**3.1 Functional MR**

Functional MRI is a non-invasive technique that visualizes brain activity indirectly by detection of local hemodynamic changes in cortical capillaries and draining veins (Frahm et al. 1994; Menon et al. 1995). This blood-oxygen level-dependent (BOLD) technique makes use of blood as an intrinsic contrast agent (Ogawa et al. 1993). A BOLD signal is based upon the increase of oxygen consumption by neuronal cells inducing a relative increase in the local perfusion (Heeger 2002; Toronov 2003). The activation spots have been shown to reflect actual neuronal activity with high spatial accuracy (typically between 1 and 5 mm) (Logothetis 2003; Logothetis & Pfeuffer 2004; Logothetis & Wandell 2004). Functional MR imaging maps reflect task-related local changes in the vascular response of brain tissue, and they are therefore an indirect measure of neural activity. Temporal resolution is generally lower than EEG (Gevins, Leong et al. 1995) or MEG (Hämäläinen M 1993) because the hemodynamic BOLD response lags behind the neural response by several seconds. There are other imaging tools that indirectly detect brain activity, such as positron emission tomography (PET) (Fox et al. 1986) (Mazziotta et al. 1982; Raichle 1983) and single-photon emission computer tomography (SPECT) (Holman and Devous 1992), but their description is beyond the scope of this chapter, except to note that they have lower spatial/temporal resolution and are less available for use in clinical scanning. At present, functional magnetic

reorganization (Duffau 2005; Duffau 2006). In addition, in some cases functional tissue is located within the tumor nidus, and it is now understood that the standard surgical principle of debulking tumor from within to avoid neurological deficits is not always safe

The concept of the eloquent area is not limited to cortical functional maps. It is also applied to the bundles of axons connecting a cortical area to secondary neurons and to other areas of a specific cortical network. Hence, the most thorough examination of a tumor requires a careful consideration of its relationship with subcortical white matter. In particular, gliomas are well known to invade white matter tracts through which they can reach the contralateral hemisphere. Accumulating evidence has demonstrated that postsurgical or post-stroke damage to subcortical critical pathways can result in irreversible deficits. There is no documented plasticity in the white matter, and recovery after interruption of a subcortical functional bundle is difficult. Hence, presurgical planning should determine whether tumor invades or simply displaces subcortical pathways. In the very recent years a new application of MR diffusion sequences imaging called Diffusion Tensor Imaging (DTI) has created the opportunity to reconstruct the anatomy of the main white matter tracts. A virtual in vivo dissection of white matter, very similar to those coming from cadaver studies, has been produced, adding new insights into the relationship between tumors and white matter bundles (Catani 2002, Ozawa 2009, Nimsky 2007). The availability of this new tool marks a period in which neuroscientists have given great resonance to connectionism to explain brain functions and neurosurgeons have focused their efforts on gaining preoperative

This brief overview of advances in understanding of the brain function has given us the opportunity to point out that the modern-era neurosurgeon should be able to preoperatively collect a large amount of information on the distinctive functional and anatomical

Functional MRI is a non-invasive technique that visualizes brain activity indirectly by detection of local hemodynamic changes in cortical capillaries and draining veins (Frahm et al. 1994; Menon et al. 1995). This blood-oxygen level-dependent (BOLD) technique makes use of blood as an intrinsic contrast agent (Ogawa et al. 1993). A BOLD signal is based upon the increase of oxygen consumption by neuronal cells inducing a relative increase in the local perfusion (Heeger 2002; Toronov 2003). The activation spots have been shown to reflect actual neuronal activity with high spatial accuracy (typically between 1 and 5 mm) (Logothetis 2003; Logothetis & Pfeuffer 2004; Logothetis & Wandell 2004). Functional MR imaging maps reflect task-related local changes in the vascular response of brain tissue, and they are therefore an indirect measure of neural activity. Temporal resolution is generally lower than EEG (Gevins, Leong et al. 1995) or MEG (Hämäläinen M 1993) because the hemodynamic BOLD response lags behind the neural response by several seconds. There are other imaging tools that indirectly detect brain activity, such as positron emission tomography (PET) (Fox et al. 1986) (Mazziotta et al. 1982; Raichle 1983) and single-photon emission computer tomography (SPECT) (Holman and Devous 1992), but their description is beyond the scope of this chapter, except to note that they have lower spatial/temporal resolution and are less available for use in clinical scanning. At present, functional magnetic

organization of each patient's brain in order to individualize surgical strategy.

