Earlier evidence of spheno-occipital synchondrosis fusion correlates with severity of midface hypoplasia in patients with syndromic craniosynostosis.

BACKGROUND: The spheno-occipital synchondrosis is an important driver of facial and cranial base growth. The current study characterizes its fusion in patients with Apert, Crouzon, and Pfeiffer syndromes and correlates early fusion with the presence, and degree, of midface hypoplasia. METHODS: A retrospective case-control study was performed of all syndromic patients treated between 1996 and 2012. Case computed tomographic scans and age- and sex-matched control scans were analyzed as demonstrating either open, partially fused, or completely fused synchondroses, and patient age at each scan was recorded. Midface hypoplasia as determined by sella-nasion-A point angle measurement at the time of midface surgery was correlated to fusion status. RESULTS: Fifty-four patients with 206 computed tomographic scans met inclusion criteria. Two hundred six age- and sex-matched control scans were also identified. Average age at computed tomographic scanning was 6.1 years. The earliest ages of partial and complete fusion were 1.1 and 7.0 years, respectively, among cases; and 6.2 and 12.7 years, respectively, among controls. The odds of synchondrosis fusion in case computed tomographic scans was 66.0 times that of controls (95 percent CI, 9.2 to 475.5 times that of controls; p < 0.000001). Average age of synchondrosis fusion was 3.5 years (range, 0.5 to 6.0 years). Average sella-nasion-A point angle at the time of midface surgery was 67.5 degrees (range, 58 to 76 degrees), with a positive correlation between earlier age of fusion and more severe midface hypoplasia (p = 0.028). CONCLUSIONS: The spheno-occipital synchondrosis fuses earlier in syndromic patients compared with age-matched controls. Moreover, there is a positive correlation between earlier fusion and degree of midface hypoplasia, although definitive causality cannot be concluded. This is the first study to demonstrate such a correlation in human subjects. CLINICAL QUESTION/LEVEL OF EVIDENCE: Risk, II.