Filed under: Brain & Nervous System
Chiari malformation (kee-AHR-ee mal-for-MAY-shun) is a condition in which brain tissue protrudes into your spinal canal. It occurs when part of your skull is abnormally small or misshapen, pressing on your brain and forcing it downward. Chiari malformation is uncommon, but improved imaging tests have led to more frequent diagnoses.
The adult form, called Chiari malformation type I, develops as the skull and brain are growing. As a result, signs and symptoms may not occur until late childhood or adulthood. The most common pediatric form, called Chiari malformation type II, is present at birth (congenital).
Treatment of Chiari malformation depends on the form, severity and associated symptoms. Regular monitoring, medications and surgery are treatment options. In some cases, no treatment is needed.
Doctors categorize Chiari malformation into four types, depending on the anatomy of the brain tissue that is displaced into the spinal canal, and whether developmental abnormalities of the brain or spine are present.
Many people with Chiari malformation have no signs or symptoms and don't need treatment. Their condition is detected only when tests are performed for unrelated disorders. However, depending on the type and severity, Chiari malformation can cause a number of problems.
The more common types of Chiari malformation are:
In Chiari malformation type I, signs and symptoms usually appear during late childhood or adulthood. Chiari II malformation is usually noted by ultrasound during pregnancy or at birth or early infancy. Although these types are less serious than the more rare pediatric forms, types III and IV, signs and symptoms still can be life disrupting.
Chiari malformation type I
Headaches, often severe, are the classic symptom of Chiari malformation. They're typically precipitated with sudden coughing, sneezing or straining. People with Chiari malformation type I can also experience:
Less often, people with Chiari malformation may experience:
Chiari malformation type II
In Chiari malformation type II, a greater amount of tissue protrudes into the spinal canal compared with type I. The signs and symptoms can include those related to a form of spina bifida, called myelomeningocele, that always accompanies Chiari II malformation. In myelomeningocele, the backbone and the spinal canal have not closed properly before birth.
Chiari malformation type III
In one of the most severe types of the condition, 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. This form of Chiari malformation is obvious at birth or by intrauterine ultrasound.
Chiari malformation type IV
In people with the even more severe Chiari malformation type IV, the brain itself has never developed normally. This form also is obvious at birth or by intrauterine ultrasound.
When to see a doctor
If you or your child has any of the signs and symptoms that may be associated with Chiari malformation, see your doctor for an evaluation.
Because many symptoms of Chiari malformation can also be associated with other disorders, a thorough medical evaluation is important. Head pain, for example, can be caused by migraines, sinus disease or a brain tumor, as well as Chiari malformation. Other signs and symptoms overlap with other conditions, such as multiple sclerosis.
Chiari malformation occurs when the section of the skull containing the cerebellum is too small or is deformed, thus putting pressure on and crowding the brain. The lowermost portion, or tonsils, of the cerebellum are displaced into the upper spinal canal. The pediatric form, Chiari II malformation, is always associated with a myelomeningocele. The adult form, Chiari I malformation, results primarily from a too small back portion of the skull.
When the cerebellum is pushed into the upper spinal canal, it can interfere with the normal flow of cerebrospinal fluid (CSF) that protects your brain and spinal cord. This impaired circulation of CSF can lead to the blockage of signals transmitted from your brain to your body, or to a buildup of spinal fluid in the brain or spinal cord. Alternatively, the pressure from the cerebellum upon the spinal cord or lower brainstem can cause neurological signs or symptoms.
In some people, Chiari malformation can become a progressive disorder and lead to serious complications. In others, there may be no associated symptoms, and no intervention is necessary. The complications associated with this condition include:
You're likely to start by seeing your family doctor or a general practitioner. However, in some cases when you call to set up an appointment, you may be referred to a doctor who specializes in disorders of the brain and nervous system (neurologist).
Because appointments can be brief, and because there's often a lot of ground to cover, it's a good idea to be well prepared for your appointment. Here's some information to help you get ready for your appointment, and what to expect from your doctor.
What you can do
Prepare a list of questions so that you can make the most of your limited time with your doctor. List your questions from most important to least important in case time runs out. For Chiari malformation, some basic questions to ask your doctor include:
In addition to the questions that you've prepared to ask your doctor, don't hesitate to ask questions during your appointment at any time that you don't understand something.
What to expect from your doctor
Your doctor is likely to ask you a number of questions. Being ready to answer them may reserve time to go over any points you want to spend more time on. Your doctor may ask:
What you can do in the meantime
To ease your discomfort while you wait to see your doctor, try taking a nonsteroidal anti-inflammatory drug (NSAID) such as ibuprofen (Advil, Motrin, others). Acetaminophen (Tylenol, others) also may relieve mild to moderate pain.
Exam and medical history
The diagnostic process begins with your doctor taking your medical history and giving you a complete physical examination. Your doctor will ask whether you're having symptoms such as head and neck pain, and will ask you to describe them. He or she will also check your fine motor skills and swallowing ability.
If you have symptoms such as head pain, and the exact cause isn't apparent to your doctor, you'll likely undergo a magnetic resonance imaging (MRI) scan of your skull, which is the definitive diagnostic tool for Chiari malformation. Your doctor might also use computerized tomography (CT).
Treatment for Chiari malformation depends on the severity and the characteristics of your condition. If you have no symptoms, your doctor likely will recommend no treatment other than monitoring with regular examinations.
When headaches or other types of pain are the primary symptom, your doctor may recommend pain medication. Some people experience symptom relief with anti-inflammatory or pain-relieving agents, such as indomethacin (Indocin). This approach may prevent or delay the need for surgery.
Reducing pressure by surgery
Surgery is the approach doctors use most often to treat symptomatic Chiari malformation. The goal is to stop the progression of changes in the anatomy of the brain and spinal canal, as well as ease or stabilize symptoms. When successful, surgery can reduce pressure on the cerebellum and the spinal cord, and restore the normal flow of spinal fluid.
In the most common operation for Chiari malformation — called posterior fossa craniectomy or posterior fossa decompression — your surgeon removes a small section of bone in the back of the skull, relieving pressure by giving the brain more room. The covering of the brain, called the dura, is then opened, and a patch is sewn in place to enlarge the covering and provide more room for the brain. This patch may be an artificial material, or it could be tissue harvested from your own leg or neck. The exact technique may vary, depending on whether a fluid-filled cavity is present, or if you have hydrocephalus. The operation takes about two to three hours, and recovery in the hospital usually requires two to four days.
Surgical risks and follow-up
The use of surgery carries risks — the possibility of infection or problems with wound healing. Discuss the pros and cons with your doctor when deciding whether surgery is the best alternative for you. The operation reduces symptoms in most people, but if nerve injury in the spinal canal has already occurred, this procedure won't reverse the damage.
After the operation, you'll need regular follow-up examinations with your doctor, including periodic imaging tests to assess the outcome of surgery and the flow of cerebrospinal fluid.