• Nobuyuki Kaneko, Warren W Boling, Takaharu Shonai, Kazumi Ohmori, Yoshiaki Shiokawa, Hiroki Kurita, and Takanori Fukushima.
• Department of Neurosurgery, West Virginia University, Morgantown, West Virginia, USA. nobuchaka32@hotmail.co.jp
• Neurosurgery. 2012 Jun 1;70(2 Suppl Operative):290-8; discussion 298-9.

BackgroundSurgery within the insula carries significant risk of morbidity, particularly hemiparesis, because of the difficulty in detecting the internal capsule boundaries.ObjectiveWe analyzed the anatomy of the insula and identified landmarks anticipated to facilitate surgery for intrinsic insular lesions.MethodsInsular region anatomy was studied in 11 cadaveric brains harvested within 72 hours postmortem. MRI of the specimens was acquired using 3.0 T with T2-weighting and 25 directions of diffusion tensor imaging. Landmarks easily recognizable during surgery were identified on the surface of the insula. The interrelationships between surface landmarks and critical structures were analyzed.ResultsThe posterior inferior insular point (PIIP) and the upper central insular point (UCIP) were newly established as landmarks on the insula. The PIIP corresponded to the obvious bend in the posterior long insular gyrus. The UCIP is the meeting point between the central insular sulcus and superior peri-insular sulcus. The corticospinal tract was identified as a high-intensity area in the posterior limb of the internal capsule on T2-weighted imaging and its course confirmed with diffusion tensor imaging tractography. The corticospinal tract took a course deep to the posterosuperior insula on T2-weighted imaging, 4.8 mm from the UCIP and 6.2 mm from the PIIP.ConclusionThe posterosuperior part of the insula forms the region at greatest risk to corticospinal tract injury. The PIIP and UCIP are crucial to understanding the relationship of the insula with the posterior limb of the internal capsule including the corticospinal tract.

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