Cameron A. Elliott

Partial intra-aortic occlusion improves perfusion deficits and infarct size following focal cerebral ischemia.

Reperfusion with intravenous tissue plasminogen activator (tPA) has been the goal of therapy for acute ischemic stroke; however, tPA is contraindicated in many patients, has low recanalization rates in major occlusions, and carries a substantial risk of symptomatic intracerebral hemorrhage. In the present study, we hypothesized that partial intra‐aortic occlusion of the abdominal aorta would increase salvage of ischemic penumbra and reduce infarct volume after focal embolic stroke in rats. We examined the effects of aortic occlusion on infarct volume, expression and activation of matrix metalloprotease‐9, and hemorrhagic transformation with or without treatment with tPA. We then examined the effects of aortic occlusion on perfusion deficits following embolic occlusion. Results showed that partial aortic occlusion significantly reduces brain infarction volume with or without treatment with tPA after focal ischemia, but does not increase risk for hemorrhagic transformation or matrix metalloprotease‐9 expression and activation. Partial intra‐aortic occlusion also reduces perfusion deficits after focal cerebral ischemia as compared to control. The present study shows that partial intra‐aortic occlusion significantly decreases infarction volume and perfusion deficits following ischemic injury in an embolic model of cerebral ischemia. Moreover, combination treatment with tPA and partial intra‐aortic occlusion further reduces infarction volume without any increase in hemorrhagic transformation.

Magnetic resonance imaging artifact following anterior cervical discectomy and fusion with a trabecular metal cage

OBJECT This study was undertaken to evaluate the impact of postoperative MRI artifact on the assessment of ongoing spinal cord or nerve root compression after anterior cervical discectomy and fusion (ACDF) using a trabecular tantalum cage or bone autograft or allograft. METHODS The authors conducted a retrospective review of postoperative MRI studies of patients treated surgically for cervical disc degenerative disease or cervical instability secondary to trauma. Standard ACDF with either a trabecular tantalum cage or interbody bone graft had been performed. Postoperative MR images were shown twice in random order to each of 3 assessors (2 spine surgeons, 1 neuroradiologist) to determine whether the presence of a tantalum interbody cage and/or anterior cervical fixation plate or screws imparted MRI artifact significant enough to prevent reliable postoperative assessment of ongoing spinal cord or nerve root compression. RESULTS A total of 63 patients were identified. One group of 29 patients received a tantalum interbody cage, with 13 patients (45%) undergoing anterior plate fixation. A second group of 34 patients received bone auto- or allograft, with 23 (68%) undergoing anterior plate fixation. The paramagnetic implant construct artifact had minimal impact on visualization of postoperative surgical level spinal cord compression. In the cage group, 98% (171/174) of the cases were rated as assessable versus 99% in the bone graft group (201/204), with high intraobserver reliability. In contrast, for the assessment of ongoing surgical level nerve root compression, the presence of a tantalum cage significantly decreased visualization of nerve roots to 70% (121/174) in comparison with 85% (173/204) in the bone graft group (p < 0.001). When sequences using turbo spin echo (TSE), a T2-weighted axial sequence, were acquired, nerve roots were rated as assessable in 88% (69/78) of cases; when only axial T2-weighted sequences were available, the nerve roots were rated as assessable in 54% (52/96) of cases (p < 0.01). The presence of anterior plate fixation had minimal impact on visualization of the spinal cord (99% [213/216] for plated cases vs 98% [159/162] for nonplated cases; p = 1.0) or nerve roots (79% [170/216] for plated cases vs 77% [124/162] for nonplated cases; p = 0.62). CONCLUSIONS Interbody fusion with tantalum cage following anterior cervical discectomy imparts significant paramagnetic artifact, which significantly decreases visualization and assessment of ongoing surgical level nerve root, but not spinal cord, compression. Anterior plate constructs do not affect visualization of these structures. TSE T2-weighted sequences significantly improve nerve root visualization and should be performed as part of a standard postoperative protocol when imaging the cervical spine following interbody implantation of materials with potential for paramagnetic artifact.

