Unilateral Occipital Transtentorial Approach with Multimodal Assistance for Resection of Large Supracerebellar Hemangioblastomas: Preliminary Experience of 2 Cases

Endoscopic Occipital Transtentorial Approach for Supracerebellar Lesions

The occipital transtentorial approach (OTA), which is often applied for superior cerebellar lesions, has an inevitable risk of homonymous hemianopsia due to the retraction of the occipital lobe. The endoscopic approach provides increased visibility of the surgical field due to the wide-angled panoramic view and is minimally invasive in approaching deep brain lesions compared to the conventional microscopic approach. However, little is known regarding endoscopic OTA for the removal of cerebellar lesions. We experienced a case of a hemangioblastoma in the paramedian superior surface of the cerebellum that was successfully treated with endoscopic OTA combined with gravity retraction while avoiding postoperative visual dysfunction. A 48-year-old woman was diagnosed with a hemangioblastoma in the superior surface of the cerebellum. She underwent tumor removal with endoscopic OTA combined with gravity retraction of the occipital lobe instead of using brain retractors. The narrower space was sufficient for surgical manipulation with a panoramic view obtained by endoscopy. The simultaneous observation of the lesion with both an endoscope and a microscope revealed the superiority of infratentorial visualization with an endoscope. Gross total removal was achieved with no postoperative complications, including visual dysfunction. Endoscopic OTA may reduce the risk of postoperative visual dysfunction because of its minimally invasive nature, which is enhanced when combined with gravity retraction. Additionally, the panoramic view of the endoscope allows favorable visualization of an infratentorial lesion, which is otherwise hidden partly by the tentorium. The use of endoscopy is compatible with OTA, and endoscopic OTA could be an option for superior cerebellar lesions for avoiding visual dysfunction.

Selection of surgical approach for cerebellar hemangioblastomas based on venous drainage patterns

Cerebellar hemangioblastomas remain surgically challenging because of the narrow, deep surgical corridors and tumor hypervascularity. Various surgical approaches are used according to the location, but optimal approaches have not been established. We propose a system of surgical approaches based on the venous drainage systems to facilitate surgical planning and achieve acceptable neurological outcomes. Cerebellar hemangioblastomas were divided into five types based on the main drainage systems: suboccipital hemangioblastomas draining to the transverse sinus (TS) or torcula, tentorial hemangioblastomas draining to the tentorial sinus or straight sinus, petrosal hemangioblastomas draining to the superior petrosal sinus (SPS), quadrigeminal hemangioblastomas draining to the galenic system, and tonsillar hemangioblastomas draining to the TS or torcula in conjunction with jugular bulb or SPS. Microsurgical approaches and patient outcome were retrospectively reviewed according to this classification. This study included 17 patients who underwent 21 operations for resection of 19 cerebellar hemangioblastomas, classified into 9 suboccipital, 4 tentorial, 2 petrosal, 2 quadrigeminal, and 2 tonsillar. Standard suboccipital craniotomies were utilized for suboccipital hemangioblastomas, the occipital transtentorial approach (OTA), and supracerebellar infratentorial approach for tentorial hemangioblastomas, the retrosigmoid approach for petrosal hemangioblastomas, OTA for quadrigeminal hemangioblastomas, and midline suboccipital approach for tonsillar hemangioblastomas. Gross total resection was achieved in all patients except one. Two patients with large hemangioblastomas (tonsillar and quadrigeminal) required second-stage operation which finally achieved gross total removal. No single approach had a significantly higher incidence of postoperative neurological deficits. Selection of the optimum surgical approach for cerebellar hemangioblastomas was successful based on the main drainage systems. Understanding of tumor growth and extension with respect to the venous drainage system is critical to select the appropriate surgical approach.