Chiari Malformation

Chiari (pronounced key-are-ee) malformation is a brain abnormality that causes the cerebellum, the part of the brain that controls balance, coordination and muscle movement, to protrude into the space normally occupied by the spinal cord. Some children are born with the condition, and others develop it as they grow

Chiari malformation causes pressure on the cerebellum, brain stem, and spinal cord that can keep them from working correctly. It can also block the movement of cerebrospinal fluid, the liquid that surrounds the brain and spinal cord and protects them from injury. When cerebrospinal fluid doesn't flow properly, it can build up in the brain and spinal cord and block communication of the brain's messages to the body.

Normally the cerebellum and parts of the brain stem sit in an indented space at the lower rear of the skull, above the foramen magnum (a funnel-like opening to the spinal canal). When part of the cerebellum is located below the foramen magnum, it is called a Chiari malformation.

Chiari malformations may develop when the bony space is smaller than normal, causing the cerebellum and brain stem to be pushed downward into the foramen magnum and into the upper spinal canal. The resulting pressure on the cerebellum and brain stem may affect functions controlled by these areas and block the flow of cerebrospinal fluid – the clear liquid that surrounds and cushions the brain and spinal cord – to and from the brain.

Most cases of Chiari malformations are congenital, which means that a child developed it in the womb and had it at birth. This is called primary or congenital Chiari malformation. In these cases, structural defects in the brain and spinal cord occur during fetal development, such as when the space at the back of the skull, where the cerebellum sits above the spine, is too small or is unusually shaped. These "cramped quarters" squeeze the cerebellum and even part of the brain stem, which controls the nerves in the face and neck, down through the foramen magnum (a funnel-like hole below the skull through which only the spinal cord usually passes). These congenital Chiari malformations may be due to a genetic mutation. They may also be related to a lack of proper vitamins or nutrients in the maternal diet.

Although doctors haven't been able to identify a gene that causes Chiari malformation, it does sometimes run in families, which indicates that it could be hereditary.

Chiari malformation can also be caused later in life if spinal fluid is drained excessively from the lumbar or thoracic areas of the spine either due to injury, exposure to harmful substances or infection. This is called acquired or secondary Chiari malformation. Primary Chiari malformation is much more common than secondary Chiari malformation.

There are four different types of Chiari malformation (I, II, III, and IV). Type I is by far the most common in children. Chiari malformations are classified by the severity of the disorder and the parts of the brain that protrude into the spinal canal and are as follows:

• Type I involves the extension of the cerebellar tonsils (the lower part of the cerebellum) into the foramen magnum, without involving the brain stem. Normally, only the spinal cord passes through this opening. Type I–which may not cause symptoms–is the most common form of Chiari malformation and is usually first noticed in adolescence or adulthood, often by accident during an examination for another condition. Type I is the only type of Chiari malformation that can be acquired.
• Type II, also called classic Chiari malformation, involves the extension of both cerebellar and brain stem tissue into the foramen magnum. Also, the cerebellar vermis (the nerve tissue that connects the two halves of the cerebellum) may be only partially complete or absent. Type II is usually accompanied by a myelomeningocele–a form of spina bifida that occurs when the spinal canal and backbone do not close before birth, causing the spinal cord and its protective membrane to protrude through a sac-like opening in the back. A myelomeningocele usually results in partial or complete paralysis of the area below the spinal opening. The term Arnold-Chiari malformation (named after two pioneering researchers) is specific to Type II malformations.
• Type III is the most serious form of Chiari malformation. The cerebellum and brain stem protrude, or herniate, through the foramen magnum and into the spinal cord. Part of the brain's fourth ventricle, a cavity that connects with the upper parts of the brain and circulates cerebrospinal fluid, may also protrude through the hole and into the spinal cord. In rare instances, the herniated cerebellar tissue can enter an occipital encephalocele, a pouch-like structure that protrudes out of the back of the head or the neck and contains brain matter. The covering of the brain or spinal cord can also protrude through an abnormal opening in the back or skull. Type III causes severe neurological defects.
• Type IV involves an incomplete or underdeveloped cerebellum–a condition known as cerebellar hypoplasia. In this rare form of Chiari malformation, the cerebellar tonsils are located in a normal position but parts of the cerebellum are missing, and portions of the skull and spinal cord may be visible.

