08/22/2025
Chiari decompression surgery removes bone at the back of the skull to widen the foramen magnum and create space for the brain. Sometimes the dura overlying the herniated tonsils is opened and a patch is sewn to expand the space, similar to letting out the waistband on a pair of pants. The goals of surgery are to control the progression of symptoms, relieve compression, and restore the normal flow of cerebrospinal fluid (CSF). The surgery takes about 2 to 5 hours and recovery in the hospital usually lasts 2 to 6 days.
What is Chiari decompression?
Posterior fossa decompression is a surgical procedure that removes bone at the back of the skull and spine to widen the space for the tonsils and brainstem.
Posterior fossa decompression surgery removes a small portion of the occipital bone to create more space for the brainstem and tonsils (suboccipital craniectomy).
In some cases the bony arch of the C1 vertebra may be removed (laminectomy). These steps expose the protective covering of the brain and spinal cord called the dura. Bone removal may relieve compression of the tonsils.
A dura patch may sewn to expand the space for cerebrospinal fluid to flow around the tonsils.
Many patients ask about minimally invasive or endoscopic surgery. Minimally invasive can mean different things: shorter skin and muscle incision, 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 needed to effectively restore normal CSF flow depends on the individual patient's anatomy and size of Chiari. The amount of bone removal should be the same in any procedure, endoscopic or standard "open" technique. 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.
Spinal fusion may be performed in addition to posterior fossa decompression surgery in certain patients with spine instability due to scoliosis, Ehler-Danlos syndrome, or other bone abnormality. Rods and screws are inserted to structurally reinforce the skull and neck vertebrae.