UNCTIONAL magnetic resonance (MR) imaging based on blood oxygen level–dependent contrast 15 has proved to be sensitive in the detection of func- tional activity in the primary sensorimotor cortex. 1,6,7,12, 13,17 This imaging method has been proposed as a nonin- vasive tool to identify essential cortex prior to surgery, thus improving surgical planning and minimizing postop- erative neurological deficits. 11,14,19 The potential clinical usefulness of this new MR imaging application has been emphasized in two pioneer studies in which a good corre- lation between motor mapping with functional MR imag- ing and invasive cortical stimulation was observed. 11,22 Although preliminary results have been encouraging, validating studies are necessary before this functional method can be widely accepted. It has not yet been estab- lished which activation task and image analysis methods are suitable for producing strong but selective activation of the primary motor cortex. Rao, et al., 16 elegantly dem- onstrated that a hand movement that activates the motor cortex may produce no activation if it is externally paced with a metronome and that imagined motor tasks (without real hand movements) activate cortical areas outside the primary motor cortex. 16,20 Thus, hand movements that display a similar external appearance may activate prima- ry motor cortex, produce no activation, or activate other nearby regions. Conversely, the activation capability of le- sions that alter normal motor functioning and distort nor- mal sulcal anatomy is not known. In this article, we discuss the ability of functional MR imaging to detect a selective activation of the primary sen- sorimotor cortex using clinically applicable methods in healthy subjects, and the feasibility of using this method to test motor activation in patients with lesions around the central sulcus. Under investigation in our study were both the activation effect of different motor tasks and the imag- ing procedures that provided identification of the rolandic cortex. Clinical Material and Methods This study was approved by the research committees of Santa Creu i Sant Pau and Bellvitge Hospitals. Healthy Subjects Twenty-five right-handed volunteers (five men and 20 women), ranging in age from 23 to 35 years, participated J. Neurosurg. / Volume 84 / January, 1996 J Neurosurg 84:7–13, 1996 Presurgical identification of the primary sensorimotor cortex by functional magnetic resonance imaging JESÚS PUJOL, M.D., GERARDO CONESA, M.D., JOAN DEUS, PH.D., PERE VENDRELL, PH.D., F ABIÁN ISAMAT , M.D., GUILLERMO ZANNOLI, PH.D., JOSEP L. MARTÍ-VILALTA, M.D., AND ANTONI CAPDEVILA, M.D. Magnetic Resonance Center of Pedralbes, Barcelona, Spain; Department of Neurosurgery, Hospital of Bellvitge and Department of Psychiatry and Clinical Psychobiology, University of Barcelona, Barcelona, Spain; Department of Neurology, Hospital of Santa Creu i Sant Pau, Autonomous University of Barcelona, Barcelona, Spain; and General Electric Medical Systems, Buc, France  The ability of functional magnetic resonance (MR) imaging to detect a selective sensorimotor cortex activation in healthy subjects and the feasibility of motor activation in patients with lesions around the central sulcus were investi- gated. Twenty-five healthy volunteers performed 100 motor activation trials, using a variety of motor tasks, which were monitored by several image analysis methods. The functional images were obtained using a 1.5-tesla standard MR imaging system magnet with blood oxygenation level–dependent contrast. Four patients were assessed using func- tional MR imaging and invasive cortical mapping. Rolandic cortex activation was observed in 98% of the trials per- formed on healthy subjects in which no head motion occurred. Nevertheless, the cortical response was not selective in a task-rest analysis due to concurrent activation of neighboring regions. Across-task comparison analyses were useful in canceling nonrelevant activity in most cases (86%). In the patient group, the region identified as the sensorimotor cortex by invasive means corresponded accurately to the area that was activated in functional MR imaging. Present data support the feasibility of detecting selective activation of the rolandic cortex, even in the clinical setting, leading the authors to suggest the usefulness of this widely available technique in surgical planning. KEY WORDS • sensorimotor cortex • functional magnetic resonance imaging • cortical mapping F 7