gms | German Medical Science

Objective: Tractography, which is available as a commercial method within functional neuronavigation, can be applied to surgery of tumors located in eloquent brain areas. Does the information about the intraoperative use and the postoperative follow-up help the neurosurgeon to improve and predict the neurological outcome?

Methods: 20 patients with tumors located within or adjacent to eloquent brain areas were studied and operated on, assisted by intraoperative functional neuronavigation, including tractography. White matter tracts were detected using iPlan 2.5 Cranial Brain Lab software on anisotropic maps acquired with a 3T Siemens Magnetom Allegra MR. We visualized the pyramidal tracts in 17 patients, optical tracts in 2, fornices in 2 – before operation and followed up 9 patients postoperatively.

Results: We compared the preoperatively and postoperatively visualized tracts and classified them as: displaced, diluted or disrupted, opposite to normal tracts in the non-affected hemisphere. Displacement of pyramidal tracts, usually augmented at the time of initial DTI control (within 2 weeks), but without neurological expression, was the common finding in gliomas. Also, the displacement of the fornices in a patient with a giant craniopharyngioma, who had preoperative short-term memory deficit and showed significant improvement after surgery, followed the same tendency: normalization of fornices’ position on 2 controls. Preoperative dilution of fibers was noticed in 2 patients with metastases and surrounding oedema, who had an incomplete motor deficit, which improved after operation. Progress was documented by the reappearance of the tracts. Disruption of fibers, caused by mechanical tumor compression, in association with fixed neurological impairment, was assessed pre- and postoperatively in a parasagittal occipital meningioma.

Conclusions: Intraoperative damage of the pyramidal tract, optical tract or fornix, not documented within these series, would disrupt the fibers, leading to irreversible neurological deficits. Displacement of the fornices, but not necessarily of the pyramidal tract can result in neurological deficits. Disruption may represent irreversible damage. Dilution can be reversible in case of oedema, but not in case of tumor infiltration. Further research is necessary in order to improve the accuracy of tract visualization, to document tumor infiltration and to better predict neurological outcome.