Normal sagittal diameter and variation in the pediatric cervical spine.

The sagittal diameter of the cervical spinal canal is traditionally evaluated when an expansile intraspinal lesion is suspected. Some workers have concluded that the normal sagittal diameter gradually decreases from C1 to C7 in some people, while in others it decreases from C1 to C3 and remains nearly constant from C4 to C7. The authors' study of 158 young individuals with no evidence of cervical cord lesions showed that gradual widening of the lower canal and even ballooning of the mid-canal are frequently seen in normal children 10 years old or younger, and occasionally in persons up to 18 years of age. The mechanism by which the canal attains a funnel-shaped appearance in adults is discussed.