, which might be potentially misleading; SEEG is a gold standard method in these cases to define resective borders.
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http://dx.doi.org/10.1016/j.eplepsyres.2020.106546DOI Listing
February 2021

Hemispherotomy for Epilepsy: The Procedure Evolution and Outcome.

Can J Neurol Sci 2020 Oct 1:1-13. Epub 2020 Oct 1.

Department of Clinical Neurological Sciences, Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada.

Hemispherectomy is a unique epilepsy surgery procedure that has undergone significant modification and evolution since Dandy's early description. This procedure is mainly indicated to treat early childhood and infancy medically intractable epilepsy. Various epileptic syndromes have been treated with this procedure, including hemimegalencephaly (HME), Rasmussen's encephalitis, Sturge-Weber syndrome (SWS), perinatal stroke, and hemispheric cortical dysplasia. In terms of seizure reduction, hemispherectomy remains one of the most successful epilepsy surgery procedures. The modification of this procedure over many years has resulted in lower mortality and morbidity rates. HME might increase morbidity and lower the success rate. Future studies should identify the predictors of outcomes based on the pathology and the type of hemispherectomy. Here, based on a literature review, we discuss the evolution of hemispherectomy techniques and their outcomes and complications.
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http://dx.doi.org/10.1017/cjn.2020.216DOI Listing
October 2020

Stroke risk, phenotypes, and death in COVID-19: Systematic review and newly reported cases.

Neurology 2020 12 15;95(24):e3373-e3385. Epub 2020 Sep 15.

From the Department of Clinical Neurological Sciences (S.F., M.B.B., P.S., C.J., D.B.D., T.E.G., D.A.S., L.A.S.), Department of Medicine (R.B.), Division of Cardiology, Department of Anatomy and Cell Biology (L.A.S.), and Department of Epidemiology and Biostatistics (R.B., D.A.S., L.A.S.), Schulich School of Medicine and Dentistry, Heart & Brain Laboratory (A.J.-R., L.A.S.), and Robarts Research Institute (L.A.S.), Western University, London, Ontario, Canada; Instituto de Neurología y Neurocirugía de Neuquén (P.C.), Argentina; Miami Cardiac & Vascular Institute (D.V.-D., I.L.), Baptist Hospital Neuroscience Center, FL; Clinical Research Development Unit of Bou Ali Sina Hospital (A.S.-R.) and Immunogenetics Research Center (N.K.), Toxoplasmosis Research Center, Mazandaran University of Medical Sciences, Sari, Iran; and Lawson Health Research Institute (L.A.S.), London, Ontario, Canada.

Objectives: To investigate the hypothesis that strokes occurring in patients with coronavirus disease 2019 (COVID-19) have distinctive features, we investigated stroke risk, clinical phenotypes, and outcomes in this population.

Methods: We performed a systematic search resulting in 10 studies reporting stroke frequency among patients with COVID-19, which were pooled with 1 unpublished series from Canada. We applied random-effects meta-analyses to estimate the proportion of stroke among COVID-19. We performed an additional systematic search for cases series of stroke in patients with COVID-19 (n = 125), and we pooled these data with 35 unpublished cases from Canada, the United States, and Iran. We analyzed clinical characteristics and in-hospital mortality stratified into age groups (<50, 50-70, >70 years). We applied cluster analyses to identify specific clinical phenotypes and their relationship with death.

Results: The proportions of patients with COVID-19 with stroke (1.8%, 95% confidence interval [CI] 0.9%-3.7%) and in-hospital mortality (34.4%, 95% CI 27.2%-42.4%) were exceedingly high. Mortality was 67% lower in patients <50 years of age relative to those >70 years of age (odds ratio [OR] 0.33, 95% CI 0.12-0.94, = 0.039). Large vessel occlusion was twice as frequent (46.9%) as previously reported and was high across all age groups, even in the absence of risk factors or comorbid conditions. A clinical phenotype characterized by older age, a higher burden of comorbid conditions, and severe COVID-19 respiratory symptoms was associated with the highest in-hospital mortality (58.6%) and a 3 times higher risk of death than the rest of the cohort (OR 3.52, 95% CI 1.53-8.09, = 0.003).

Conclusions: Stroke is relatively frequent among patients with COVID-19 and has devastating consequences across all ages. The interplay of older age, comorbid conditions, and severity of COVID-19 respiratory symptoms is associated with an extremely elevated mortality.
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http://dx.doi.org/10.1212/WNL.0000000000010851DOI Listing
December 2020

Can we accurately lateralize the epileptogenic zone in patients who have seizure clusters? A study using stereo-electroencephalography.

Epilepsy Res 2020 10 23;166:106405. Epub 2020 Jun 23.

Department of Clinical Neurological Sciences, Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada; Department of Epidemiology and Biostatistics, Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada; Neuro-epidemiology Unit, Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada. Electronic address:

Objective: To determine if the ictal onset recorded with stereoelectroencephalography (SEEG) during clusters of seizures is reliable to identify the laterality of the epileptogenic zone.

Background: In the presurgical evaluation of patients with focal drug-resistant epilepsy, the presence of bilateral ictal onset is usually associated with a poor surgical outcome. It has been reported that the laterality of seizures can be influenced during seizure clusters, although this remains controversial. Most studies have addressed this issue using scalp EEG which could erroneously determine the laterality of the ictal onset.

