The cerebellum is a small portion of the brain that co-ordinates various muscular movements such as speech, posture, and balance of the body. It is located above the foramen magnum at the lower end of the skull just above the brain stem.
Chiari malformation refers to a structural defect in the cerebellum, in which a part of it, the cerebellar tonsils, protrudes into the spinal canal. When the cerebellar tonsils are pushed down into the foramen magnum and into the spinal canal, pressure is created on the brainstem. This blocks the flow of cerebrospinal fluid, a clear fluid cushioning the brain and spinal cord. The block in the flow of the cerebrospinal fluid disrupts normal functioning of the brain and spinal cord and causes fluid to accumulate in the spinal cord (syringomyelia) or brain (hydrocephalus). Chiari malformation can occur in adults as well as in children.
Chiari malformation is associated with symptoms such as head, neck, chest and general body pain, imbalance, hearing loss, sleep apnoea, swallowing difficulty, arm and leg numbness and impaired thinking. Chiari malformation can be managed with regular monitoring and medications. However, severe cases would require surgery.
Surgery performed to decompress the protruded cerebellar tonsils is called Chiari decompression surgery. This surgery relieves pressure on the spinal column and creates more space for the cerebellum. It also normalizes the flow of the cerebrospinal fluid to and from the brain thereby relieving related symptoms.
Chiari decompression surgery is indicated to relieve abnormal collection of cerebrospinal fluid in the brain and spinal cord. Other indications of the surgery include:
- To relieve compression of the brainstem and spinal cord
- To restore normal flow of cerebrospinal fluid
- To control symptoms
Chiari decompression surgery is performed under the effect of general anaesthesia.
Your surgeon will place your head in a skull fixation device to hold it in place during the surgery. A strip of hair is shaved along the area of the planned incision and the scalp is prepared with an antiseptic solution.
Your surgeon makes a 3-inch-long cut in the middle of the neck to view the skull and upper spine.
Sub occipital craniectomy is performed to remove a small part of the skull bone from the back of your head. Laminectomy is conducted to remove the curved bony structure of the C1 vertebra. The removal of the bone will relieve the compression of the cerebellar tonsils and restore normal flow of cerebrospinal fluid. The protective covering of the brain and spinal cord called dura is now visible. The dura is opened to expose the tonsils if necessary.
Your surgeon may perform electrocautery to burn away and shrink the stretched tonsils.
A piece of the pericranium, deep scalp tissue, or a synthetic material will be used to suture the dural opening and cover the cerebellum.
The sutured line will be sealed with a sealant to prevent leakage of cerebrospinal fluid. Finally, the neck muscles and skin is sutured to close the incision.
Following the surgery, your throat may be sore due to the inserted breathing tube.
- You may be prescribed medications to relieve pain, headache and nausea.
- You should avoid all activities that could increase pressure in your head, such as bending, straining during a bowel movement or prolonged coughing.
- Avoid regular house chores, lifting heavy objects, and sitting for a prolonged time. Resume driving only after consulting with your doctor.
- Keep the incision clean and dry
- Contact your doctor immediately if you experience fluid drainage, swelling, fever or fluid accumulation around the incision.
- You will be taught exercises to improve neck healing and mobility. Recovery can take months or longer.
Risks and complications
As with any surgery, Chiari decompression surgery involves certain risks and complications. They include:
- Head and neck pain
- Cerebrospinal fluid leakage
- Pseudomeningocele (Cerebrospinal fluid accumulation under neck tissues)
- Brain or nerve damage