Nicole Brennan

Joint activation of the supplementary motor area and presupplementary motor area during simultaneous motor and language functional MRI.

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.

Motor and Sensory Mapping

Functional magnetic resonance imaging (fMRI) enhances the understanding of neuroanatomy and functions of the brain and is becoming an accepted brain-mapping tool for clinicians, researchers, and basic scientists alike. A noninvasive procedure with no known risks, fMRI has an ever-growing list of clinical applications, including presurgical mapping of motor, language, and memory functions. fMRI benefits patients and allows neurosurgeons to be aware of, and to navigate, the precise location of patient-specific eloquent cortices and structural anomalies from a tumor. Optimizing preoperative fMRI requires tailoring the fMRI paradigm to the patients clinical situation and understanding the pitfalls of fMRI interpretation.

Identification of the Corticobulbar Tracts of the Tongue and Face Using Deterministic and Probabilistic DTI Fiber Tracking in Patients with Brain Tumor

BACKGROUND AND PURPOSE: The corticobulbar tract of the face and tongue, a critical white matter tract connecting the primary motor cortex and the pons, is rarely detected by deterministic DTI fiber tractography. Detection becomes even more difficult in the presence of a tumor. The purpose of this study was to compare identification of the corticobulbar tract by using deterministic and probabilistic tractography in patients with brain tumor. MATERIALS AND METHODS: Fifty patients with brain tumor who underwent DTI were studied. Deterministic tractography was performed by using the fiber assignment by continuous tractography algorithm. Probabilistic tractography was performed by using a Monte Carlo simulation method. ROIs were drawn of the face and tongue motor homunculi and the pons in both hemispheres. RESULTS: In all subjects, fiber assignment by continuous tractography was ineffectual in visualizing the entire course of the corticobulbar tract between the face and tongue motor cortices and the pons on either side. However, probabilistic tractography successfully visualized the corticobulbar tract from the face and tongue motor cortices in all patients on both sides. No significant difference (P < .08) was found between both sides in terms of the number of voxels or degree of connectivity. The fractional anisotropy of both the face and tongue was significantly lower on the tumor side (P < .03). When stratified by tumor type, primary-versus-metastatic tumors, no differences were observed between tracts in terms of the fractional anisotropy and connectivity values (P > .5). CONCLUSIONS: Probabilistic tractography successfully reconstructs the face- and tongue-associated corticobulbar tracts from the lateral primary motor cortex to the pons in both hemispheres.

Blood Oxygen Level Dependent Functional Magnetic Resonance Imaging for Presurgical Planning

Functional magnetic resonance imaging (fMRI) has become a common tool for presurgical sensorimotor mapping, and is a significant preoperative asset for tumors located adjacent to the central sulcus. fMRI has changed surgical options for many patients. This noninvasive tool allows for easy display and integration with other neuroimaging techniques. Although fMRI is a useful preoperative tool, it is not perfect. Tumors that affect the normal vascular coupling of neuronal activity will affect fMRI measurements. This article discusses the usefulness of blood oxygen level dependent (BOLD) fMRI with regard to preoperative motor mapping.

Clinical Applications of Functional MR Imaging

Functional magnetic resonance (fMR) imaging for neurosurgical planning has become the standard of care in centers where it is available. Although paradigms to measure eloquent cortices are not yet standardized, simple tasks elicit reliable maps for planning neurosurgical procedures. A patient-specific paradigm design will refine the usability of fMR imaging for prognostication and recovery of function. Certain pathologic conditions and technical issues limit the interpretation of fMR imaging maps in clinical use and should be considered carefully. However, fMR imaging for neurosurgical planning continues to provide insights into how the brain works and how it responds to pathologic insults.

Vascular Reactivity Maps in Patients with Gliomas Using Breath-Holding BOLD fMRI

To evaluate whether breath‐holding (BH) blood oxygenation level‐dependent (BOLD) fMRI can quantify differences in vascular reactivity (VR), as there is a need for improved contrast mechanisms in gliomas.

Corpus Callosum Diffusion and Language Lateralization in Patients with Brain Tumors: A DTI and fMRI Study

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).

Language Mapping Using fMRI and Direct Cortical Stimulation for Brain Tumor Surgery: The Good, the Bad, and the Questionable.

Abstract 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.

fMRI activation in the middle frontal gyrus as an indicator of hemispheric dominance for language in brain tumor patients: a comparison with Broca’s area

IntroductionFunctional MRI (fMRI) can assess language lateralization in brain tumor patients; however, this can be limited if the primary language area—Broca’s area (BA)—is affected by the tumor. We hypothesized that the middle frontal gyrus (MFG) can be used as a clinical indicator of hemispheric dominance for language during presurgical workup.MethodsFifty-two right-handed subjects with solitary left-hemispheric primary brain tumors were retrospectively studied. Subjects performed a verbal fluency task during fMRI. The MFG was compared to BA for fMRI voxel activation, language laterality index (LI), and the effect of tumor grade on the LI.ResultsLanguage fMRI (verbal fluency) activated more voxels in MFG than in BA (MFG = 315, BA = 216, p < 0.001). Voxel activations in the left-hemispheric MFG and BA were positively correlated (r = 0.69, p < 0.001). Mean LI in the MFG was comparable to that in BA (MFG = 0.48, BA = 0.39, p = 0.06). LIs in MFG and BA were positively correlated (r = 0.62, p < 0.001). Subjects with high-grade tumors demonstrate lower language lateralization than those with low-grade tumors in both BA and MFG (p = 0.02, p = 0.02, respectively).ConclusionMFG is comparable to BA in its ability to indicate hemispheric dominance for language using a measure of verbal fluency and may be an adjunct measure in the clinical determination of language laterality for presurgical planning.

Resection of glioma in an fMRI-defined “split” Broca’s area

Gross total resection of gliomas can be limited by the involvement of tumor in eloquent areas. Moreover, lesions can impart cortical reorganization and make the precise determination of hemispheric dominance and localization of language function even more difficult. Preoperative mapping with functional magnetic resonance imaging (fMRI), intraoperative imaging modalities, and intraoperative direct cortical stimulation enable surgeons to map the functional topography of the brain in relation to the tumor and perform a safe maximal resection. In this report, we present a patient with left frontal glioma of complex morphology, wherein the tumor was enveloped by Broca’s area on fMRI. Intraoperative mapping and intraoperative magnetic resonance imaging (iMRI) allowed gross total resection of the tumor with preservation of language function and illustrate the utility of multiple contemporary modalities in the surgical management of low-grade gliomas located in eloquent cortices.