Microsurgical anatomy and clinical application of infratentorial supracerebellar keyhole approach

Abstract To explore the feasibility of applying the infratentorial supracerebellar keyhole approach for removing tumors of pineal region. Infratentorial supracerebellar keyhole approach was performed in 16 cadaveric heads with intracranial vessels perfused by colored latex. The microscopic structure was observed. The anatomic structure was measured with Stryker Navigation System and the data were analyzed with the SPSS 10.0 software. And further, infratentorial supracerebellar keyhole approach was performed in 11 clinical cases with tumors located in the posterior third ventricle and pineal region, based on the individualized imaging features. Only the central group bridging veins on the cerebellum tentorial surface needed to be sacrificed under infratentorial supracerebellar keyhole approach, and other vessels could be preserved well. The distance between the bridging veins of both left and right medial group could reach (35 +/- 6) mm when they were fully dissected, thus offering enough surgical space for applying this keyhole approach. When the culmen of cerebellum was retracted, the pineal body, Galen vein and its tributary, quadrigeminal bodies, even trochlear nerve could be observed. When the underlayer choroid of the third ventricular roof was dissected medially and inferiorly to the posterior choroidal artery, the posterior third ventricle could be reached. If the tentorium of cerebellum was cut open between the straight sinus and the lateral sinus, the surgical field could be enlarged anteriorly and superiorly to the longitudinal fissure region above the tentorium. Eight of the 11 pineal region tumors sized 2-5 cm in diameter were totally removed, and 3 were subtotally resected. For one case, posterior cranial fossa decompression and ventriculoperitoneal shunt were performed postoperatively. Another one patient suffered from transient mutism and steady fixation after surgery. Other patients had no adverse effect. Infratentorial supracerebellar keyhole approach can be applied for removing the pineal region tumors without interfering the adjacent deep venous system, and can enter the third ventricle in a nearly non-traumatic way. If necessary the tentorium can be cut open to expose supra-tentorial structures. It can be regarded as a better choice for surgeries in this region.