Contralesional macrostructural plasticity of the insular cortex in patients with glioma: A VBM study

To assess the homotopic structural plasticity in case of unilateral damage of the insula.

To detect changes in gray matter volumes of the contralesional insula from structural MRIs, we used voxel-based morphometry (VBM) in a sample of 84 patients with a diffuse low-grade glioma invading the left insula (insL group; n = 47) or the right insula (insR group; n = 37).

The region of interest-based VBM analysis highlighted a large cluster of voxels with gray matter volume increase in the contralesional insula in both patient groups (k = 2,214 voxels for insL and k = 879 voxels for insR, p < 0.05, family-wise error corrected) compared with 24 age-matched healthy controls. Gray matter volume was increased for the entire insula (t ₆₉ = 3.63, p = 0.0016 for insL; t ₅₉ = 3.54, p = 0.0024 for insR, Bonferroni corrected), whereas no significant changes were found in 2 control regions for both patient groups. Furthermore, an increase of 24.6% and 31.6% in the gray matter volume was observed in the insula-related VBM cluster for insL and insR patients, respectively, compared with healthy controls (t ₆₉ = 7.39, p = 2.59 × 10^-10 and t ₅₉ = 7.51, p = 3.61 × 10^-10).

The reported results demonstrate that slow-growing but massive lesion infiltration of the insula induces marked increase of gray matter volume in the contralateral one. Our findings give support for a homotopic reorganization that might be a physiologic basis for the high level of functional compensation observed in patients with glioma.