2026 Proffered Presentations
S014: TRANS ATLANTO OCCIPITAL MEMBRANE APPROACH TO THE FOURTH VENTRICLE AND BRAINSTEM THROUGH THE FORAMEN OF MAGENDIE WITHOUT CRANIOTOMY
Alexander Sanikidze, MD, PhD; David Pitskhelauri, MD, PhD; Alexander Konovalov,, MD, PhD; Igor Pronin, MD, PhD; Elina Kudieva, MD, PhD; Ruslan Ishkinin, MD, PhD; Shakhzod Tursunkulov, MD; Tatiana Melnikova-Pitskhelauri; Burdenko Neurosurgery Center
Introduction: Improvements in surgical microscopy, microsurgical techniques, endoscopy, and diagnostic methods have made minimally invasive keyhole surgery increasingly popular and have contributed to improved outcomes in the surgical treatment of a wide variety of intracranial pathologies.
For this reason, we propose the trans-atlanto-occipital membrane approach to the fourth ventricle when the distance between the opisthion and the posterior arch of the atlas reaches 10–17 millimeters.
Methods: Fifteen patients with lesions of the fourth ventricle and brainstem underwent microsurgical resection through the atlanto-occipital membrane approach without any bone resection. Tumors were localized in fourth ventricle in 11 (73%) patients and in the brainstem in 4 patients (27%). Among these lesions, 14 were tumors and one was a cavernous malformation.
Among the fourth-ventricle tumors, there were 3 (28%) lesions occupying the entire fourth ventricle and 8 (72%) lesions were localized in a caudal part of the fourth ventricle. Among all tumors of the fourth ventricle in 3 (28%) cases, the tumor extended into the cisterna magna through an enlarged foramen of Magendie. Brainstem lesions in all 4 cases were located in the dorsal pons.
According to preoperative MRI and CT scans, the distance between the posterior arch of the atlas and the opisthion ranged from 9.2 to 16.5 millimeters (median 13 millimeters).
The surgery was performed with the patient in the Concorde position. The trajectory of the surgical approach was directed from the skin incision located above the C2 spinous process and extended 3.5–4 centimeters rostrally along the midline, providing a low-angle surgical trajectory to the foramen of Magendie.
Results: Gross total resection was achieved in 12 patients (80%), subtotal resection in one, partial resection in one, and open biopsy in one patient. The rate of gross total resections was higher in the fourth-ventricle group - 10 of 11 patients (91%)—compared with the brainstem group—one of 4 patients (25%, cavernous malformation). The duration of surgery from skin incision to skin suturing ranged from 54 to 165 minutes (median 97 minutes).
Surgical complications occurred in only one patient (meningoencephalitis), which was successfully treated with intravenous antibiotic therapy. A pseudomeningocele (8.9 cubic centimeters and 14.7 cc) was observed in two patients, which resolved within two months after the surgery. No CSF leakage was observed. After the operation, one patient experienced pain in the neck area with a VAS score of 3, and pain was barely noticeable (46.7% of patients) or completely absent (46.7% of patients) in the remaining fourteen patients.
Conclusions: This minimally invasive trans-atlanto-occipital membrane approach to the fourth ventricle and dorsal brainstem tumors provides adequate visualization and a working space for surgery to the caudal part of the fourth ventricle and brainstem when the patient’s anthropometric parameters are suitable.