Demographics, Interests, and Quality of Life of Canadian Neurosurgery Residents

BACKGROUND Neurosurgical residents face a unique combination of challenges, including long duty hours, technically challenging cases, and uncertain employment prospects. We sought to assess the demographics, interests, career goals, self-rated happiness, and overall well-being of Canadian neurosurgery residents. METHODS A cross-sectional survey was developed and sent through the Canadian Neurosurgery Research Collaborative to every resident enrolled in a Canadian neurosurgery program as of April 1, 2016. RESULTS We analyzed 76 completed surveys of 146 eligible residents (52% response rate). The median age was 29 years, with 76% of respondents being males. The most popular subspecialties of interest for fellowship were spine, oncology, and open vascular neurosurgery. The most frequent self-reported number of worked hours per week was the 80- to 89-hour range. The majority of respondents reported a high level of happiness as well as stress. Sense of accomplishment and fatigue were reported as average to high and overall quality of life was low for 19%, average for 49%, and high for 32%. Satisfaction with work-life balance was average for 44% of respondents and was the only tested domain in which significant dissatisfaction was identified (18%). Overall, respondents were highly satisfied with their choice of specialty, choice of program, surgical exposure, and work environment; however, intimidation was reported in 36% of respondents and depression by 17%. CONCLUSIONS Despite a challenging residency and high workload, the majority of Canadian neurosurgery residents are happy and satisfied with their choice of specialty and program. However, work-life balance, employability, resident intimidation, and depression were identified as areas of active concern.

Operative Landscape at Canadian Neurosurgery Residency Programs

Background Currently, the literature lacks reliable data regarding operative case volumes at Canadian neurosurgery residency programs. Our objective was to provide a snapshot of the operative landscape in Canadian neurosurgical training using the trainee-led Canadian Neurosurgery Research Collaborative. METHODS Anonymized administrative operative data were gathered from each neurosurgery residency program from January 1, 2014, to December 31, 2014. Procedures were broadly classified into cranial, spine, peripheral nerve, and miscellaneous procedures. A number of prespecified subspecialty procedures were recorded. We defined the resident case index as the ratio of the total number of operations to the total number of neurosurgery residents in that program. Resident number included both Canadian medical and international medical graduates, and included residents on the neurosurgery service, off-service, or on leave for research or other personal reasons. RESULTS Overall, there was an average of 1845 operative cases per neurosurgery residency program. The mean numbers of cranial, spine, peripheral nerve, and miscellaneous procedures were 725, 466, 48, and 193, respectively. The nationwide mean resident case indices for cranial, spine, peripheral nerve, and total procedures were 90, 58, 5, and 196, respectively. There was some variation in the resident case indices for specific subspecialty procedures, with some training programs not performing carotid endarterectomy or endoscopic transsphenoidal procedures. CONCLUSIONS This study presents the breadth of neurosurgical training within Canadian neurosurgery residency programs. These results may help inform the implementation of neurosurgery training as the Royal College of Physicians and Surgeons residency training transitions to a competence-by-design curriculum.

Progressive contralateral hippocampal atrophy following surgery for medically refractory temporal lobe epilepsy

OBJECTIVE Determine the extent and time course of volumetric changes in the contralateral hippocampus following surgery for medically refractory temporal lobe epilepsy (TLE). METHODS Serial T1-weighted MRI brain scans were obtained in 26 TLE patients pre- and post-temporal lobe epilepsy surgery as well as in 12 control subjects of similar age. Patients underwent either anterior temporal lobectomy (ATL) or selective amygdalohippocampectomy (SAH). Blinded, manual hippocampal volumetry (head, body, and tail) was performed in two groups: 1) two scan group [ATL (n=6); SAH (n=10)], imaged pre-surgery and on average at 5.4 years post-surgery; and 2) longitudinal group [ATL (n=8); SAH (n=2)] imaged pre-surgery and on post-operative day 1, 2, 3, 6, 60, 120 and a delayed time point (average 2.4 years). RESULTS In the two scan group, there was atrophy by 12% of the unresected contralateral hippocampus (p<0.001), with atrophy being most pronounced (27%) in the hippocampal body (p<0.001) with no significant differences seen for the hippocampal head or tail. In the longitudinal group, significant atrophy was also observed for the whole hippocampus and the body with atrophy seen as early as post-operative day #1 which progressed significantly over the first post-operative week (1.3%/day and 3.0%./day, respectively) before stabilizing over the long-term to a 13% reduction in total volume. There was no significant difference in atrophy compared by surgical approach (ATL vs. SAH; p=0.94) or side (p=0.31); however, atrophy was significantly more pronounced in patients with ongoing post-operative seizures (hippocampal body, p=0.019; whole hippocampus, p=0.048). There were no detectable post-operative neuropsychological deficits attributable to contralateral hippocampal atrophy. SIGNIFICANCE Significant contralateral hippocampal atrophy occurs following TLE surgery, which begins immediately and progresses over the first post-operative week. The observation that seizure free patients had significantly less atrophy of the contralateral hippocampus after surgery suggests the possibility of an early post-operative imaging marker to predict surgical outcome.

