OP39 THE ROLE OF EARLY INTRA-OPERATIVE MRI IN SUBTOTAL RESECTION OF OPTIC-HYPOTHALAMIC GLIOMAS IN CHILDREN

INTRODUCTION: Optic pathway/hypothalamic gliomas (OPHGs) are generally benign but situated in an exquisitely sensitive brain region. They follow an unpredictable course and are often impossible to completely resect. We describe a series of OPHGs in 11 patients who underwent surgical resection of their tumour with the aid of intra-operative MRI (iMRI) and discuss their post-surgical outcome. METHOD: All patients with OPHGs managed surgically utilising iMRI at Alder Hey Children's Hospital between 2010 and 2013 were prospectively identified. Demographic and relevant clinical data were obtained. MRI was used to estimate tumour volume pre-operatively and post-resection. If iMRI suggested that further resection was possible, second look surgery was performed followed by post-operative imaging to establish the final status of resection. Tumour volume was estimated for each MR image using the MRIcron software package. RESULTS: Control of tumour progression was achieved in all patients. 7 patients had second look surgery with significant tumour resection following iMRI without any surgically related morbidity. The mean additional quantity of tumour removed following second look surgery as a percentage of the initial total volume was 26.3% (range 11.2-59.2%). 1 patient developed permanent diabetes insipidius unrelated to gross tumour resection, and 3 patients developed a partial ACTH deficit that were easily managed. CONCLUSION: OPHG resection poses a technical difficulty due to their eloquent location. iMRI allows the surgeon to evaluate the tumour resection, and decide whether further resection can be achieved safely. We have demonstrated that utilising iMRI, significantly greater tumour resection can be safely achieved.