Diffusion tensor imaging the medial longitudinal fasciculus in INO: opportunities and challenges.

The medial longitudinal fasciculus (MLF) is a white matter pathway in the brainstem that plays a key role in coordinating eye movements. Injury to the MLF leads to abnormalities in eye movements that can be measured with high precision by oculography, making it an ideal eloquent pathway to study imaging/function correlates. Tractography is an emerging method for identifying white matter pathways and offers the tantalizing promise of noninvasive, quantitative characterization of tissue integrity underlying functional deficits. However, the small caliber of the MLF and partial volume averaging with signal from nearby cerebrospinal fluid pose severe technical challenges to tractography-based delineation of the MLF. We discuss progress toward the goal of imaging the MLF and potential benefits of achieving this goal. Initial work suggests that ultra-high field (7 tesla) may complement tractography for characterizing the MLF.