- Horizontal plane in sagittal view, bisection line along the sylvian fissure
- Perpendicular plane intersected at the level of the foramen of Monro
(existing of the resulting quadrants)
- Zone I: anterior-superior
- Zone II: posterior-superior
- Zone III: posterior-inferior
- Zone IV: anterior-inferior
- for tumors occupying > 1 zone, write e.g. "Zone I + II"
- tumors occupying all 4 zones are defined as "giant"
ReferenceSanai N, Polley M-Y, Berger MS. Insular glioma resection: assessment of patient morbidity, survival, and tumor progression. J Neurosurg 2010; 112:1-9.