All About Chiari Malformation

All About Chiari MalformationChiari malformations (CM) are structural defects in the cerebellum where the lower part of the brain pushes down into the spinal canal. Chiari malformations are named for Hans Chiari, an Australian pathologist who first identified types 1 and 3 in 1891. Julius Arnold further expanded the Type 2 Chiari malformation definition. Chiari malformations are also called Arnold Malformations (ACM), hindbrain, or tonsillar ectopia.
At American Neurospine Institute, PLLC, we offer treatment and management of Chiari malformation customized to your needs to improve your quality of life.

What Causes Chiari Malformations

If CM occurs during fetal stages, it’s known as congenital or primary CM. Several factors may cause primary CM, such as:

  • Genetic mutations that may cause the fetus to develop abnormally
  • Infection or high fever during pregnancy may affect fetal development.
  • Lack of proper vitamins and nutrients during pregnancy, such as folic acid, may affect fetal development
  • Fetal development may be affected by exposure to hazardous chemicals, illegal drugs, or alcohol

Types of Chiari malformations

There are four main types, but types 1 and 2 are the most common.

Chiari Malformation Type 1
Chiari malformation type 1 may not have any symptoms and often goes undetected until adolescence or adulthood; it develops when the skull and brain are still growing. The lowest part of the back of the brain extends into the spinal canal. This can pressure the brainstem and spinal cord and obstruct fluid flow.

Chiari Malformation Type 2
This is also known as classic CM or pediatric Chiari malformation. It is more severe than type 1, and generally, symptoms become apparent during childhood. It is invariably associated with spina bifida, a congenital disability that occurs due to incomplete closure of the posterior spinal cord and bony vertebral arch (lamina). This anomaly leaves a portion of the spinal cord exposed through the spinal canal, typically forming a sac filled with cerebrospinal fluid, meninges, and portions of the spinal cord and nerves (myelomeningocele). This type can also be associated with other significant neurological conditions, including complex anomalies of the brain.

Chiari Malformation Type 3
Chiari malformation type 3 is extremely rare and more severe than Chiari malformation types 1 and 2. It can involve severe neurological defects and may have life-threatening complications. It is often accompanied by hydrocephalus, a fluid accumulation in the brain.

Chiari Malformation Type 4
This is the most severe form and is usually fatal during infancy. Unlike types 1-3, Chiari malformation type 4 is not associated with herniation of the brain through the foramen magnum. In this condition, the brain is underdeveloped (hypoplastic) or fails to develop (aplastic)

Chiari Malformation Type 0
Some individuals with this type of CM have minimal or no herniation of the cerebellar tonsils through the foramen magnum. They, however, have syringomyelia despite the lack of cerebellar tonsil herniation.

Chiari Malformation Symptoms

The signs and symptoms of Chiari malformation vary significantly from person to person. Some people may be asymptomatic (show no symptoms). In contrast, others may have severe manifestations such as neurological deficit symptoms that can occur in different combinations and generally reflect dysfunction of the cerebellum, brainstem, spinal cord, and lower cranial nerves. Some only appear in childhood, adolescence, or early childhood. Common symptoms include:

  • Severe headache felt at the base of the head
  • Dizziness
  • Poor coordination and balance problems
  • Muscle weakness
  • Neck pain
  • Double vision (diplopia), abnormal sensitivity to light(photophobia), blurred vision, involuntary eye movements (nystagmus), and pain behind the eyes.
  • Apnea
  • Scoliosis
  • Breathing problems
  • Hearing loss
  • Trouble swallowing

Conditions Associated with Chiari Malformations

The following conditions are associated with Chiari malformation:

  • Hydrocephalus: This is an excessive buildup of fluid in the brain. A CM can block the normal flow of this fluid and cause pressure within the head that can result in mental impairment and an enlarged or misshapen skull. Severe hydrocephalus, if left untreated, can be fatal.
  • Spina bifida: This is the incomplete closing of the backbone and membraneas around the spinal cord.
  • Syringomyelia: Is a disorder in which a CFS-filled tubular cyst called syrinx forms within the spinal cord and presses on nerves, resulting in pain, weakness, and stiffness and may include a loss of the ability to feel extremes of hot or cold, especially in the hands


Diagnosis is based on detailed patient history and a thorough clinical and neurological exam. The doctor will perform a physical exam and check the person’s memory, reflexes, cognition, balance (functions controlled by the cerebellum), touch, sensation in the hands and feet, and motor skills (functions controlled by the spinal cord).
The doctor may also order imaging tests, including:

  • Magnetic resonance imaging (MRI) helps to show bones and soft tissues. It can help show the extent the cerebellum is extending to the spinal cord
  • Cine MRI to measure and assess cerebrospinal fluid (CSF) flow.
  • Computed tomography (CT) scans may help to clarify congenital bony abnormalities at the base of the skull.
  • X-rays can reveal skeletal malformations such as skull defects, abnormalities of cervical vertebrae, abnormal curvature, or abnormal spine motion.

Treatment of Chiari Malformation

Treatment depends on the severity of the symptoms. For mild symptoms that do not interfere with daily life and activities, your health will be regularly monitored with MRIs. Pain relief medications may be prescribed to alleviate headaches.

More severe cases may need surgery. The goals of surgery are to:

  • Optimal decompression of nerve tissue
  • Relieve pressure on the brain and spinal cord
  • Reconstruction of normal CFS flow around and behind the cerebellum
  • Re-establish normal fluid circulation through and around the area

Surgical procedures to treat Chiari malformation include:
Posterior fossa decompression: This is the most common procedure to treat Chiari malformation. This involves the removal of a small portion of the bottom of the skull called the posterior fossa and sometimes part of the spinal column to correct the irregular bony structure.

Laminectomy: The surgeon may also need to remove a small portion of bones covering the spinal column to restore the flow of cerebrospinal fluid and allow more room for the spinal cord.

Electrocautery: This creates more room and allows the cerebrospinal fluid (CFS) to drain; surgeons may apply a small amount of electricity to shrink a small part of the brain called the cerebellar tonsils. The cerebellar tonsils retract without causing neurologic damage.

Duraplasty: In this decompression surgery, the surgeon opens the dura (a membrane on the outside of the brain). Then the surgeon sews in a patch to make the membrane larger so the brain has more room. This procedure enlarges the area and relieves pressure on the brain.

For more information, contact American Neurospine Institute, PLLC, today or schedule an appointment online.

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