Parasellar Schwannomas: Extradural vs Extra-Intradural Surgical Approach.

BACKGROUND

Schwannomas of the parasellar region may arise from the trigeminal, oculomotor, trochlear, and abducens nerves.

OBJECTIVE

To define the tumor origin, location, and dural relationship (extradural vs extra-intradural vs cisternal) on preoperative magnetic resonance imaging (MRI), in order to plan the best surgical approach (purely extradural vs extra-intradural).

METHODS

Twenty-four patients with parasellar schwannomas who underwent surgery were retrospectively analyzed. Twenty arose from the trigeminal nerve (7 intracavernous and 13 within the Meckel's cave), 3 from the oculomotor nerve, and 1 from the abducens nerve. The preoperative identification of the tumor location (extradural vs extra-intradural vs cisternal) and the nerve of origin was defined on MR sequences. All patients were operated on through a pterional approach (extradural or extra-intradural route).

RESULTS

The tumor location was correctly defined on MRI in 22 out of 24 cases (92%) and the nerve of origin in 22 (92%). An extradural approach without intradural exploration was performed in all 5 intracavernous trigeminal schwannomas, in 11 out of 13 of the Meckel's cave, and in 2 schwannomas of the oculomotor nerve. Two schwannomas of the Meckel's cave with transgression of the medial dural wall, 1 of the oculomotor nerve, and the abducens nerve schwannoma required an extra-intradural approach. Complete tumor resection was obtained in 19 out of 24 cases (80%).

CONCLUSION

The pterional extradural approach is sufficient for Dolenc type I and II trigeminal schwannomas, excepting for those transgressing the inner dural layer. Schwannomas of the oculomotor and abducens nerves with cisternal location require an extradural-intradural approach.