Craniocervical instability (CCI) is a medical condition where there is excessive movement of the vertebrae at the atlanto-occipital joint and the atlanto-axial joint, that is, between the skull and the top two vertebrae (C1 and C2). This can cause neuronal injury and compression of nearby structures including the spinal cord, brain stem, vertebral artery or vagus nerve, causing a constellation of symptoms. It is frequently co-morbid with atlanto-axial instability, Chiari malformation and tethered cord syndrome.
