Recent advances in functional neuroimaging techniques have revolutionised the approach to neurosurgical planning. Functional magnetic resonance imaging (fMRI) techniques include blood-oxygenlevel- dependent (BOLD) and diffusion tensor imaging (DTI) methodologies for non-invasively imaging brain activation and white matter fibres, respectively. In the last decade these techniques have evolved from purely research imaging tools used in cognitive neuroscience studies to clinically viable tools recognised by the medical community and regulatory bodies. These techniques hold considerable potential in the field of neurosurgical treatment planning.^1,2

The goal of pre-operative treatment planning for tumour resection or seizure disorders is to differentiate eloquent cortex from structural brain lesions in close proximity, and to establish language lateralisation pre-operatively, in order to minimise surgical risk and post-operative neurological deficits. In addition to providing influential information regarding pre-operative risk assessment, the information provided by BOLD and DTI techniques is also critical to the neurosurgeon for developing intraoperative strategies and/or therapeutic approaches that otherwise might not be considered.

Procedures historically used as surgical mapping tools include the Wada test and direct electrical stimulation.^3–6 However, these techniques are invasive and can impose some risk to the patients.

In the last few years, several prospective studies have been conducted with the goal of quantifying relative costs and benefits of using fMRI as an alternative pre-operative planning procedure, and evaluating concordance with currently used assessment tools. Studies directly comparing fMRI with Wada testing have demonstrated that fMRI imaging results significantly influence diagnostic and therapeutic decision-making, increase the confidence with which critical brain regions are identified and alter the surgical approach.^7,8

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