Located in the lower back part of the skull, the cerebellum is the part of the brain responsible for balance. Structurally, the human skull has an indented space at its base. However, when this space is malformed and not as large as needed, the cerebellum and brainstem are pressed down, causing a blockage in the flow of cerebrospinal fluid. Known as a Chiari malformation (CM), this condition can contribute to many different symptoms, including:

  • dizziness
  • muscle weakness
  • numbness
  • vision problems
  • headache
  • problems with balance and coordination

There are three types of CM:

  • Type I—The most common, it is often discovered by accident and typically does not even bring about symptoms.
  • Type II—Also known as Arnold-Chiari malformation, it is usually is a form of spina bifida called a myelomeningocele. This is characterized by the spinal cord protruding through an opening in the back when the spinal canal and backbone do not close in vitro.
  • Type III—This most serious type is the cause of numerous neurological defects. Conditions sometimes associated with CM include hydrocephalus, syringomyelia, and spinal curvature.


While medications may help with pain and other symptoms, surgery is the only way to correct functional problems or stop the progression of damage to the central nervous system. Multiple surgeries may be required.


Expected outcome depends on the type of CM, of course. While most people with Type I CM aren’t even aware they have the condition because they have no symptoms, many who have severe types of CM experience relief from their symptoms and extended periods of stability following corrective surgery. However, any paralysis is usually irreversible.