• Ismail Bozkurt, Ulkun Unlu Unsal, Salim Senturk, and Ali Fahir Ozer.
• Department of Neurosurgery, Medical Park Ankara Hospital, Ankara, Türkiye. ibozkurt85@gmail.com.
• Eur Spine J. 2025 Feb 3.

Background & ObjectivesBasilar invagination (BI) represents a complex anomaly of the craniovertebral junction, characterized by the displacement of the odontoid process towards the foramen magnum. Current surgical interventions include anterior decompression and combined anterior-posterior decompression with posterior fusion. Traditional methods for odontoid resection encompass transoral, transnasal, and endonasal approaches. However, these techniques are fraught with significant risks. Furthermore, the restricted exposure provided by the endonasal corridor's anatomical limitations hampers surgical manipulation, prompting spine surgeons to seek alternative techniques. This report details a case of BI managed through an endoscopic posterolateral odontoidotomy, showcasing an innovative surgical approach. We aim to describe our experience in partially removing the odontoid via posterolateral approach with a novel endoscopic technique, preventing the need for additional approach and related complications.MethodsA 16-year-old male patient presented with complaints of imbalance and difficulty swallowing. Clinical examination revealed upper extremity muscle weakness, ataxic gait, and dysphagia. Upon the diagnosis of BI, a posterior occipito-cervical fusion was performed. However, six months postoperatively, the patient returned with exacerbated symptoms. During the subsequent surgical intervention, the odontoid body was resected using a posterolateral transmass endoscopic approach. Due to the patient's neck and shoulder anatomy, cranial angulation of the endoscope was restricted, necessitating the retention of the odontoid tip.ResultsPost-operative CT revealed that the tip was closer to the base and a subarachnoid space was formed. Follow-up CT after a year showed a complete migration of the tip to the base of C2 with a clear decompression of the brainstem.ConclusionOur findings demonstrate that partial or total resection of the odontoid process via a posterolateral approach is feasible using endoscopic techniques. The endoscopic posterolateral transmass odontoidotomy should be considered a viable alternative method and route for patients necessitating partial or total odontoidectomy.© 2025. The Author(s).

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