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Chiari Malformation Types: How Are They Different?

Chiari Malformation Types: How Are They Different?

Chiari malformations (CMs) are a structural problem at the base of the skull. They occur when the cerebellum, which normally sits above an opening in the skull called the foramen magnum, pushes through the opening and down into the spinal canal.

This condition can lead to severe complications, including hydrocephalus, a buildup of cerebrospinal fluid within the cranial cavity, and spina bifida, a hole in the spinal column where it doesn’t fuse properly during development. CMs are estimated to affect less than one in 1,000 people.

At Center for Neurosurgery Las Vegas, board-certified neurosurgeon Dr. Scott Glickman and his team offer surgical options for their patients with Chiari malformations. Here’s what you need to know about the different types of CMs and what can be done to treat them.

Causes of and risk factors for Chiari malformation

When CM results from a developmental problem in the brain and spinal cord during pregnancy, it’s called a primary or congenital Chiari malformation. When it’s caused later in life, say, if an excessive amount of cerebrospinal fluid is drained as a result of traumatic injury, disease, or infection, it’s called an acquired or secondary Chiari malformation. This is less common than the primary form.

CMs may run in some families, suggesting a genetic link, though research is still in an early phase. Another possible risk factor is exposure to toxins during pregnancy.

The difference between the types of Chiari malformation

Doctors divide CMs into three types, depending on which parts of the brain tissue are displaced into the spinal canal and which developmental problems of either the brain or spine are evident.

Type I

A small or deformed skull while the fetus is still developing pushes the cerebellum slightly through the foramen magnum. This is the most common form.

People with a type I Chiari malformation experience severe headaches at the base of the skull, often after a sudden fit of coughing or sneezing. Other symptoms include:

Many people with type I CM don’t display any symptoms, and the condition may not be discovered until many years later during routine testing for another condition.

Type II

The cerebellum and brain stem tissue both extend through the foramen magnum, and nerve tissue connecting the halves of the cerebellum may be missing. This type is usually accompanied by a myelomeningocele, a form of spina bifida.

Since people with type II Chiari malformation have a greater amount of tissue extending into the spinal canal, it almost always leads to the failure of the spinal canal and the backbone to close properly before birth. Patients experience:

Spinal curvature, such as scoliosis or kyphosis, are also common in this type. So is tethered spinal cord syndrome, a neurologic disorder caused when the spinal cord attaches itself to the base of the spine, causing an abnormal stretching of the cord.

Type III

This is the most serious type of CM, as some of the cerebellum and brain stem spill through an opening formed in the back of the skull. Symptoms appear in infancy and cause debilitating and life-threatening complications, including severe neurological problems and a high mortality rate.

Treating Chiari malformation

CMs not accompanied by symptoms might not need treatment. Dr. Glickman may recommend a wait-and-see approach using periodic MRIs for routine monitoring.

Often, though, especially for types II and III, surgery is the only treatment available to alleviate symptoms and stop the ongoing damage to the central nervous system. In fact, you might need more than one surgery to address all issues.

The most common surgery for CM is posterior fossa decompression. It’s a procedure that creates more space for the cerebellum, thereby relieving pressure on the spinal cord and helping restore the normal flow of cerebrospinal fluid.

In the case of hydrocephalus, Dr. Glickman may insert a shunt in the head to drain the excess cerebrospinal fluid into either the chest cavity or the abdomen. There, it’s absorbed by the body.

The exact course of treatment depends on the type of CM you have, the severity of symptoms, and your overall health.

To learn more about Chiari malformations, or to schedule a consultation with Dr. Glickman, contact Center for Neurosurgery Las Vegas by calling 702-929-8242, texting us at 725-210-0057, or booking your appointment online.

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