The growth of the foramen magnum in Crouzon syndrome.

BACKGROUND: Though the craniovertebral junction is often abnormal in children with Crouzon's syndrome, no study had measured accurately the size of their foramen magnum (FM). PATIENTS AND METHODS: We compared the FM size (area, diameters) on computed tomography examination in 21 children with a genetically confirmed Crouzon's syndrome prior to any surgery and in 23 control children without craniofacial abnormalities. We extrapolated the growth pattern in both groups.
RESULTS: We found a statistically significant smaller FM area (p=0.0228), FM sagittal diameter (p=0.0287), and FM sagittal posterior diameter (p=0.0023) in children with Crouzon's syndrome. No differences were detected with regard to the transversal diameter. Hydrocephalus in children with Crouzon's syndrome was associated with a small FM area (p=0.05), small sagittal diameter (p=0.023), small sagittal posterior diameter (p=0.0173), and reduced transversal diameter (p=0.03985). No association of the aforementioned findings was found with the position of the cerebellar tonsils or the lambdoid suture functional state (open or fused). Comparable results were observed among the two genetic forms (exon 8 or 10 mutations). Concerning the growth pattern, a first phase of rapid increase and a second phase of slow increase could be recognized in all the measurements in both populations, though with some significant differences. DISCUSSION AND
CONCLUSIONS: The growth of FM follows a biphasic pattern in both Crouzon's and control children. The sagittal diameter and the global size of the FM are mostly affected in children with Crouzon's syndrome. The small FM, especially its posterior part, is likely to play a key role in the physiopathology of hydrocephalus.