We thank the editor for the invitation to reply to the letter by Dr. Buscemi and colleagues, and we also thank the authors for their interesting and important comments on our paper. Our team concurs that using a multistage approach combining multiple mapping methods (pre-and intraoperatively) can optimize surgical outcomes. The authors also emphasize some of the benefits of DES relative to fMRI. Indeed, we also perform DES at our center, and we have published a number of papers on this technique.1–3 Recognizing the importance of using DES on patients whose lesions are close to language areas, we agree with the authors that eloquent cortex can only be really defined through disruptive methods.
Our team strongly supports the view that a multistage approach to surgery that includes brain mapping is essential in optimizing cognitive outcome. Concurrently, each mapping technique has significant limitations. The limitations of fMRI are widely appreciated and are discussed at length in the literature.4 The conceptual and practical limitations of DES are equally striking, although less widely appreciated. As it is currently executed, more than 40% of sites report cases in which DES fails to predict postsurgical language impairment.5 A multistage approach is also essential because DES is not practical with every patient. For example, DES may not be possible in children, patients with significant language deficits, or individuals with severe anxiety. Furthermore, DES requires a well-trained multidisciplinary team with a high level of expertise, which may not be available in many clinical settings.
For these reasons, it is essential to have noninvasive techniques like fMRI for those patients for whom DES is not practical. In those individuals in particular, it is critical to understand the limitations of language mapping with preoperative fMRI. For instance, our group has recently shown that prior brain surgery around Broca’s area reduces fMRI estimates of language laterality in this region.6 Continued research that integrates these two technologies will help us understand better how these methods compare and how to improve our noninvasive techniques for language mapping.
Another important point raised in this commentary emphasizes the growing focus on SpTR as a means of improving overall survival outcomes.7,8 However, with extensive resections comes a larger risk of language impairment. It should therefore be noted that another key component of a multistage approach to optimizing surgical outcome should be routine pre- and postsurgical neurocognitive testing. Through such testing we can assess if outcomes were in fact optimized. In addition, during planning, patterns of preoperative impairment and preservation of language can help guide surgical decision-making.
In conclusion, we agree that a multistage approach is essential in optimizing neurosurgery in patients with brain tumors in neighboring language regions. It is vital to use whatever techniques are available to maximize patients’ longevity and quality of life, while recognizing the limitations of each.
Acknowledgments
This research has received financial support from the National Institute on Deafness and Other Communication Disorders, grant no. K01DC016904, “Comprehensive pre-surgical identification of the critical language network in tumor patients.”
Contributor Information
Monika M. Połczyńska, David Geffen School of Medicine at UCLA, University of California, Los Angeles, CA.
Christopher F. Benjamin, Yale University, New Haven, CT.
Susan Y. Bookheimer, David Geffen School of Medicine at UCLA, University of California, Los Angeles, CA.
References
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