Methods: We examined all consecutive patients who underwent SEEG with bilateral hemispheric coverage at our institution between January 2013 and September 2018. We assessed the presence of seizure clusters (clinical or subclinical), their laterality by SEEG and the surgical outcome of the patients. A descriptive clinical and electrographic analysis was performed.

Results: Of 143 patients who underwent SEEG recordings, we identified only six patients who had bilateral ictal onset that went on to resective surgery. In all six patients the discordant seizures occurred during a seizure cluster. Three of these patients were seizure free at last follow up.

Conclusion: Discordant seizures obtained during a seizure cluster may not necessarily mean that the patient has bilateral epilepsy, and therefore a poor post-surgical outcome. Seizure clusters may not reliably lateralize the epileptogenic zone.
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http://dx.doi.org/10.1016/j.eplepsyres.2020.106405DOI Listing
October 2020

Stereoelectroencephalography Versus Subdural Strip Electrode Implantations: Feasibility, Complications, and Outcomes in 500 Intracranial Monitoring Cases for Drug-Resistant Epilepsy.

Neurosurgery 2020 07;87(1):E23-E30

Department of Clinical Neurological Sciences, Schulich School of Medicine and Dentistry, Western University, London, Canada.

Background: Both stereoelectroencephalography (SEEG) and subdural strip electrodes (SSE) are used for intracranial electroencephalographic recordings in the invasive investigation of patients with drug-resistant epilepsy.

Objective: To compare SEEG and SSE with respect to feasibility, complications, and outcome in this single-center study.

Methods: Patient characteristics, periprocedural parameters, complications, and outcome were acquired from a pro- and retrospectively managed databank to compare SEEG and SSE cases.

Results: A total of 500 intracranial electroencephalographic monitoring cases in 450 patients were analyzed (145 SEEG and 355 SSE). Both groups were of similar age, gender distribution, and duration of epilepsy. Implantation of each SEEG electrode took 13.9 ± 7.6 min (20 ± 12 min for each SSE; P < .01). Radiation exposure to the patient was 4.3 ± 7.7 s to a dose area product of 14.6 ± 27.9 rad*cm2 for SEEG and 9.4 ± 8.9 s with 21 ± 22.4 rad*cm2 for SSE (P < .01). There was no difference in the length of stay (12.2 ± 7.2 and 12 ± 6.3 d). The complication rate was low in both groups. No infections were seen in SEEG cases (2.3% after SSE). The rate of hemorrhage was 2.8% for SEEG and 1.4% for SSE. Surgical outcome was similar.

Conclusion: SEEG allows targeting deeply situated foci with a non-inferior safety profile to SSE and seizure outcome comparable to SSE.
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http://dx.doi.org/10.1093/neuros/nyaa112DOI Listing
July 2020

Seizure Freedom in Temporal Plus Epilepsy Surgery Following Stereo-Electroencephalography.

Can J Neurol Sci 2020 05;47(3):374-381

Department of Clinical Neurological Sciences, Western University, London, Ontario, Canada.

Background: "Temporal plus" epilepsy (TPE) is a term that is used when the epileptogenic zone (EZ) extends beyond the boundaries of the temporal lobe. Stereotactic electroencephalography (SEEG) has been essential to identify additional EZs in adjacent structures that might be part of the temporal lobe/limbic network.

Objective: We present a small case series of temporal plus cases successfully identified by SEEG who were seizure-free after resective surgery.

Methods: We conducted a retrospective analysis of 156 patients who underwent SEEG in 5 years. Six cases had TPE and underwent anterior temporal lobectomy (ATL) with additional extra-temporal resections.

Results: Five cases had a focus on the right hemisphere and one on the left. Three cases were non-lesional and three were lesional. Mean follow-up time since surgery was 2.9 years (SD ± 1.8). Three patients had subdural electrodes investigation prior or in addition to SEEG. All patients underwent standard ATL and additional extra-temporal resections during the same procedure or at a later date. All patients were seizure-free at their last follow-up appointment (Engel Ia = 3; Engel Ib = 2; Engel Ic = 1). Pathology was nonspecific/gliosis for all six cases.

Conclusion: TPE might explain some of the failures in temporal lobe epilepsy surgery. We present a small case series of six patients in whom SEEG successfully identified this phenomenon and surgery proved effective.
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http://dx.doi.org/10.1017/cjn.2020.26DOI Listing
May 2020

Robot-Assisted Insular Depth Electrode Implantation Through Oblique Trajectories: 3-Dimensional Anatomical Nuances, Technique, Accuracy, and Safety.

Oper Neurosurg (Hagerstown) 2020 03;18(3):278-283

Department of Clinical Neurological Sciences, Schulich School of Medicine and Dentistry, Western University, London, Canada.

Background: The insula is a deep cortical structure that has renewed interest in epilepsy investigation. Invasive EEG recordings of this region have been challenging. Robot-assisted stereotactic electroencephalography has improved feasibility and safety of such procedures.

Objective: To describe technical nuances of three-dimensional (3D) oblique trajectories for insular robot-assisted depth electrode implantation.

Methods: Fifty patients who underwent robot-assisted depth electrode implantation between June 2017 and December 2018 were retrospectively analyzed. Insular electrodes were implanted through oblique, orthogonal, or parasagittal trajectories. Type of trajectories, accuracy, number of contacts within insular cortex, imaging, and complication rates were analyzed. Cadaveric and computerized tomography/magnetic resonance imaging 3D reconstructions were used to visualize insular anatomy and the technical implications of oblique trajectories.

