The surgery makes more room in the skull for the cerebellum and brainstem. This relieves some pressure on the brain. The surgery also lets cerebrospinal fluid (CSF) flow in a more normal way, which may relieve some symptoms. If your child also has syringomyelia, this surgery usually lets the cyst drain so your child doesn’t need surgery on the cyst itself.
Removing bone from the skull
During the surgery, the neurosurgeon makes a cut (incision) at the back of your child’s head and removes a small piece of bone from the base of your child’s skull. This step makes the normal hole in the base of the skull (foramen magnum) bigger so there’s more room for the brain, spinal cord and CSF. The back of your child’s skull is called the posterior fossa. The base where the bone is removed is called the suboccipital area. Taking out the bone here is called suboccipital craniectomy.
Removing bone from the neck
The surgeon may also need to remove the back part of the first bone of the spine (first cervical vertebrae or C1) to make enough room for your child’s brain. Taking out the back of this bone is called C1 laminectomy. Some children who have surgery need only suboccipital craniectomy and C1 laminectomy.
Opening the membrane over the brain
Where the bone was removed from the skull, the surgeon may open up the tough membrane (dura mater) that covers your child’s brain. Opening up the membrane (intradural surgery) makes more room for CSF to flow. Not all children who have surgery need this step.
Shrinking the cerebellum
With the membrane open, the surgeon may use a method to make the bottom parts of the cerebellum (cerebellar tonsils) smaller. At Seattle Children’s, we do not destroy or cut out (resect) any of the cerebellum. We sometimes use electrocautery – a way to shrink the cerebellar tonsils by touching them with a tool that is heated by an electric current. Shrinking the cerebellar tonsils makes more room for CSF.
Patching the membrane
If the membrane was opened, the surgeon closes and protects the area by sewing a patch on it. The patch usually comes from tissue that’s deep under your child’s scalp but outside your child’s skull (pericranium). This tissue makes a good patch because your child’s body is likely to accept the tissue, and it’s less likely to leak than some other types of patches. Other options include taking tissue from some other part of your child’s body (the covering of a neck muscle or a strong band of tissue from their leg, called fascia lata) or using a synthetic patch.
Finally, the neurosurgeon brings the skin back together and closes the incision.
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