New Language Mapping Technique Advances Brain Surgery

Researchers from the University of California, San Francisco (UCSF; USA) tested negative language mapping on 250 consecutive patients (146 men and 104 women) over a period of eight years, all of whom had gliomas--a common and often fatal brain tumor--affecting the dominant hemisphere of their brain. One week following surgery, 194 of the 250 patients (77.6%) retained the language function they had prior to surgery. Six months later, only four of the 243 surviving patients (1.6%) exhibited worsened language function. Cumulatively, the neurosurgeons stimulated 3281 cortical sites in the brains of the 250 patients.

The language map generated during the study showed that areas processing language function in the brain are widely distributed, sometimes varying in location by as much as several centimeters from patient to patient. This has implications for language organization models, which are currently based on the assumption that specific language functions have fixed anatomic locations. The researchers identified new regions involved in speech production, reading, and naming, and used this data to generate a three-dimensional cortical language map that is more detailed and integrates more data than any language map of the brain ever generated. The findings were published in the January 3, 2008, issue of The New England Journal of Medicine (NEJM).

"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,” said lead author Nader Sanai, M.D., a senior resident in neurologic surgery at UCSF. "It represents a comprehensive set of language coordinates that will serve as a guide for neurosurgeons to plan operations more safely and effectively.”

Negative brain mapping 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 in traditional language mapping methods. After the craniotomy, the neurosurgeon "maps” the brain by stimulating a one square centimeter section 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), but rather is driven by localization of negative sites. i.e., areas that contain no language function.


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