Transsylvian versus transcortical approach to insular glioma: analysis of the extent of resection and postoperative neurological complications in propensity score-matched comparative patient cohorts.

Objective: This study aimed to analyze the comparative tumor resection rates and complication profiles of the transsylvian (TS) and transcortical (TC) approaches to the insular glioma (IG) and emphasize the concept of onco-microneurosurgery as a key to surgical success in these difficult areas.

Methods: A retrospective analysis of a single surgeon's prospectively maintained data of surgically resected, newly diagnosed IGs in adult patients (≥ 18 years old) was conducted. Propensity score matching was performed with a tolerance limit of 0.05 for comparison of the TS and TC cohorts. The extent of resection (EOR) was categorized with 90% resection as a cutoff. Neurological complications persisting beyond 3 months were considered permanent complications. These two variables were combined to derive a Composite Postoperative Outcome Index (CPOI) and graded as 0, 1a, 1b, or 2.

Results: Fifty-two patients (male-to-female ratio of 2.25:1) were studied, with 26 patients in each group. Radical tumor resection (≥ 90%) was obtained in 77% patients (n = 40), with transient and permanent neurological complication rates of 46.2% (n = 24) and 15.4% (n = 8), respectively. A significantly higher rate of maximal safe resection (CPOI grade 0) was obtained using a TS approach for the entire TS cohort (p = 0.008), as well as subgroups of non-giant segmental IGs (p = 0.011) and those with specific Berger-Sanai zone II involvement (p = 0.01). The TC approach was found to be significantly safer in giant IGs when a subtotal resection was performed (p = 0.03). Permanent neurological complications with ≥ 90% EOR (CPOI grade 1b) were significantly higher in the TC group (p = 0.009), including non-giant segmental IGs (p = 0.001) and those specifically involving Berger-Sanai zone II (p = 0.01) of the insula. Long-term functional status and disease progression were similar in both groups.

Conclusions: These results suggest the continued role of the TS approach in IG resection in the contemporary era. Irrespective of the approach, the key variable appears to be a meticulous microsurgical technique, supplemented by the available adjuncts, in the preservation of perforator arteries and subcortical circuitry. Thus, an optimally designed, individual institution-tailored hybrid onco-microneurosurgical approach is the most pragmatic approach to IGs.