Longitudinal hippocampal and extra-hippocampal microstructural and macrostructural changes following temporal lobe epilepsy surgery

OBJECTIVES 1) Characterize the evolution of microstructural changes in the contralateral, non-operated hippocampus-using longitudinal diffusion tensor imaging (DTI)-following surgery for temporal lobe epilepsy (TLE). 2) Characterize the downstream extra-hippocampal volumetric changes of the fornix and mammillary bodies after TLE surgery. 3) Examine the relationship between these measures and seizure/cognitive outcome. METHODS Serial structural and DTI brain MRI scans were collected in 25 TLE patients pre- and post-surgery (anterior temporal lobectomy, ATL - 13; selective amygdalohippocampectomy, SelAH - 12) and in 12 healthy controls. Contralateral hippocampal fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD) and radial diffusivity (RD) were computed with manual hippocampal tracings as volumes of interest following co-registration to anatomical images. Fornix and mammillary body volumetry was performed by manual segmentation. RESULTS After surgery, the non-resected hippocampus showed significant postoperative decline in FA (p = 0.0001), with increase of MD (p = 0.01) and RD (p = 0.0001). In contrast to the timing of our previously reported volume changes where atrophy is observed in the first week, diffusion changes occurred late, taking 1-3 years to develop and are not significant at one week after surgery. Diffusion changes are accompanied by delayed limbic circuit volume loss in the mammillary bodies (35%; p < 0.0001) and fornix (24%; p < 0.0001) compared to baseline. There was no correlation between postoperative diffusion or structural changes and memory score nor did the degree of postoperative change in hippocampal DTI parameters, mammillary body volume or fornix volume vary significantly based on seizure outcome. SIGNIFICANCE Differences observed in the timing of postoperative volume (first week) and FA/MD (one year) changes would suggest that early contralateral hippocampal atrophy is not secondary to fluid shifts (dehydration) while the late DTI changes suggest ongoing microstructural changes extending beyond the early postoperative period. Postoperative hippocampal diffusion changes are accompanied by delayed mammillary body and fornix volume loss which did not differ when stratified by seizure outcome nor was correlated with degree of hippocampal diffusion change. Finally, we did not identify any significant correlation between postoperative diffusion parameter change and memory performance.

A.06 Selective amygdalohippocampectomy in pediatric medically refractory temporal lobe epilepsy yields worse seizure outcomes

Background: Selective amygdalohippocampectomy (SAH) is a surgical option in well-selected cases of pediatric medically refractory temporal lobe epilepsy (TLE). The objective of this study was to compare the surgical outcome and the rate of reoperation for ongoing or recurrent seizures between SAH and anterior temporal lobectomy (ATL) in pediatric TLE. Methods: Retrospective review of 78 pediatric intractable TLE patients referred to the Comprehensive Epilepsy Program at our institution between 1988 and 2015 treated initially with either a trans-middle temporal gyrus SAH (19) or ATL (59). Patients underwent baseline long-term video electroencephalography and 1.5-Tesla MRI. Neuropsychological testing was performed preoperatively and 12-months postoperatively (including reoperations). Results: The mean follow-up was 64 months (range, 12-186 months). The average age at initial surgery was 10.6±5 years with an average delay of 5.7±4 years between seizure onset and surgery. Ultimately 78% were seizure-free (61/78) at most recent follow-up. Seizure freedom after initial surgical treatment was achieved in 81% of patients who underwent ATL (48 patients) versus 42% in SAH (8 patients; p<0.001). Of patients with ongoing disabling seizures following SAH, reoperation (ATL) was offered in 8 resulting in seizure freedom in 63%, without interval neuropsychological decline. Conclusions: SAH amongst well-selected pediatric TLE results in significantly worse seizure control compared with ATL.

