Basilar invagination associated with brainstem tumor opposite the odontoid process

An 8-year-old girl presented with the symptom of nasal regurgitation and hoarseness of voice. Investigations revealed severe basilar invagination and a large intra-axial pons-medulla brainstem tumor adjoining the tip of the odontoid process. The child underwent lateral mass plate and screw atlantoaxial fixation and attempted craniovertebral junction realignment. Biopsy of the brainstem tumor was done during the same surgical procedure. Histology of the brainstem tumor revealed it to be a pilocytic astrocytoma. Simultaneous presence of brainstem tumor and basilar invagination is a rare clinical association and a complex therapeutic challenge. The possible cause of genesis of brainstem tumor in an unusual location is speculated.