Coronal T2-weighted MRI at the level of the optic chiasm as an imaging parameter of the anterior perforated substance. The imaginary line (the Optic Chiasm – Insular Recess line) is drawn, from the optic chiasm medially to the insular recess laterally, to identify the anterior perforated substance (yellow line). The Porto Alegre line (Red Line) is as ascendent line from the lateral end of the OC-IR line and represents the lateral limit of the lateral LSTa inside the central core. In cases which the medial border of insular tumor crosses this line medially there is a great probability of involvement of the LSTa by the tumor.