Search Results

You are looking at 1 - 8 of 8 items for

  • Author or Editor: Susan Y. Bookheimer x
Clear All Modify Search
Full access

Nader Pouratian and Susan Y. Bookheimer

The adjacency of intracranial pathology to canonical regions of eloquence has long been considered a significant source of potential morbidity in the neurosurgical care of patients. Yet, several reports exist of patients who undergo resection of gliomas or other intracranial pathology in eloquent regions without adverse effects. This raises the question of whether anatomical and intracranial location can or should be used as a means of estimating eloquence. In this review, the authors systematically evaluate the factors that are known to affect anatomical-functional relationships, including anatomical, functional, pathology-related, and modality-specific sources of variability. This review highlights the unpredictability of functional eloquence based on anatomical features alone and the fact that patients should not be considered ineligible for surgical intervention based on anatomical considerations alone. Rather, neurosurgeons need to take advantage of modern technology and mapping techniques to create individualized maps and management plans. An individualized approach allows one to expand the number of patients who are considered for and who potentially may benefit from surgical intervention. Perhaps most importantly, an individualized approach to mapping patients with brain tumors ensures that the risk of iatrogenic functional injury is minimized while maximizing the extent of resection.

Restricted access

Nader Pouratian, Susan Y. Bookheimer, David E. Rex, Neil A. Martin and Arthur W. Toga

Object. The goal of this study was to evaluate the utility of preoperative functional magnetic resonance (fMR) imaging in the prediction of whether a given cortical area would be deemed essential for language processing by electrocortical stimulation mapping (ESM).

Methods. The authors studied patients with vascular malformations, specifically arteriovenous malformations (AVMs) and cavernous angiomas, in whom blood-flow patterns are not normal and in whom a perfusion-dependent mapping signal may be questionable. Ten patients were studied (seven harboring AVMs and three with cavernous angiomas). The authors used a battery of linguistic tasks, including visual object naming, word generation, auditory responsive naming, visual responsive naming, and sentence comprehension, to identify brain regions that were consistently activated across expression and comprehension linguistic tasks. In a comparison of ESM and fMR imaging activations, the authors varied the matching criteria (overlapping activations, adjacent activations, and deep activations) and the radii of influence of ESM (2.5, 5, and 10 mm) to determine the effects of these factors on the sensitivity and specificity of fMR imaging. The sensitivity and specificity of fMR imaging were dependent on the task, lobe, and matching criterion. For the population studied, the sensitivity and specificity of fMR imaging activations during expressive linguistic tasks were found to be up to 100 and 66.7%, respectively, in the frontal lobe, and during comprehension linguistic tasks up to 96.2 and 69.8%, respectively, in the temporal and parietal lobes. The sensitivity and specificity of each disease population (patients with AVMs and those with cavernous angiomas) and of individuals were consistent with those values reported for the entire population studied.

Conclusions. The authors conclude that preoperative fMR imaging is a highly sensitive preoperative planning tool for the identification of which cortical areas are essential for language and that this imaging modality may play a future role in presurgical planning for patients with vascular malformations.

Restricted access

Darrin J. Lee, Nader Pouratian, Susan Y. Bookheimer and Neil A. Martin

Object

The authors conducted a study to determine the factors associated with right-sided language dominance in patients with cerebrovascular malformations.

Methods

Twenty-two patients with either arteriovenous malformations (AVMs [15 cases]) or cavernous malformations (7 cases) underwent functional MR (fMR) imaging studies of language function; a 3.0-T head-only unit was used. Lateralization indices were calculated separately for Broca and Wernicke areas. Lesion size, Spetzler-Martin grade, and the distance between the lesion and anatomically defined language cortex were calculated for each patient.

Results

Right-sided language dominance occurred in 5 patients, all of whom had AVMs within 10 mm of canonical language areas. Three patients had right-sided language dominance in the Wernicke area alone whereas 2 had right-sided language dominance in both Broca and Wernicke areas. Wada testing and intraoperative electrocortical stimulation were performed as clinically indicated to corroborate fMR imaging findings.

Conclusions

The primary factor associated with right-sided language dominance was the AVM being within 10 mm of anatomically defined language areas. The lesion size and the Spetzler-Martin grade were not significant factors. Anomalous fMR imaging laterality was typically confined to the language area proximate to the lesion, with the distal language area remaining in the left hemisphere dominant. This study emphasizes the need to map each case individually in patients with left perisylvian AVMs. Assumptions about eloquent cortex based on anatomical landmarks (a key component of Spetzler-Martin grading) may have to be reconsidered.

Full access

Nader Pouratian, Susan Y. Bookheimer, David E. Rex, Neil A. Martin and Arthur W. Toga

Object

The goal of this study was to evaluate the utility of preoperative functional magnetic resonance (fMR) imaging in the prediction of whether a given cortical area would be deemed essential for language processing by electro-cortical stimulation mapping (ESM).

Methods

The authors studied patients with vascular malformations, specifically arteriovenous malformations (AVMs) and cavernous angiomas, in whom blood-flow patterns are not normal and in whom a perfusion-dependent mapping signal may be questionable. Ten patients were studied (seven harboring AVMs and three with cavernous angiomas). The authors used a battery of linguistic tasks, including visual object naming, word generation, auditory responsive naming, visual responsive naming, and sentence comprehension, to identify brain regions that were consistently activated across expression and comprehension linguistic tasks. In a comparison of ESM and fMR imaging activations, the authors varied the matching criteria (overlapping activations, adjacent activations, and deep activations) and the radii of influence of ESM (2.5, 5, and 10 mm) to determine the effects of these factors on the sensitivity and specificity of fMR imaging. The sensitivity and specificity of fMR imaging were dependent on the task, lobe, and matching criterion. For the population studied, the sensitivity and specificity of fMR imaging activations during expressive linguistic tasks were found to be up to 100 and 66.7%, respectively, in the frontal lobe, and during comprehension linguistic tasks up to 96.2 and 69.8%, respectively, in the temporal and parietal lobes. The sensitivity and specificity of each disease population (patients with AVMs and those with cavernous angiomas) and of individuals were consistent with those values reported for the entire population studied.

