Subthalamic nucleus (STN) beta-triggered adaptive deep brain stimulation (ADBS) has been shown to provide clinical improvement comparable to conventional continuous DBS (CDBS) in people with Parkinson's disease (PD) with less energy delivered to the brain and less stimulation induced side-effects. However, several questions remain unanswered. First, there is a normal physiological reduction of STN beta band power just prior to and during voluntary movement. ADBS systems will therefore reduce or cease stimulation during movement and could therefore compromise motor performance compared to CDBS. Second, beta power was smoothed and estimated over time periods of 400ms or longer in most previous ADBS studies. A shorter smoothing period could have the advantage of being more sensitive to changes in beta power which could enhance motor performance. In this study, we addressed these two questions by evaluating the effectiveness of STN beta-triggered ADBS using a standard 400ms and a shorter 200ms smoothing window during reaching movements. Results from 13 people with PD showed that STN beta-triggered ADBS is effective in improving motor performance during reaching movements as it better preserves gamma oscillation than CDBS in people with PD, and that shortening the smoothing window does not result in any additional behavioural benefit. ADBS significantly improved tremor compared with no DBS but was not as effective as CDBS. When developing ADBS systems for PD, it might not be necessary to track very fast beta dynamics; combining beta, gamma, and motor decoding might be more beneficial with additional biomarkers needed for optimal treatment of tremor.

Subthalamic nucleus (STN) beta-triggered adaptive deep brain stimulation (ADBS) has been shown to provide clinical improvement comparable to conventional continuous DBS (CDBS) with less energy delivered to the brain and less stimulation induced side-effects. However, several questions remain unanswered. First, there is a normal physiological reduction of STN beta band power just prior to and during voluntary movement. ADBS systems will therefore reduce or cease stimulation during movement in people with Parkinson’s disease (PD) and could therefore compromise motor performance compared to CDBS. Second, beta power was smoothed and estimated over a time period of 400 ms in most previous ADBS studies, but a shorter smoothing period could have the advantage of being more sensitive to changes in beta power which could enhance motor performance. In this study, we addressed these two questions by evaluating the effectiveness of STN beta-triggered ADBS using a standard 400 ms and a shorter 200 ms smoothing window during reaching movements. Results from 13 people with PD showed that reducing the smoothing window for quantifying beta did lead to shortened beta burst durations by increasing the number of beta bursts shorter than 200 ms and more frequent switching on/off of the stimulator but had no behavioural effects. Both ADBS and CDBS improved motor performance to an equivalent extent compared to no DBS. Secondary analysis revealed that there were independent effects of a decrease in beta power and an increase in gamma power in predicting faster movement speed, while a decrease in beta event related desynchronization (ERD) predicted quicker movement initiation. CDBS suppressed both beta and gamma more than ADBS, whereas beta ERD was reduced to a similar level during CDBS and ADBS compared with no DBS, which together explained the achieved similar performance improvement in reaching movements during CDBS and ADBS. In addition, ADBS significantly improved tremor compared with no DBS but was not as effective as CDBS. These results suggest that STN beta-triggered ADBS is effective in improving motor performance during reaching movements in people with PD, and that shortening of the smoothing window does not result in any additional behavioural benefit. When developing ADBS systems for PD, it might not be necessary to track very fast beta dynamics; combining beta, gamma, and information from motor decoding might be more beneficial with additional biomarkers needed for optimal treatment of tremor.

s vi238NEURO-ONCOLOGY • NOVEMBER 2017isocitrate dehydrogenase (IDH)-1 mutation by immunohistrochemistry and two patients had unknown IDH status. Pre-and post-operative median KPS were 90 (60-100) and 80 (40-100) respectively. Eleven patients had difficulty weaning steroids (4 patients initiated steroids peri-operatively, 7 patients prior to surgery). For rGBM post-LITT median PFS was 3.36 months (95% CI (0.21, 0.51)) and median OS was 18.48 months (95% CI (0.66,NA)) with 5 deaths. Median PFS and OS for nGBM has not been reached. Eighteen patients (86%) received post-LITT chemotherapy of which eight initiated treatment >3 weeks post-LITTdue to poor functionality (6), pregnancy (1), and patient choice (1). Among the patients receiving chemotherapy, time to initiation of chemotherapy was not associated with PFS or OS. Chemotherapy in rGBM cohort included lomustine (6), temozolomide (5), bevacizumab (3), bevacizumab + lomustine (1), lapatinib (1), and Novo-TTF (1). Median time to initiation ofi bevacizumab (4 patients) after LITT was 30.5 (17-45) days, without complications. CONCLUSIONS: LITT may be an effective cytoreductive treatment for glioblastoma. Timing of onset of chemotherapy after LITT for glioblastoma is not associated with PFS or OS. SURG-12. INTRAOPERATIVE MAGNETIC RESONANCE SPECTROSCOPY (iMRS) FOR GLIOMA SURGERY

NEURO-ONCOLOGY • JANUARY 2018brain tumor management. The target population for the PROM will be brain Tumor patients (adult and pediatric). The PROM would collect information from patients preoperatively and Post-operatively. The conceptual domains for neuro-oncology PROM will include health related quality of life (physical, mental, social and emotional), symptoms (specific to neurooncology) including weakness, memory, taste, seizure, incontinence, neurooncology specific disability and functional status. In conclusion, there is an emergent need to develop a neuro-oncological surgery PROM to address the specific unmet needs of the field of neuro-oncological surgery. The proposed framework would be beneficial in further study and development of the PROM.