Background: Studies of deep brain stimulation (DBS) require accurate electrode localization and image registration. We used anatomical fiducials to investigate localization and registration errors in patients who underwent subthalamic nucleus (STN) DBS for Parkinson’s disease (PD). Methods: We conducted a retrospective analysis of patients who underwent bilateral STN DBS for PD. Pre and post operative MRI scans were non-linearly normalized to a standard template (MNI152NLin2009bAsym). Four raters localized DBS electrodes (Lead-DBS), the anterior commissure (AC) and posterior commissure (PC). Errors between rater localizations were calculated (fiducial localization error; FLE). We transformed AC and PC coordinates from template to patient space to calculate the fiducial registration error (FRE)Results: Ninety-nine patients were analyzed, with a median FLE of 0.76mm, 0.74mm, 0.71mm and 0.66mm for the right electrode, left electrode, AC and PC respectively (no significant difference, Wilcoxon sign rank). The median FRE was 1.59mm for AC and 1.21mm for PC, significantly higher than FLE at those coordinates (Wilcoxon sign rank, p<0.001). Conclusions: Raters can accurately localize DBS electrodes, AC and PC from clinical images with sub-millimetric accuracy. Higher FREs at AC and PC suggested registration errors may contribute more than localization errors to electrode uncertainty in a common space.

Background: Therapeutic response from subthalamic nucleus (STN) deep brain stimulation (DBS) for Parkinson disease (PD) has been associated with proximity to an ideal target, commonly in the dorsal sensorimotor STN. Automated registration and atlas-based segmentation has allowed for contact localization within STN subnuclei. We sought to apply these methods to characterize the spatial distribution of our active contact placements. Methods: We conducted a retrospective analysis of 55 patients who underwent bilateral STN DBS for PD. Post-operative CT/MRI scans were non-linearly registered into a standard space, and DBS-electrodes were localized using Lead-DBS. 3-dimensional meshes from a segmented atlas (Ewert 2017) were utilized. Analysis was performed in MATLAB R2019b. Results: Mean active contacts were within sensorimotor STN bilaterally, located posteroinferiorly compared to reported ideal targets. Centroids fell within (left/right): sensorimotor (46%/40%), associative (22%/22%), limbic (0%/2%) and outside STN (32%/36%). Principal components analysis demonstrated most spatial variance is explained by the first component (left 65.8%, right 61.9%). Conclusions: We obtained contact locations in relation to STN subnuclei, allowing for an anatomically guided approach to our analysis. 66% of the active contacts were located within the STN, and most of the spatial variation occurred along a single dimension. Future directions include utilizing subnuclei localizations to investigate clinical outcomes.

Introduction: Chronic facial pain is a prevalent group of conditions and when refractory to common treatments poses a social and economic burden. The last decade has seen a multitude of advancements in the multimodal management of pain. Ablative or neuromodulatory interventions targeting the nucleus caudalis (NC) of the trigeminocervical complex is one such treatment that has remained underutilized. Methods: Here we present a systematic review of the literature and historical perspective regarding interventions targeting the NC. We examine the various intervention techniques, clinical indications, and procedural efficacy. A novel outcome reporting scheme was devised to allow comparison between studies using differing outcome reporting methods. Results: A review of the literature revealed 49 retrospective studies published over the last 80 years, reporting on 858 patients. The most common technique was the open NC dorsal root entry zone nucleotomy/tractotomy (n=515, 60.0%); however, there has been an emergence of novel approaches such as endoscopic (n=6, 0.7%) and spinal cord stimulation (n=20, 2.3%) in the last 10 years. Regardless of intervention technique or preoperative diagnosis, 90.4% of patients demonstrated some improvement from treatment. Conclusion: This systematic review highlights recent advancements in NC intervention technique and the wide range of facial pain syndromes for which these interventions show promising efficacy. New and less invasive techniques continue to emerge, however prospective studies remain absent in the literature. Future work should address efficacy comparisons between intervention type and preoperative diagnosis.

Background: Mastery of microsurgical skills requires regular hands-on practice. Simulation is increasingly recognized as an important supplement to operative training experience. The live rat femoral artery model is the gold standard model for microneurosurgical skills simulation. We present an 11-year experience incorporating simulation-based microsurgical training into an established Canadian neurosurgery program. Methods: Postgraduate year 2 (PGY-2) neurosurgery residents completed a one-year curriculum spanning 17 training sessions divided into 5 modules of increasing fidelity. Both perfused duck wing and live rat vessel training modules were used. Three modules comprised live microvascular anastomosis. Trainee performance was video recorded and blindly graded using the Objective Structured Assessment of Technical Skills Global Rating Scale. Results: Eighteen participants completed 107 microvascular anastomoses. There was significant improvement in six measurable skills during the curriculum. Mean overall score was significantly higher on the fifth attempt compared to the first attempt for all 3 live anastomotic modules (p<0.001). Each module had a different improvement profile across the skills assessed. The greatest improvement was observed during artery-to-artery anastomosis. Conclusions: This high-fidelity microsurgical simulation curriculum demonstrated a significant improvement in the six microneurosurgical skills assessed, supporting its use as an effective teaching model. Transferability to the operative environment is actively being investigated.