Results: Forty-one patients (98 insular electrodes) were included. Thirty (73.2%) patients had unilateral insular coverage. Average insular electrodes per patient was 2.4. The mean number of contacts was 7.1 (SD ± 2.91) for all trajectories and 8.3 (SD ± 1.51) for oblique insular trajectories. The most frequently used was the oblique trajectory (85 electrodes). Mean entry point error was 1.5 mm (0.2-2.8) and target error was 2.4 mm (0.8-4.0), 2.0 mm (1.1-2.9) for anterior oblique and 2.8 mm (0.8-4.9) for posterior oblique trajectories. There were no complications related to insular electrodes.

Conclusion: Oblique trajectories are the preferred method for insular investigation at our institution, maximizing the number of contacts within insular cortex without traversing through sulci or major CSF fissures. Robot-assisted procedures are safe and efficient. 3D understanding of the insula's unique anatomical features can help the surgeon to improve targeting of this structure.
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http://dx.doi.org/10.1093/ons/opz154DOI Listing
March 2020

Surgical treatment of extra-hypothalamic epilepsies presenting with gelastic seizures.

Epileptic Disord 2019 Jun;21(3):307-317

Epilepsy Program, Department of Clinical Neurological Sciences, London Health Sciences Centre, University Hospital, London, ON, Canada.

We provide an overview of the surgical outcome of extra-hypothalamic epilepsies with gelastic seizures based on an original case report and a summary of the literature. Twenty-two articles providing information on the outcome of resective surgery in 39 patients with extra-hypothalamic gelastic seizures from the temporal (19 patients) or frontal lobe (20 patients) were selected. We add another case of temporal lobe gelastic seizures to the literature with a video demonstrating the mirthful component of this patient's laughing seizures. Drug-refractory cases of gelastic seizures from the temporal or frontal lobes are amenable to surgical treatment following thorough investigation with imaging, as well as scalp and intracranial EEG.
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http://dx.doi.org/10.1684/epd.2019.1076DOI Listing
June 2019

Interhypothalamic adhesions in endoscopic third ventriculostomy.

Childs Nerv Syst 2019 09 6;35(9):1565-1570. Epub 2019 Jun 6.

Division of Neurosurgery, University of Alberta, Edmonton, Alberta, Canada.

Introduction: An interhypothalamic adhesion (IHA) is a gray mater-like band of tissue traversing across the third ventricle anterior to the mammillary bodies and is similar but distinct from an interthalamic adhesion. These rare anatomic anomalies can be detected with magnetic resonance imaging or, incidentally, during endoscopic ventricular surgery.

Methods: All cases of interhypothalamic adhesions visualized during endoscopic third ventriculotomy (ETV), outside of the myelomeningocele setting, were identified from two institutions. Retrospective chart and imaging reviews were conducted and compared to intraoperative videos and photos for all cases. IHA variables collected included the following size, location, multiplicity, and associated anatomic anomalies.

Results: Four cases of interhypothalamic adhesions were identified during ETV-all of which, either partially or completely, obscured access to the third ventricular floor. The IHAs in our cohort were duplicated in two patients, large (> 3 mm and severely obstructing access to the third ventricular floor) in three patients, and adherent to the floor of the third ventricle in three patients. All four patients had primary absence of the septum pellucidum. Previous reports found associations of IHAs with other congenital, particularly midline, abnormalities. The IHAs in our cohort affected the surgery in three of four cases including misdirecting the ventriculostomy and requiring retraction or division of the IHA. In no case was postoperative pituitary or hypothalamic dysfunction observed.

Conclusions: Although interhypothalamic adhesions are rare, these anomalies must be recognized as they may hinder access to the third ventricular floor. IHAs may be large, multiple, or adherent to adjacent ventricular structures, they can misdirect or occlude the ventriculostomy or impart risk of bleeding and hypothalamic injury. Techniques for management of IHA include aborting the attempt, re-siting the ventriculostomy, or retracting or dividing the IHA, which enabled technically successful ETV in three of four patients in this series.
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http://dx.doi.org/10.1007/s00381-019-04231-yDOI Listing
September 2019

An assessment of K channel function in human cerebral arteries.

Am J Physiol Heart Circ Physiol 2019 04 25;316(4):H794-H800. Epub 2019 Jan 25.

Department of Physiology and Pharmacology, University of Western Ontario , London, Ontario , Canada.

In the rodent cerebral circulation, inward rectifying K (K) channels set resting tone and the distance over which electrical phenomena spread along the arterial wall. The present study sought to translate these observations into human cerebral arteries obtained from resected brain tissue. Computational modeling and a conduction assay first defined the impact of K channels on electrical communication; patch-clamp electrophysiology, quantitative PCR, and immunohistochemistry then characterized K2.x channel expression/activity. In keeping with rodent observations, computer modeling highlighted that K blockade should constrict cerebral arteries and attenuate electrical communication if functionally expressed. Surprisingly, Ba (a K channel inhibitor) had no effect on human cerebral arterial tone or intercellular conduction. In alignment with these observations, immunohistochemistry and patch-clamp electrophysiology revealed minimal K channel expression/activity in both smooth muscle and endothelial cells. This absence may be reflective of chronic stress as dysphormic neurons, leukocyte infiltrate, and glial fibrillary acidic protein expression was notable in the epileptic cortex. In closing, K2.x channel expression is limited in human cerebral arteries from patients with epilepsy and thus has little impact on resting tone or the spread of vasomotor responses. NEW & NOTEWORTHY K2.x channels are expressed in rodent cerebral arterial smooth muscle and endothelial cells. As they are critical to setting membrane potential and the distance signals conduct, we sought to translate this work into humans. Surprisingly, K2.x channel activity/expression was limited in human cerebral arteries, a paucity tied to chronic brain stress in the epileptic cortex. Without substantive expression, K2.x channels were unable to govern arterial tone or conduction.
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http://dx.doi.org/10.1152/ajpheart.00022.2019DOI Listing
April 2019

