SAT0513 Osteoid Osteoma of The Odontoid Process of The Axis: A Rare Cause of Neck Pain

Background Osteoid osteoma is painful benign tumor that comprises approximately 3% of all bone tumors and approximately 10% of all benign bone tumors. Most of the cases occur in the first three decades and two to three times more frequently in men than in women. The tumor is very uncommon after the age of 40 years or during infancy. More than 50% of osteoid osteomas involve long tubular bones especially those of the lower extremities. Osteoid osteoma of the spine is relatively uncommon. Pain is the primary symptom of initial and recurrent disease, although reports of osteoid osteoma without the presence of pain exist. It is often difficult to diagnose, especially when the patient does not complain of pain. Objectives Here we report our patient who had an osteoid osteoma at the odontoid process of the second cervical vertebra (axis). Case presentation A 48-year-old woman was admitted to the of physical medicine and rehabilitation department with an 8-month history of neck pain. There was no history of previous injury. For the first 4 months, she had intermittent neck pain, but there after severe neck pain developed during the nighttime that sometimes kept her awake. Her neck pain was relieved transiently by non-steroidal anti-inflammatory drugs (NSAIDs). The pain was worsened 4 months prior to presentation and was associated with frequent occipital headaches. External immobilization with a soft neck collar could not control her symptoms. Physical examination revealed limitation of rotation and extension with neck pain. Neurologic examination was normal. There was no spinal tenderness. Her laboratory data was within the normal ranges. Computed tomography showed an oval nidus and marked sclerosis around the lesion at the odontoid process of the axis (Figure 1A-C). Since the patient refused surgery and considering the benign nature of osteoid osteoma, we prescribed NSAID to the patient. With the treatment, the patient9s symptoms improved and the range of motion of the cervical spine was also recovered. At one-year follow-up, the patient is free of symptoms with the conservative treatment. Conclusions Osteoid osteoma most frequently involves the posterior vertebral elements. An osteoid osteoma of the odontoid process of C2 is rare. Previously, only three cases between the ages 14–18 were reported to have osteoid osteoma involving the odontoid process of the axis. To the best of our knowledge this is the first case of osteoid osteoma involving the odontoid process in an adult female patient. Our patient demonstrated the typical radiological appearance of osteoid osteoma on imaging modalities. Since surgery is risky regarding the damage of the spinal cord, and/or vertebral artery, conservative approach should be considered for the treatment of osteoid osteoma of the cervical spine, especially the odontoid process. Surgery may be suggested to the patients who do not respond to palliative treatment. Disclosure of Interest None declared