Many kids with type I Chiari malformation have no signs and symptoms and don't even know that they have a malformation. They find out about it only when they're tested for another problem.

But if a Chiari malformation is severe enough to block the flow of cerebrospinal fluid or put significant pressure on the brain or spinal cord, a child's nervous system can be affected. Symptoms can include dizziness and problems with balance and coordination. This means a child might fall down a lot, walk unusually, have trouble grasping items, or have poor hand-eye coordination.

Other symptoms can include:

• Neck or chest pain
• Headaches that are brought on by coughing, sneezing, or laughing
• Difficulty swallowing, which may cause gagging, choking, or vomiting
• Difficulty speaking
• Rapid eye movements or vision problems like light sensitivity or blurred vision
• Hearing problems like a tinnitus (ear ringing) or hearing loss
• Weakness, numbness, tingling, or other abnormal feelings in the arms and legs
• insomnia
• Depression

Signs of Chiari malformation in babies include:

• Irritability when being fed
• Excessive drooling
• Weak cry
• Trouble gaining weight
• Arm weakness
• Developmental delays

Some children with Chiari malformations also have cognitive and behavioral problems. Doctors aren't sure whether a Chiari malformation directly causes these problems or whether they're simply the child's way of reacting to the condition and its symptoms.

Since the symptoms of Chiari malformations vary greatly and may mimic many other conditions, it's important to get an accurate diagnosis. If your child has already been diagnosed and you feel unsure about your child's diagnosis, the neurology team at Cook Children's is happy to provide a second opinion.

Individuals who have a Chiari malformation often have these related conditions:

• Hydrocephalus is an excessive buildup of cerebrospinal fluid in the brain. A Chiari malformation can block the normal flow of this fluid, resulting in pressure within the head that can cause mental defects and/or an enlarged or misshapen skull. Severe hydrocephalus, if left untreated, can be fatal. The disorder can occur with any type of Chiari malformation, but is most commonly associated with Type II.
• Spina bifida is the incomplete development of the spinal cord and/or its protective covering. The bones around the spinal cord don't form properly, leaving part of the cord exposed and resulting in partial or complete paralysis. Individuals with Type II Chiari malformation usually have a myelomeningocele, a form of spina bifida in which the bones in the back and lower spine don't form properly and extend out of the back in a sac-like opening.
• Syringomyelia, or hydromyelia, is a disorder in which a cerebrospinal fluid-filled tubular cyst, or syrinx, forms within the spinal cord's central canal. The growing syrinx destroys the center of the spinal cord, resulting in pain, weakness, and stiffness in the back, shoulders, arms, or legs. Other symptoms may include headaches and a loss of the ability to feel extremes of hot or cold, especially in the hands. Some individuals also have severe arm and neck pain.
• Tethered cord syndrome occurs when the spinal cord attaches itself to the bony spine. This progressive disorder causes abnormal stretching of the spinal cord and can result in permanent damage to the muscles and nerves in the lower body and legs. Children who have a myelomeningocele have an increased risk of developing a tethered cord later in life.
• Spinal curvature is common among kids, teens and young adults with syringomyelia or Chiari malformation Type I. Two types of spinal curvature can occur in conjunction with Chiari malformations: scoliosis, a bending of the spine to the left or right; and kyphosis, a forward bending of the spine. Spinal curvature is seen most often in children with Chiari malformation, whose skeleton has not fully matured.
• Certain hereditary syndromes that affect neurological and skeletal abnormalities, other disorders that affect bone formation and growth, fusion of segments of the bones in the neck, and extra folds in the brain may also appear in children, teens and young adults with Chiari malformations.