(Duffau et al. 2005; Berger et al. 2010; Spena et al. 2010).

information about subcortical pathways.

**3. Preoperative brain mapping** 

**3.1 Functional MR** 

resonance imaging (fMRI) is the most widely used method of functional neuroimaging in both the clinical and research environments. For the latter purpose, and unlike more invasive mapping methods, fMR allows for the study of subjects who are free from neurological illness and enables the modeling of brain processes and of individual differences in brain organization. These are the principal factors that account for the enormous advancements brought by fMR to the understanding brain functional organization.

The two predominant diagnostic aims of presurgical fMR are the localization of eloquent brain areas and their relationships with the tumor, and the determination of the dominant hemisphere for language. As a clinical research tool, fMR can be performed longitudinally pre- and postoperatively to identify neuroplastic changes in brain activity.

Any clinical application of fMRI involves a "paradigm," a defined functional measurement including stimulation, and a task that is presumed to activate the cortical area to be studied. For motor function, the patient is scanned while performing an active blocked motor task. The task consists of 12 seconds of foot plantarflexion/dorsiflexion, hand opening/closing, or tongue movement, with a frequency of 0.5 Hz, followed by 12 seconds of rest for a total acquisition time of 5 minutes. The sensory cortex test is similar, with an active condition of 0.5-Hz brushing of the foot or hand. Language is investigated as follows: in the active condition, the patient listens to a list of nouns and generates associated verbs for 21 seconds; in the rest condition, the patient counts from 1 to 10 for 15 seconds. These paradigms are those usually performed in our routine. For further technical details refer to the bibliography (Moritz & Haughton 2003; Gaillard 2004).

Due to its good spatial resolution and direct correlation to surface anatomy BOLD-fMRI has been used since shortly after its first description (Bandettini et al. 1992) (Kwong et al. 1992; Ogawa et al. 1992) for presurgical localization of the primary sensorimotor cortex in patients with rolandic brain tumors (Jack et al. 1994), for determination of the language dominant hemisphere in patients with left frontal or temporo-parietal tumors (Desmond 1995), and for the localization of Broca and Wernicke language areas (FitzGerald et al. 1997; Stippich et al. 2003; Stippich et al. 2007).

The most relevant concern in presurgical visualization of eloquent areas is the reliability of the spatial position and the extent of the spot of activation as depicted on the fMR. It is important to clarify that the spots of activation are strictly related to the statistical threshold chosen for data evaluation. Even with the use of one or more fixed statistical thresholds, BOLD signal intensities and cluster sizes differ significantly from one patient to another and between different paradigms (e.g. foot movement, hand movement), even when examinations are carried out in a standardized way. This has a direct impact on the planning of the neurosurgeons, who may, based on an fMR map, consider a determined eloquent area to be wider or narrower than it actually is. To address this matter, comparisons of presurgical fMRI data with a reference procedure such as CSES have been performed. In patients with lesions around the central sulcus (Dymarkowski et al. 1998; Achten et al. 1999; Roux et al. 1999), many studies have reported highly concordant data of presurgical fMRI and CSES, with correlation ranging from 83% to 92% (Majos et al. 2005; Lehericy et al. 2000; Spena et al. 2010). However, for language areas, the utility of fMRI to predict the presence of language epicenters in or around the tumor surface is diminished. This is seen in our results (42.8%) as well as in previous works that have indicated variable sensitivities and specificities ranging from 59% to 100% and from 0% to 97%, respectively

Multimodal Approach to the Surgical Removal of Gliomas in Eloquent Brain Regions 345

The "eloquence" of a brain region is not only determined by importance of neuron functions. In order to maintain correct functioning of a neural network it is crucial that all the groups of neurons are connected. Consequently, neurosurgeons must try to spare subcortical functional bundles (at least the largest and more essential), otherwise connections between cortical epicenters will be damaged. The seminal works by Kringler, through post-mortem dissections (Agrawal et al. 2011), demonstrated the complex organization of the white matter into bundles of different length and thickness that connect either one gyrus to another or to very distant parts of the brain. Unfortunately these observations are hardly applicable during surgery, when white matter appears as a uniform tissue that can be infiltrated by the tumor. In recent years a new, non-invasive pre-operative technique of white matter signal analysis has been introduced: diffusion tensor imaging (DTI). This is a modification of diffusion weighted imaging (DWI) that is sensitive to the preferential diffusion of brain water along white matter fibers and can detect subtle changes in white matter tracts in disease (Nucifora et al. 2007). The random, diffusion-driven displacements in diffusion magnetic resonance imaging allow microscopic-scale resolution of tissue structure. As diffusion is a three-dimensional process, molecular mobility in tissues can be anisotropic, as in brain white matter. With DTI, diffusion anisotropy effects can be fully extracted, characterized, and exploited, providing even more exquisite detail of tissue

