J Neurosurg: Spine / May 2, 2014 DOI: 10.3171/2014.3.SPINE13684 1 ©AANS, 2014 P athology of the craniocervical junction represents one of the more challenging spinal abnormalities in terms of surgical management. Numerous patholo- gies can lead to abnormal degeneration of the craniocervi- cal junction, including osteoarthritis, rheumatoid arthritis (RA), 13,23,25 Down’s syndrome, 25,39 neoplasia, 25 trauma, 1 and Chiari malformation. 13,31 Lesions in this location have been traditionally accessed through an anterior approach to reduce mass effect on the brainstem and high cervical spinal cord. Often a large pannus forms in this location as a result of instability among the osseous and ligamentous elements as well as the joint complexes, leading to an ab- normal ibrous complex. Therefore instability can result in an upward translation of the upper cervical elements into the cranial vault and compress the neural elements at the cervicomedullary junction. This anterior pathology can lead to numerous symptoms including cranial neu- ropathies, 8,30 bulbar pathology, 8,10,11 intracranial hyperten- sion, 8,9 cervical myelopathy, 25,30 respiratory suppression, 25 pain, 8,10,11 and even hydrocephalus. Several terms are used to describe degenerative pa- thology at the craniocervical junction. Benke et al. de- scribe the unique pathologies of “basilar invagination,” “basilar impression,” and “cranial settling.” 3 Basilar in- vagination is a superior protrusion of the dens and loss of skull height due to congenital abnormalities. Basilar impression is attributed to skull base softening, usually caused by an acquired condition such as Paget’s disease or osteomalacia. Cranial settling occurs when there is vertical subluxation of the dens caused by the loss of liga- mentous support structures commonly seen in rheuma- toid 30 or psoriatic arthritis. Multiple radiographic measurements have been de- veloped to quantify the degree of pathology at the cra- niocervical junction (Table 1). 6,7,12,27,28,36,37,41 They all seek to address malalignment of the upper cervical spine with regard to the skull base (Fig. 1). Just as there are multiple etiologies of craniocervical pathologies, there are multiple surgical approaches to treat disorders of this region when patients are symptomatic and Treatment of craniocervical instability using a posterior-only approach Report of 3 cases RichaRd M. Y oung, M.d., 1 Jonathan h. SheRMan, M.d., 1 JoShua J. Wind, M.d., 1 ZachaRY Litvack, M.d., M.c.R., 1 and JoSeph o’BRien, M.d., M.p.h. 2 Departments of 1 Neurological Surgery and 2 Orthopaedic Surgery, George Washington University Medical Center, Washington, DC The object of this study was to demonstrate that a posterior-only approach for craniocervical junction pathol- ogy is feasible with intraoperative reduction. The authors reviewed 3 cases of craniocervical instability. All patients had craniocervical instability according to radiological imaging and various methods of measurement, with results outside the normal range. Posterior instrumentation aided the intraoperative reduction techniques while maintaining structural integrity and the desired fusion construct. No anterior approach was necessary in any of the patients. Neu- rological symptoms resolved in two patients and signiicantly improved in another. Follow-up imaging demonstrated stable constructs. There are many approaches to anterior cervical pathology at the craniocervical junction. Posterior instrumented reduction and stabilization of the occipitocervical spine can be safely achieved, obviating the need for a transoral approach in the setting of craniocervical junction settling. (http://thejns.org/doi/abs/10.3171/2014.3.SPINE13684) keY WoRdS • craniocervical instability • basilar invagination • cranial settling • cervical fusion This article contains some figures that are displayed in color online but in black-and-white in the print edition. Abbreviations used in this paper: OC = occipitocervical; RA = rheumatoid arthritis; SSEP = somatosensory evoked potential.