Effect of focal and nonfocal cerebral lesions on functional connectivity studied with MR imaging

BACKGROUND AND PURPOSE: Functional connectivity MR (fcMR) imaging is used t o map regions of brain with synchronous, regional, slow fluctuations in cer ebral blood flow. We tested the hypothesis that focal cerebral lesions do n ot eradicate expected functional connectivity. METHODS: Functional MR (fMR) and fcMR maps were acquired for 12 patients wi th focal cerebral tumors, cysts, arteriovenous malformations, or in one cas e, agenesis of the corpus callosum. Task activation secondary to test liste ning, finger tapping, and word generation was mapped by use of fMR imaging. Functional connectivity was measured by selecting "seed" voxels in brain r egions showing activation (based on the fMR data) and cross correlating wit h every other voxel (based on data acquired while the subject performed no task). Concurrence of the fMR and fcMR maps was measured by comparing the l ocation and number of voxels selected by both methods. RESULTS: Technically adequate fh IR and fcMR maps were obtained for all pat ients. In patients with focal lesions, the fMR and fcMR maps correlated clo sely. The fcMR map generated for the patient with agenesis of the corpus ca llosum failed to reveal functional connectivity between blood flow in the l eft and right sensorimotor cortices and in the frontal lobe language region s. Nonetheless, synchrony between blood flow in the auditory cortices was p reserved. On average, there was 40% concurrence between all fMR and fcMR ma ps. CONCLUSION: Patterns of functional connectivity remain intact in patients w ith focal cerebral lesions. Disruption of major neuronal networks, such as agenesis of the corpus callosum, may diminish the normal functional connect ivity patterns. Therefore, functional connectivity in such patients cannot be fully demonstrated with fcMR imaging.