gms | German Medical Science

Functional magnetic resonance imaging becomes important to the neurosurgeon at four key stages in the clinical management of his patients: 1) assessing the feasibility of radical surgical resection, 2) surgical planning, 3) selecting patients for invasive functional mapping procedures and, 4) intraoperative visualization of functional areas. In this prospective study we have examined the occurrence of a new post-operative motor deficit, as a function of a lesion's distance from the functional areas, as provided by functional magnetic resonance imaging.

Sixty-seven patients (34 male, 33 female, aged 22-76 years, mean age 51 years) with different pathologies in close proximity to the motor cortex, were included in the protocol. Pre-operative EPI T2* BOLD imaging was performed during standardized paradigms for hand, foot and tongue movement. Data analysis was done with BrainVoyager software (Brain Innovation, Maastricht, NL). For functional neuronavigation we use the Vector Vision2 system (BrainLAB, Heimstetten, Germany). Outcome was analyzed as a function of a lesions distance to functional motor areas, resection grade, lesion size, patient age and histology. Regarding the distance of a lesion to the motor areas (=LAD), four risk groups were graded. The end point of this study was the clinical outcome 15 days post-operatively.

Gross total resection was achieved in 56 patients. 11 patients (low grade glioma = 4, glioblastoma = 7) had a subtotal resection. The neurological outcome improved in 22 patients (33%), was unchanged in 36 patients (54%) and deteriorated in 9 patients (13%). Significant predictors of a new neurological deficit were a lesion to activation distance < 5mm (p<0,01) and subtotal resection (p<0,05).

The determination of a lesion's proximity to the primary motor cortex, based on pre-operative functional MRI, may be a key in predicting the risk of post-operative deterioration. Our data suggest that a lesion to activation distance < 5mm is associated with a higher risk for neurological deterioration. Taking the potential errors of functional imaging, image fusion, as well as patient registration in the OR into account, we suggest performing cortical stimulation within a 10 mm LAD. For a distance > 10 mm a complete resection can be achieved safely.