The authors investigated the changes in the bone architecture and the characteristics of the neck and craniovertebral region in selected cases of basilar invagination. The reversal in these changes that occurred after decompression and fixation are analyzed. The implications of such an analysis in understanding the pathogenesis of a number of features that are characteristically associated with basilar invagination are evaluated.
One hundred and seventy selected patients with basilar invagination who underwent atlantoaxial joint distraction-fixation surgery at the authors' institution between 1999 and April 2008 were reviewed. The study was prospective after June 2006. A variety of parameters were used for radiological and physical assessments. The evaluation was done on the basis of pre- and postoperative imaging studies and clinical photographs. In the 41 prospective cases, additional direct physical measurements of the neck were performed.
Prior to surgery there were several physical changes such as reduced neck length, torticollis, exaggerated lordosis of the cervical spine, and reduced craniospinal angulation. Other findings included reduced discspace height, significant posterior cervical osteophyte formation, assimilation of atlas (72%), single-level (29%) or multiple-level (3%) cervical fusions, and an increase in the spinal subarachnoid space both above and below the level of maximum neural compression at the tip of the odontoid process. After surgical decompression of the region, there was remarkable recovery in craniovertebral alignments, and an increase in neck length (maximum up to 42 mm) was obvious on physical and radiological examination in 85% of patients. The disc-space height increased and there was a reversal of altered cervical lordosis, craniospinal angulation (maximum up to 36°), and torticollis.
It appears that a number of physical spinal changes characteristically associated with basilar invagination such as a short neck, exaggerated neck lordosis, torticollis, cervical spondylotic changes and fusions are potentially reversible after decompression and stabilization of the craniovertebral junction.
Abbreviation used in this paper: CVJ = craniovertebral junction.
ChamberlainWE: Basilar impression (platybasia). A bizarre developmental anomaly of the occipital bone and upper cervical spine with striking and misleading neurologic manifestations. Yale J Biol Med11:487–4961939