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Chiari Malformation


Disease: Chiari Malformation Chiari Malformation
Category: Neurological diseases
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Disease Definition:

When part of the skull is abnormally small or misshapen, pressing on the brain and forcing it downward, Chiari malformation occurs, a condition in which brain tissue protrudes into the spinal cord. This condition is diagnosed more frequently now thanks to improved imaging tests.

Signs and symptoms may not occur until late childhood or adulthood, because the adult form which is called Chiari malformation type I develops as the skull and brain are growing. However, the most common pediatric form is present at birth, called Chiari malformation type II.

Chiari malformation isn’t a common disease. The form of the condition, severity and associated symptoms are the things that determine treatment of Chiari malformation. Sometimes no treatment may be necessary. Treatment options in general include medications, regular monitoring and surgery.

Work Group:

Prepared by: Scientific Section

Symptoms, Causes


Depending on the anatomy of the brain tissue that is displaced into the spinal canal, and whether development abnormalities of the brain or spine are present, Chiari malformation is categorized into four types.

A number of problems can be caused by Chiari malformation depending on the severity and type of the condition, although in some cases the condition can be detected only when tests are performed for unrelated disorders, as those people may have no signs and symptoms and may not need treatment.

Type I (adult) and type II (pediatric) are the more common types of Chiari malformation.
During late childhood or adulthood is when signs and symptoms of Chiari malformation type I usually appear. Chiari II malformation is usually noted by ultrasound during pregnancy or at birth or early infancy. Signs and symptoms can still be life disrupting, though these types are less serious than the more rare pediatric forms, types III and IV.

Chiari malformation type I:
The classic symptom of Chiari malformation is headaches, which are often severe. Usually, sneezing, straining or sudden coughing precipitate these headaches. The following symptoms may be experienced by people with Chiari molformation type I:


  • Difficulty swallowing, sometimes accompanied by vomiting, choking and gagging
  • Unsteady gait (problems with balance)
  • Slurred speech
  • Poor hand coordination (fine motor skills)
  • Vision problems, such as blurred or double vision
  • Numbness and tingling of the feet and hands
  • Neck pain, which sometimes runs down the shoulders
  • Dizziness

The following symptoms may be, less often, experienced by people with Chiari malformation:

  • Poor bladder control
  • Abnormal breathing, particularly sleep apnea characterized by periods of breathing cessation during sleep
  • Chest pain, in a band-like pattern around the chest
  • Ringing or buzzing in the ears (tinnitus)
  • Curvature of the spine (scoliosis) related to spinal cord impairment

Chiari malformation type II:
Compared with Chiari malformation type I, a greater amount of tissue protrudes into the spinal canal in type II. The signs and symptoms related to a form of spina bifida called myelomeningocele that always accompanies Chiari II malformation, can be included in the signs and symptoms of this type. The backbone and the spinal canal don’t close properly before birth in myelomeningocele..

Chiari malformation type III:
A portion of the lower back part of the brain (cerebellum) or the brainstem extends through an abnormal opening in the back of the skull, in Chiari malformation type III, one of the most severe types of the condition. This form of Chiari malformation is obvious at birth or during intrauterine ultrasound.

Chiari malformation type IV:
The brain itself has never developed normally in people with the even more severe Chiari malformation type IV. This form of Chiari malformation is also obvious at birth or by intrauterine ultrasound.
A doctor should be seen when someone experiences any of the signs and symptoms that may be associated with Chiari malformation. A Thorough medical evaluation is important because many symptoms of Chiari malformation can be associated with other disorders as well. For example, head pain could be caused by Chiari malformation, migraines, sinus disease, or brain tumor. Other signs and symptoms overlap with other conditions such as multiple sclerosis.


When the section of the skull containing the cerebellum is too small or deformed, putting pressure on and crowding the brain, Chiari malformation occurs. The lowermost portion, or tonsils, of the cerebellum are displaced into the upper spinal canal. A small back portion of the skull is the primary cause of Chiari I malformation. While a myelomeningocele is always associated with Chiari II malformation.

The cerebellum can interfere with the normal flow of cerebrospinal fluid (CSF) that protects the brain and spinal cord, when it is pushed into the upper spinal canal. A buildup of spinal fluid in the brain or spinal cord or a blockage of signals transmitted from the brain to the body can be caused by this impaired circulation of CSF. Instead, neurological signs or symptom may result due to the pressure from the cerebellum upon the spinal cord or lower brainstem.

Research into a possible hereditary component is still in its early phase, although there is some evidence that Chiari malformation runs in some families.



There may be no associated symptoms in some people, making intervention unnecessary; while in others, Chiari malformation can become a progressive disorder and cause serious complications. Here are the complications that are associated with this condition:

In this condition, which develops in some people with Chiari malformation, a cavity or cyst (syrinx) forms within the spinal column. It may be associated with injury or displacement of nerve fibers in the spinal cord, although the mechanism connecting Chiari malformation with syringomyelia is not understood. The cavity tends to be filled with fluid when it forms, and can additionally impair the function of the spinal cord.

Because of the crowding and pressure on the spinal cord, paralysis may occur, which is in most cases permanent even after surgical treatment.

To divert and drain the cerebrospinal fluid to another area of the body, placement of a flexible tube (shunt) may be required in this accumulation of excess fluid within the brain.

Early in infancy in general, death is common when a child is born with Chiari malformation type IV.


The severity and characteristics of the condition are the things that determine the type of treatment for Chiari malformation. No treatment other than monitoring with regular examination will be recommended when the patient doesn’t have any symptoms; while medication is likely to be recommended when headaches or other types of pain are the primary symptoms. The need for an operation may be delayed or even prevented by the approach that supports giving the patient anti-inflammatory or pain-relieving agents, such as indomethacin, as this approach has made some people experience symptoms relief.

Reducing pressure by surgery:
To treat symptomatic Chiari malformation, surgery is the most common approach. Easing or stabilizing symptoms, as well as stopping the progression of changes in the anatomy of the brain are the goals of surgery. Restoring the normal flow of spinal fluid and reducing pressure on the cerebellum and the spinal cord can be achieved by a successful surgery.

Relieving pressure by giving the brain more room, the surgeon removes a small section of bone in the back of the skull in the most common operation for Chiari malformation called posterior fossa craniectomy or posterior fossa decompression. A patch is sewn in place to enlarge the covering and provide more room for the brain after opening this covering of the brain called dura. The patch tissue could be harvested from the neck or leg of the patient, or it may be an artificial material. Depending on whether a fluid-filled cavity is present or if the patient has hydrocephalus, the exact technique may vary. Two or four days in the hospital may be enough to recover from the operation which takes about two to three hours.

Risks and follow-up care:
The possibility of infection or problems with wound healing is among the risks that surgery may be associated with. When deciding whether surgery is the best alternative for a patient, he/she should discuss the pros and cons with the doctor. This procedure won't reverse the damage if nerve injury in the spinal canal has already occurred prior to surgery, though the operation reduces symptoms in most people.

To assess the outcome of surgery and the flow of cerebrospinal fluid, the patient will need regular follow-up examinations with the doctor, including imaging tests after the operation.


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