A Preliminary Investigation Report on Using Probabilistic Fiber Tractography to Track Human Auditory Pathways

Diffusion tensor imaging is currently the only noninvasive way to map subcortical white matter tractography. Radiologists and neurologists often fail to reconstruct the complex auditory pathways when applying the most commonly used approach, deterministic fiber tracking, as this method is limited in spatial and angular resolution. A different fiber-tracking method involving a probabilistic approach could partly compensate for these limitations. We investigated efficiency and potential usefulness of probabilistic fiber tracking in depicting human auditory pathways in healthy individuals and patients with unilateral vestibular schwannoma (VS).

Eight healthy volunteers and 14 patients with unilateral VS underwent diffusion tensor imaging. Probabilistic fiber tracking of the auditory pathways for each subject was carried out using FSL software. Tracking rate, reliability of results, fiber volume, fiber length, and fractional anisotropy values were considered in assessing reliability and sensitivity of this method. Fiber length and fiber volume were analyzed separately for the healthy group and VS group.

Good tracking sensitivity and consistency were shown in healthy subjects and patients with VS. For fiber length, the 8 healthy subjects exhibited significant between-sides differences, whereas the 14 patients with VS showed no such difference. For fiber volume, there was a statistically significant difference between groups, as the patients with VS displayed a smaller fiber volume on the nontumor side. Fractional anisotropy values revealed no significant autologous or between-group differences. These results match results of previous anatomic and neurologic studies.

The auditory pathway can be depicted well by probabilistic fiber tracking. This method can compensate in part for weaknesses of the widely used deterministic tractography approach in depicting fine and complicated subcortical fibers.