Complex craniocervical junction anomalies

The musculoskeletal configuration of the craniocervical junction is highly complex. Congenital or acquired anomalies in the interface between the skull and cervical spine can not only cause headache, neck pain and joint instability but also lead to neurological deficits that affect swallowing and breathing and cause weakness and spasticity.

Neurosurgeons at Mayo Clinic in Rochester, Minnesota, have experience treating these complex cases in children as young as infants. A number of these cases involve children who have developed new problems after previous surgeries. A sizable number also involve children with genetic syndromes that correlate with atlantoaxial and occipital cervical instability, such as Down syndrome. Other cases arise from high-energy trauma, generally falls or motor vehicle accidents.

"Because of the complex anatomy in the craniocervical junction, children can present with a variety of physical symptoms and findings," says Nicholas M. Wetjen, M.D., a pediatric neurosurgeon at Mayo Clinic's campus in Minnesota. "Our primary goal is to reverse or prevent any neurological problems by decompressing the brainstem and spinal cord while realigning the bones on the spine and stabilizing the joints."

Mayo Clinic's interdisciplinary approach ensures that children with craniocervical junction anomalies see not only a pediatric neurosurgeon but also specialists in neurology, otolaryngology, sleep medicine and occupational therapy, as needed. "Our patients have a comprehensive evaluation within a relatively short time frame, with very good communication between all the specialists," Dr. Wetjen says.

3-D printing to model anatomy

One of the challenges of treating craniocervical junction anomalies in children is obtaining clear imaging to guide surgery. At Mayo Clinic, models of a patient's individual anatomy are generated by 3-D printers, FIGURE based on extensive imaging of the patient through MRIs and CT scans.

"It can be difficult to make sense of this complex anatomy just on serial imaging or even with 3-D reconstruction of the imaging on a video screen," Dr. Wetjen says. "But printing a 3-D model helps us grasp the relationships within the anatomy, to see the limits on where we can decompress, and the size of the bones where we might want to insert instrumentation."

The 3-D-printed models, developed by Mayo Clinic radiologists and neurologists, provide essential information for treating young patients. "We don't have much biomechanical data of this region of the spine for kids," Dr. Wetjen notes. "We don't have cadaver studies of how children's bones move with one other."

Another challenge is balancing the risks and benefits of surgery in very young patients. "If a baby has a complex craniocervical junction anomaly with pending severe neurological problems, we might do surgery to get decompression and immobilization," Dr. Wetjen says. "Sometimes, custom-made braces can be used to hold the cranium and spine in position. But if the baby is not really active or mobile yet and the child is asymptomatic, we might wait to see how the deformity changes with bone growth."

The limited mobility that can result from fusing bones is another consideration. "We'd like to preserve neck rotation, flexion and extension," Dr. Wetjen says. "The risks of treatment have to be weighed against the risk of instability."

Research at Mayo Clinic is shedding further light on the most appropriate surgical approaches to the pediatric craniocervical junction. In a study published in the April 2016 issue of Journal of Neurosurgery: Spine, Mayo Clinic researchers found that the relationship between C2 and the hard palate varies significantly with sex and age. Specifically, the distance from the base of C2 to the hard palate was found to be shorter in females than in males, and shorter in the early and late decades of life compared with the middle decades. The findings have relevance in determining optimal surgical approaches to the anterior craniocervical junction.

"For some kids with congenital anomalies that push the anterior spine into the brainstem, we're not able to decompress or to use traction to achieve realignment. We then consider approaching through the nose or mouth to remove the portion of bone that is pressing on the spinal cord. The position of the hard palate relative to C2 helps determine whether we have enough space for that approach," Dr. Wetjen says.

"Balancing the risks involved in treating craniocervical junction anomalies can be very complicated," he adds. "The anatomy in this area is unique in every patient."

For more information

Mallory GW, et al. The rise and fall of the craniocervical junction relative to the hard palate: A lifetime story. Journal of Neurosurgery: Spine. 2016;24:521.