Transcallosal-Transchoroidal Approach for a Symptomatic Third Ventricular Cavernous Malformation in a Pediatric Patient: Surgical Video

Abstract

Cavernous malformations of the third ventricle are rare, deep-seated lesions that pose a formidable surgical challenge due to the rich, surrounding anatomy. Despite the potential morbidity of surgical treatment, the possibility of catastrophic, spontaneous hemorrhage in this location is even more feared and aggressive treatment is warranted, especially if the patient had suffered previous hemorrhages and is currently symptomatic. We demonstrate this approach (Video 1) on a 16-year-old boy who presented with right-sided hemiparesis (power grade 4), intense headaches, difficulties with learning and concentration, and memory loss, mainly affecting short-term memory. The patient had a previous unsuccessful excision at another center 3 months after initial hemorrhage. The absence of hydrocephalus and medial thalamic location favored a modified transcallosal transchoroidal (or subchoroidal) approach. Due to the anatomy of the lesion, no other microsurgical approaches were considered. The surgery at our center (second attempt) was performed 5 months after initial hemorrhage. The head was placed in neutral position, with a slight elevation of the vertex and the midline in a vertical position. A callosotomy had already been performed during the patient's first excision attempt at another center. Although dissection through the tela choroidea is commonly performed medially to the choroidal fissure when one wants to enter the third ventricle, we chose to carefully dissect through this structure laterally, because this thalamic lesion extended almost into the ependymal surface of the third ventricle. This way, the choroidal plexus became a protective cushion for the fornix. On entering the third ventricle, a mulberry-like lesion was readily identified and the cavernoma was located. The central contents of the cavernoma were dissected initially, causing relative deflation of the lesion and more maneuverability to dissect it away from the surrounding structures. Neuromonitoring was used to avoid brainstem injury. Postoperative magnetic resonance imaging showed complete resection with no signs of hemorrhage or ischemia. The patient was discharged on postoperative day 5 with no new neurologic deficits. The patient was also able to return to school after 1 month and showed complete recovery. Unfortunately, neuropsychologic evaluation was unavailable to understand his improvement better. Microsurgical dissection images in this video are a courtesy of the Rhoton Collection, American Association of Neurological Surgeons (AANS)/Neurosurgical Research and Education Foundation (NREF).

Keywords: Cavernoma of the third ventricle; Cavernous malformation; Cavernous malformation of the third ventricle; Third ventricular cavernous malformation; Transcallosal; Transcallosal-transchoroidal approach; Transchoroidal.