Q&A: Chiari surgery
Below are answers to questions commonly asked by our patients at the Mayfield Chiari Center. Keep in mind that there is wide variability in surgical technique and that surgery is tailored to a patient's unique anatomy and symptoms.
Q: What about minimally invasive endoscopic Chiari surgery? I’ve heard that it’s better than a standard “open” surgery?
A: Many patients have read online or heard about minimally invasive or endoscopic Chiari surgery. Minimally invasive can mean many different things: smaller skin incision, less neck muscle splitting, no dura opening, no shrinkage of the tonsils, or use of ultrasound and endoscopes. Despite what the words “minimally invasive” suggest, the amount of bone removal necessary to effectively restore normal CSF flow should be the same in any procedure, endoscopic or open. Each patient’s anatomy and size of Chiari is different and only a surgeon with direct knowledge of your case can determine if a minimally invasive technique is appropriate. As with all new techniques, studies comparing the long-term results and risks of minimally invasive surgery with conventional surgery are needed.
It’s also important to understand that some minimally invasive techniques used for children (whose skulls are still growing) may or may not be appropriate for adults.
We perform the least invasive procedure that is effective for the patient’s unique anatomy. We constantly seek to improve the results and lessen the side effects of surgery.
Q: Why do some surgeons remove bone from the vertebra in the neck?
A: The amount of tonsillar herniation is a determining factor to remove the arch of the C1 vertebra (e.g., someone with 4mm herniation versus someone with 20mm herniation). If a person is young or athletic, we always try to avoid disturbing the C1 vertebra. There have been cases where a person can develop craniospinal instability years after their surgery, either by a neck injury or the natural aging process. Some surgeons prefer to shrink the tonsils rather than remove the bone of C1.
Q: Will more of my brain sag out of my head if you remove bone from the skull?
A: No. The bone removal (3cm x 3cm x 4cm) is in the very middle of the skull to allow the tonsils to hang. The cerebellar hemispheres are supported by bone along the undersides of the skull. Cases of cerebellar slumping (or cerebellar ptosis) that you may have heard about are rare complications caused by too much bone removal. It’s important to have surgery performed by a Chiari expert to avoid reconstructive surgery.
Q: Does my syrinx cavity need to be drained with a shunt?
A: No. Years ago placing a shunt into the syrinx cavity was common, but long-term results and problems with shunt clogging have made this technique uncommon and used only for special cases. Adequate decompression of the brainstem and fourth ventricle will allow CSF flow and pressure to normalize and should eventually lead to disappearance of the syrinx on its own.
Q: Why do some surgeons open the dura and some do not?
A: Sometimes bone removal alone is enough to relieve the compression and restore CSF flow (especially in children). Surgeons may use ultrasound to test the movement of CSF and determine if opening the dura and sewing a patch (duraplasty) is necessary. However, in adults the dura is less pliable, so a graft is sewn to enlarge the space. The technique is similar to a tailor letting out the waistband on a pair of pants. While avoiding dura opening may decrease the risk of CSF leak, inadequate decompression may increase the risk of a poor result and lead to reoperation.
Q: Is there a difference in dura patch material?
A: Many patch materials are available, ranging from autologous (patient’s own) tissue to a variety of cadaveric and synthetic materials. We prefer to use patch material obtained from the pericranium (tissue overlying the skull) or a synthetic collagen material.
Q: Does Chiari recur after surgery?
A: True anatomical recurrence of Chiari I is rare. There are many reasons why some patients consider their surgery unsuccessful or “failed.” Technical failure of the surgery means obstructed CSF flow at the foramen magnum. Failure of some symptoms to resolve does not always mean failure of the surgical repair. A cine MRI study is used to evaluate CSF flow.
Scarring of tissue, inadequate removal of bone, new neck or head trauma, increased brain pressure, and tethered cord can be causes of recurrence. Surgical complications such as cerebellar slumping or spinal instability can also cause recurrence.
Q: Why do some people have multiple surgeries?
A: At our center, we see many patients with previous surgery (done by other surgeons) who have had an inadequate decompression to restore normal CSF flow. Either the bone removal was too small or the dura was not opened to adequately expand the space. Delayed post-operative scarring may also lead to repeat surgery. Cine flow and MRI studies play a major role in determining the need for reoperation.
reviewed by: John M. Tew, MD
The information in this Q&A is not intended to be a substitute for professional medical advice, nor is it intended to serve as medical diagnosis or treatment. The information is presented for the sole purpose of disseminating health information. It is not intended and must not be taken to be the provision or practice of medical, nursing, or professional health care advice or services in any jurisdiction. Always seek the advice of your physician or other qualified health provider if you have questions regarding a medical condition, and always seek the advice of your physician or provider before starting any new treatment.