Endonasal odontoidectomy for basilar impression and brainstem compression due to radiation fibrosis.

INTRODUCTION Basilar invagination and basilar impression both refer to the displacement of the odontoid process into the foramen magnum, although the former is congenital and the latter is due to secondary etiology. Many etiologies for basilar impression exist, including trauma, Paget’s disease of the bone, osteogenesis imperfecta, rickets, and rheumatoid pannus. To our knowledge there have been no reports of basilar impression caused by radiation fibrosis of the odontoid process. We present this case with the subsequent novel indication for an endonasal transclival odontoidectomy. A 66-year-old female with a history of advanced tonsillar carcinoma treated with primary radiation therapy 6 years prior presented with neck pain and falls. She was significantly deconditioned, wheel-chair bound, with progressive wasting, fatigue, cervical instability, and pain. She also exhibited significant trismus (1 cm). Computed tomography (CT) imaging revealed basilar impression with severe narrowing of the spinal canal to 6 mm at the level of the foramen magnum along with brainstem compression (Fig. 1A,B). Given her significant trismus, a transoral approach to the odontoid was not a viable option without a mandibulotomy. The nasopalatine line showed that transnasal access to the odontoid process was feasible. We provide a detailed description and video of the surgical approach (Video 1).