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“This study represents a paradigm shift in language mapping during brain tumor resection,” said senior author Mitchel Berger, MD, professor and chairman of the University of California, San Francisco Department of Neurological Surgery. “Not only have we proven this technique can be safely relied upon for brain tumor resection, we have shown functional language organization to be much more diverse and individualized than previously thought.”
“Accurately understanding cortical language organization has clinical implications for more than just brain tumor patients,” said lead author Nader Sanai, MD, senior resident in neurological surgery at UCSF. “Any patient with a seizure-disorder, stroke or head injury who has language-related difficulties can now be better understood in the context of this revised anatomy.”
The technique, which Berger and his team helped pioneer, is known as “negative brain mapping.” It eliminates neurosurgeons’ dependence on traditional language mapping methods that typically require the removal of large sections of skull and extensive brain mapping while the patient is awake. It also allows for smaller craniotomies that expose only the tumor and a small margin of surrounding brain tissue, rather than several centimeters or more of the patient’s brain. After the craniotomy, the neurosurgeon “maps” the brain by stimulating a section (1 cm by 1 cm) at a time with a bipolar electrode. The strategy does not require positive identification of language sites (defined as an arrest in speech, inability to name objects or read, or difficulty in articulating words), as in traditional brain mapping, but rather is driven by localization of negative sites -- areas that contain no language function.
“Nearly half our patients had no positive language sites in the area exposed, yet their functional outcomes remained nearly identical or better than patients who underwent extensive positive language mapping,” said Sanai. “In addition, our results show that negative language mapping can be relied upon even when language function is already affected by tumor growth.”
“The map we have generated addresses the critical question of how cortical language sites for motor speech, naming and reading are distributed within the dominant hemisphere of the human brain,” added Sanai. “It represents a comprehensive set of language coordinates that will serve as a guide for neurosurgeons to plan operations more safely and effectively.”
COMPAMED.de; Source: University of California - San Francisco