Transcallosal transbiforaminal approach to the third ventricle.

BACKGROUND: Colloid cysts are benign intracranial lesions but can show signs of severe obstructive hydrocephalus and present with sudden death. The approaches to colloid cysts have been described by many authors. The treatment modalities can be classified as endoscopic and microsurgical. Bilateral access through the foramen is commonly used with transcallosal surgery to reach the third ventricle but has never been described. Cystic lesions can be excised safely with both approaches but the excision of a solid lesion is still challenging despite advances in microsurgical techniques.

METHODS: After routine callosotomy, each foramen of Monroe can be identified with the landmarks of the lateral ventricle. The foramens can be widened with limited manipulation. The solid lesion can be excised with limited traction of the third ventricle and surrounding neural structures. Tumor control can be achieved with the biforaminal approach but the tumor excision should be performed from the right foramen due left side forniceal memory dominance.

RESULTS: The postoperative period was uneventful, and the patient was discharged without any memory deficit.

CONCLUSION: Manipulation of both fornices increases the risk of significant memory system deficits. Safer and harmless excision can be achieved with the transbiforaminal approach if the tumor excision is performed from the right foramen.