Cervicomedullary Compression at the Craniovertebral Junction by Clivus Hyperplasia

Abstract

The craniovertebral junction (CVJ), which is composed of the distal third of the clivus, the occiput, the atlas, the axis, and the foramen magnum, is complex anatomically and includes important neurovascular structures1,2. Together, these structures enclose the cervicomedullary junction (CMJ) and the lower four cranial nerves. Signs and symptoms of abnormal conditions affecting the CVJ are varied and typically begin insidiously. They may be referable to the brainstem, cervical cord, cerebellum, cervical nerve roots, or lower cranial nerves or the vascular supply to these structures. Anterior compression at the CVJ can occur in many types of abnormalities: malformations (basilar invagination or cranial settling, atlas assimilation, os odontoideum, and atlantoaxial fixed dislocation), tumor, trauma, chronic inflammatory diseases (most frequently, rheumatoid arthritis [RA]), and osteomyelitis3-7. Not uncommonly, congenital ventral compression of the CVJ is discovered on postmortem examination8. We present an unusual case of anterior CVJ compression in a healthy woman due to hyperplasia of the clivus with horizontal segmentation and degeneration of the atlanto-occipital and atlantoaxial joints. The presenting symptoms were suggestive of carpal tunnel syndrome. The patient was informed that the data concerning the case would be submitted for publication, and she provided consent. A forty-two-year-old female school bus driver presented to our neurology clinic with bilateral upper-arm, forearm, and hand numbness and tingling, which she had experienced for two years; the left side was more symptomatic than the right. She had minimally impaired sensation in the thumb and index finger of the left hand. Deep tendon reflexes were intact bilaterally. Physical examination demonstrated positive Phalen and Tinel signs over the carpal tunnel bilaterally. An electrophysiology study revealed mild demyelination in the left distal median nerve and notable demyelination in the right distal median nerve consistent with bilateral carpal tunnel …