Diffusion tensor imaging of brainstem tumors: axonal degeneration of motor and sensory tracts

Abstract

<jats:sec> <jats:title>Object</jats:title> <jats:p>Diffusion tensor (DT) imaging has been used to predict postoperative motor function in patients with supratentorial tumors. The authors sought to determine whether DT imaging and white matter tractography could detect axonal degeneration in patients with brainstem tumors.</jats:p></jats:sec> <jats:sec> <jats:title>Methods</jats:title> <jats:p>A cross-sectional, retrospective study of 7 patients with brainstem tumors and 8 healthy volunteers was performed. The DT imaging data were normalized and regions of interest (ROIs) with the highest probability of sensory and motor connections were selected using the Talairach Atlas to identify the 3D millimetric coordinates of white matter tracts. An iterative process involving fractional anisotropy (FA), apparent diffusion coefficients (ADCs), and color maps was developed to precisely select ROIs in the bilateral sensory and motor tracts. The FA and ADC values were calculated for each ROI.</jats:p></jats:sec> <jats:sec> <jats:title>Results</jats:title> <jats:p>The FA values of sensory and motor tracts significantly differed between the patient and healthy volunteer groups (p &lt; 0.05), whereas no significant changes were found in the splenium or genu of the corpus callosum. The FA values were altered proximal and distal to the brainstem tumors with a bimodal peak of antegrade decreased FA involving second- and third-order sensory axons and retrograde decreased FA of motor axons.</jats:p></jats:sec> <jats:sec> <jats:title>Conclusions</jats:title> <jats:p>This study demonstrates changes in diffusion properties of sensory and motor tracts consistent with degeneration to further characterize brainstem tumors in children, and the results warrant the planning of prospective trials. The rigorous methods the authors describe may provide valuable information when planning biopsies or debulking of unusual brainstem tumors, as well as improve prognostication of the possible functional tract recovery following therapy.</jats:p></jats:sec>

Brain Tumor Therapy-Induced Changes in Normal-Appearing Brainstem Measured With Longitudinal Diffusion Tensor Imaging

“…Without applying sophisticated algorithms for correction of susceptibility artifacts, our experience indicated that the quality of DTI datasets in children is sufficient for visualizing and delineating major motor and sensory neural tracts in the brainstem (23-24). However, continued improvements in DTI acquisition, distortion correction, and fiber tractography are needed to further resolve brainstem nuclei, fiber tracts of small caliber, and decussating fibers in the medulla and cerebellar peduncles.…”

Potential New Therapies for Pediatric Diffuse Intrinsic Pontine Glioma

“…Diffuse intrinsic pontine glioma (DIPG) is an extensively invasive malignancy of the brainstem with little notable mass effect (Helton et al, 2008; Caretti et al, 2014). These tumors account for >80% of pediatric brainstem gliomas (Guillamo et al, 2001; Salmaggi et al, 2008; Rineer et al, 2010).…”

Reduced-Distortion Diffusion MRI of the Craniovertebral Junction

“…17,18 Furthermore, fractional anisotropy has been shown to be a good clinical biomarker in detecting the lesions in the brain stem or the posterior fossa, as well as effects of radiation therapy. [19][20][21] Acute stroke lesions in the brain stem are also often missed by DWI because of susceptibility artifacts. 22,23 Here we show that RS-EPI results-qualitatively and quantitatively-in significantly less distortion than SS-EPI in the diffusion trace images, especially at the base of the temporal lobe and the cerebellum.…”