Endoscopic Endonasal Odontoidectomy and Occipitoaxial Fixation for Basilar Invagination With Platybasia and Atlas Occipitalization Associated With Trichorhinophalangeal Syndrome

Basilar invagination is a craniovertebral junction deformity characterized by the upward migration of the odontoid process toward the foramen magnum.This condition is frequently associated with congenital anomalies such as platybasia and atlas occipitalization.On the other hand, trichorhinophalangeal syndrome is a rare autosomal dominant skeletal dysplasia characterized by distinctive craniofacial features, brachydactyly, and abnormalities in endochondral ossification.This study describes the surgical treatment performed in a 39-year-old man with genetically confirmed trichorhinophalangeal syndrome and basilar invagination with platybasia and atlas occipitalization.These malformations caused severe ventral cervicomedullary compression.Computed tomography angiography also revealed an aberrant vertebral artery with atlas occipitalization.The procedure was performed in a single session, combining endonasal endoscopic odontoidectomy for immediate anterior decompression with posterior occipitoaxial fixation (C0-C2).To reduce the risk of vascular injury due to the vertebral artery anomaly, C2 translaminar screws were used instead of pedicle or transarticular screws.This approach achieved complete decompression, short stabilization, and rapid, sustained neurological recovery, highlighting hybrid minimally invasive strategies for complex craniovertebral junction pathology.Key aspects are the following: Firstly, endoscopic endonasal odontoidectomy is the standard for ventral decompression, providing a direct route, less oropharyngeal morbidity, and faster recovery.Secondly, in instability, C0-C2 occipitocervical fixation is the minimal sufficient posterior stabilization, avoiding unnecessary multilevel fixation and preserving subaxial motion.Lastly, translaminar instrumentation is advised to reduce vascular injury risk in atypical vertebral artery anatomy, common in craniovertebral junction malformations.