DTI has been applied to patients with brain tumors for different purposes. First, measures of mean diffusivity and fractional anisotropy have been used to differentiate normal white matter, edematous brain, and enhancing tumor margins (Sinha 2002, Lu 2003). Anisotropy is reduced in cerebral lesions due to the loss of structural organization (Wieshmann et al. 1999; Mascalchi et al. 2005). It seems that the abnormalities on DTI are more significant than those seen on T2-weighted images in high grade gliomas, but not in metastatic tumors (Beppu et al. 2003; Price et al. 2003). Second, DTI may distinguish if the white matter fibers are displaced (Wieshmann et al. 2000; Gossl et al. 2002), infiltrated, or disrupted by the tumor (Wittwer et al. 2002). Finally, the most fascinating application of DTI is the fiber-tracking technique (DTI-FT) that is able to identify and reconstruct the main white matter connections. This information is very useful for presurgical planning, delineating the spatial relationships of eloquent structures and tumors in order to preserve the functional pathways intraoperatively (Holodny et al. 2002; Tummala et al. 2003; Henry et al. 2004). Since the images generated by DTI-fiber tracking are the result of complex mathematical modeling aimed at resolving the hypercomplex structure of white matter, several authors have worked to answer some practical problems. For instance, what degree of correspondence do the images have to the actual anatomy of the bundles? What is the relationship of the bundle(s) to the tumor (displaced, infiltrated, interrupted)? And, most importantly, what is the function of the bundle(s)? Must it be spared or can it be sacrificed? DTI-FT is currently intended to virtually reconstruct white matter tracts, but it is not able to investigate the function related to a tract. CSES is the gold standard to map subcortical pathways, and DTI-FT findings can be integrated with intraoperative CSES with or without the implementation of intraoperative navigation devices (Henry et al. 2004; Kinoshita et al. 2005; Bello et al. 2008; Ozawa et al. 2009, Leclercq et al. 2010; Spena et al. 2010). The fundamental observation that preoperative DTI-FT cannot itself account for the determination of the presence or absence of functional subcortical tracts in or in the vicinity

**3.2 Diffusion tensor imaging and fiber tracking** 

microstructure.

(Petrovich et al. 2005, Rutten et al. 2002). Aside from methodological issues, language areas are organized in a large-scale network that is widely variable. Functional MRI maps the entire cortical network involved in a specific task, and it is normally not able to differentiate between essential and substitutable epicenters. These studies mainly addressed the reliability of the position of the focus of an activation spot but no data were produced regarding the extent of those spots (Fig. 1). Furthermore, since a BOLD signal is generated by an increase in blood flow, the presence of infiltration by vascularized tumor can completely alter the local microvascular organization and potentially hamper the reliability of the BOLD signal (Holodny et al. 1999; Ulmer et al. 2004). Therefore, the use of presurgical BOLD activations on fMR to predict resection margins and surgical risks of neurological damage is not routinely indicated. The data available to quantify a safe distance between functional activation and resection borders (Hall et al. 2005; Krishnan et al. 2004) with respect to surgically induced neurological deficits are still very limited and do not justify any general conclusion or recommendation. Moreover, since fMR imaging is only intended to visualize cortical activity, no information is gained about subcortical white matter bundles and connections.

Fig. 1. (A) Preoperative MR showing a retrocentral glioblastoma invading the central gyri. (B). Preoperative fMR showing that the area of the hand seems to be infiltrated by the tumor, and the activation spot seems to be interrupted (red arrow; q< 0.05 FDR corrected, minimum cluster size K>5 voxels in the native resolution). (C) Intraoperative stimulation demonstrated that the infiltrated postcentral gyrus was still functional (hand sensibility: 6, 7, 10) and so was not removed.

