Interhemispheric Transcallosal Interforniceal Approach for Retroforaminal Colloid Cysts of the Third Ventricle: Technical Note & Case Series

BACKGROUND AND OBJECTIVES: Colloid cysts are benign intracranial tumors that are surgically challenging. Their position varies from the foramen of Monro to the Sylvian aqueduct displacing the fornices and internal cerebral veins in different directions. Accordingly, various surgical approaches have been described. Each corridor, microsurgical or endoscopic, carries advantages and drawbacks related to the surrounding anatomy. We present a technical note highlighting key nuances in the management of 4 posteriorly located colloid cysts of the third ventricle, treated using the interhemispheric transcallosal interforniceal approach. A step-by-step description of the technique is provided along with an accompanying surgical video. METHODS: We retrospectively reviewed the cases of colloid cysts operated on at our institution and selected those that were approached by an interhemispheric transcallosal interforniceal route. RESULTS: Cases 1 and 2 were patients with asymptomatic colloid cysts, but with a high risk of acute hydrocephalus. Both had a large colloid cyst with overlying fornices, laterally displaced internal cerebral veins and narrow foramen of Monro. Case 3 was a patient with a recurrent colloid cyst with similar anatomic characteristics that was first operated on endoscopically using a transventricular approach and presented with postoperative memory loss. The second surgery was performed through an interforniceal approach. Postoperatively no cognitive worsening was reported. Case 4 was a young patient previously treated with the placement of a ventriculoperitoneal shunt. Cyst volume increased and a surgery was performed using a transcallosal interforniceal approach with no complication. CONCLUSION: The interhemispheric transcallosal interforniceal approach represents a valuable option to achieve a safe and effective resection of colloid cysts situated posterior to the foramen of Monro, while preserving cognitive function.