The Transventricular Preforniceal Approach Can Be Used in Cases Where the Space between the Anterior Commissure and the Venous Angle Is Enlarged.

Surgical treatment for tumors located at the third ventricle and/or hypothalamic regions is significantly challenging due to the surrounding crucial neural and vascular structures. In 2013, the transventricular preforniceal approach was reported for exophytic chiasmatic/hypothalamic astrocytomas extending into the anterior third ventricle. Although this approach may be safe and effective for selected patients, this approach can only be applied when the space between the anterior commissure and the fornix is stretched by the tumor. Here, we report an easy method to preoperatively identify patients who are amenable to tumor removal via the transventricular preforniceal approach. Four glioma cases whose tumors were successfully removed via the transventricular preforniceal approach were studied. This included a hypothalamic glioblastoma case and three optic hypothalamic pilocytic astrocytoma cases. Preoperative three-dimensional contrast-enhanced magnetization-prepared rapid gradient echo was obtained from all cases for use in the surgical navigation system. Using this image, we analyzed the method to preoperatively define the cases for whom this approach is applicable. We were able to preoperatively identify the anterior commissure in three cases and the venous angle in all cases using the magnetization-prepared rapid gradient echo images. Posterior shift of the venous angle detected in these cases indicated that the space between the anterior commissure and fornix was stretched by the tumor. The tumor was successfully removed in these cases without severe neurological deterioration. Using three-dimensional contrast-enhanced magnetic resonance imaging to detect the posterior shift of the venous angle assists in preoperatively identifying hypothalamic glioma patients who are amenable to the transventricular preforniceal approach.