Anatomy and white matter connections of the inferior frontal gyrus

The inferior frontal gyrus (IFG) is involved in the evaluation of linguistic, interoceptive, and emotional information. A detailed understanding of its subcortical white matter anatomy could improve postoperative morbidity related to surgery in and around this gyrus. Through GQI-based fiber tracking validated by gross anatomical dissection as ground truth, we characterized the fiber tracts of the IFG based on relationships to other well-known neuroanatomic structures. Diffusion imaging from the Human Connectome Project for 10 healthy adult controls was used for fiber tracking analysis. We evaluated the IFG as a whole based on its connectivity with other regions. All tracts were mapped in both hemispheres, and a lateralization index was calculated based on resultant tract volumes. Ten cadaveric dissections were then performed using a modified Klingler technique to demonstrate the location of major tracts. We identified four major connections of the IFG: a white matter bundle corresponding the frontal aslant tract connecting to the superior frontal gyrus; the superior longitudinal fasciculus connecting to the inferior parietal lobule, lateral occipital area, posterior temporal areas, and the temporal pole; the inferior fronto-occipital fasciculus connecting to the cuneus and lingual gyrus; and the uncinate fasciculus connecting to the temporal pole. A callosal fiber bundle connecting the inferior frontal gyri bilaterally was also identified. The IFG is an important region implicated in a variety of tasks including language processing, speech production, motor control, interoceptive awareness, and semantic processing. Postsurgical outcomes related to this region may be better understood in the context of the fiber-bundle anatomy highlighted in this study. Clin. Anat. 32:546-556, 2019. © 2019 Wiley Periodicals, Inc.