Conclusions

The authors conclude that preoperative fMR imaging is a highly sensitive preoperative planning tool for the identification of which cortical areas are essential for language and that this imaging modality may play a future role in presurgical planning for patients with vascular malformations.

Restricted access

Nader Pouratian, Andrew F. Cannestra, Susan Y. Bookheimer, Neil A. Martin and Arthur W. Toga

Object. Electrocortical stimulation mapping is regarded as the gold standard of intraoperative mapping for predicting functional outcomes. Nevertheless, methodologies across institutions are inconsistent. Although many vary and maximize stimulation currents at each cortical site, some use a single current level to map the entire exposed cortex. The former comes at the cost of possibly inducing additional afterdischarge activity. The authors retrospectively reviewed their experience with intraoperative electrocortical stimulation mapping to characterize variability of both mapping and afterdischarge thresholds.

Methods. Seventeen patients satisfied the study inclusion criteria. Significant variability in mapping thresholds was identified within individuals and across the patient population. Moreover, a statistically significant difference in mapping thresholds was demonstrated between the frontal and parietal/temporal lobes (p = 0.007, one-way analysis of variance). The authors report a surprisingly high incidence of afterdischarge during mapping, wide variability in afterdischarge thresholds within individuals and across the study population, and mapping thresholds regularly exceeding afterdischarge thresholds in neighboring cortex. Differences in afterdischarge thresholds across lobes only approached significance (p = 0.086).

Conclusions. To maximize identification of eloquent cortices in some clinical situations, it may be advantageous to maximize currents at each cortical site regardless of adjacent afterdischarge threshold rather than to map the entire exposed cortex at a single current level. Moreover, the current findings highlight the need for electrocorticography during electrocortical stimulation mapping, both to identify when afterdischarges occur and to verify stimulation by recording stimulation artifacts. The advantages and limitations of maximizing currents at each cortical site as well as mapping at a single current level are discussed.

Restricted access

Nader Pouratian, Susan Y. Bookheimer, Gregory Rubino, Neil A. Martin and Arthur W. Toga

✓ Category-specific naming deficits and differential brain activation patterns have been reported in patients naming living as opposed to nonliving objects. The authors report on a case in which they used preoperative functional magnetic resonance (fMR) imaging, intraoperative electrocortical stimulation mapping (ESM), and postoperative neuropsychological testing to map language function. Using the latter two modalities, the authors identified a specific locus for category-specific naming in the posterior inferior temporal lobe, presumably a part of the basal temporal language area. Preoperative fMR imaging findings revealed the presence of a language area in the inferior temporal lobe; intraoperative ESM results indicated that this cortical area may be category specific for living objects; and after resection of the area, the results of postoperative neuropsychological testing confirmed that the patient made significantly more errors while naming living objects compared with nonliving ones (p < 0.001), independent of the effects of word frequency and with an intact system of object recognition and comprehension. These authors are the first to identify a specific and well-localized area of category-specific naming in the inferior temporal lobe and to demonstrate congruence of intraoperative and postoperative category-specific naming deficits. They also emphasize the roles of preoperative and intraoperative testing in predicting clinical outcomes.

Full access

Nader Pouratian, Sameer Sheth, Susan Y. Bookheimer, Neil A. Martin and Arthur W. Toga

Perfusion-dependent brain mapping modalities, such as functional magnetic resonance imaging, positron emission tomography, and optical imaging of intrinsic signals, have become increasingly popular for neurosurgical guidance because they offer a relatively rapid and noninvasive means of mapping brain function. These modalities are unique because they rely on perfusion-related signals that are coupled with neuronal activity to map the brain instead of measuring electrophysiological responses. They consequently present unique challenges to the clinician in terms of understanding the significance and limitations of the maps they produce. In particular, one must be aware of limitations of the modalities with respect to spatial specificity, sensitivity, and reliability of these maps and how the presence of intracranial lesions may further complicate these issues.

The authors review the evolution, interpretation, and limitations of perfusion-based brain mapping techniques, with special attention to clinical implications of the brain maps.

Restricted access

Nader Pouratian, Susan Y. Bookheimer, Alyssa M. O'Farrell, Nancy L. Sicotte, Andrew F. Cannestra, Donald Becker and Arthur W. Toga

✓ The organization of language in the brains of multilingual persons remains controversial. The authors investigated language representations in a proficient bilingual patient by using a novel neuroimaging technique, intraoperative optical imaging of intrinsic signals (iOIS), and a visual object naming task. The results indicate that there are cortical areas that are activated by the use of both English and Spanish languages (superior temporal sulcus, superior and middle temporal gyri, and parts of the supramarginal gyrus). In addition, language-specific areas were identified in the supramarginal (Spanish) and precentral (English) gyri. These results suggest that cortical language representations in bilingual persons may consist of both overlapping and distinct components. Furthermore, this study demonstrates the utility of iOIS in detecting topographical segregation of cognitively distinct cortices.