Congenital deformation of the posterior arch of the atlas: Subluxation of the atlanto-axial joint with temporary quadriplegia.

Instabilities of the craniocervical junction can be of rheumatic, traumatic, or congenital origin. The reported patient has a congenital malformation of the cervical spine, which is frequently observed in patients with Klippel-Feil syndrome. Her posterior arch of the atlas (C1) is hypoplastic and a chronic subluxation of the atlanto-axial joint would be possible. Although most common fusions in Klippel-Feil syndrome patients exist at C2/3, the majority of studies about Klippel-Feil syndrome deal with pediatric or adolescent individuals. Through extreme flexion of her neck, there was a compression of the spinal cord by the odontoid process. This led to a quadriplegia lasting about 10 min. Over the following weeks, all of her symptoms started to diminish. This situation turned out to be the third episode involving temporary neurological disorders in this 60-year-old female's life.