Establishment of epilepsy surgery in Peru.

Neurology 2018 08;91(8):368-370

From the Epilepsy Program, Department of Clinical Neurological Sciences (D.A.S., J.G.B.), and Department of Anesthesia (M.F.A.), Schulich School of Medicine and Dentistry, Western University, London, Canada; Department of Epilepsy (C.M.V., J.C.D., W.Z.-L.), Instituto Nacional de Ciencias Neurologicas; and Departments of Neurology (A.B.) and Neurosurgery (E.B.), Hospital Nacional Edgardo Rebagliati Martins, Lima, Peru.

Epilepsy surgery is a well-established treatment for certain types of intractable epilepsy. While there is a relatively high number of epilepsy surgery centers in Canada and the United States, the same cannot be said about many other parts of the world, such as South America. Although there are notable exceptions, such as Brazil and Colombia, formal epilepsy surgery centers have been lacking in many South American countries, including Peru. Although sporadic cases have been performed in Peru, there was no formal epilepsy surgery center in the country as of 2011. Beginning in 2008, with the support of the Partnering Epilepsy Centers in America program of the North American Commission of the International League Against Epilepsy, the Epilepsy Program at Western University in London, Canada, was partnered with the Department of Epilepsy at the Instituto Nacional de Ciencias Neurologicas in Lima. This was the beginning of a long-term relationship that culminated in the establishment of the first 2 formal epilepsy surgery centers in Peru. The purpose of this communication is to briefly summarize the establishment of 2 independent epilepsy surgery programs in Peru and to document the methods with which this accomplishment was achieved.
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http://dx.doi.org/10.1212/WNL.0000000000006029DOI Listing
August 2018

Intracranial Electroencephalographic Monitoring: From Subdural to Depth Electrodes.

Can J Neurol Sci 2018 05 12;45(3):336-338. Epub 2018 Apr 12.

Epilepsy Program,Department of Clinical Neurological Sciences,Schulich School of Medicine and Dentistry,Western University,London,Ontario,Canada.

At the London Health Sciences Centre Epilepsy Program, stereotactically implanted depth electrodes have largely replaced subdural electrodes in the presurgical investigation of patients with drug-resistant epilepsy over the past 4 years. The rationale for this paradigm shift was more experience with, and improved surgical techniques for, stereoelectroencephalography, a possible lower-risk profile for depth electrodes, better patient tolerability, shorter operative time, as well as increased recognition of potential surgical targets that are not accessible to subdural electrodes.
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http://dx.doi.org/10.1017/cjn.2018.4DOI Listing
May 2018

Novel connectivity map normalization procedure for improved quantitative investigation of structural thalamic connectivity in temporal lobe epilepsy patients.

J Magn Reson Imaging 2018 12 23;48(6):1529-1539. Epub 2018 Mar 23.

Imaging Research Laboratories, Robarts Research Institute - Western University, London, Ontario, Canada.

Background: Connectivity studies targeting the thalamus have revealed patterns of atrophy and deafferentiation in temporal lobe epilepsy (TLE). The thalamus can be parcellated using probabilistic tractography to demonstrate regions of cortical connectivity; however, sensitivity to smaller or less connected regions is low.

Purpose/hypothesis: To investigate thalamic structural connectivity in a wider range of cortical and limbic structures in TLE patients using a novel connectivity map normalization procedure.

Study Type: Retrospective.

Population/subjects: Patients (N = 23) with medication-resistant TLE and 34 healthy age-matched controls.

Field Strength/sequence: For T and diffusion weighting a spoiled gradient sequence was used (41 gradient directions [b = 1000]). For T mapping balanced steady-state free precession was used. Images were acquired at 3T.

Assessment: Probabilistic tractography and a novel normalization procedure allowed comparison of groups with respect to thalamic connected volume, quantitative MRI, and diffusion tensor imaging (DTI) metrics.

Statistical Tests: Independent samples t-test, Cohen's d, and Mann-Whitney tests.

Results: Following normalization, significant differences in thalamic connected volumes were found in left TLE vs. controls bilaterally within the posterior parahippocampal gyrus (L: P = 0.007, confidence interval [CI]: [173.306,1044.41], effect size [ES] = 1.072; R: P = 0.017, CI: [98.677,947.653], ES = 0.945), and contralaterally in the anterior temporal neocortex (P = 0.01, CI: (-2348.09, -333.719), ES = -1.021). This procedure revealed differences in thalamic connected volumes, where previously published procedures could not, and provided a basis for exploratory analysis of quantitative MRI and DTI metrics.

