BACKGROUNDIn recent years, keyhole microsurgery has become an important subject of modern minimally invasive neurosurgery. In this study, minimally invasive techniques avoiding unnecessary tissue injuries were applied to refine traditional approaches for the removal of third ventricular tumors within a limited operative filed.

METHODSIndividualized keyhole approaches were designed according to the characteristics of third ventricular tumors and their growth patterns. A series of keyhole approaches such as supraorbital subfrontal approach, infratentorial supracerebellar approach, interhemispheric transcallosal approach, pterional approach were taken to enter the third ventricle anteriorly, posteriorly, superiorly or laterally, respectively. A total of 34 removed tumors in or extended into the third ventricle included 11 craniopharyngiomas, 10 pituitary adenomas, 2 pinealomas, 1 cholesteatoma, 3 germinomas, and 7 gliomas.

RESULTSTotal tumor resection was done in 27 (79.4%) of the patients, and subtotal resection in 7 patients (20.6%). Residual tumor was due to tight adherence of germinoma to the vein of Galen (1 patient), craniopharyngioma to the pituitary stalk (3), supratentorial extension of pineal region gliomas (1), suprasellar extension of gliomas (1) and giant pituitary adenoma (1). Complications such as brain contusion, postoperative hemorrhage and infection were not associated with keyhole approaches. Extended incision or enlarged bone flap was not made because of episode during operation or inadequate exposure.

CONCLUSIONSKeyhole approaches are safe, effective and minimally invasive in the surgical treatment of tumors deeply seated in the third ventricle. Individualized keyhole approach ensures a successful treatment. Tumors in the upper middle part of the third ventricle can be exposed by the interhemispheric transcallosal keyhole approach. Tumors of the posterior third ventricle may be well exposed by the infratentorial supracerebellar keyhole approach. Tumors of the anterior third ventricle can be entered by either a supraorbital subfrontal keyhole approach or a pterional keyhole approach.