The innovation: Invasive surgery found to provide better outcomes for patients with neurological disorder
Chiari malformations are a common neurological disorder that usually occur when part of the skull does not form properly, causing the bottom of the cerebellum to extend down into the spinal canal. About 10% of children with Chiari malformations type 1 (CM-1) need surgery to create space at the base of the skull to relieve symptoms and prevent serious health problems.
Neurosurgeons, however, have long debated which surgical technique provides the best outcomes. The team of pediatric neurosurgeons at Children’s Medical Center Dallas, part of Children’s Health℠, recently tackled this question by conducting multiple, large studies of children who have had surgery for Chiari malformations type 1.
An important goal of surgery is to resolve syrinxes, which are fluid-filled cysts inside the spinal cord that can develop if the Chiari malformation blocks the flow of cerebrospinal fluid (CSF). The team found that more invasive techniques were more likely to improve syrinxes, and did not increase rates of postoperative complications, compared with less invasive techniques.
“Neurosurgeons have been afraid of the invasive techniques out of concern that they have more complications,” says Bruno Braga, M.D., Pediatric Neurosurgeon at Children’s Health and Associate Professor at UT Southwestern. “Our findings show that these techniques are safe as well as more effective.”
The big picture: Lacking guidance on the best approach to surgery
About 1% of all children have a Chiari malformation. Often, they are incidental findings made during an MRI for other issues, and no treatment is needed.
Children will need surgery if they have symptoms, like headaches that get worse with coughing or physical strain, or if they have a syrinx (syringomyelia), according to Dr. Braga. Left untreated, syringomyelia can lead to problems such as weakness and loss of sensation in the arms and legs and curvature of the spine (scoliosis).
“The issue is that nobody knows which type of surgery is best for which type of patient,” Dr. Braga says. “Studies have never consistently recommended that if a patient has a syrinx, do this technique, and if a patient has only symptoms, do this technique.”
All surgeries for Chiari malformations include a posterior fossa decompression (PFD) in which a small piece of bone is removed from the base of the skull. The PFD creates space for the brain and restores the normal flow of CSF. Often, a duraplasty to remove part of the dura mater at the bottom of the skull and create additional space is performed.
In fact, the Children’s Health team only performs PFD with duraplasty (PFDD) because many studies have found the PFD alone is not as effective as PFDD.
If neurosurgeons do not see CSF flowing after they complete the PFDD, they can perform up to three additional techniques during the surgery:
- An arachnoid dissection (PFDD + AD) to open up the arachnoid membrane beneath the dura mater. This step allows CSF to drain more appropriately from the fourth ventricle, where it is produced, down to the spinal canal.
- If PFDD + AD does not restore normal CSF flow, a tonsil coagulation (PFDD + TC) can shrink the tonsils and open up space for the brain, thus allowing CSF flow.
- If needed, part of the tonsils can be resected (PFDD + TR). This is the most invasive technique and involves removing part of the tonsils to clear a path for CSF to flow from the fourth ventricle.
Key details: Patient data reveals effectiveness and safety of tonsil resection
To better understand the outcomes and risks of the four surgical techniques, the Children’s Health pediatric neurosurgery team analyzed the many surgeries they have performed.
One study reviewed cases for 437 children from ages 3 months to 18 years, who underwent PFDDs between 2001 and 2021. About half of the children (221) had a syrinx before surgery. They found that the syrinx was resolved in 80% of the patients who had PFDD + TC or PFDD + TR compared with 59% of the patients who did not undergo tonsil manipulation (PFDD or PFDD + AD).
Rates of postoperative complications, such as head and neck pain, inflammation (meningitis) or CSF leaks, were low overall. More significantly, these complications were not more likely among children who underwent the more invasive procedures.
Another study of 454 children treated at Children’s Health between 2001 and 2019 looked at whether the size of the opening at the base of the skull, called the foramen magnum (FM), affected surgical outcomes. The team found that for patients with larger FM openings (> 34 mm), PFDD + TR was associated with greater syrinx improvement and symptom relief than the other techniques (PFDD, PFDD + AD and PFDD + TC).
“Some previous studies found that resection was more effective but, as a side effect, produced more complications. These studies, however, involved fewer patients,” Dr. Braga says. “The selling point of our studies is they are the largest looking at pediatric patients who had resection.”
Why Children’s Health: Extensive expertise with complicated techniques
Dr. Braga attributes the low complication rate to the team’s extensive experience. As a high-volume referral center for North Texas, Children’s Health performs 25 to 40 PFDDs each year. Many of the procedures include additional techniques.
The experience has helped the team identify the most important principles for reducing complications with PFDD + TR, which include avoiding additional tonsil manipulation once CSF starts flowing from the fourth ventricle and avoiding any manipulation of the pia mater, the inner membrane just above the brain that is in contact with the brainstem.
If other centers keep these steps in mind, they can prevent scarring, and thus complications, even if they have less experience with the procedure. “They know how to do it but they abandoned the technique because of concern for higher complications. If they do it safely and meticulously, they are going to have better results than what earlier smaller studies found – without the complications,” Dr. Braga says.