Absence of the odontoid process with atlanto-axial subluxation; anaesthetic aspects.

Anaesthesia in patients with an unstable atlanto-axial joint is fraught with hazards.' Manipulation of the neck during intubation may lead to considerable subluxation in both flexion and extension movements, with pressure from the vertebral body and the odontoid peg. This can significantly reduce the sagittal diameter of the cervical cord, with the possibility of transient or even permanent neurological damage. The case reported is unusual in that in addition to atlanto-axial subluxation the odontoid process was completely absent. CASE HISTORY. A 28-year-old man previously diagnosed as having ankylos-ing spondylitis was to have general anaesthesia for dental extractions. He gave a 12-year history of bilateral temporo-mandibular joint ankylosis requiring three surgical procedures under general anaesthesia, the most recent in 1987 involving gap arthroplasty with insertion of silastic blocks. Postoperative mouth opening was 20 mm. All surgical procedures required blind naso-tracheal intubation as mouth opening was insufficient to allow laryngoscopy. He gave a 10-year history of back pain, was HLA B-27 positive but X-rays of his thoraco-lumbar spine were normal. No cardiovascular or respiratory abnormality was detected. Anaesthesia was induced using thiopentone 300 mg with gallamine 20 mg and alfentanil 1 mg. Gentle manual ventilation was commenced using 1 % halothane in 66 % nitrous oxide in oxygen. Otrivine nasal drops were instilled into both nostrils and blind naso-tracheal intubation was easily performed using a 9 mm cuffed endotracheal tube. Extubation was carried out whilst deeply anaesthetised. Prior to anaesthesia the dental house surgeon had ordered a lateral X-ray of the upper airway, but this was not considered helpful as it really was a lateral view of the cervical spine. Some days postoperatively a radiologist noted that there was marked atlanto-axial subluxation. In follow-up, plain films of the lateral cervical spine in flexion, extension and neutral positions demonstrated considerable