Delineation of the Safe Zone in Surgery of Sylvian Insular Triangle: Morphometric An

20/09/2011

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BACKGROUND: Surgery within the insula carries significant risk of morbidity, particularly hemiparesis, due to difficulty in detecting the internal capsule boundaries.

OBJECTIVE: We analyzed the anatomy of the insula and identified landmarks anticipated to facilitate surgery for intrinsic insular lesions.

METHODS: Insular region anatomy was studied in 11 cadaveric brains harvested within 72 hours postmortem. Magnetic resonance imaging (MRI) of the specimens was acquired using 3.0 tesla with T2-weighting and 25 directions of diffusion tensor imaging (DTI). Landmarks easily recognizable during surgery were identified on the surface of the insula. The interrelationships between surface landmarks and critical structures were analyzed.

RESULTS: The 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 periinsular 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 DTI tractography. The corticospinal tract took a course deep to the posterosuperior insula on T2-weighted imaging, 4.8mm from the UCIP and 6.2mm from the PIIP.

CONCLUSION: The 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.

Full article access for Neurosurgery subscribers at Neurosurgery-Online.com.