Cervical Myelopathy Caused by a Split Atlas Anomaly: A Case
A previously healthy, 18-year-old male patient presented with a 6-month history of paresthesia of both arms and legs, cervical pain, and walking difficulty after a minor neck trauma (he fell from his height and landed on the occiput, with hyperflexion of the cervical spine). His symptomatology was improving gradually, but there was no bowel or bladder dysfunction.

At the time of admission, physical examination revealed a walk with mowing on the right side, pain on palpation of the upper cervical spine, contracture of the paravertebral muscles, and limited cervical range of motion. The neurological assessment revealed pyramidal syndrome with bilateral upper and lower limbs hyperreflexia, bilateral Babinski sign, and Hoffman’s reflex present. Motor function and sensory examination were normal in the left upper limb and lower limbs. In the right upper extremity, motor function was rated 3–4 out of 5, with hypoesthesia in the C7–C8 territory. Furthermore, examination of the perineal area was unremarkable.

Plain radiographs were interpreted as normal, and dynamic radiological assessment did not show any instability. CT scan revealed partial aplasia of the anterior and posterior arches of the C1 vertebra, resulting in a split atlas with a platybasia and basilar impression. MRI showed cord compression at the atlas ring and intramedullary high T2 signal intensity area. It decided to perform a decompressive laminectomy and occipitocervical fusion using a posterior approach because the patient had neurological symptoms. During the procedure, the bony defect in the posterior arch of C1 was replaced by a connective tissue cord, compressing the dural sheath.

The patient underwent laminectomy of C1, the release of the tissue cord, enlargement of the foramen magnum, occipitocervical fixation, and posterior grafting at the expense of the posterior iliac crest. The patient’s symptoms recovered completely 1 month after rehabilitation, and the fusion was consolidated at the 4-month visit. Neck pain completely resolved, the function was normal, and he remained asymptomatic at the 18-month follow-up.