Surgical morbidity of transsylvian versus transcortical approaches to insular gliomas

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OBJECTIVE

The choice of transsylvian versus transcortical corridors for resection of insular gliomas remains controversial. Functional pathway compromise from transcortical transgression and vascular injury during transsylvian dissection are the primary concerns. In this study, data from a single-center experience with both approaches were compared to determine whether one approach was associated with a higher rate of morbidity than the other.

METHODS

The authors identified 100 consecutive patients who underwent resection of pure insular gliomas at the Barrow Neurological Institute. Volumetric analysis was performed using FLAIR and contrast-enhanced T1-weighted MRI for low- and high-grade gliomas, respectively, for extent of resection (EOR) and diffusion-weighted sequences were used to detect for postoperative ischemia. Step-wise logistic regression analysis was performed to identify predictors of neurological morbidity.

RESULTS

Data from 100 patients with low-grade or high-grade insular gliomas were analyzed. Fifty-two patients (52%) underwent a transsylvian approach, and 48 patients (48%) underwent a transcortical approach. The mean (± SD) EOR was 91.6% ± 12.4% in the transsylvian group and 88.6% ± 14.2% in the transcortical group (p = 0.26). Clinical outcome metrics for the 2 groups were similar. Overall, 13 patients (25%) in the transsylvian group and 10 patients (21%) in the transcortical group had evidence of ischemia on postoperative MR images. For both approaches, high-grade histology was associated with permanent morbidity (p = 0.01). For patients with gliomas located within the superior-posterior quadrant of the insula, development of postoperative ischemia was associated with only the transsylvian approach (46% vs 0%, p = 0.02).

CONCLUSIONS

Areas of restricted diffusion are common on postoperative MRI following resection of insular gliomas, but only a minority of these patients develop permanent neurological deficits. Insular glioma patients with high-grade histology may be at particular risk for developing symptomatic postoperative ischemia. Both the transcortical and transsylvian corridors are associated with reasonable morbidity profiles, although gliomas situated within the superior-posterior quadrant of the insula are more safely accessed with a transcortical approach.

ABBREVIATIONS DTI = diffusion tensor imaging; EOR = extent of resection; MCA = middle cerebral artery; WHO = World Health Organization.

Article Information

Correspondence Nader Sanai: Barrow Neurological Institute, Phoenix, AZ. nader.sanai@bnaneuro.net.

INCLUDE WHEN CITING Published online April 5, 2019; DOI: 10.3171/2018.12.JNS183075.

Disclosures The authors report no conflict of interest concerning the materials or methods used in this study or the findings specified in this paper.

© AANS, except where prohibited by US copyright law.

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    Representative illustration of the zones of the insula as described by the Berger-Sanai classification. The anterior-posterior border is defined by the foramen of Monro, and the superior-inferior border is defined by the sylvian fissure. Copyright Barrow Neurological Institute. Published with permission.

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    Representative illustration of the transcortical approach to an insular glioma located in zone II. A corticectomy through “silent” cortex obviates the need for retraction and opens a wide surgical corridor to the tumor. Copyright Barrow Neurological Institute. Published with permission.

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    Representative illustration of the transsylvian approach to an insular glioma located in zone II. Significant frontal lobe retraction may be required to gain adequate access to the insula. Copyright Barrow Neurological Institute. Published with permission.

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