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J. Neurosurg. Feb 2008 Sajedha Mahmood

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J. Neurosurg. Feb 2008 Sajedha Mahmood

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  1. Preoperative functional magnetic resonance imaging assessment of higher-order cognitive function in patients undergoing surgery for brain tumorsC. Amiez, P Kostopoulos, A-S Champod, D Louis Collins, J Doyon, R Del Maestro, M PetridesMontreal Neurological Institute, Dept Neurology & Neurosurgery, McGill University, Canada J. Neurosurg. Feb 2008 Sajedha Mahmood

  2. Background • 75000 cases of primary brain tumours /year in developed countries • Survival rate dependent on extent of resection and histological characteristics • PET and fMRI used to map sensory and motor functions and define areas of language processing with aim to preserve these functions • Higher motor functions (retrieving memory, response based on conditional rules) depends on integrity of frontal cortex • This study looks at fMRI in 4 patients preoperatively with tumours close to rostral part of dorsal premotor cortex (PMdr) • Task developed to assess selection between competing motor responses • Basic motor function not affected by PMdr

  3. Methods • Neuroimaging using fMR while performing a visuomotor conditional task and 2 control tasks (motor and visual) • Tasks developed in healthy controls • Pre-task training 1 d prior to scanning session until performance >95% correct on 2 consecutive sets of 40 trials

  4. Methods • 4 patients with Grade II oligodendrogliomas • Preoperative determination of visuomotor region with fMRI • Postoperative fMRI at 2 months to ensure the functional region had not been resected • Neuropsychological testing to establish postoperative cognitive status • fMRI data transferred to neuronavigation system preoperatively with identification of anatomical landmarks using a 3D pointer

  5. Methods • 1 patient: intraoperative assessment of PMdr function during tumour resection • Assessment 30 min prior to surgery, in operating room post anaesthesia but prior to surgical intervention and during the surgery • 1 patient had 6 functional runs, others 5 runs • Each run had 3 blocks of trials repeated twice in same order • Each run lasted 7 min • First trial onset synchronised with scanner acquisition

  6. Imaging • Each patient scanned using 1.5 T Sonata MRI system • Comparison of pre and postoperative anatomical data • After high-resolution T1-weighted anatomical scan, images sensitive to BOLD signals were acquired • BOLD signals obtained in visuomotor task compared with signals in motor control to identify region with greater response to visuomotor task • Comparison of signals from motor control task with visual control task to identify hand region in primary motor cortex • Images realigned and analysed using specific software • Pre- and postoperative imaging data edited to account for any change in brain shape postoperatively using ANIMAL software • Part of the tumour located closest to the PMdr region resected last

  7. Results • Locations of activity peaks assessed based on stereotactic coordinates and sulcal and gyral patterns • Functional region involved localised in PMdr in anterior part of precentral gyrus continuing on dorsal branch of superior precentral sulcus in all patients • Relationship of functional peak to tumour different in each patient • Primary hand motor region localised in a region clearly different from regions involved in visuomotor tasks • Post-OP IQ rates: 1- 125, 2-113, 3-103, 4-100 • Success rates for subjects 1 - 4 (pre/postoperatively): • Visuomotor: 95.3, 100, 96.9, 99.4 % / 98.8, 98.8, 98.1, 99.4% • Motor: 96,100,100, 99.4% • Visual: 100, 100, 100, 100%

  8. Results • 3 patients had gross-total tumour resection as assessed by post-OP images • 1 patient had sub-total (80%) resection due to intraoperative sensorimotor weakness • No change in tumour volume in 2 years follow-up

  9. Conclusions • Sensorimotor conditional ability essential for everyday tasks e.g. correct response at traffic lights etc • Animal and human studies have shown lesions in PMdr result in deficits in sensorimotor performance • Functional neuroimaging useful in minimising cognitive deficits by accurate localisation of involved regions • Intraoperative behavioural assessment can be helpful during surgical procedure in modifying the approach

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