Cortical reorganization demonstrated by diffusion tensor tractography analyzed using functional MRI activation

White Matter Change Revealed by Diffusion Tensor Imaging in Gliomas

Background

Tumor-related white matter change is detected at late stages with magnetic resonance imaging (MRI), when mass effect or prominent edema is present. We analyzed if diffusion tensor imaging (DTI) white matter change earlier than conventional MRI.

Methods

Twenty-six patients with gliomas (World Health Organization grade II, 5; grade III, 12; and grade IV, 9) within 2 cm from the posterior limb of the internal capsule (IC) were studied. Fifteen normal adults were enrolled as controls. Fluid attenuation inversion recovery MRI showed a high signal change at the posterior limb of the IC (HSIC) in 9 patients with grade III or IV gliomas. We classified the gliomas as WHO grade II (gliomas II), grade III or IV without HSIC [gliomas III/IV(-)] and grade III or IV with HSIC [gliomas III/IV(+)], as an indicator of the increase in the severity of the white matter changes. Fractional anisotropy (FA) and apparent diffusion coefficients (ADC) were calculated for the pyramidal tract. Tumor progression along pyramidal tract was evaluated by follow-up MRI in 16 patients at 40±18 months.

Results

FA showed no significant difference between gliomas II and control (p=0.694), but was lower in gliomas III/IV(-) and gliomas III/IV(+) (p<0.001). ADCs were higher in gliomas II, gliomas III/IV(-) and gliomas III/IV(+) than control (p<0.001). Tumor progression was detected in 2/16 patients.

Conclusion

DTI detected white matter changes that appeared to be normal in MRI. ADC changed even in low grade glioma, indicating ADC may be a better parameter for the early detection of white matter change.

From research to clinical practice: implementation of functional magnetic imaging and white matter tractography in the clinical environment

In the last two decades functional magnetic resonance imaging (fMRI) has dominated research in neuroscience. However, only recently has it taken the first steps in translation to the clinical field. In this paper we describe the advantages of fMRI and DTI and the possible benefits of implementing these methods in clinical practice. We review the current clinical usages of fMRI and DTI and discuss the challenges and difficulties of translating these methods to clinical use. The most common application today is in neurosurgery. fMRI and DTI are done preoperatively for brain tumor patients who are having tumors removed and for epilepsy patients who are candidates for temporal resection. Imaging results supply the neurosurgeon with essential information regarding possible functional damage and thereby aid both in planning and performing surgery. Scientific research suggests more promising potential implementations of fMRI and DTI in improving diagnosis and rehabilitation. These advanced imaging methods can be used for pre-symptomatic diagnosis, as a differentiating biomarker in the absence of anatomical measurements, and for identification of mental response in the absence of motor-sensory abilities. These methods can aid and direct rehabilitation by predicting the success of possible interventions and rehabilitation options and by supplying a measure for biofeedback. This review opens a window to the state of the art neuroimaging methods being implemented these days into the clinical practice and provides a glance to the future clinical possibilities of fMRI and DTI.

Identification of spinothalamic tract and its related thalamocortical fibers in human brain

Little is known about the spinothalamic tract (STT) and its related thalamocortical fibers. In the current study, we attempted to identify the STT and related thalamocortical fibers in the human brain, using diffusion tensor tractography (DTT). We recruited 23 healthy volunteers for this study. Diffusion tensor images (DTIs) were scanned using 1.5-T, and the STT and medial lemniscus (ML) were obtained using FMRIB software. Normalized DTI tractography was reconstructed using the Montreal Neurological Institute (MNI) echo-planar imaging (EPI) template supplied with the SPM. The STT began at the posterolateral medulla and ascended to the ventral posterior-lateral (VPL) nucleus of the thalamus, through the pontine tegmentum posterolateral to the ML, and through the mesencephalic tegmentum posterior to the ML. STT-related thalamocortical fibers originated from the VPL nucleus of the thalamus and ascended through the posterior limb of the internal capsule and the posterior portion of the corona radiata, terminating at the primary somatosensory cortex. We identified the STT and its related thalamocortical fibers using DTT. These results would be helpful in the clinical field and also in research on somatosensory function in the human brain.