White matter tract alterations assessed with diffusion tensor imaging and tractography in patients with solid posterior fossa tumors

Background: This study assesses the tract alterations observed before and after resection of solid posterior fossa tumors (PFTs) using diffusion tensor imaging (DTI) and white matter tractography (WMT).
Materials and Methods: Pre- and post-surgical DTI and WMT data were acquired in eight patients undergoing surgical resections of PFT. A tensor deflection algorithm was used to reconstruct the tracts adjacent to the lesions. The tracts were evaluated regarding their spatial orientation and integrity. A software additionally assessed the luminosity and pixel values from specific regions of interest (ROIs) quantifying the magnitude of tract alterations. The individual neurological condition was additionally evaluated.
Results: In eight tumors (metastases (4), neurinomas (2) and meningiomas (2), the preoperative WMT revealed different tract alterations, including deviation (all cases), deformation (7 cases), thinning (8 cases) and apparent tract interruption (4 cases). The ROI histograms from noncompromised tracts showed a tendency for value concentration and peak formation, while affected tracts showed different dispersion patterns. After tumor resection, the compromised white matter tracts showed a resolution (3 cases) or reduction (5 cases) of the deviation. Postoperatively, 7 cases of tract thinning and 3 cases with tract interruptions showed an improvement. The comparison between ROI histograms from preoperative and postoperative compromised tracts mostly revealed a postoperative accentuated reduction of the luminosity with a simultaneous increase of pixels and improved histogram definition (homogeneous values distribution). At this time (5 weeks post-surgery), several neurological functions had improved to different levels.
Conclusions: Preoperative and postoperative tract alterations in patients with solid PFT can be accurately assessed with WMT. The magnitude of tract changes can be quantitatively analyzed by assessing color, signal brightness in compromised bundles.