Transcavum septum pellucidum interforniceal approach for the colloid cyst of the third ventricle Operative nuance.

BACKGROUND: Despite their unfavorable locations, lesions of the third ventricle can be successfully removed via an interhemispheric, transcallosal approach. In cases with normal ventricular anatomy, this approach requires unilateral or bilateral identification of the foramen of Monro.

TECHNIQUE: However, in the presence of abnormal ventricular configuration such as cavum septum pellucidum (CSP), this basic knowledge needs to be modified. After routine callosotomy, there may be a confusion while entering the CSP due to the invisualization of ventricular landmarks such as the foramen of Monro, thalamostriate vein, and choroid plexus. The floor of the CSP is formed by the fornices, and a direct approach to the interforniceal area is easier via the CSP. But the interforniceal approach is not a routine way to reach the third ventricle, which has higher risks than other modalities.

CONCLUSION: This approach should be planned and used in selected cases of the CSP. Opening of the walls of CSP is recommended both to expose both the foramen of Monro and to gain safe access to the third ventricle before manipulating the interforniceal area.