C.03: CNSS K.G. McKenzie Memorial Prize in Clinical Research (2nd place): Progressive contralateral hippocampal atrophy following surgery for medically refractory temporal lobe epilepsy

Background: It remains difficult to predict which patients will experience ongoing seizures or neuropsychological deficits following Temporal Lobe Epilepsy (TLE) surgery. MRI allows measurement of brain structures, such as the contralateral (non-resected) hippocampus (cHC) after TLE surgery. Preliminary evidence suggests that the cHC atrophies following surgery, however, the time course of this atrophy, relation to cognitive deficits and seizure outcome remains unclear. Methods: T1-weighted MR imaging and hippocampal volumetry in 26 TLE patients pre- and post-TLE surgery (and 12 controls) as: 1) two-scan group (TSG) (pre- and post-operatively at 5.4 years) and 2) longitudinal group (LG; pre- and on post-operatively on day 1,2,3,6,60,120 and at an average 2.4 years. Seizure outcome and pre- and post-operative neuropsychological assessment was performed. Results: The TSG had significant atrophy by 12% of the unresected cHC (p Conclusions: Significant cHC atrophy following TLE surgery that begins immediately, progresses over the first week, and remains signficantly depressed. The severity postoperative cHC atrophy may represent an early biomarker of the propensity for delayed seizure recurrence.

Hyperostosis frontalis interna requiring craniotomy for intracranial hypertension.

benign metabolic craniopathy involving focal lamellar bone deposition along the inner table of the frontal bones. Although some cases of HFI may be symptomatic with intrusive bone growth causing cognitive slowing, seizures or mood disturbance, rarely will HFI present in a dramatic manner. Here, we report a case of HFI causing marked intracranial hypertension, tonsilar herniation and bilateral posterior cerebral artery (PCA) ischemia treated successfully with bi-hemispheric decompressive craniotomy and cranioplasty.

Neuroimaging highlight - cerebral abscess crossing midline.

CASE REPORT An 81-year-old right handed man presented to another institution with an episode of acute confusion. On exam he was mildly confused and complained of a headache. He exhibited no focal neurological findings. Laboratory and overall examination was non contributory. Investigation included a computed axial tomography scan which demonstrated the left frontal mass. To further characterize the lesion an MRI was obtained. The right frontal lesion had a ring enhancing pattern after gadolinium contrast injection (Figure 1). There was a large cystic component to the mass with a significant amount of surrounding vasogenic edema that was seen to cross the midline through the rostrum and genu of the corpus callosum (Figure 2). On diffusion weighted sequences the lesion demonstrated restricted diffusion (Figure 3), commonly associated with abscess or infarction but has been well described in the setting of high grade tumors and correlates to necrosis within the tumor.1 Given the location of the lesion and the pattern of transcallosal dissemination the imaging was felt to be most consistent with glioblastoma multiforme. After several conversations with the family and the patient it was decided that in order to maximize the patient’s quality of life an aggressive resection was inappropriate. The family was offered the choice of proceeding directly to a course of palliative radiotherapy and / or chemotherapy or performing a stereotactic biopsy to first confirm the diagnosis. The biopsy was undertaken using the frameless MRI needle guided biopsy using the Stealth system (Medtronic, Minneapolis, MN) and the Olivier arm (Phillips Medical Systems). There was no pus or fluid identified by the surgeon at the time of biopsy. The area of the lesion targeted was the enhancing component of the lesion in an attempt to sample from what was considered to be the most active component of the lesion. Following the biopsy the patient was not felt to be safe for discharge and was kept in hospital while awaiting the results. The final pathological results were reported eight days after the biopsy and were consistent with cerebral tissue containing chronic inflammatory and reactive changes. Over this time the patient began to clinically deteriorate with a fluctuating level of consciousness and the development of the syndrome of inappropriate anti-diuretic hormone requiring treatment. The MRI was repeated and again demonstrated restriction of diffusion. There was frank