LE JOURNAL CANADIEN DES SCIENCES NEUROLOGIQUESSuppl. 2 -S25 areas of abnormal T2/FLAIR or contrast enhancement can contain infiltrative tumour cells. The presence of isolated diffusion restriction may be a useful predictor of disease progression and prognosis but further investigation into the nature and behavior of isolated DWI lesions is required. P.044Prospective clinical detection of 2-hydroxyglutarate to predict IDH-mutant gliomas using magnetic resonance spectroscopy: preliminary results We will recruit 150 patients presenting with a newly suspected glioma. All patients will undergo MRS scans for 2-HG pre-operatively and the neuropathologist will determine IDH status post-operatively based on immunohistochemistry and DNA sequencing. Pre-operative detection of 2-HG will be compared to post-operative IDH status. Results: To date, of 34 eligible subjects, 29 have glioma determined by pathology. Seven of these were IDH-mutant positive by pathology, of which 3 were detected by MRS. One glioma positive for 2-HG on MRS turned out to be IDH mutant negative on pathology. Conclusions: Prospective detection of 2-HG via MRS is feasible in the clinical setting. Additional subjects as well as refinement of our MRS protocol may yield higher sensitivity and specificity of this novel and clinically relevant diagnostic tool. Background: Spontaneous hemorrhage from angiographically occult vascular malformations is not a rare occurrence. We present a case of in-hospital cavernous malformation rupture after initial normal CT. Methods: A 55-year-old female presented with severe headache with onset during activity, and normal neurological examination. Rapid neurological deterioration occurred 60 minutes following the CT scan. The patient was intubated, and repeat CT scan showed significant parafalcine ICH and intrahemispheric SAH. ICU transfer and expectant management led to neurological recovery and discharge to rehabilitation. Results: The patient underwent angiography on initial admission which was negative. A delayed MRI showed the presence of a cavernous malformation. This was followed conservatively with repeat imaging. The malformation remained stable. Conclusions: Our unique case highlights the sudden onset of hemorrhage occurring almost immediately following normal brain imaging. A cavernous malformation was discovered to be the cause, and was observed. MS P.046Multiple intracranial mycotic aneurysms and management dilemma in postinterventional cerebral vasospasm: a case report AA Al Jishi (Hamilton) Background: Intracranial mycotic aneurysms are rare forms of vascular abnormalities. They are typically fragile and have high tendency to bleed. Even when they are successfully secured upon intervention, the medical management can be challenging in presence of other non-ruptured aneurysms and concomitant cerebral vasospasm. Methods: A 31 year old female was admitted with right sided large intracerebral hemorrhage due to ruptured mycotic MCA aneurysm. She was also known with severe tricuspid regurgitation from drug abuse. Ot...

Suppl. 2 -S28to 3/week. Seizures last only 2-3 seconds, without postictal confusion leading to improvements in neuropsychological function. AED dosages are not reduced. Conclusions: Successful intracranial EEG localization of otherwise non-lesional non-resectable seizure focus permits the use of deep brain stimulation that effectively reduces refractory seizure frequency. P.027Investigation of hippocampal sub-structures in HS and non-HS focal temporal lobe epilepsy at 7T Background: The clinical identifi cation of hippocampal sclerosis (HS) is important in predicting surgical outcomes in patients with temporal lobe epilepsy (TLE). In cases where gross hippocampal sclerosis is not identifi able clinically, a more detailed analysis of hippocampal subfi elds using ultra-high-fi eld magnetic resonance imaging (MRI) may reveal areas of abnormality, which was the focus of our study. Methods: Patients (N=13) with drug-resistant TLE (9 no-HS, 4 HS) and 20 age-matched healthy controls were scanned and compared using a 7T MRI protocol. Using a manual segmentation scheme to delineate hippocampal subfi elds, subfi eld-specifi c volume changes were studied between the two groups. In addition, radiological patient assessment at 7T was correlated with measured subfi eld changes. Results: Volumetry of the hippocampus at 7T in HS patients revealed signifi cant ipsilateral subfi eld losses in CA1 and CA4DG. Volumetry also uncovered subfi eld volume losses in 33% of no-HS patients, which had not been detected conventionally. Furthermore, 89% of no-HS patients showed abnormality (internal architecture or size) at 7T, identifi ed by radiologists blinded to the patient's initial classifi cation. Conclusions: These preliminary fi ndings indicate that hippocampal subfi eld volumetry assessed at 7T may be superior to conventional visual inspection by a neuroradiologist in the identifi cation of hippocampal pathologies in TLE. P.028Incidence and management of seizures and epilepsy after ischemic stroke: a systematic review

Background: Endoscopic endonasal trans-sphenoidal surgery (EETS) is a commonly used approach for the surgical treatment of primary pituitary adenomas. The role of this approach in patients with recurrent disease remains unclear. Here we review a high-volume institutional experience with repeat EETS for recurrent pituitary adenomas and compare outcomes against primary surgeries. Methods: A retrospective chart review of patients who underwent EETS at Toronto Western Hospital from 2008-2016 for pituitary adenomas was completed. Baseline patient characteristics and surgical outcomes were recorded for each surgery. Primary and repeat operations were compared for analysis using Fisher’s exact test and t-test where appropriate. Results: 347 primary and 48 repeat surgery patients were identified. The median follow-up was 3.6 years (range 0-10.6 years). Rates of GTR, optic decompression, endocrinopathy cure, and visual improvement in repeat EETS were 44%, 21%, 22%, and 21%, respectively. While these rates are lower when compared to primary surgeries (75% p<0.001, 58% p<0.001, 75% p=0.01, 37% and p=0.04), they demonstrate that desirable outcomes are still achievable after EETS for recurrent disease. Conclusions: These results from a quaternary-care centre suggest that repeat EETS is a viable option that is safe and effective at improving the visual and endocrine status in select patients with recurrent pituitary disease.

Background: Vestibular schwannoma (VS) is the most common tumour of the cerebellopontine angle and poses a significant morbidity for patients. While many exhibit benign behaviour, others have a more aggressive nature. There is a need for a better understanding of the molecular landscape, and important subgroups therein, of this disease. Methods: We select all VS from our tumour bank with both methylation and RNA profiling. Unsupervised clustering methods were used to define two distinct molecular subgroups of VS which were explored using computational techniques including bulk deconvolution analysis, gene pathway enrichment analysis, and drug repurposing analysis. Methylation data from two other cohorts were used to validate our findings. Results: A total of 75 tumours were analyzed. Consensus clustering and similarity network fusion defined two subgroups (“immunogenic” and “proliferative”) with significant differences in immune, stroma, and tumour cell abundance. Gene network analysis and computational drug repurposing found critical differences in targets of immune checkpoint inhibition PD-1 and CTLA-4, the MEK pathway, and the epithelial-to-mesenchymal transition program with associated candidate drug targets, suggesting a need for subgroup-specific treatment/trial design in the future. Conclusions: We leverage computational tools with multi-omic molecular data to define two robust subgroups of vestibular schwannoma with differences in microenvironment and therapeutic vulnerabilities.