Functional MRI in the presurgical evaluation of patients with brain tumors: characterization of the statistical threshold.

We investigated whether an optimal statistical threshold could be obtained in healthy controls and patients with brain tumors undergoing presurgical functional MRI assessment. The volumes of activation of the primary motor cortex (PMC) and the lateral prefrontal cortex (PFC) were measured for the tumor and nontumor sides in 24 patients and 8 controls using four parameters; p values ranged between 10(-2) and 10(-31). The mean r value for first activation in the PMC was higher in controls than for both the tumor and nontumor sides in patients. The mean r value for 'first activation in the noise area' and 'PMC and PFC ratio' in controls was significantly different from the mean r value for the tumor and nontumor sides in patients (p < 0.05). The magnitude of the range of r values for the nontumor side was closer to the tumor side data than to the control data. It is imperative to evaluate functional MRI data with a wide range of statistical parameters, especially in the assessment of tumor patients. 2009 S. Karger AG, Basel.