Data Conclusion: The novel connectivity map normalization scheme proposed here successfully allowed comparison between a wider range of cortical and limbic structures. Multiple volumetric and quantitative MRI and DTI-related differences between TLE patients and controls were revealed following normalization. With validation from a larger cohort, thalamo-temporal connection aberrancies may become useful biomarkers of disease states and probabilistic tractography as a procedure for identification of thalamic targets in modulatory therapies for TLE.

Level Of Evidence: 3 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018;48:1529-1539.
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http://dx.doi.org/10.1002/jmri.26013DOI Listing
December 2018

Prohibited Arc Angles During Leksell Frame-Based Stereotaxy.

World Neurosurg 2018 Apr 31;112:123-125. Epub 2018 Jan 31.

Epilepsy Program, Department of Clinical Neurological Sciences, Division of Neurosurgery, London Health Sciences Centre, University Hospital, London, Ontario, Canada. Electronic address:

Background: During Leksell frame-based stereotaxy the lateral trajectory can be obstructed by the arc supports at certain combinations of the X-coordinate and arc angle.

Objective: To provide a matrix with usable and prohibited combinations of the X-coordinate and arc angle to faciliate finding lateral stereotactic trajectories with the Leksell frame in standard configuration.

Methods: Various combination settings of the X-coordinate and arc angle were tested for a Leksell Multi-Purpose Stereotactic Arc mounted on a Leksell Coordinate Frame G.

Results: A matrix of usable and prohibited combinations of the X-coordinate and arc angle is provided.

Conclusions: The matrix will help to facilitate surgical work flow during stereotactic procedures involving the Leksell frame.
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http://dx.doi.org/10.1016/j.wneu.2018.01.068DOI Listing
April 2018

Refractory Epilepsy: The Role of Positron Emission Tomography.

Can J Neurol Sci 2018 01;45(1):30-34

1Department of Clinical Neurological Sciences,London Health Sciences Centre,London,Ontario,Canada.

Rationale: Presurgical localization of the epileptogenic focus is critical to successful surgery. Traditionally, localization of the epileptogenic focus depends on seizure semiology, scalp video-electroencephalography (vEEG), magnetic resonance imaging (MRI), neuropsychological assessment, and, when needed, intracranial EEG (iEEG). We aimed to explore the role of positron emission tomography (PET) in the presurgical evaluation of patients with refractory epilepsy.

Methods: A retrospective review was conducted on patients from London Health Sciences Centre (London, Ontario) with refractory epilepsy who underwent PET from September of 2011 to April of 2016. The accuracy of epileptogenic focus localization was compared between different investigative modalities (MRI, vEEG, iEEG, PET), and the outcomes were documented, including seizure freedom after surgical resection, improvement of seizure frequency, guidance for further investigations, and exclusion of patients from further evaluation. Patients who underwent surgery were followed up at 3 months and onward.

Results: We identified 62 patients with refractory epilepsy who underwent PET. The mean age was 34 years (range=20-68). A total of 36 had concordant PET and vEEG findings: 6 had surgical resection and either became seizure-free (29.4%) or had improvement in seizure frequency (5.9%) at 3 months; 11 had surgical resection and either became seizure-free (29.4%) or had improvement in seizure frequency (35.3%) at 3 months, but required iEEG for final verification.

Conclusions: PET has an important role in presurgical evaluation of patients with refractory epilepsy. It may allow resection of the epileptogenic focus without the need for iEEG, guiding intracranial electrode placement for further localization of the epileptogenic focus, or exclusion of patients from further evaluation.
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http://dx.doi.org/10.1017/cjn.2017.244DOI Listing
January 2018

Operative Nuances of Stereotactic Leksell Frame-Based Depth Electrode Implantation.

Oper Neurosurg (Hagerstown) 2018 09;15(3):292-295

Epilepsy Program, Department of Clinical Neurological Sciences, Division of Neu-rosurgery, London Health Sciences Cen-tre, University Hospital, London, Ontario, Canada.

Background: For intracranial electroencephalographic monitoring, stereotactically implanted depth electrodes are increasingly used at epilepsy centers around the world.

Objective: To identify pearls and pitfalls from our experience with stereotactic Leksell (Elekta AB, Stockhom, Sweden) frame-based depth electrode implantation.

Methods: An intraoperative video of the implantation technique was recorded.

Results: A detailed description and a video on how to implant depth electrodes using the stereotactic Leksell frame is provided.

Conclusion: Neurosurgeons implanting depth electrodes for intracranial electroencephalographic monitoring might find the technical nuances and caveats described in this technical note useful for their practice.
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http://dx.doi.org/10.1093/ons/opx245DOI Listing
September 2018

Awake perimetry testing for occipital epilepsy surgery.

J Neurosurg 2018 11;129(5):1195-1199

Epilepsy Program, Divisions of1Neurosurgery and.

With the patient awake during surgery, the authors used a simple technique to determine which part of a patient's brain was essential for vision. This technique allows the surgeon to remove as much as the seizure-producing brain as possible by avoiding the areas that are critical for vision.
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http://dx.doi.org/10.3171/2017.6.JNS17846DOI Listing
November 2018

Case Report: Free Latissimus Dorsi Flap in Combination With Subdural Space Reduction for the Prevention of Recurrent Hemorrhage Following Hemispherectomy.

