Brain ‘mapping’ involves recognition of functional areas of the brain by measurement of evoked electrical responses, or by observation of physiological responses due to direct brain stimulation. Since it is not always easy to recognize one area of the brain from the next by anatomical considerations at the time of surgery, this functional mapping offers additional guidance to the surgeon and protection to the patient by assuring that the surgical site is in the appropriate place. It also allows the surgeon to judge how close s/he is to critical areas of the brain that need to be preserved.

Technique:
There are multiple techniques to functional mapping. The most common involves placement of a sterile grid of contacts on the brain surface for the measurement of SSEP potentials to identify the central sulcus (fissure of Rolando), which separates motor and sensory strips on the side of the brain.

Brain Mapping

Depiction of an SSEP

Summary:

Upside:

• Provides a ‘functional’ localization to the surgeon.

Downside:

• Sensory mapping has very little in the way of downside, unless the mapping grid is being blindly placed, which may lead to bleeding.
• Motor stimulation of the brain can cause seizure.
• Both techniques require highly trained monitoring personnel and surgical familiarity.

Selected References
Bello, L.; Acerbi, F.; Giussani, C.; Baratta, P.; Taccone, P.; Songa, V.; Fava, M.; Stocchetti, N.; Papagno, C. & Gaini, S. M. (2006), ‘Intraoperative language localization in multilingual patients with gliomas.’, Neurosurgery 59(1), 115--25; discussion 115-25.

Bello, L.; Gallucci, M.; Fava, M.; Carrabba, G.; Giussani, C.; Acerbi, F.; Baratta, P.; Songa, V.; Conte, V.; Branca, V.; Stocchetti, N.; Papagno, C. & Gaini, S. M. (2007), ‘Intraoperative subcortical language tract mapping guides surgical removal of gliomas involving speech areas.’, Neurosurgery 60(1), 67--80; discussion 80-2.

Berger, M. S.; Kincaid, J.; Ojemann, G. A. & Lettich, E. (1989), ‘Brain mapping techniques to maximize resection, safety, and seizure control in children with brain tumors.’, Neurosurgery 25(5), 786--792.

Prabhu,
M. P. M. P. M. M. M. H. L. M. & Jellish, P. (2007), ‘Cortical Mapping in the Resection of GliomasPart III: Surgical Considerations', Contemporary Neurosurgery 29. Sakurada, K.; Sato, S.; Sonoda, Y.; Kokubo, Y.; Saito, S. & Kayama, T. (2007), ‘Surgical resection of tumors located in subcortex of language area.‘, Acta Neurochir (Wien) 149(2), 123--130.