In the past, it was estimated that the condition occurs in about one in every 1,000 births. However, the increased use of diagnostic imaging has shown that Chiari malformation may be much more common. Complicating this estimation is the fact that some children who are born with the condition may not show symptoms until adolescence or adulthood, if at all. Chiari malformations occur more often in women than in men and Type II malformations are more prevalent in certain groups, including people of Celtic descent.

Many people with Chiari malformations have no symptoms and their malformations are discovered only during the course of diagnosis or treatment for another disorder.

If your doctor suspects a Chiari malformation, your child will be carefully examined and tested for things like speech, memory, cognition, balance, touch, reflexes, sensation, and motor skills. In addition, your doctor will probably want your child to undergo one or more of these tests:

• Magnetic resonance imaging (MRI) is the imaging procedure most often used to diagnose a Chiari malformation. Like CT, it is painless and noninvasive and is performed at an imaging center or hospital. MRI uses radio waves and a powerful magnetic field to produce either a detailed three-dimensional picture or a two-dimensional "slice" of body structures, including tissues, organs, bones, and nerves. Depending on the part(s) of the body to be scanned, MRI can take up to an hour to complete.
• An X-ray uses electromagnetic energy to produce images of bones and certain tissues on film. An X-ray of the head and neck cannot reveal a Chiari malformation but can identify bone abnormalities that are often associated with Chiari malformation. This safe and painless procedure can be done in a doctor's office and takes only a few minutes.
• Computed tomography (also called a CT scan) uses X-rays and a computer to produce two-dimensional pictures of bone and vascular irregularities, certain brain tumors and cysts, brain damage from head injury, and other disorders. Scanning takes about 3 to 5 minutes. This painless, noninvasive procedure is done at an imaging center or hospital on an outpatient basis and can identify hydrocephalus and bone abnormalities associated with Chiari malformation.
• Magnetic resonance imaging (MRI) is the imaging procedure most often used to diagnose a Chiari malformation. Like CT, it is painless and noninvasive and is performed at an imaging center or hospital. MRI uses radio waves and a powerful magnetic field to produce either a detailed three-dimensional picture or a two-dimensional "slice" of body structures, including tissues, organs, bones, and nerves. Depending on the part(s) of the body to be scanned, MRI can take up to an hour to complete.

"Right now, surgery is the only treatment option for clinically symptomatic Chiari malformations. Our process for the surgery requires a greater amount of time, but the protocols we've implemented have radically changed the level of safety available." - John Honeycutt, M.D.

There is no cure for Chiari malformation. However, most children who don't have symptoms won't require treatment. If your child does have Chiari malformation but doesn't have any symptoms, he or should continue to see their doctors for regular checkups to make sure that their condition doesn't change.

When symptoms do occur, treatment will focus on relieving them and stopping further damage to the brain and spinal cord (for example, medications may be used to ease symptoms like headaches and neck pain). And sometimes the doctor will recommend limiting activities that worsen symptoms.

For severe symptoms, surgery is the only treatment available to correct functional disturbances or halt the progression of damage to the central nervous system. If your child is referred for surgery, you will meet with the surgeon and your neurology team to determine the best plan of action for your child.

A common procedure for kids with Chiari malformation is decompression. It helps to relieve pressure on the brain and spinal cord, restore the flow of cerebrospinal fluid, and prevent additional damage. This surgery usually takes several hours and involves removing part of the skull and a portion of the spine's top vertebra.

Another surgical option involves implanting a shunt or tube to help drain cerebrospinal fluid and relieve pressure on the brain. Shunts are commonly used to help children who have hydrocephalus or syringomyelia.

Infants and children with myelomeningocele may require surgery to reposition the spinal cord and close the opening in the back.

While surgery is not a cure for Chiari malformations, in certain cases it can provide relief and help to restore your child's ability to do the everyday things that kids do, like run, jump, play, read, write and share special moments with family and friends. In other words, enjoy childhood as much as possible.