Nonetheless, functional MRI is still an important source of non-invasive diagnostic information that can reduce the number of invasive diagnostic procedures, such as the Wada test. We use fMRI in preoperative planning mainly to understand the activation pattern, the location of the pre- or postcentral gyrus, and the approximate distance to the tumor. If the distance from the activation spot is greater than one gyrus or the subcortical infiltration is minimal, we may even choose not to perform an awake surgery with CSES. For tumors in language areas, we calculate the lateralization index that, together with neuropsychological testing, gives an indication about the dominant hemisphere. We strongly recommend precise intraoperative control of functional structures in every situation where there is suspected tumor invasion of an eloquent area.

#### **3.2 Diffusion tensor imaging and fiber tracking**

344 Advances in the Biology, Imaging and Therapies for Glioblastoma

(Petrovich et al. 2005, Rutten et al. 2002). Aside from methodological issues, language areas are organized in a large-scale network that is widely variable. Functional MRI maps the entire cortical network involved in a specific task, and it is normally not able to differentiate between essential and substitutable epicenters. These studies mainly addressed the reliability of the position of the focus of an activation spot but no data were produced regarding the extent of those spots (Fig. 1). Furthermore, since a BOLD signal is generated by an increase in blood flow, the presence of infiltration by vascularized tumor can completely alter the local microvascular organization and potentially hamper the reliability of the BOLD signal (Holodny et al. 1999; Ulmer et al. 2004). Therefore, the use of presurgical BOLD activations on fMR to predict resection margins and surgical risks of neurological damage is not routinely indicated. The data available to quantify a safe distance between functional activation and resection borders (Hall et al. 2005; Krishnan et al. 2004) with respect to surgically induced neurological deficits are still very limited and do not justify any general conclusion or recommendation. Moreover, since fMR imaging is only intended to visualize cortical activity, no information is gained about subcortical white matter

Fig. 1. (A) Preoperative MR showing a retrocentral glioblastoma invading the central gyri. (B). Preoperative fMR showing that the area of the hand seems to be infiltrated by the tumor, and the activation spot seems to be interrupted (red arrow; q< 0.05 FDR corrected, minimum cluster size K>5 voxels in the native resolution). (C) Intraoperative stimulation demonstrated that the infiltrated postcentral gyrus was still functional (hand sensibility: 6, 7,

Nonetheless, functional MRI is still an important source of non-invasive diagnostic information that can reduce the number of invasive diagnostic procedures, such as the Wada test. We use fMRI in preoperative planning mainly to understand the activation pattern, the location of the pre- or postcentral gyrus, and the approximate distance to the tumor. If the distance from the activation spot is greater than one gyrus or the subcortical infiltration is minimal, we may even choose not to perform an awake surgery with CSES. For tumors in language areas, we calculate the lateralization index that, together with neuropsychological testing, gives an indication about the dominant hemisphere. We strongly recommend precise intraoperative control of functional structures in every

situation where there is suspected tumor invasion of an eloquent area.

bundles and connections.

10) and so was not removed.

The "eloquence" of a brain region is not only determined by importance of neuron functions. In order to maintain correct functioning of a neural network it is crucial that all the groups of neurons are connected. Consequently, neurosurgeons must try to spare subcortical functional bundles (at least the largest and more essential), otherwise connections between cortical epicenters will be damaged. The seminal works by Kringler, through post-mortem dissections (Agrawal et al. 2011), demonstrated the complex organization of the white matter into bundles of different length and thickness that connect either one gyrus to another or to very distant parts of the brain. Unfortunately these observations are hardly applicable during surgery, when white matter appears as a uniform tissue that can be infiltrated by the tumor. In recent years a new, non-invasive pre-operative technique of white matter signal analysis has been introduced: diffusion tensor imaging (DTI). This is a modification of diffusion weighted imaging (DWI) that is sensitive to the preferential diffusion of brain water along white matter fibers and can detect subtle changes in white matter tracts in disease (Nucifora et al. 2007). The random, diffusion-driven displacements in diffusion magnetic resonance imaging allow microscopic-scale resolution of tissue structure. As diffusion is a three-dimensional process, molecular mobility in tissues can be anisotropic, as in brain white matter. With DTI, diffusion anisotropy effects can be fully extracted, characterized, and exploited, providing even more exquisite detail of tissue microstructure.