Oper Neurosurg (Hagerstown) 2018 06;14(6):E63-E65

Division of Neurosurgery, Department of Clinical Neurological Sciences, Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada.

Background And Importance: Extensive cerebral resections for the treatment of epilepsy may result in a large intracranial dead space that is prone to recurrent hemorrhage, either due to mechanical dislodgement or the development of extensive subdural membranes. Several techniques have been proposed to decrease the risk of hemorrhage by either reducing or filling the remaining intracranial dead space.

Clinical Presentation: We present a case of persistent hemorrhage following functional hemispherectomy in a patient with a large porencephalic cyst. A treatment strategy involving both subdural space reduction and cranial vault filling with a vascularized free latissimus dorsi flap is discussed.

Conclusion: Subdural space reduction and cranial vault filling with a vascularized free latissimus dorsi flap is a viable treatment alternative in patients with large areas of intracranial dead space.
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http://dx.doi.org/10.1093/ons/opx159DOI Listing
June 2018

A Consult Is Just a Page Away: A Prospective Observational Study on the Impact of Jinxing on Call Karma in Neurosurgery.

Can J Neurol Sci 2017 Jul 21;44(4):420-423. Epub 2017 Feb 21.

2Department of Neurosurgery,University Hospital Zurich,Zurich,Switzerland.

Objective: Our aim was to assess the impact of jinxing on "call karma" in neurosurgery.

Methods: We conducted a prospective observational study on 15 residents on call for the neurosurgery service, recording the total number of admissions, consults, deaths encountered, surgeries performed, hours of sleep and subjective call rating on a numeric rating scale (NRS) of 0-10 in terms of general awfulness.

Results: Some 204 on-call nightshifts were analyzed, of which 61 (29.9%) were jinxed and 143 (70.1%) were nonjinxed. Jinxes seemed to occur in clusters. The baseline parameters (experience, type of call coverage and superstition level) of the study groups were well balanced. A trend toward more surgeries was observed during jinxed nights, where residents slept significantly less (mean 147.8±96.2 vs. 180.9±106.1 min, p=0.037) and rated their on-call experience worse on the NRS (4.4±2.2 vs. 3.5±2.0, p=0.011), while there was no significant difference in number of admissions, consults or deaths.

Conclusions: The act of jinxing ought to be avoided in the neurosurgical setting, as it might be potentially harmful to resident call karma, irrespective of level of experience, resources and personal beliefs.
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http://dx.doi.org/10.1017/cjn.2016.457DOI Listing
July 2017

Successful Long-term Nerve Root Stimulation for Chronic Neuropathic Pain: A Real World, Single Center Canadian Experience.

Pain Physician 2017 02;20(2):95-106

Department of Clinical Neurological Sciences, Division of Neurosurgery Western University; London, ON, Canada.

Background: Spinal cord stimulation (SCS) is a well-established treatment for chronic neuropathic pain in the lower limbs. However, some patients have pain in distributions that are difficult to target specifically and consistently with SCS. This often involves pain in the groin or upper limbs, or pain limited to a specific dermatome. We hypothesized that dorsal nerve root stimulation (DNRS) would provide similar pain relief for these patients, compared to our results using SCS.

Objectives: In this study we report our experience treating patients with chronic neuropathic pain using SCS and DNRS.

Study Design: Open label, prospective study that includes all patients treated with a new trial stimulator system at a single center between July 1, 2011, and October 31, 2013.

Setting: Academic university neurosurgical pain center.

Methods: One hundred thirty-two consecutive patients had trials of spinal stimulation. Seventy-six patients went on to permanent implants, of which 26 received only DNRS, 47 only SCS, and 3 both. The technique was selected based on clinical assessment and intraoperative test stimulation. Other than pain location and diagnosis, the DNRS and SCS groups had similar baseline characteristics. Follow-up is reported at 12 months. Patients were assessed using a visual analogue scale (VAS) for pain, the SF-36 for quality of life, and the morphine equivalent daily dose (MEDD).

Results: At 12 months, the average VAS score for the DNRS group had decreased from 7.5 (SD 1.4) to 4.4 (SD 2.6) and 47% of patients with permanent implants achieved > 50% pain reduction. There were improvements in all subscores and component summary scores of the SF-36. The MEDD had been reduced in 55% of the patients with available data. There was no significant difference in complication or revision rates between the 2 groups.

Limitations: Patients were not randomized to treatment groups, and instead were assigned to SCS or DNRS based on what was expected to provide superior pain coverage. There is incomplete follow-up data for some patients due to missed clinic visits.

Conclusions: In our study, DNRS provided excellent pain reduction, quality of life improvement, and opioid medication use decreases. We conclude that it is an effective long-term treatment for chronic neuropathic pain.Key words: Spinal cord stimulation, dorsal nerve root stimulation, lumbar, thoracic, cervical, neuropathic pain, neuromodulation, clinical effectiveness, chronic pain, visual analogue scale.
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February 2017

Rapid Recovery from Paraplegia in a Patient with Foix-Alajouanine Syndrome.

World Neurosurg 2017 Jan 26;97:750.e1-750.e3. Epub 2016 Oct 26.

Division of Neurosurgery, Department of Clinical Neurological Sciences, London Health Sciences Centre, University Hospital, London, Ontario, Canada.

Background: Foix-Alajouanine syndrome is defined as acute neurologic deterioration in the setting of a spinal dural arteriovenous fistula.

