Purpose The purpose of this study was to compare the deterministic and probabilistic tracking methods of diffusion tensor white matter fiber tractography in patients with brain tumors. Materials and Methods We identified 29 patients with left brain tumors <2 cm from the arcuate fasciculus who underwent pre-operative language fMRI and DTI. The arcuate fasciculus was reconstructed using a deterministic Fiber Assignment by Continuous Tracking (FACT) algorithm and a probabilistic method based on an extended Monte Carlo Random Walk algorithm. Tracking was controlled using two ROIs corresponding to Broca’s and Wernicke’s areas. Tracts in tumoraffected hemispheres were examined for extension between Broca’s and Wernicke’s areas, anterior-posterior length and volume, and compared with the normal contralateral tracts. Results Probabilistic tracts displayed more complete anterior extension to Broca’s area than did FACT tracts on the tumor-affected and normal sides (p < 0.0001). The median length ratio for tumor: normal sides was greater for probabilistic tracts than FACT tracts (p < 0.0001). The median tract volume ratio for tumor: normal sides was also greater for probabilistic tracts than FACT tracts (p = 0.01). Conclusion Probabilistic tractography reconstructs the arcuate fasciculus more completely and performs better through areas of tumor and/or edema. The FACT algorithm tends to underestimate the anterior-most fibers of the arcuate fasciculus, which are crossed by primary motor fibers.

Background and Purpose To evaluate whether breath-holding (BH) BOLD fMRI can quantify differences in vascular reactivity (VR), as there is a need for improved contrast mechanisms in gliomas. Methods 16 patients (gliomas, grade II=5, III=2, IV=9) were evaluated using the BH paradigm: 4second single deep breath followed by 16seconds of BH and 40seconds of regular breathing for 5 cycles. VR was defined as the difference in BOLD signal between the minimal signal seen at the end of the deep breath and maximal signal seen at the end of BH (peak-to-trough). VR was measured for every voxel and compared for gray vs. white matter and tumor vs. normal contralateral brain. VR maps were compared to the areas of enhancement and FLAIR/T2 abnormality. Results VR was significantly lower in normal white matter than gray matter (p<0.05) and in tumors compared to the normal, contralateral brain (p<0.002). The area of abnormal VR (1103±659mm2) was significantly greater (p=0.019) than the enhancement (543±530mm2), but significantly smaller (p=0.0011) than the FLAIR abnormality (2363±1232mm2). However, the variability in the areas of gadolinium contrast enhancement versus VR abnormality indicates that the contrast mechanism elicited by BH (caused by abnormal arteriolar smooth muscles) appears to be fundamentally different from the contrast mechanism of gadolinium enhancement (caused by the presence of “leaky” gap junctions). Conclusions BH maps based on peak-to-trough can be used to characterize VR in brain tumors. VR maps in brain tumor patients appear to be caused by a different mechanism than gadolinium enhancement.

BACKGROUND AND PURPOSE Examining how left-hemisphere brain tumors might impact both the microstructure of the corpus callosum (CC) as measured by fractional anisotropy (FA) values in diffusion tensor imaging (DTI) as well as cortical language lateralization measured with functional MRI (fMRI). METHODS fMRI tasks (phonemic fluency and verb generation) were performed in order to detect activation in Broca’s and Wernicke’s area. Twenty patients with left-hemisphere brain tumors were investigated. fMRI results were divided into left dominant (LD), right dominant (RD), or codominant (CD) for language function. DTI was performed to generate FA maps in the anterior and posterior CC. FA values were correlated with the degree of language dominance. RESULTS Patients who were LD or RD for language in Broca’s area had lower FA in the anterior CC than those who were CD for language (median for CD = .72, LD = .66, RD = .65, P < .09). Lateralized versus CD group level analysis also showed that CD patients had higher FA in the anterior CC than patients who displayed strong lateralization in either hemisphere (median for CD = .72, lateralized = .65, P < .05). CONCLUSION Our preliminary observations indicate that the greater FA in CD patients may reflect a more directional microstructure for the CC in this region, suggesting a greater need for interhemispheric transfer of information. Because brain tumors can cause compensatory codominance, our findings may suggest a mechanism by which interhemispheric transfer is facilitated during plasticity in the presence of a tumor.