DTI has been applied to patients with brain tumors for different purposes. First, measures of mean diffusivity and fractional anisotropy have been used to differentiate normal white matter, edematous brain, and enhancing tumor margins (Sinha 2002, Lu 2003). Anisotropy is reduced in cerebral lesions due to the loss of structural organization (Wieshmann et al. 1999; Mascalchi et al. 2005). It seems that the abnormalities on DTI are more significant than those seen on T2-weighted images in high grade gliomas, but not in metastatic tumors (Beppu et al. 2003; Price et al. 2003). Second, DTI may distinguish if the white matter fibers are displaced (Wieshmann et al. 2000; Gossl et al. 2002), infiltrated, or disrupted by the tumor (Wittwer et al. 2002). Finally, the most fascinating application of DTI is the fiber-tracking technique (DTI-FT) that is able to identify and reconstruct the main white matter connections. This information is very useful for presurgical planning, delineating the spatial relationships of eloquent structures and tumors in order to preserve the functional pathways intraoperatively (Holodny et al. 2002; Tummala et al. 2003; Henry et al. 2004). Since the images generated by DTI-fiber tracking are the result of complex mathematical modeling aimed at resolving the hypercomplex structure of white matter, several authors have worked to answer some practical problems. For instance, what degree of correspondence do the images have to the actual anatomy of the bundles? What is the relationship of the bundle(s) to the tumor (displaced, infiltrated, interrupted)? And, most importantly, what is the function of the bundle(s)? Must it be spared or can it be sacrificed? DTI-FT is currently intended to virtually reconstruct white matter tracts, but it is not able to investigate the function related to a tract. CSES is the gold standard to map subcortical pathways, and DTI-FT findings can be integrated with intraoperative CSES with or without the implementation of intraoperative navigation devices (Henry et al. 2004; Kinoshita et al. 2005; Bello et al. 2008; Ozawa et al. 2009, Leclercq et al. 2010; Spena et al. 2010). The fundamental observation that preoperative DTI-FT cannot itself account for the determination of the presence or absence of functional subcortical tracts in or in the vicinity

Multimodal Approach to the Surgical Removal of Gliomas in Eloquent Brain Regions 347

calculation and characterization of fractional anisotropy have allowed for a more precise reconstruction of the white matter bundles by depicting complex distributions of intravoxel fiber orientation. This new algorithm, called diffusion spectrum imaging (DSI), is a very promising technological advancement (Kuo et al. 2008; Wedeen et al. 2008, Canales-Rodríguez et al. 2010), but unfortunately these methods require very long sessions (up to 60

Fig. 3. Man, 42 years old. Three episodes of absence. A) On preoperative MR a temporal mass is demonstrated. B) DTI showed a fascicle just beside the mass that seemed

interrupted. No other tract was visualized inside the tumor. By looking at the position and direction, this bundle was referred to the inferior longitudinal fasciculus (ILF). C) CSES confirmed at the subcortical level of naming disturbances (8, 9, 10, 11); consequently resection was arrested, and no language deficit was diagnosed at follow-up. (D) Postoperative MRI confirmed the subtotal resection as well as the functionality of the

**4. Intraoperative brain mapping: Awake surgery and cortical and subcortical** 

Direct electrical stimulation of the brain surface is a technique that has regained greater interest worldwide in the past decade than it has had since its introduction by Foerster, Penfield and Rasmussen in 1930 (Foerster 1931, Penfield & Boldrey 1937, Penfield & Erickson 1941, Penfield & Rasmussen 1950). More recently Berger introduced the technique of subcortical stimulation to spare functional white matter bundles that are very often infiltrated by gliomas (Berger 1994). Indeed, refinement of technical equipment and, mostly, the

infiltrated white matter although DTI-FT showed absence of fibers.

**electrical stimulation (CSES) 4.1 Introduction and indications** 

minutes) of MR scanning that are sometimes unsuitable for patients.

of the tumor is clearly demonstrated by cases of cystic tumors in which, because of the absence of infiltration and edema, the white matter tract reconstructions are very reliable (fig. 2). DTI-FT underestimates the presence of functional tracts in the context of the tumor, as demonstrated by our finding of 60.4% of infiltrated functional white matter predicted by

Fig. 2. (A) Male, 43 years old. Preoperative MR showing a large and partly cystic oligodendroglioma (WHO III) in the central area. (B) DTI-FT demonstrates the displacement of the pyramidal tract anteriorly and the close contact to the cystic portion of the tumor. (C) Intraoperative image demonstrating the presence of talamo-cortical fibers at the subcortical level in the anterior aspect of the surgical cavity (11, 12 paraesthesia of the shoulder and neck). (D) On immediate postoperative MRI there was no residual tumor and the patient had no postoperative deficit confirming the DTI-ft hypothesis that the tract was neither damaged nor infiltrated.

