LAUSR

BACKGROUND Neuroendoscopy offers wide and close surgical views with fine illumination, even in deep surgical sites. Furthermore, transcylinder surgery has the advantage that a tubular retractor can protect critical neurovascular structures in the surgical corridor. These advantages of neuroendoscopy and transcylinder surgery can contribute to safer and less invasive surgical approaches for deep-seated fourth ventricular lesions, for which various critical neurovascular structures exist along the surgical route. CASE DESCRIPTION A 54-year-old man with a fourth ventricular cavernoma underwent tumor resection via the endoscopic transcylinder trans-Magendie foraminal approach. A 6.8-mm transparent sheath (cylinder) was introduced into the fourth ventricle via the foramen of Magendie without incisions in the inferior medullary velum or the tela choroidea, resulting in the minimal retraction of and trauma to critical neurovascular structures in the surgical corridor. Under the view of a 2.7-mm rigid neuroendoscope, the lesion was completely removed with preservation of a venous anomaly on the ventral side of the aqueduct of Sylvius. Neuroendoscopy could offer a fine surgical view even under continuous irrigation with artificial cerebrospinal fluid; it prevented collapse of the fourth ventricle and facilitated anatomical understanding by the surgeons. The postoperative course was uneventful. CONCLUSIONS Our novel approach can be an effective surgical option for fourth ventricular lesions with minimal cerebellar retraction and injury.