Mapping language sites in cerebral cortex

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Mapping language sites in cerebral cortex (Sanai
et al., NEJM 2008) Stimulate brain regions in
dominant hemisphere of conscious patients during
surgery for brain tumor resection, before tumor
resection, to minimize post-operative language
deficits. Craniotomy over the tumor 3cm max,
with anesthesia. Apply lidocaine, open dura,
withdraw anesthesia. Apply electrical
stimulation to 1 sq cm areas while patient
counts, reads, names objects. Determine which
exposed brain regions in each patient are
involved in speaking, reading, and naming.
(Neurons cant function normally while being
stimulated electrically, so if the region is
involved in a task, the patient will be unable to
perform the task while that region is stimulated.)
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Frontal-Lobe Language Sites
Sanai N et al. N Engl J Med 200835818-27
Red squares total number of sites
stimulated Blue squares of sites causing
speech dysfunction when stimulated
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Temporal-Lobe Language Sites
Red squares total number of sites
stimulated. Blue squares of sites causing
speech dysfunction when stimulated. None of the
temporal lobe sites tested caused complete speech
arrest.
Sanai N et al. N Engl J Med 200835818-27
4
Parietal-Lobe Language Sites
Red squares total number of sites
stimulated. Blue squares of sites causing
speech dysfunction when stimulated. None of the
parietal lobe sites tested caused complete speech
arrest.
Sanai N et al. N Egl J Med 200835818-27
5
Negative Language Sites
Sanai N et al. N Engl J Med 200835818-27
Upper value total number of patients with no
detectable language function at that site Lower
value of patients with no detectable language
function at that site
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Authors Conclusions Language sites are highly
variable in their location. Current models of
language localization in the dominant hemisphere
insufficiently reflect the true diversity and in
vivo patterns of cortical language organization.
(Sanai N et al. N Engl J Med 200835818-27) Add
itional Conclusion Pictures of Brocas area in
anatomy textbooks may give a misleading
impression that motor speech is produced by a
relatively small and constant (from person to
person) brain region.