Samir Sur

Laser thermal ablation for mesiotemporal epilepsy: Analysis of ablation volumes and trajectories

To identify features of ablations and trajectories that correlate with optimal seizure control and minimize the risk of neurocognitive deficits in patients undergoing laser interstitial thermal therapy (LiTT) for mesiotemporal epilepsy (mTLE).

Transradial access: lessons learned from cardiology

Innovations in interventional cardiology historically predate those in neuro-intervention. As such, studying trends in interventional cardiology can be useful in exploring avenues to optimise neuro-interventional techniques. One such cardiology innovation has been the steady conversion of arterial puncture sites from transfemoral access (TFA) to transradial access (TRA), a paradigm shift supported by safety benefits for patients. While neuro-intervention has unique anatomical challenges, the access itself is identical. As such, examining the extensive cardiology literature on the radial approach has the potential to offer valuable lessons for the neuro-interventionalist audience who may be unfamiliar with this body of work. Therefore, we present here a report, particularly for neuro-interventionalists, regarding the best practices for TRA by reviewing the relevant cardiology literature. We focused our review on the data most relevant to our audience, namely that surrounding the access itself. By reviewing the cardiology literature on metrics such as safety profiles, cost and patient satisfaction differences between TFA and TRA, as well as examining the technical nuances of the procedure and post-procedural care, we hope to give physicians treating complex cerebrovascular disease a broader data-driven understanding of TRA.

Utilizing CT with Maximum Intensity Projection Reconstruction Bypassing CTA Improves Time to Groin Puncture in Large Vessel Occlusion Stroke Thrombectomy

Background and Purpose: Prior to thrombectomy for proximal anterior circulation large vessel occlusion (LVO) stroke, recent trials have utilized CT angiography (CTA) for vascular imaging immediately following noncontrast CT (NCCT) for decision-making, but thin-section NCCT with automated maximum intensity projection (MIP) reconstruction also has high accuracy in demonstrating the site of an occluding thrombus. We hypothesized that performing thin-section NCCT with MIP alone prior to thrombectomy improves the time to groin puncture (GP) compared to performing CTA after NCCT. Materials and Methods: We performed a retrospective cohort study of anterior circulation LVO thrombectomy at our tertiary care academic medical center. All stroke patients evaluated with thin-section NCCT (0.625 mm) with automated MIP reconstructions alone and those who had additional CTA were included. We excluded transfer patients, in-hospital strokes, posterior circulation strokes, and patients that were evaluated with stroke imaging other than NCCT or CTA prior to thrombectomy. The study groups were compared for duration from NCCT to GP and total stroke imaging duration. Results: From March 2008 through August 2015, 34 thrombectomy patients met the inclusion/exclusion criteria - 13 in the NCCT and 20 in the NCCT+CTA group. The total stroke imaging duration was shorter in the NCCT group than in the NCCT+CTA group (2 min [1-6] vs. 28 min [23-65]; p < 0.001). The NCCT-only group had a shorter time from NCCT to GP (68 min [32-99] vs. 104 min [79-128]; p = 0.030). Conclusion: Avoiding advanced imaging for patients with anterior circulation LVO in whom thin-section NCCT with MIPs reveals a hyperdense sign significantly shortens the imaging-to-GP time.

Role of heparin during endovascular therapy for acute ischemic stroke

OBJECTIVES Systemic heparinization has become the mainstay anticoagulant in neurointerventional procedures to prevent thromboembolic complications. Its benefit during endovascular therapy for acute stroke however has not been established. The purpose of this study is to retrospectively evaluate the impact of heparin during endovascular therapy for acute ischemic stroke (AIS). PATIENTS AND METHODS We performed a retrospective review of our interventional stroke database from February 2009 to September 2012 for patients with anterior circulation AIS with ICA-T or MCA M1 occlusions. 76 patients were categorized into 2 groups: intraprocedural vs. no intraprocedural heparin use. Outcomes measured included reperfusion (modified TICI scale), cerebral hemorrhages (ECASS criteria), and 90-day outcomes (modified Rankin scale). RESULTS Baseline characteristics were similar between heparin and non-heparin treated patients, except for presence of CAD (6% vs. 30%, p=0.01), Coumadin (0% vs. 11%, p=0.04), and NIHSS (15.6±5.0 vs. 18.1±4.6, p=0.03). There was a nonsignificantly higher reperfusion rate achieved in heparin-treated patients compared to non heparin-treated patients (63% vs. 50%, p=0.35). Patients who received heparin had significantly lower rates of hemorrhage (p=0.02). Multivariate logistic regression for good outcome revealed only age (OR 0.86; 95% CI 0.78-0.95; p<0.01), ASPECTS (OR 2.14; 95% CI 1.01-4.50; p=0.04), and successful reperfusion (OR 19.25; 95% CI 2.37-155.95; p<0.01) independently associated with mRS 0-2 at 90 days. CONCLUSION The use of intraprocedural heparin in patients with AIS from MCA M1 or ICA-T occlusion was found safe. The impact of heparinization is unclear and warrants further evaluation.