DTI compared to the postoperative MRI and intraoperative stimulation results (fig. 3). A typical image featured a white matter bundle in close vicinity to the tumor without any information on how much of the pathway or pathway function was invaded. The tracking of fibers in the vicinity of or within lesions is complicated due to changes in diseased tissue, such as elevated water content (edema), tissue compression, and degeneration. These changes deform the architecture of the white matter, and, in some cases, prevent selection of the seed region of interest (ROI) from which to begin fiber tracking. To overcome this problem, some investigators have suggested posing a seed ROI in the white matter area subjacent to the maximal fMRI activity (i.e., for the pyramidal tract, in the precentral cortex) with the target ROI in the cerebral peduncle (Schomberg et al. 2006; Smits et al. 2007; Staempfli et al. 2007). Also notable is that in language areas, DTI might emphasize the presence of white matter tracts when subcortical stimulation did not show a zone of positive response, favoring an unnecessarily conservative surgery, whereas direct stimulation would have indicated removal of the entire portion of non-eloquent tissue. More recent advances in

of the tumor is clearly demonstrated by cases of cystic tumors in which, because of the absence of infiltration and edema, the white matter tract reconstructions are very reliable (fig. 2). DTI-FT underestimates the presence of functional tracts in the context of the tumor, as demonstrated by our finding of 60.4% of infiltrated functional white matter predicted by

Fig. 2. (A) Male, 43 years old. Preoperative MR showing a large and partly cystic

damaged nor infiltrated.

oligodendroglioma (WHO III) in the central area. (B) DTI-FT demonstrates the displacement of the pyramidal tract anteriorly and the close contact to the cystic portion of the tumor. (C) Intraoperative image demonstrating the presence of talamo-cortical fibers at the subcortical level in the anterior aspect of the surgical cavity (11, 12 paraesthesia of the shoulder and neck). (D) On immediate postoperative MRI there was no residual tumor and the patient had no postoperative deficit confirming the DTI-ft hypothesis that the tract was neither

DTI compared to the postoperative MRI and intraoperative stimulation results (fig. 3). A typical image featured a white matter bundle in close vicinity to the tumor without any information on how much of the pathway or pathway function was invaded. The tracking of fibers in the vicinity of or within lesions is complicated due to changes in diseased tissue, such as elevated water content (edema), tissue compression, and degeneration. These changes deform the architecture of the white matter, and, in some cases, prevent selection of the seed region of interest (ROI) from which to begin fiber tracking. To overcome this problem, some investigators have suggested posing a seed ROI in the white matter area subjacent to the maximal fMRI activity (i.e., for the pyramidal tract, in the precentral cortex) with the target ROI in the cerebral peduncle (Schomberg et al. 2006; Smits et al. 2007; Staempfli et al. 2007). Also notable is that in language areas, DTI might emphasize the presence of white matter tracts when subcortical stimulation did not show a zone of positive response, favoring an unnecessarily conservative surgery, whereas direct stimulation would have indicated removal of the entire portion of non-eloquent tissue. More recent advances in calculation and characterization of fractional anisotropy have allowed for a more precise reconstruction of the white matter bundles by depicting complex distributions of intravoxel fiber orientation. This new algorithm, called diffusion spectrum imaging (DSI), is a very promising technological advancement (Kuo et al. 2008; Wedeen et al. 2008, Canales-Rodríguez et al. 2010), but unfortunately these methods require very long sessions (up to 60 minutes) of MR scanning that are sometimes unsuitable for patients.

Fig. 3. Man, 42 years old. Three episodes of absence. A) On preoperative MR a temporal mass is demonstrated. B) DTI showed a fascicle just beside the mass that seemed interrupted. No other tract was visualized inside the tumor. By looking at the position and direction, this bundle was referred to the inferior longitudinal fasciculus (ILF). C) CSES confirmed at the subcortical level of naming disturbances (8, 9, 10, 11); consequently resection was arrested, and no language deficit was diagnosed at follow-up. (D) Postoperative MRI confirmed the subtotal resection as well as the functionality of the infiltrated white matter although DTI-FT showed absence of fibers.
