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Chiari Malformation

What is chiari malformation?

Chiari malformation, also known as an Arnold-Chiari malformation, is a congenital (present at birth) defect occurring in the back of the head where the brain and spinal cord connect.

There are four types of Chiari malformations:

  • Type 1 – Occurring when the base of the skull and upper spinal area do not form properly, a type 1 Chiari malformation commonly goes unnoticed until problems arise in the adolescent or adult years of life. The headaches most typical of Chiari I malformations are usually located at the back of the head, and are often made worse by exertion.
  • Type 2 – The most common of all Chiari malformations, type 2 is caused by part of the back of the brain shifting downward through the bottom of the skull.
    • Type 2 Chiari malformations are typically seen in infants who are born with spina bifida, a neurological condition that causes a portion of the spinal cord and the surrounding structures to develop outside, instead of inside, the body.
    • Type 2 Chiari malformations can also be associated with hydrocephalus, a condition in which there is an overproduction or lack of absorption of the cerebral spinal fluid (CSF) that is found inside of the ventricles (fluid-filled areas) inside of the brain. The increased fluid causes the pressure inside of the head to increase and the skull bones to expand to a larger-than-normal appearance.
  • Type 3 – Type 3 Chiari malformations occur when the back of the brain protrudes out of an opening in the back of the skull area.
  • Type 4 – Type 4 Chiari malformations occur when the back of the brain fails to develop normally.

What causes chiari malformation?

The exact cause of Chiari malformation is unknown; however, it is believed that problems during fetal development may cause abnormal brain function.

Theories suggest that the following may predispose the fetus to problems that affect the normal development of the head during pregnancy:

  • exposure to hazardous chemicals/substances
  • lack of proper vitamins and nutrients in the diet
  • infection
  • prescription or illegal drug and alcohol consumption 

Learn more about chiari malformation

George Jallo with Mom

The Great Imitator: Discussion on Chiari Malformation
Watch a recording of an online webinar on chiari malformations. Learn how this condition often imitates other neurological diseases, can be diagnosed without obvious symptoms, and how surgical treatment can improve quality of life.

George Jallo with patient

What is chiari malformation?
Johns Hopkins pediatric neurosurgeon George Jallo, MD, defines chiari malformation and explains its symptoms, causes, and treatment options.

To make an appointment or request a consultation, contact Johns Hopkins Pediatric Neurosurgery at 410-955-7337.


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