Relationships Between Surgical Approach, Tumor Classification Scheme, and Early Neurocognitive Outcome After Awake Craniotomy for Resection of Insular Glioma

BACKGROUND AND OBJECTIVES: Insular glioma resection harbors similar risk of neurocognitive function (NCF) decline as other tumor locations. However, differences in outcome according to transsylvian vs transcortical surgical approach and tumor characteristics remain unknown. This study investigates the impact of these factors on postoperative changes in neuropsychological status in patients with insular glioma. METHODS: Retrospective review identified 53 patients with newly diagnosed insular glioma (47% high-grade; 75% left hemisphere). All patients underwent awake craniotomy for resection through either the transsylvian (64%) or transcortical (36%) approach. Patients completed neuropsychological testing preoperatively and within 2 months postoperatively. Tumor location was described with Berger-Sanai zones collapsed into anterior, posterior, superior, and inferior groups. Tumor extension was characterized with the Pitskhelauri scheme into insula only, insula with extension (lobar or medial), and predominantly extra-insular groups. RESULTS: A significant postoperative NCF decline was observed across various domains, but most frequently and with largest effect (partial η 2 ) in memory (0.29-0.44) and verbal fluency (0.39). There was no interaction between the surgical approach and the mean change on any NCF test although the transcortical approach was associated with higher frequency of postoperative decline in verbal fluency (61% vs 26%, P = .014). Left hemisphere tumor was associated with poorer outcome in half of the tests administered (all P < .01). Predominantly extra-insular tumors showed a greater reduction in fluency than insula-only tumors ( P = .024), and the number of Berger-Sanai quadrants involved was inversely associated with the change in executive functioning (r = −0.34, P = .018). Poorer executive function outcome was also found in anterior compared with posterior tumors ( P = .014), and recognition memory outcome was worse for inferior than superior insular lesions ( P = .021). CONCLUSION: NCF decline is common in the relatively early term after resection of insular glioma. Outcomes were largely similar across surgical approaches although hemisphere involved, tumor extension, and insular zone localization convey differential domain-specific risk of NCF decline after resection.