A Preliminary Feasibility Study Report Of Using Probabilistic Fiber Tractography In Reconstructing Human Auditory Pathway

Background Diffusion tensor MRI is the only currently available way enabling non-invasive identification of subcortical white matter structures. One generally admitted limitation of deterministic tractography, which is the most widely adopted method in neurological pathway research, is its inefficiency in identifying crossing or kissing fibers. Although auditory pathway visualization is thought be one of the most important task in modern neurosurgical research, the fact that the acoustic radiation crosses with major white matter makes it difficult to identify the complex intrinsic organization of the auditory pathway by deterministic tractography. The aim of this preliminary study is to investigate the feasibility of using probabilistic tractography to reconstruct auditory pathway both in healthy and vestibular schwannoma induced deaf people, as well as the potential value in hearing rehabilitation.Method In the first part of the study, four copies of diffusion MRI data for probabilistic fiber tracking were acquired in 8 healthy volunteers with no history of neurological or hearing disorders. Two data processors was asked to process two copies respectively, each copy was only used to track one single auditory pathway in either side of brain. The repeatability of the procedure and the reliability of the results was evaluated by intra-individual, inter-individual or inter-group difference. In the next part, two copies of diffusion MRI data of 14 unilateral vestibular schwannoma patients were retrospectively collected for probabilistic fiber tracking, auditory pathway on both sides were tracked in one single data. Tracking sensitiveness, fiber consistency, fiber volume as well as FA values were recorded. Inter-hemisphere, inter-individual and inter-group differences were calculated to assess the feasibility of using probabilistic tractography in reconstructing auditory pathway of vestibular schwannoma induced deaf person.Result For the first part, the tracking sensitiveness of the two data processors was 68.8% and 62.5%, respectively. Full length and fiber volumes showed a typical variation in both groups,which matched with previous related studies well. The results showed no significant inter-group difference. In the second part, significant inter-group difference was not found neither. The only significant difference was found in the volumes between injured side and uninjured side. The remained recorded parameters showed no significant intra-and inter-individual difference. Such results also provided an support to previous related study.Conclusion Probabilistic tractography have better identifiability in identifying crossing or kissing intracranial fibers than deterministic tractography. The present study introduced a new possible method in auditory pathway reconstruction. The results indicated that probabilistic tractography could be of great value in clinical auditory pathway research, especially for those who suffer from hearing loss caused by NF2 related bilateral vestibular schwannoma. In order to get more convincing conclusions, higher qualified equipment are required and better designed prospective randomized controlled clinical trials should be conducted.