A retro-odontoid pseudotumor treated with fixation and tumor resection by the lateral approach: illustrative case

Abstract

Background: A retro-odontoid pseudotumor is not a condition that requires resection. However, pathological diagnosis is required when a tumor such as a meningeal tumor or chordoma is suspected. The authors report a case of a large lesion treated with posterior fixation and tumor resection using a lateral approach.

Observations: A 77-year-old man visited the authors' department complaining of neck pain and decreased dexterity of the upper extremities. Magnetic resonance imaging showed a large, beak-shaped lesion behind the dens and severe compression of the spinal cord. Surgery consisted of occipitocervical-C2 fixation, followed by tumor resection with a left lateral approach. The pathological diagnosis was consistent with a retro-odontoid pseudotumor. The tumor was resected to a relatively large extent and shrank over time, leading to complete disappearance.

Lessons: Pathological examination is also possible with a posterior approach if the tumor can be reached through the lateral edge of the dura. In that situation, the amount of resection is limited, and there is a risk of spinal cord compression. Intradural dissemination of tumors is a concern with the transdural approach. If tumor resection by the posterior approach is difficult, the lateral approach can facilitate tumor resection.

Keywords: CT = computed tomography; MRI = magnetic resonance imaging; O = occipitocervical; lateral approach; retro-odontoid pseudotumor; tumor resection.

FIG. 1.

Preoperative imaging studies. Radiographs in the flexion position (A), neutral position (B), and extension position (C) show reduced mobility of the subaxial spine. The atlantodental interval was 3.3 mm. MRI showed a large, beak-shaped lesion behind the dens and severe compression of the spinal cord (D and E). CT showed bone components in the compression lesion behind the dens (F and G).

FIG. 2.

Intraoperative findings. O–C2 fusion was performed (A). The patient’s position was changed from the prone position to the lower right lateral decubitus position (B). The locations of C1 and C2 were marked on the skin with reference to the fluoroscopy (C), and the 10-cm skin incision was made to pass over the sternocleidomastoid muscle (D).

FIG. 3.

The sternocleidomastoid muscle was detached from the occipital bone and retracted anteriorly, and the splenius capitis muscle was moved posteriorly (A). The inferior oblique muscle was detached to expose the C1 transverse process (B). The transverse foramen of C1 was opened with a high-speed drill (C) to protect the vertebral arteries (red tape). The resected lesion was submitted for pathological examination (D).

FIG. 4.

Postoperative imaging studies. Anteroposterior (A) and lateral (B) radiographs. CT performed 1 week after the operation revealed that the amount of excised C1 was the posterior half of the C1 transverse foramen (C and D). MRI performed 5 months after the operation showed that the retro-odontoid pseudotumor had completely disappeared (E and F).