Anterior transpetrosal approach for petroclival tumors

Methods: The petroclival or prepontine tumors originating medial to the trigeminal nerve include meningiomas, trigeminal neurinomas, laterally extended chordomas and prepontine epidermoids. They frequently show middle fossa or parasellar extensions, and have been one of the difficult tumors making necessary a combined large craniotomy or multiple step surgery. Here I will present a surgical method of tumor removal through a key hole, epidurally created in a petrous apex. The technical points are presented based on my experience of 84 cases. This approach has the following advantages: (1) One-staged epidural surgery to the petroclival and dumbbell parasellar-clival lesions through a small craniotomy. (2) Minimal venous complication compared to the presigmoid approach. (3) Minimal facial and lower cranial nerves injury by jumping into the petroclival area medial to the IAM. (4) Bloodless tumor removal being possible by detachment of the tentorial artery. (5) Hearing preservation by limited petrous resection. More than two-thirds of the petroclival tumors were operated by this approach alone. Even larger tumors could be accessible in case the attachment was limited in the upper half of the clivus, and medial to the internal auditory canal. Partial labyrinthectomy or the second staged suboccipital approach was added for tumors with wider attachment. For the tumors with high extension over the posterior clinoid, the zygomatic arch was removed to reduce the retraction on the temporal lobe. Results: There was no perioperative mortality. Only four patients with petroclival meningioma were disabled, and others (95%) were independent. The tumor was totally removed in 90% of neurinomas or epidermoids, 64% of meningiomas and 50% of chordomas. The tumor invasion into the cavernous sinus or the tumor adhesive to the brain stem had a course of subtotal resection. The residual tumors were treated by radiosurgery in 12 patients. The tumor recurred in 5 (6%), and 3 patients died (3.6%) during an average 7-year follow-up period.