We describe frontal language reorganization in a 50–60 year-old right-handed patient with a low-grade left frontotemporal insular glioma. Pre-operative fMRI revealed robust activation in the left superior temporal gyrus (Wernicke Area, WA) and in the right inferior frontal gyrus (right anatomical homolog of Broca Area, BA). Intra-operative cortical stimulation of the left inferior frontal gyrus and adjacent cortices elicited no speech deficits, and gross total resection including the expected location of BA resulted in no speech impairment. We employed statistical inference methods to reconstruct the functional brain network and determined how different brain areas connect with one another. We found that the right homolog of the BA in this patient functionally connected to the same areas as the left BA in a typical healthy control. As opposed to the functional connection of the left BA in a healthy brain, the right BA did not connect directly with the left WA, but connected indirectly, mediated by the pre-Supplementary Motor Area and the Middle Frontal Gyrus. This case illustrates that pre-surgical fMRI may be used to identify atypical hemispheric language reorganization in the presence of brain tumor and that network theory opens the possibility for future insight into the neural mechanism underlying the language reorganization.

Language functional magnetic resonance imaging for neurosurgical planning is a useful but nuanced technique. Consideration of primary and secondary language anatomy, task selection, and data analysis choices all impact interpretation. In the following chapter, we consider practical considerations and nuances alike for language functional magnetic resonance imaging in the support of and comparison with the neurosurgical gold standard, direct cortical stimulation. Pitfalls and limitations are discussed.

Cortical reorganization of function due to the growth of an adjacent brain tumor has clearly been demonstrated in a number of surgically proven cases. Such cases demonstrate the unmistakable implications for the neurosurgical treatment of brain tumors, as the cortical function may not reside where one may initially suspect based solely on the anatomical magnetic resonance imaging (MRI). Consequently, preoperative localization of eloquent areas adjacent to a brain tumor is necessary, as this may demonstrate unexpected organization, which may affect the neurosurgical approach to the lesion. However, in interpreting functional MRI studies, the interpreting physician must be cognizant of artifacts, which may limit the accuracy of functional MRI in the setting of brain tumors.

Recent research showed that the supplementary motor area (SMA) can be divided into a rostral pre-SMA, involved in higher-level processing and a caudal SMA proper, involved with motor execution. As surgical insults to the medial frontal lobes may cause variable neurological deficits and an incomplete understanding of structure-function relationships of the SMA exists, we sought to determine whether a common locus of functionality can be established using functional MRI. Results reveal a commonly activated region between these two areas, using simultaneous motor and language tasks. A higher percentage signal change was measured in comparison with those found using individual tasks. Results contribute to the structural and functional knowledge of the SMA and may enable distinction between permanent and transient SMA syndromes.

An abundance of evidence points to a pre-supplementary motor area (pre-SMA) role in human language. This study explores the pre-SMA resting state connectivity network and the nature of its connections to known language areas. We tested the hypothesis that by seeding the pre-SMA, one would be able to establish language laterality to known cortical and sub-cortical language areas. We analyzed data from 30 right-handed healthy controls and performed the resting state functional MRI (rfMRI). A seed based analysis using a manually drawn pre-SMA region of interest (ROI) template was applied. Time course signals in the pre-SMA ROI were averaged and cross-correlated to every voxel in the brain. Results show that the pre-SMA has significant left-lateralized functional connectivity to the pars opercularis within Broca's area. Among cortical regions, pre-SMA functional connectivity is strongest to the pars opercularis Additionally, pre-SMA connectivity was shown to exist to other cortical language-association regions, including Wernicke's Area, supramarginal gyri, angular gyri(, and middle frontal gyri. Among sub-cortical areas, considerable left-lateralized functional connectivity occurs to the caudate and thalamus while cerebellar sub-regions show right-lateralization. The current study reveals that the pre-SMA most strongly connects to the pars opercularis within Broca's area and that cortical connections to language areas are left-lateralizedamong a sample of right-handed patients. We provide rfMRI evidence that the functional connectivity of the pre-SMA is involved in semantic language processing and that this identification may be useful for establishing language laterality in pre-operative neurosurgical planning.