Purpose: To prospectively determine the sensitivity and specificity of functional magnetic resonance (MR) imaging for mapping language and motor functions in patients with a focal mass adjacent to eloquent cortex, by using intraoperative electrocortical mapping (ECM) as the reference standard.
Materials and methods: The ethics committee approved the study, and patients gave written informed consent. Thirty-four consecutive patients (16 women, 18 men; mean age, 43.2 years) were included who met the following three criteria: They had a focal mass in or adjacent to eloquent cortex of the language or motor system, they had the ability to perform the functional MR imaging task, and they had to undergo surgery with intraoperative ECM. Functional MR imaging with verb generation (n = 17) or finger tapping of the contralateral hand (n = 17) was performed at 1.5 T with a block design and an echo-planar gradient-echo T2*-weighted sequence. Cortex essential for language or hand motor functions was mapped with ECM. A site-by-site comparison between functional MR imaging and ECM was performed with the aid of a neuronavigational device. Sensitivity and specificity were calculated according to task performed, histopathologic findings, and tumor grade. Exact 95% confidence intervals were calculated for each sensitivity and specificity value.
Results: For 34 consecutive patients, there were 28 with gliomas, two with metastases, one with meningioma, and three with cavernous angiomas. A total of 251 cortical sites were tested with ECM; overall functional MR imaging sensitivity and specificity were 83% and 82%, respectively. Sensitivity (65%) was lower and specificity (93%) was higher in World Health Organization grade IV gliomas compared with grade II (sensitivity, 93%; specificity, 79%) and III (sensitivity, 93%; specificity, 76%) gliomas. At 3 months after surgery, language proficiency was unchanged in 15 patients; functionality of the contralateral arm was unchanged in 14 patients and improved in one patient.
Conclusion: Functional MR imaging is a sensitive and specific method for mapping language and motor functions.