Os Odontoideum Clinical Presentation

Updated: Apr 07, 2021
  • Author: Eeric Truumees, MD; Chief Editor: Jeffrey A Goldstein, MD  more...
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A significant but unknown percentage of those with os odontoideum remain asymptomatic. In this population, os odontoideum may be detected incidentally after screening or after an unrelated trauma. Given the frequency of asymptomatic os odontoideum, when symptoms do occur, it is difficult to determine with certainty that the os odontoideum is the true cause. Symptoms of os odontoideum may include the following:

  • Local mechanical neck pain
  • Torticollis and headache
  • Neurovascular symptoms

More rarely, patients may present with thoracic pain only. [48]

In patients with cervical instability, hypermobility of C1 on C2 may lead to direct compression on the spinal cord or embarrassment of its blood supply. As a result, neurologic symptoms may develop. [49, 50]  These neurologic symptoms range from a transitory episode of diffuse paresis following trauma to progressive myelopathy to complete spinal cord injury. [51]  Weakness and ataxia usually predominate over sensory changes.

Less frequently, atlantoaxial instability results in vertebral artery compression precipitating neurovascular symptoms. These vascular symptoms arise from the cervical cord and brainstem ischemia and encompass a bewildering array of signs and symptoms. Early sequelae include ataxia, syncope, vertigo, and visual disturbances. Later, cerebellar and brainstem infarcts and seizures are seen. [52, 53]  In one report, onset of Ondine’s curse (central hypoventilation syndrome) in an 18-year-old was ascribed to os odontoideum. Sudden death is rare but can occur. [54]


Physical Examination

When os odontoideum is suspected, a thorough physical examination is mandatory. Begin with a complete neck and cervical spine examination. Evaluate for tenderness, range of motion (ROM), and associated anomalies. A careful neurologic examination should include assessment of cerebellar and brainstem function, gait evaluation, and a Romberg test. In patients with atlantoaxial instability, upper-motor-neuron findings are commonly identified and may include spasticity, hyperreflexia, clonus, and proprioceptive loss.