Tumor Size is the Most Significant Predictor of Preoperative Neuropsychological Deficits in Patients with Glioblastoma

Introduction: Glioblastoma (GBM) is an aggressive brain tumor where maximal safe resection is standard treatment. While increasing extent of resection improves outcomes, it can also cause functional impairment. In addition to anatomic/functional imaging and standard neurologic exam, neuropsychological (NP) testing (a more detailed exam of neurologic functioning) can aid in treatment decisions. NP testing has been associated with improved outcomes, but there remains a paucity of evidence relating the location of GBM to specific NP deficits. This study investigates the relationship between GBM location and preoperative NP deficits in patients with GBM.

Methods: 43 consecutive patients with newly diagnosed GBM who underwent preoperative NP testing were included. Tumors were masked on T1 weighted images in MRIcron and normalized to the Montreal Neurological Institute (MNI) coordinate system using SPM12. Voxel based lesion mapping (VLSM) was completed with NiiStat. The impact of tumor location and size on RBANs index scores was calculated with independent t-test, ANOVA, and linear regression.

Results: Temporal (n=15), frontal (n=14), and multilobar (n=8) were the most common tumor locations. The median tumor volume was 26.5 mL. Left hemisphere tumors were associated with worse immediate memory (p = 0.005) and language ability (p = 0.001). Tumor size was associated with worse immediate memory (p < 0.001), visuospatial skills (p = 0.03), language skills (p < 0.001), attention (p = 0.031), and total RBANs score (p = 0.001). On VLSM analysis, only language ability localized (to the left inferior longitudinal fasciculus).

Conclusion : These data suggest that GBM size is the most prominent driver of neuropsychological deficits rather than lobe, with hemisphere remaining an important factor. Furthermore, these data support plasticity and network theory of function in GBM, adding to the body of evidence supporting the development and use of functional imaging modalities for preoperative planning in patients with GBM.