Arnold-Chiari malformation

Chiari malformation is a condition where brain tissue extends into the spinal canal. This happens when a part of the skull is abnormally shaped or is smaller than usual. In this case, the skull puts pressure on the brain, pushing it downwards.
 
To correct it, surgery for Chiari malformation, also known as posterior fossa decompression surgery, aims to relieve pressure on the cerebellum and spinal cord. This is achieved by removing a section of bone from the back of the skull, which creates more space for the brain and allows cerebrospinal fluid to flow more freely.