Nicole Petrovich Brennan BA, Presenter: Nothing to Disclose

Kyung K. Peck PhD, Abstract Co-Author: Nothing to Disclose

Andrei I. Holodny MD, Abstract Co-Author: Nothing to Disclose

Productive speech localizes mainly in the inferior frontal gyrus (IFG) (Broca’s area) of the dominant hemisphere. fMRI activation in the middle frontal gyrus (MFG) is also common during fMRI productive speech tasks and supports verbal working memory. We hypothesized that the MFG may lateralize reliably, perhaps providing a surrogate anatomical area for laterality measurements in patients where Broca's Area (IFG) is obscured by tumor and/or artefact from prior surgery.

Ten 100% right-handed, native English speaking patients with gliomas were included. Two patients had lesions in the left inferior frontal region. Eight had lesions either in the left temporal or parietal lobe or the right hemisphere. Block design fMRI was performed on both 3T and 1.5T. Hemispheric and region-of-interest (ROI) laterality indices were calculated for each patient during each of three possible fMRI tasks using the formula (L-R/L+R). Data was analyzed using correlation analysis in AFNI. ROIs included IFG and MFG. Ten patients performed phonemic fluency, three performed verb generation and four performed semantic fluency. A total of seventeen measurements were included.

All 10 patients lateralized speech to the left hemisphere as expected using a hemispheric ROI. Fourteen of 17 LI measurements in the putative Broca's Area lateralized to the left hemisphere (3 indicated co-dominant speech). Sixteen of seventeen measurements in the MFG lateralized speech to the left hemisphere (one co-dominant). Interestingly, in 15 measurements the laterality index for the MFG was higher (more strongly lateralized to the left-hemisphere) than inferior frontal gyrus. This difference was statistically significant (p= 0.002).

MFG lateralizes reliably on fMRI and may be able to be used a surrogate marker for language lateralization in patients with brain tumors. The extent to which the greater MFG LI in comparison to the Broca's Area LI represents normal speech function or a compensatory effect in a lesion compromised brain should be further investigated.

MFG activates reliably in fMRI speech tasks and may be used to determine hemispheric dominance. The consistent appearance of this anatomical area may add to neurosurgical decision-making.

Petrovich Brennan, N, Peck, K, Holodny, A, Reliable Lateralization of the Middle Frontal Gyrus during fMRI Speech Tasks in Brain Tumor Patients.  Radiological Society of North America 2008 Scientific Assembly and Annual Meeting, February 18 - February 20, 2008 ,Chicago IL. http://archive.rsna.org/2008/6021949.html