Reliability of functional MR imaging with word-generation tasks for mapping Broca's area

BACKGROUND AND PURPOSE: Functional MR (fMR) imaging of word generation has been used to map Broca's area in some patients selected for craniotomy. The purpose of this study was to measure the reliability, precision, and accur acy of word-generation tasks to identify Broca's area. METHODS: The Brodmann areas activated during performance of word-generation tasks were tabulated in 34 consecutive patients referred for fMR imaging m apping of language areas. In patients performing two iterations of the lett er word-generation tasks, test-retest reliability was quantified by using t he concurrence ratio (CR), or the number of voxels activated by each iterat ion in proportion to the average number of voxels activated from both itera tions of the task. Among patients who also underwent category or antonym wo rd generation or both, the similarity of the activation from each task was assessed with the CR. In patients who underwent electrocortical stimulation (ECS) mapping of speech function during craniotomy while awake, the sites with speech function were compared with the locations of activation found d uring fMR imaging of word generation. RESULTS: In 31 of 34 patients, activation was identified in the inferior fr ontal gyri or middle frontal gyri or both in Brodmann areas 9, 44, 45, or 4 6, unilaterally or bilaterally, with one or more of the tasks. Activation w as noted in the same gyri when the patient performed a second iteration of the letter word-generation task or second task. The CR for pixel precision in a single section averaged 49%. In patients who underwent craniotomy whil e awake, speech areas located with ECS coincided with areas of the brain ac tivated during a word-generation task. CONCLUSION: fMR imaging with word-generation tasks produces technically sat isfactory maps of Broca's area, which localize the area accurately and reli ably.