*History of trauma*

Congenital AO fusion with widened ADI

Findings:

There is fusion of C1 to the clivus with a markedly hypoplastic posterior arch of C1. The atlantodental interval is widened. These findings were also present on the MR performed 6 months prior to the acute trauma.

Discussion/Differential Diagnosis:

Congenital atlanto-occipital fusion, also known as C1 assimilation or C1 occipitalization is one of the most common anatomic variants at the craniocervical junction. It is considered a segmentation failure with a fibrous or osseous coalition of the 4th occipital and 1st cervical sclerotomes. Symptomatology varies with the degree of canal narrowing and ligamentous instabilities. If asymptomatic, these are typically left alone if there is no canal narrowing or instability. Surgical treatment may include decompression and fusion. If canal narrowing is present, a syndromic association should be considered such as achondroplasia, mucopolysaccharidosis, or Down syndrome, but it is unlikely that this would be the first or only manifestation of these processes.

This case was prepared with the assistance of Joshua Hall, UC undergraduate

BACK TO MAIN PAGE