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Introduction
Procedure
Risks
Alternative Treatments
Chiari malformations are structural defects in the cerebellum, the part of the brain that controls balance. Normally the cerebellum and parts of the brainstem sit in an indented space at the lower part of the skull, above the foramen magnum, which is a funnel-like opening that leads to the spinal canal). When part of the cerebellum moves (herniates) below the level of the foramen magnum, the anomaly is called a Chiari malformation, as depicted in the figure below.
When the cerebellum is pushed below the foramen magnum, it can put pressure on the brainstem and medulla oblongata (the connection between the brainstem and the spinal cord). This pressure can lead to symptoms that are associated with Chiari malformations.
In patients with significant symptoms, surgical repair of the malformation may be needed to decompress the brainstem and reverse or stop the progression of symptoms. The main goal of this surgery (also known as posterior fossa decompression or suboccipital decompression) is to create additional room behind the brainstem by removing bone from the back of the skull and spine so that the brainstem and the herniated part of the cerebellum can coexist in that space without putting pressure on each other.
After induction of general anesthesia, an incision is made in the back of the upper part of the neck as shown below.
The muscles of the neck are then dissected until the bone of the bottom part of the skull and the upper part of the spine are revealed. A portion of the skull and the back of the upper spine (demarcated in the figure below by the dashed line) is then removed.
The covering of the brain and spinal cord (called the dura mater) is then opened in an oval manner, revealing the herniated portion of the cerebellum and the brainstem, as illustrated below.
A patch of tissue is then sewn to the opening in the dura mater in order to enlarge the space that is occupied by the herniated cerebellum and the brainstem. The bone opening is left as is and the muscle and skin is sutured closed prior to the termination of the operation.
Due to advances in medicine and technology, surgical procedures are generally considered to be safe, and a great majority of patients who undergo surgery will not experience any complications. However, there are certain risks involved in any procedure which are important to be aware of in order to make an informed treatment decision.
Risks Specific to this Procedure: The risks associated with this surgery include, but are not limited to, damage to brain or cerebellum leading to increased neurologic problems, loss of hearing, facial weakness, swallowing difficulty, facial numbness, impaired memory and/or cognition, weakness or paralysis, numbness, seizures, loss of speech, ringing in the ear, dizziness, balance problems, cerebrospinal fluid leakage requiring placement of lumbar drain, and need for further surgery.
Infection: Invasion of tissue by bacteria or other germs occurs to some degree whenever a cut, incision or puncture is made. In most instances, through the natural defense mechanisms of the body, healing of the affected area occurs without difficulty. In some instances antibiotic medicines are prescribed and at times additional surgical measures may be necessary to combat infection.
Hemorrhage: The cutting of blood vessels causes bleeding and this occurs in every surgical incision. This bleeding is usually controlled without difficulty. At times, blood transfusions are required to replace blood loss. If blood transfusions are given, there are additional risks of liver inflammation, hepatitis, and the possibility of receiving Acquired Immune Deficiency Syndrome (AIDS). There is no absolutely reliable way to predict these unwanted reactions, some of which may be quite serious and even lead to death.
Drug Reactions: Unexpected allergies, lack of proper response to medications or illness caused by the prescribed drugs are possibilities. It is important for you to inform your physician and your anesthesiologist or certified registered nurse anesthetist of any problem you or your family have had with reactions to drugs and which medications you have taken in the past six months, including over-the-counter drugs, especially aspirin.
Anesthesia Reactions: There may be unusual or unexpected responses to the gases, drugs or methods used to anesthetize you which can lead to difficulties with lung, heart or nerve function. Eating or drinking before anesthesia increases the risks of vomiting which may cause significant complications. Inform your anesthesiologist or certified registered nurse anesthetist of problems you and your family have had with anesthesia.
Blood Vessel Inflammation and Clotting: It is impossible to predict the occurrence of blood vessel inflammation and clotting problems. If blood clots form, they can move from where they formed to other areas of the body and cause injury.
Injury to Other Organs: Because of the closeness of other organs to the area being operated on, there may be injury to other organs. The stress of surgery or the procedure may also harm other organ systems of the body.
The alternative management modalities for this procedure (depending on the nature of the symptoms) are physical therapy, pain management using medications or injections, certain alternative medicine therapies (acupuncture), possibly other surgical procedures, and expectant management with no treatment at all. If the decision is made to not have this procedure, there may be associated risks which need to be discussed with a physician.
