title: Retro-odontoid mass without atlantoaxial instability causing cervical myelopathy: a case report of transdural surgical resection.
abstract: BACKGROUND
  Retro-odontoid mass rarely occur in patients with noninflammatory retro-odontoid lesions without atlantoaxial instability. We describe a rare case of retro-odontoid mass without atlantoaxial instability operated on by a transdural approach.
  
  
  METHODS
  The patient was an 83-year-old man who presented with a retro-odontoid mass causing symptomatic cervical myelopathy. Preoperative magnetic resonance imaging (MRI) revealed that the mass was severely compressing the spinal cord. We operated on it via a C1 laminectomy and performed tumor resection by a transdural approach. Pathological findings from the operative specimen confirmed the diagnosis; histopathological examination revealed that the mass contained fibrinoid material, and collagenous tissue with myxoid changes, but no granulation or a granulomatous lesion. Postoperative MRI confirmed spinal cord decompression. The patient's symptoms were alleviated, and he has not had a recurrence or cervical instability in the 7 years since his surgery.
  
  
  CONCLUSIONS
  We successfully used a transdural approach in the present case and have observed no recurrence for 7 years postoperatively. C1 laminectomy is reportedly beneficial, especially for elderly patients, given the risk of other surgical options using an anterior transoral approach or posterior fusion. However, most tumors do not attenuate after C1 laminectomy alone; hence, we think that tumor resection by the transdural approach is one effective method to perform enucleation of the tumor after C1 laminectomy.
authors.affiliation: Department of Orthopaedic Surgery, Graduate School of Medical and Dental Sciences, Kagoshima University , Kagoshima, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Tominaga
authors.affiliation: The Near-Future Locomotor Organ Medicine Creation Course (Kusunoki Kai), Graduate School of Medical and Dental Sciences, Kagoshima University , Kagoshima, Japan.
authors.forename: Takao
authors.initials: T
authors.lastname: Setoguchi
authors.affiliation: Department of Orthopaedic Surgery, Graduate School of Medical and Dental Sciences, Kagoshima University , Kagoshima, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Nagano
authors.affiliation: Department of Orthopaedic Surgery, Graduate School of Medical and Dental Sciences, Kagoshima University , Kagoshima, Japan.
authors.forename: Ichiro
authors.initials: I
authors.lastname: Kawamura
authors.affiliation: Department of Orthopaedic Surgery, Graduate School of Medical and Dental Sciences, Kagoshima University , Kagoshima, Japan.
authors.forename: Masahiko
authors.initials: M
authors.lastname: Abematsu
authors.affiliation: Department of Orthopaedic Surgery, Graduate School of Medical and Dental Sciences, Kagoshima University , Kagoshima, Japan.
authors.forename: Takuya
authors.initials: T
authors.lastname: Yamamoto
authors.affiliation: Department of Medical Joint Materials, Medical Joint Materials, Graduate School of Medical and Dental Sciences, Kagoshima University , Kagoshima, Japan.
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Ishidou
authors.affiliation: Department of Orthopaedic Surgery, Graduate School of Medical and Dental Sciences, Kagoshima University , Kagoshima, Japan.
authors.forename: Kanehiro
authors.initials: K
authors.lastname: Matsuyama
authors.affiliation: Department of Orthopaedic Surgery, Kirishima Orthopaedic Surgery , Kirishima, Japan.
authors.forename: Kosei
authors.initials: K
authors.lastname: Ijiri
authors.affiliation: Department of Orthopaedic Surgery, Yonemori Hospital , Kagoshima, Japan.
authors.forename: Fumito
authors.initials: F
authors.lastname: Tanabe
authors.affiliation: Department of Orthopaedic Surgery, Graduate School of Medical and Dental Sciences, Kagoshima University , Kagoshima, Japan.
authors.forename: Setsuro
authors.initials: S
authors.lastname: Komiya
keywords: Bone; Spinal cord diseases