Case Description: This case report on a young patient with an unusual clinical onset of Foix-Alajouanine syndrome coincidentally occurring after his outpatient clinic appointment illustrates how prompt surgical treatment can result in rapid recovery of neurologic function despite preoperative paraplegia.

Conclusions: Venous hypertension with subsequent rapid resolution after surgical treatment is the pathophysiological mechanism underlying a dural arteriovenous fistula, in contrast to historical views suggesting that these lesions result from irreversible venous thrombosis, resulting in necrotic myelopathy.
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http://dx.doi.org/10.1016/j.wneu.2016.10.101DOI Listing
January 2017

Outcome of temporal lobe epilepsy surgery evaluated with bitemporal intracranial electrode recordings.

Epilepsy Res 2016 11 11;127:324-330. Epub 2016 Aug 11.

Epilepsy Program, Department of Clinical Neurological Sciences, Western University, London, Ontario, Canada. Electronic address:

Background: Temporal lobe epilepsy (TLE) with unclear lateralization may require intracranial implantation of electrodes (IIE). We retrospectively assessed the association between the use of IIE and long-term outcomes in patients undergoing anterior temporal lobectomy (ATL).

Participants And Methods: We retrospectively reviewed the records of 1,032 patients undergoing epilepsy surgery at our center from 1977 to 2006. Patients who underwent ATL were included. Seizure outcome was assessed through final follow-up. Those who underwent scalp and IIE (mostly evaluated with temporal subdural strip electrodes) were compared.

Results: From 497 patients who underwent ATL, 139 did so after IIE placement in the temporal lobes. Mean age at surgery was 32.3±12.3years and median duration of follow-up 24 months (range: 6-36). Fifty-three percent of those evaluated with IIE were seizure-free at their last available visit (vs. 68% evaluated with only scalp EEG, p=0.002). Patients with lesional TLE generally had a better outcome (65.5% seizure free) than those without lesions (56.3%, p=0.093), especially for unilateral TLE diagnosed with IIE. In a multivariate Cox regression analyses adjusted for gender, neuropsychological concordance, pathological findings, and post-operative seizures, bilateral TLE predicted seizure recurrence in IIE patients (HR=2.08, 95% CI: 1.08-4.0, p=0.029).

Conclusions: More than a half of those who undergo IIE in suspected TLE are seizure free after ATL. IIE allows for the identification of surgical candidates.
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http://dx.doi.org/10.1016/j.eplepsyres.2016.08.008DOI Listing
November 2016

Knowledge and Attitudes About Epilepsy Surgery Among Family Doctors in Ontario.

Can J Neurol Sci 2016 Sep;43(5):672-7

London Health Sciences Centre,Western University,London,Ontario,Canada.

Background: Approximately 30% of patients with epilepsy have medically intractable seizures, and a proportion of them are candidates for surgical treatment. The efficacy and safety of epilepsy surgery have been supported by a large number of studies, yet only a small minority of such patients in Ontario receive surgery.

Methods: Family physicians in Ontario were surveyed regarding demographics, referral practices and general knowledge about epilepsy surgery. Four hundred surveys were mailed to randomly selected family physicians using contact information from the College of Physicians and Surgeons of Ontario website.

Results: The response rate was 50%. The majority of family physicians (81%) always refer patients with epilepsy, most often to neurologists. General knowledge of epilepsy was mixed, with 53.7% feeling that surgery should be considered in selected cases for the treatment of epilepsy, though 53.2% did not know what type of epilepsy could be surgically treated.

Conclusions: The results suggest a relatively low level of knowledge among family physicians in terms of when surgery ought to be considered, the types of epilepsy that are amenable to surgical treatment and the risks and benefits of epilepsy surgery. A lack of knowledge in these areas may partly underlie the low referral rates of epilepsy patients, though the results show that the majority of family physicians refer their patients with epilepsy to neurologists. Other factors must be considered, such as access to neurologists, epileptologists and surgical resources. Education campaigns directed at family physicians may improve knowledge and change referral practices. Future studies need to examine these possibilities.
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http://dx.doi.org/10.1017/cjn.2016.277DOI Listing
September 2016

Investigation of hippocampal substructures in focal temporal lobe epilepsy with and without hippocampal sclerosis at 7T.

J Magn Reson Imaging 2017 05 26;45(5):1359-1370. Epub 2016 Aug 26.

Schulich School of Medicine and Dentistry - Western University, London, Ontario, Canada.

Purpose: To provide a more detailed investigation of hippocampal subfields using 7T magnetic resonance imaging (MRI) for the identification of hippocampal sclerosis in temporal lobe epilepsy (TLE).

Materials And Methods: Patients (n = 13) with drug-resistant TLE previously identified by conventional imaging as having hippocampal sclerosis (HS) or not (nine without HS, four HS) and 20 age-matched healthy controls were scanned and compared using a 7T MRI protocol. Using a manual segmentation scheme to delineate hippocampal subfields, subfield-specific volume changes and apparent transverse relaxation rate ( R2*) were studied between the two groups. In addition, qualitative assessment at 7T and clinical outcomes were correlated with measured subfield changes.

