About arnold-chiari malformation

What is arnold-chiari malformation?

Chiari malformations are a group of complex brain abnormalities that affect the area in lower back of the skull where the brain and spinal cord connect. Chiari malformations are thought to be present at birth (congenital), although in many cases they may not become apparent until adulthood. In extremely rare cases, a Chiari malformation may be acquired during life.

The exact cause of Chiari malformations are not known, but often the cavity near the base of the skull (posterior fossa) is narrow and abnormally small in relation to the size of the cerebellum, which this portion of the skull encloses. Researchers believe that in some cases the small posterior fossa may cause the developing brain, specifically the cerebellum and the brainstem, to be pushed downward. Part of the cerebellum (known as the cerebellar tonsils) may protrude (herniate) through the foramen magnum, which is the normal opening found in the occipital bone at the base of the skull and the neck. The tonsils thus interfere with the flow of cerebrospinal fluid (CSF) to and from the skull and spinal canal, potentially leading to accumulation of cerebral spinal fluid in the subarachnoid spaces of the brain and spine.

A Chiari malformation can also cause pressure on the brain and produce hydrocephalus (pressure due to excessive cerebrospinal fluid accumulation in the brain) and the spinal cord, potentially causing a wide variety of symptoms. In fact, no two cases of Chiari malformation are exactly alike and the associated symptoms are highly variable. The severity of Chiari malformations can vary dramatically as well. In some cases, affected individuals may not develop any symptoms (asymptomatic); in others, severe, potentially debilitating or life-threatening symptoms can develop.

Traditionally, Chiari malformations have been defined and classified by how much of the cerebellar tonsils protrude through the foramen magnum. A diagnosis of a Chiari malformation usually signifies that the cerebellar tonsils protrude below the foramen magnum (often cited as at least 5 millimeters). However, researchers have determined that the length of tonsil descent in a Chiari malformation does not always correspond to the severity of symptoms or to the response to treatment. In fact, some individuals are classified as having Chiari malformation type 0, in which there is minimal or no descent of the cerebellar tonsils. These individuals still have symptoms associated with a Chiari malformation, most likely due to abnormalities in the flow of cerebrospinal fluid within the skull and spinal canal. Research is ongoing to understand the complex, underlying mechanisms that cause Chiari malformations.

Chiari malformations are named for Hans Chiari, an Austrian pathologist, who first identified type I-III in 1891. Julius Arnold further expanded the definition of Chiari malformation type II and some medical sources began using the name Arnold-Chiari malformation. Nowadays, some medical sources use Arnold-Chiari malformation as a broad term for all forms. Chiari malformations have also been known as congenital tonsillar herniation, tonsillar ectopia or tonsillar descent.

What are the symptoms for arnold-chiari malformation?

The more common types of Chiari malformation are:

  • Type 1
  • Type 2

Although these types are less serious than the rarer pediatric form, type 3, signs and symptoms still can be life disrupting.

Chiari malformation type 1

In Chiari malformation type 1, signs and symptoms usually appear during late childhood or adulthood.

Headaches, often severe, are the classic symptom of Chiari malformation. They generally occur after sudden coughing, sneezing or straining. People with Chiari malformation type 1 can also experience:

  • Neck pain
  • Unsteady gait (problems with balance)
  • Poor hand coordination (fine motor skills)
  • Numbness and tingling of the hands and feet
  • Dizziness
  • Difficulty swallowing, sometimes accompanied by gagging, choking and vomiting
  • Speech problems, such as hoarseness

Less often, people with Chiari malformation may experience:

  • Ringing or buzzing in the ears (tinnitus)
  • Weakness
  • Slow heart rhythm
  • Curvature of the spine (scoliosis) related to spinal cord impairment
  • Breathing problems, such as central sleep apnea, which is when a person stops breathing during sleep

Chiari malformation type 2

In Chiari malformation type 2, a greater amount of tissue extends into the spinal canal compared with that in Chiari malformation type 1.

The signs and symptoms can include those related to a form of spina bifida called myelomeningocele that nearly always accompanies Chiari malformation type 2. In myelomeningocele, the backbone and the spinal canal don't close properly before birth.

Signs and symptoms may include:

  • Changes in breathing pattern
  • Swallowing problems, such as gagging
  • Quick downward eye movements
  • Weakness in the arms

Chiari malformation type 2 is usually noted with ultrasound during pregnancy. It may also be diagnosed after birth or in early infancy.

Chiari malformation type 3

In the most severe type of the condition, Chiari malformation type 3, a portion of the lower back part of the brain (cerebellum) or the brainstem extends through an opening in the back of the skull. This form of Chiari malformation is diagnosed at birth or with an ultrasound during pregnancy.

This type of Chiari malformation has a higher mortality rate and may also cause neurological problems.

What are the causes for arnold-chiari malformation?

Chiari malformation type 1 occurs when the section of the skull containing a part of the brain (cerebellum) is too small or is deformed, thus putting pressure on and crowding the brain. The lower part of the cerebellum (tonsils) is displaced into the upper spinal canal.

Chiari malformation type 2 is nearly always associated with a form of spina bifida called myelomeningocele.

When the cerebellum is pushed into the upper spinal canal, it can interfere with the normal flow of cerebrospinal fluid that protects the brain and spinal cord.

This impaired circulation of cerebrospinal fluid can lead to the blockage of signals transmitted from the brain to the body, or to a buildup of spinal fluid in the brain or spinal cord.

Alternatively, the pressure from the cerebellum on the spinal cord or lower brainstem can cause neurological signs or symptoms.

What are the treatments for arnold-chiari malformation?

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 and MRIs.

When headaches or other types of pain are the primary symptom, your doctor may recommend pain medication.

Reducing pressure with surgery

Doctors usually treat symptomatic Chiari malformation with surgery. 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 spinal cord and restore the normal flow of spinal fluid.

In the most common surgery for Chiari malformation, called posterior fossa decompression, the surgeon removes a small section of bone in the back of the skull, relieving pressure by giving the brain more room.

In many cases, the covering of the brain, called the dura mater, may be opened. Also, a patch may be 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 another part of the body.

Your doctor may also remove a small portion of the spinal column to relieve pressure on the spinal cord and allow more space for the spinal cord.

The surgical technique may vary, depending on whether a fluid-filled cavity (syrinx) is present, or if you have fluid in your brain (hydrocephalus). If you have a syrinx or hydrocephalus, you may need a tube (shunt) to drain the excess fluid.

Surgical risks and follow-up

Surgery involves risks, including the possibility of infection, fluid in the brain, cerebrospinal fluid leakage or problems with wound healing. Discuss the pros and cons with your doctor when deciding whether surgery is the most appropriate treatment for you.

The surgery 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 surgery, 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.

What are the risk factors for arnold-chiari malformation?

There's evidence that Chiari malformation runs in some families. However, research into a possible hereditary component is still in its early phase.

Is there a cure/medications for arnold-chiari malformation?

If you have no symptoms, your doctor likely will recommend no treatment other than monitoring with regular examinations and .

Doctors usually treat symptomatic Chiari malformation with surgery. 

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