Background: Microsurgical techniques remain a cornerstone of neurosurgical training. Despite this, neurosurgical microvascular case volumes are decreasing as endovascular and minimally invasive options expand. As such, educators are looking towards simulation to supplement operative exposure. We review a single institution’s experience with a comprehensive, longitudinal microsurgical simulation training program, and evaluate its effectiveness. Methods: Consecutive postgraduate year 2 (PGY-2) neurosurgery residents completed a one-year curriculum spanning 17 training sessions divided into 5 modules of increasing fidelity. Both perfused duck wing and live rat femoral vessel training modules were used. Trainee performance was video recorded and blindly graded using the Objective Structured Assessment of Technical Skills Global Rating Scale. Results: Eighteen participants completed 107 microvascular anastomoses during the study. There was significant improvement in six measurable skills during the curriculum. Mean overall score was significantly higher on the fifth attempt compared to the first attempt for all 3 live anastomotic modules (p<0.001). Each module had a different improvement profile across the skills assessed. The greatest improvement was observed during artery-to-artery anastomosis. Conclusions: This high-fidelity microsurgical simulation curriculum demonstrated a significant improvement in the six microneurosurgical skills assessed, supporting its use as an effective teaching model. Transferability to the operative environment is actively being investigated.

Background: Arterial Hemodynamics have been implicated in hemorrhage from cerebral arteriovenous malformations (AVMs). The correlation between hemodynamic characteristics and the tendency of AVMs to rupture has been explored in the past, and various theories have been proposed to explain the clinical presentation of AVMs as a hemorrhage vs. seizure. Methods: We monitored feeder artery pressures in 45 patients with AVMS (16 presenting with hemorrhage, 29 without) during super selective angiography and AVM embolization. Results: Mean feeder artery pressure (FP) was found to be 49mm Hg. The mean FP in patients presenting with hemorrhage was somewhat higher than in those without hemorrhage, but the difference was not statistically significant (53.8 mm Hg vs 47.0 mm Hg, p=0.13). Systemic mean pressure was found to correlate with AVM size (r=-0.31, p=0.037). Significant predictors of feeder artery pressure were systemic pressure, AVM size, and the distance of microcatheter from the circle of Willis. Meanwhile, the presence or absence of venous outflow stenosis and the position of the AVM nidus (superficial or deep to the cortical surface) were the most significant predictors of AVM hemorrhage vs seizures. Conclusions: Anatomic factors may be more important than arterial hemodynamic factors in determining the clinical presentation of cerebral AVMs.

Background: Ventriculoperitoneal (VP) shunting is a common treatment for hydrocephalus. Complications of VP shunt include infection, malfunction, and hemorrhage. Vascular complications such as pseudoaneurysm are rare, and usually involve the choroid plexus or branches of the external carotid artery. We present the case of a fusiform pseudoaneurysm of the middle cerebral artery arising due to VP shunt insertion. Methods: A 36-year-old female presented with a hypertensive cerebellar hemorrhage and hydrocephalus. This was treated with VP shunt placement with limited dural opening. Three weeks afterward there developed a diffuse intraventricular hemorrhage associated with hemorrhage at the cortical insertion site of the ventricular catheter. CT and catheter angiography revealed a fusiform pseudoaneurysm of the M4 segment of the MCA immediately adjacent to the ventricular catheter. Results: The VP shunt was removed, and the aneurysmal segment was coagulated and occluded. Delayed repeat VP shunt insertion was performed through the same entry point and trajectory via a larger dural opening. Conclusions: Pseudoaneurysm formation secondary to catheter insertion is a rare complication. To our knowledge, this is the second reported case of a cortical branch pseudoaneurysm in an adult. Careful consideration should be given to vascular anatomy when planning shunt insertions, and cruciate dural opening for local cortex visualization may help avoid this complication.

Background: Persistent fetal carotid-vertebrobasilar anastomoses are rare, with an incidence of <1%. The most common anomaly seen in this group is a persistent primitive trigeminal artery; others such as a persistent hypoglossal artery account for less than 15% of all persistent fetal anastomoses, making this finding exceedingly rare. Methods: We present the case of a 32-year-old-female with Poland syndrome (right-sided), who presented with thunderclap headache and reduced level of consciousness secondary to diffuse subarachnoid hemorrhage and hydrocephalus. CT and catheter angiography demonstrated an aneurysm of the V4 segment of the right vertebral artery arising from a persistent right hypoglossal artery, with an absent ipsilateral vertebral artery proximal to the anomaly. Results: Hydrocephalus was treated with an EVD, followed by a successful embolization of the V4 aneurysm with Axium coils. Subsequent MR studies demonstrated minimal recanalization of the aneurysm, and small foci of possible infarcts in the hippocampi. Four months later, the patient has some persistent short term memory difficulties but is otherwise neurologically intact. Conclusions: We present a rare finding of a persistent fetal hypoglossal artery with an associated vertebral aneurysm. The aneurysm was successfully treated endovascularly through coil embolization with minimal residual -neurological deficit. This vascular anomaly was ipsilateral to her Poland Syndrome defects.