Optical Coherence Tomography: Future Applications in Cerebrovascular Imaging

Cross-sectional imaging of biological tissue microstructure using optical backscattering was first demonstrated in 1991.1 The technique, known as optical coherence tomography (OCT), uses low-coherence interferometry to produce a 2-dimensional image of optical scattering from tissues in a way that resembles pulse-echo imaging in ultrasound. Huang et al1 revealed promising clinical and research applications with their in vitro demonstrations of this novel imaging technique in both the peripapillary area of the retina and the coronary arteries. The first in vivo clinical application of OCT was reported in 1993, when it permitted detailed, noninvasive imaging of the anterior eye chamber, as well as other structures, such as the fovea and the optic disc of the retina.2–5 Collaboration between this pioneering group and the New England Eye Center has led to its routine use in ophthalmologic diagnostics and its subsequent commercial availability in 1996.6 Recent advancements in OCT technology have broadened its application to retinal vasculature and nontransparent tissues.7–10 OCT angiography has permitted noninvasive evaluation of retinal vascular abnormalities ranging from detecting neovascularization to quantifying ischemia.11 OCT use in areas ranging from developmental biology research to clinical applications in the fields of gastroenterology, urology, and neurosurgery have now been investigated.8,12–23 Optimization of OCT technology as an imaging modality has been achieved with the use of real-time imaging yielding greater image acquisition rates and laser light sources, which have improved image resolution.12,24–27 The recent US Food and Drug Administration approval of OCT for intravascular imaging has provided an unprecedented level of detail, on the micron level, in the evaluation of vascular pathologies that involve individual vessel wall layers.28 This has also sparked interest in the translation of the technology into the field of …

Transradial cerebral angiography: techniques and outcomes

Background Despite several retrospective studies analyzing the safety and efficacy of transradial access (TRA) versus transfemoral access (TFA) for cerebral angiography, this transition for neurointerventional procedures has been gradual. Nonetheless, based on our positive initial institutional experience with TRA for mechanical thrombectomy in acute ischemic stroke patients, we have started transitioning more of our cerebral angiography cases to TRA. Here we present our single institution experience. Methods We performed a retrospective review of patients receiving TRA cerebral angiography at our institution between January 2016 and February 2017. We present our experience transitioning from TFA to TRA, including our criteria for patient selection, technical nuances, patient experience, complications, and operator learning curve. Results We included 148 angiograms performed in 141 people by one of four operators. No major complications were observed, and the technical success of the procedures was consistent with those of TFA. Marked improvement in operator efficiency was achieved in a short number of cases during this transition when looking at operator proficiency as a function of angiograms performed and days of exposure to TRA (4.3 vs 3.6 min/vessel, P<0.05). Conclusions Safety and efficiency can be preserved while transitioning to TRA. While further investigation is necessary to support transition to TRA, these findings should call for a re-evaluation of the role of TRA in catheter cerebral angiography.

Current applications and future perspectives of robotics in cerebrovascular and endovascular neurosurgery

Advances in robotic medicine have been adopted by various surgical subspecialties as the benefits of this technology become more readily apparent: precision in narrow operative windows, tremor controlled movements, and modestly improved outcomes, among others. Vascular neurosurgery, in particular, remains open to newer and more cutting edge treatment options for complex pathologies, and robotics may be on the horizon for such advances. We seek to provide a broad overview of these innovations in vascular neurosurgery for both practitioners well acquainted with robotics and those seeking to become more familiar. Technologies under development for cerebrovascular and endovascular neurosurgery include robot assisted angiography, guided operative microscopes, coil insertion systems, and endoscopic clipping devices. Additionally, robotic systems in the fields of interventional cardiology and radiology have potential applications to endovascular neurosurgery but require proper modifications to navigate complex intracerebral vasculature. Robotic technology is not without drawbacks, as broad implementation may lead to increased cost, training time, and potential delays in emergency situations. Further cultivation of current multidisciplinary technologies and investment into newer systems is necessary before robotics can make a sizable impact in clinical practice.

