An Updated Algorithm for Radiographic Screening of Upper Cervical Instability in Patients With Down Syndrome

Abstract

Study design: Retrospective evaluation of cervical spine images from 2006-2012 for the purposes of "screening" children with Down syndrome for instability.

Objective: To determine whether a full series of cervical spine images including flexion/extension lateral (FEL) radiographs was needed to avoid missing upper cervical instability.

Summary of background data: The best algorithm, measurements, and criteria for screening children with Down syndrome for upper cervical instability are controversial. Many authors have recommended obtaining flexion and extension views. We noted that patients who require surgical stabilization due to myelopathy or cord compression typically have grossly abnormal radiographic measurements on the neutral upright lateral (NUL) cervical spine radiograph.

Methods: The atlanto-dental interval, space available for cord, and basion axial interval were measured on all films. The Weisel-Rothman measurement was made in the FEL series. Clinical outcome of those with abnormal measurements were reviewed. Sensitivity, specificity, and positive and negative predictive values of NUL and FEL radiographs for identifying clinically significant cervical spine instability were calculated.

Results: A total of 240 cervical spine series in 213 patients with Down syndrome between the ages of 4 months and 25 years were reviewed. One hundred seventy-two children had an NUL view, and 88 of these patients also had FEL views. Only one of 88 patients was found to have an abnormal atlanto-dental interval (≥6 mm), space available for cord at C1 (≤14 mm), or basion axial interval (>12 mm) on an FEL series that did not have an abnormal measurement on the NUL radiograph. This patient had no evidence of cord compression or myelopathy.

Conclusions: Obtaining a single NUL radiograph is an efficient method for radiographic screening of cervical spine instability. Further evaluation may be required if abnormal measurements are identified on the NUL radiograph. We also propose new "normal" values for the common radiographic measurements used in assessing risk of cervical spine instability in patients with Down syndrome.

Level of evidence: Level IV.

Keywords: Atlanto-axial instability; Down syndrome; Occipito-cervical instability; Pediatric cervical spine; Radiographic screening.