Results: Volumetry of the hippocampus at 7T in HS patients revealed significant ipsilateral subfield atrophy in CA1 (P = 0.001) and CA4+DG (P < 0.001). Volumetry also uncovered subfield atrophy in 33% of patients without HS, which had not been detected using conventional imaging. R2* was significantly lower in the CA4+DG subfields (P = 0.001) and the whole hippocampus (P = 0.029) of HS patients compared to controls but not significantly lower than the group without HS (P = 0.077, P = 0.109). No correlation was found between quantitative volumetry and qualitative assessment as well as surgical outcomes (Sub, P = 0.495, P = 0.567, P = 0.528; CA1, P = 0.104 ± 0.171, P = 0.273, P = 0.554; CA2+CA3, P = 0.517, P = 0.952, P = 0.130 ± 0.256; CA4+DG, P = 0.052 ± 0.173, P = 0.212, P = 0.124 ± 0.204; WholeHipp, P = 0.187, P = 0.132 ± 0.197, P = 0.628).

Conclusion: These preliminary findings indicate that hippocampal subfield volumetry assessed at 7T is capable of identifying characteristic patterns of hippocampal atrophy in HS patients; however, difficulty remains in using imaging to identify hippocampal pathologies in cases without HS.

Level Of Evidence: 2 J. MAGN. RESON. IMAGING 2017;45:1359-1370.
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http://dx.doi.org/10.1002/jmri.25447DOI Listing
May 2017

Coprolalia as a manifestation of epileptic seizures.

Epilepsy Behav 2016 07 16;60:99-106. Epub 2016 May 16.

Department of Clinical Neurological Sciences, Western University, London, Ontario, Canada; Department of Physiology and Pharmacology, Western University, London, Ontario, Canada; Department of Medical Imaging, Western University, London, Ontario, Canada; Department of Psychology, Western University, London, Ontario, Canada. Electronic address:

Objective: The aim of this study was to investigate the lateralizing and localizing value of ictal coprolalia and brain areas involved in its production.

Methods: A retrospective search for patients manifesting ictal coprolalia was conducted in our EMU database. Continuous video-EEG recordings were reviewed, and EEG activity before and during coprolalia was analyzed using independent component analysis (ICA) technique and was compared to the seizures without coprolalia among the same patients.

Results: Nine patients were evaluated (five women), eight with intracranial video-EEG recordings (icVEEG). Four had frontal or temporal lesions, and five had normal MRIs. Six patients showed impairment in the language functions and five in the frontal executive tasks. Two hundred six seizures were reviewed (60.7% from icVEEG). Ictal coprolalia occurred in 46.6% of them, always associated with limbic auras or automatisms. They arose from the nondominant hemisphere in five patients, dominant hemisphere in three, and independently from the right and left hippocampus-parahippocampus in one. Electroencephalographic activity always involved orbitofrontal and/or mesial temporal regions of the nondominant hemisphere when coprolalia occurred. Independent component analysis of 31 seizures in seven patients showed a higher number of independent components in the nondominant hippocampus-parahippocampus before and during coprolalia and in the dominant lateral temporal region in those seizures without coprolalia (p=0.009). Five patients underwent surgery, and all five had an ILAE class 1 outcome.

Significance: Ictal coprolalia occurs in both males and females with temporal or orbitofrontal epilepsy and has a limited lateralizing value to the nondominant hemisphere but can be triggered by seizures from either hemisphere. It involves activation of the paralimbic temporal-orbitofrontal network.
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http://dx.doi.org/10.1016/j.yebeh.2016.04.040DOI Listing
July 2016

Peri-rolandic Seizures Manifesting as Reflex-induced Paroxysmal Involuntary Movements.

Can J Neurol Sci 2016 May 18;43(3):448-51. Epub 2016 Jan 18.

1Department of Clinical Neurological Sciences,Western University,London,Canada.

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http://dx.doi.org/10.1017/cjn.2015.326DOI Listing
May 2016

In vivo MRI signatures of hippocampal subfield pathology in intractable epilepsy.

Hum Brain Mapp 2016 Mar 17;37(3):1103-19. Epub 2015 Dec 17.

Department of Medical Biophysics, Western University, London, Ontario, Canada.

Objectives: Our aim is to assess the subfield-specific histopathological correlates of hippocampal volume and intensity changes (T1, T2) as well as diff!usion MRI markers in TLE, and investigate the efficacy of quantitative MRI measures in predicting histopathology in vivo.

Experimental Design: We correlated in vivo volumetry, T2 signal, quantitative T1 mapping, as well as diffusion MRI parameters with histological features of hippocampal sclerosis in a subfield-specific manner. We made use of on an advanced co-registration pipeline that provided a seamless integration of preoperative 3 T MRI with postoperative histopathological data, on which metrics of cell loss and gliosis were quantitatively assessed in CA1, CA2/3, and CA4/DG.

Principal Observations: MRI volumes across all subfields were positively correlated with neuronal density and size. Higher T2 intensity related to increased GFAP fraction in CA1, while quantitative T1 and diffusion MRI parameters showed negative correlations with neuronal density in CA4 and DG. Multiple linear regression analysis revealed that in vivo multiparametric MRI can predict neuronal loss in all the analyzed subfields with up to 90% accuracy.

Conclusion: Our results, based on an accurate co-registration pipeline and a subfield-specific analysis of MRI and histology, demonstrate the potential of MRI volumetry, diffusion, and quantitative T1 as accurate in vivo biomarkers of hippocampal pathology.
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http://dx.doi.org/10.1002/hbm.23090DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6867266PMC
March 2016