title: Microsurgical excision of a retro-odontoid disc hernia via a far-lateral approach: successful treatment of a rare cause of myelopathy: case report.
abstract: OBJECTIVE
  Among mass lesions causing myelopathy at the craniovertebral junction, retro-odontoid intervertebral disc hernias are very rare, with only four such cases reported in the literature.
  
  
  METHODS
  A 77-year-old woman with this rare condition complained of motor and sensory disturbances in her extremities. Magnetic resonance imaging scans demonstrated an extradural mass lesion at the craniovertebral junction, compressing the lower medulla oblongata and the upper cervical cord posteriorly.
  
  
  METHODS
  The lesion, which was partly mucinous cartilaginous and partly fatty and fibrous, was meticulously removed via a left far-lateral approach. The lesion was not neoplastic but was determined to be composed of fibrocartilaginous tissue, consistent with disc material. Postoperatively, the patient's sensory disturbances and motor weakness improved, and magnetic resonance imaging scans demonstrated marked shrinkage of the lesion.
  
  
  CONCLUSIONS
  Sagittal, T1-weighted, magnetic resonance imaging scans demonstrated a low-intensity band between the odontoid process and the body of the axis, which suggested a persistent cartilaginous band. Although upward migration of a herniated disc from the lower cervical spine and degeneration of retro-odontoid ligaments might be possible causes, a persistent cartilaginous band extending between the odontoid process and the body of the axis was considered to be the more likely origin of the retro-odontoid intervertebral disc hernia. Because the far-lateral surgical approach does not require retraction of the cervical cord and provides safe access to the lesion at the craniovertebral junction, it is a suitable surgical method for this condition.
authors.affiliation: Department of Neurosurgery, Teikyo University Ichihara Hospital, 3426-3 Anegasaki, Ichihara City, Chiba 299-0111, Japan. akirakun@med.teikyo-u.ac.jp
authors.forename: Akira
authors.initials: A
authors.lastname: Matsuno
authors.forename: Michi
authors.initials: M
authors.lastname: Nakashima
authors.forename: Mineko
authors.initials: M
authors.lastname: Murakami
authors.forename: Tadashi
authors.initials: T
authors.lastname: Nagashima
mesh_terms: D000368:Aged; D001268:Atlanto-Axial Joint / Q000473:pathology / Q000601:surgery; D001368:Axis, Cervical Vertebra / Q000473:pathology / Q000601:surgery; D019299:Decompression, Surgical; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D007405:Intervertebral Disc Displacement / Q000175:diagnosis / Q000473:pathology / Q000601:surgery*; D008279:Magnetic Resonance Imaging; D008866:Microsurgery; D009777:Occipital Bone / Q000473:pathology / Q000601:surgery; D009809:Odontoid Process / Q000473:pathology / Q000601:surgery*; D013117:Spinal Cord Compression / Q000175:diagnosis / Q000473:pathology / Q000601:surgery*