Off-label use of the Angioseal vascular closure device for femoral arteriotomy: retrospective analysis of safety and efficacy

Background Angioseal, an arteriotomy closure device (ACD), functions as a collagen plug that physically closes arteriotomy sites and can simultaneously induce platelet activation and aggregation. When used ‘on-label’, the safety and efficacy profile of Angioseal is superior compared with those of other ACDs. However, Angioseal is sometimes deployed in less than ideal situations. Therefore, we sought to assess the safety and efficacy of ‘off-label’ Angioseal use in patients undergoing femoral arteriotomies. Methods We performed a retrospective review of all femoral arterial angiograms executed at our institution between 2008 and 2014. Patients whose femoral punctures did not fit the criteria for on-label Angioseal use were included, and were dichotomized based on vascular closure (off-label Angioseal vs manual compression). Results Of the 521 patients (1023 angiograms) reviewed, 303 (58.2%) patients had off-label Angioseal groin punctures. Mean patient age was 46.2±14.0 years, and 113 were men. 234 patients (77%) had off-label Angioseal deployment while 69 (22%) individuals received manual pressure, serving as controls. Demographic and procedural variables were nearly identical between the two groups but the Angioseal group comprised mostly patients that underwent neurointerventional procedures and thus received intraprocedural heparinization (41%) more often than the manual compression group (19%). The overall rate of major complications associated with off-label Angioseal deployment was low (<0.85%), and clinical complications were not independently associated with Angioseal use (OR 0.76 (95% CI 0.06 to 8.86); p=0.69). Conclusions Off-label use of Angioseal was found to be safe and was not associated with an increased complication rate in our cohort.

Genetic associations of intracranial aneurysm formation and sub-arachnoid hemorrhage

Risk factors for cerebral aneurysms typically include age, hypertension, smoking, and alcohol usage. However, the possible connection of aneurysms with genetic conditions such as Marfans syndrome, polycystic kidney disease, and neurofibromatosis raises the question of possible genetic risk factors for aneurysm, and additionally, genetic risk factors for rupture. We conducted a literature review using the PubMed database for studies regarding genetic correlation with cerebral aneurysm formation as well as rupture from December 2008 to Jun 2015. Twenty-one studies related to IA formation and 10 concerning IA rupture that met our criteria were found and tabulated. The most studied gene and the strongest association was 9p21/CDKN2, which is involved in vessel wall remodelling. Other possible genes that may contribute to IA formation include EDNRA and SOX17; however, these factors were not studied as robustly as CDKN2. Multiple factors contribute to aneurysm formation and rupture and the contributions of blood flow dynamics and comorbidities as mentioned previously, cannot be ignored. While these elements are important to development and rupture of aneurysms, genetic influence may predispose certain patients to formation of aneurysms and eventual rupture.

Ablation dynamics during laser interstitial thermal therapy for mesiotemporal epilepsy

Introduction The recent emergence of laser interstitial thermal therapy (LITT) as a frontline surgical tool in the management of brain tumors and epilepsy is a result of advances in MRI thermal imaging. A limitation to further improving LITT is the diversity of brain tissue thermoablative properties, which hinders our ability to predict LITT treatment-related effects. Utilizing the mesiotemporal lobe as a consistent anatomic model system, the goal of this study was to use intraoperative thermal damage estimate (TDE) maps to study short- and long-term effects of LITT and to identify preoperative variables that could be helpful in predicting tissue responses to thermal energy. Methods For 30 patients with mesiotemporal epilepsy treated with LITT at a single institution, intraoperative TDE maps and pre-, intra- and post-operative MRIs were co-registered in a common reference space using a deformable atlas. The spatial overlap of TDE maps with manually-traced immediate (post-ablation) and delayed (6-month) ablation zones was measured using the dice similarity coefficient (DSC). Then, motivated by simple heat-transfer models, ablation dynamics were quantified at amygdala and hippocampal head from TDE pixel time series fit by first order linear dynamics, permitting analysis of the thermal time constant (τ). The relationships of these measures to 16 independent variables derived from patient demographics, mesiotemporal anatomy, preoperative imaging characteristics and the surgical procedure were examined. Results TDE maps closely overlapped immediate ablation borders but were significantly larger than the ablation cavities seen on delayed imaging, particularly at the amygdala and hippocampal head. The TDEs more accurately predicted delayed LITT effects in patients with smaller perihippocampal CSF spaces. Analyses of ablation dynamics from intraoperative TDE videos showed variable patterns of lesion progression after laser activation. Ablations tended to be slower for targets with increased preoperative T2 MRI signal and in close proximity to large, surrounding CSF spaces. In addition, greater laser energy was required to ablate mesial versus lateral mesiotemporal structures, an effect associated with laser trajectory and target contrast-enhanced T1 MRI signal. Conclusions Patient-specific variations in mesiotemporal anatomy and pathology may influence the thermal coagulation of these tissues. We speculate that by incorporating demographic and imaging data into predictive models we may eventually enhance the accuracy and precision with which LITT is delivered, improving outcomes and accelerating adoption of this novel tool.