J. Neurosurg. Feb 2008 Sajedha Mahmood

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

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

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

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

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

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

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%

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

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