Accuracy and limitation of functional magnetic resonance imaging for identification of the central sulcus: Comparison with magnetoencephalography in patients with brain tumors

The aim of the present study was to clarify the accuracy and limitation of functional magnetic resonance imaging (fMRI) for the identification of the central sulcus affected by brain tumors. Twelve normal volunteers and 11 pa tients with intracranial tumors adjacent to the central sulcus underwent fM RI and magnetoencephalography (MEG). Three patients were evaluated again af ter surgery. fMRI was performed with a 1.5 Tesla scanner during repetitive opening and closing of each hand. Cross-correlation function was used to id entify activation areas, and the central sulcus was defined as the nearest sulcus to the highest activation spats that were determined by elevating co rrelation coefficient threshold. Somatosensory-evoked fields were measured using a whole head MEG system. The central sulcus was defined as the neares t sulcus to the N20m for the median nerve stimulus. fMRI and MEG coincided in defining the central sulcus in all 24 hemispheres of volunteers and all 10 examined nonaffected hemispheres of patients. The fMRI-defined central s ulcus coincided with the MET-defined central sulcus in nine (82%) but did n ot in two (18%) affected hemispheres of patients. The preoperative mismatch disappeared after surgery in one of the two patients. The present study in dicates that fMRI successfully defined the central sulcus in most of the pa tients with brain tumors. However, in a few cases, fMRI was not reliable pr obably due to venous dow changes by tumor compression and/or compensational activity by brain tissues surrounding the primary sensorimotor cortex. For precise functional assessment of the brain affected by intracranial tumors , combination of fMRI and MEG will be recommended. (C) 1999 Academic Press.