FREQUENCY OF ATLANTOAXIAL SUBLUXATION AND NEUROLOGIC INVOLVEMENT IN PATIENTS WITH ANKYLOSING-SPONDYLITIS

Objective. To determine the prevalence of anterior and vertical atlant oaxial subluxation (AAS) and its neurological effect in a consecutive sample of Mexican patients with ankylosing spondylitis (AS). Methods. Consecutive patients with a diagnosis of AS who attended 2 secondary c are outpatient rheumatology clinics in the city of Guadalajara within a period of 6 mo were included in the study. Patients had prospective rheumatologic and neurologic assessments using structured questionnair es and examinations. Recorded variables included demographic data, dis ease characteristics, neurologic symptoms and signs, and axial mobilit y measurements. Somatosensory evoked potentials (SSEP) were performed in all patients. Patients also underwent standard cervical spine radio graphy with anteroposterior open mouth, and neutral, full flexion and extension lateral views. Results. We studied 103 patients. Mean age wa s 35 yrs, 74% were male, and mean disease duration was 10 yrs (+/- SD 7.9). Anterior AAS was observed in 22 patients (21%, 95% CI 13-29%) an d vertical AAS in 2 cases (2%, 95% CI 0-7%). Ossification of the poste rior longitudinal ligament (OPLL) was present in 16 patients. Statisti cally significant associations were observed between anterior AAS and SSEP (p < 0.0001) and OPLL (p = 0.04). The degree of radiologic sacroi liitis was also associated with anterior AAS. After completion of the study, 2 patients required surgical fusion due to severe cervical cord compression. Conclusion. The prevalence of AAS and OPLL in this popul ation was higher than previously reported in other settings. The assoc iation of anterior AAS with OPLL and radiological sacroiliitis could i dentify a subgroup of patients with more severe axial enthesopathy. Al though clinically significant neurologic complications are not frequen t in these patients, AAS may cause severe spinal cord compression requ iring surgical fusion.