Chiari malformation (also known as Arnold–Chiari malformation) is a condition in which brain tissue extends into your spinal canal. It occurs when part of the skull is abnormally small or misshapen pressing on the brain and forcing it downward. Chiari malformation is uncommon, but improved imaging tests have led to more frequent diagnoses.

What are the symptoms?

Doctors categorize Chiari malformation into three 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. Chiari malformation type I develops as the skull and brain are growing. 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.

Chiari Malformation Type I
Chiari malformation type I 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 lower part of the cerebellum is displaced into the upper spinal canal.

Severe headaches are the classic symptom of Chiari malformation. They generally occur after sudden coughing, sneezing or straining. People with Chiari malformation type I can also experience neck pain; balance problems; poor hand coordination, numbness and tingling of the hands and feet; dizziness, difficulty swallowing, sometimes accompanied by gagging, choking and vomiting; vision problems (blurred or double vision); and speech problems (hoarseness). Less frequent symptoms are ringing or buzzing in the ears, weakness, slow heart rhythm, curvature of the spine (scoliosis) related to spinal cord impairment, and abnormal breathing, such as central sleep apnea, characterized by periods of breathing cessation during sleep.

Chiari Malformation Type II
In Chiari malformation type II, which is present at birth, a greater amount of tissue extends into the spinal canal compared with Chiari malformation type I. The signs and symptoms can include those related to a form of spina bifida called myelomeningocele that nearly always accompanies Chiari malformation type II. In myelomeningocele, the backbone and the spinal canal have not closed properly before birth.

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. The pressure from the cerebellum upon the spinal cord or lower brainstem can cause neurological symptoms.
Symptoms may include: changes in breathing pattern, swallowing problems (gagging), quick downward eye movements and weakness in arms.

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 diagnosed at birth or by an ultrasound during pregnancy.

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

As many symptoms of Chiari malformation can also be associated with other disorders, a complete overall medical evaluation is important. In some cases, 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:

  • Hydrocephalus – an accumulation of excess fluid within the brain (hydrocephalus) may require placement of a flexible tube (shunt) to divert and drain the cerebrospinal fluid to another area of the body.
  • Spina bifida – a condition in which the spinal cord or its covering isn’t fully developed. Part of the spinal cord is exposed, which can cause serious conditions such as paralysis. People with Chiari malformation type II usually have a form of spina bifida called myelomeningocele.
  • Syringomyelia – a condition in which a cavity or cyst (syrinx) forms within the spinal column.
  • Tethered cord syndrome – in this condition, the spinal cord attaches to the spine and causes the spinal cord to stretch. This can lead to serious nerve and muscle damage in the lower body.

To diagnose the condition, the doctor will review a patient’s medical history and symptoms and conduct a physical examination. The doctor will also order imaging tests to diagnose and determine the cause of the condition. Tests may include:

A Magnetic Resonance Imaging (MRI) scan uses powerful radio waves and magnets to create a detailed view of your body. This safe, painless test produces detailed 3-D images of structural abnormalities in your brain that may be contributing to your symptoms. It can also provide images of the cerebellum and determine whether it extends into the spinal canal. An MRI is often used to diagnose Chiari malformation. An MRI can be repeated over time, and it can be used to monitor the progression of the disorder.
The doctor may recommend other imaging techniques, such as a Computerized Tomography (CT) scan. A CT scan uses X-rays to obtain cross-sectional images of the body.

What are the treatment options?

Treatment for Chiari malformation depends on the severity and the characteristics of the condition. If a patient has no symptoms, the doctor likely will not recommend treatment other than monitoring with regular examinations and MRIs. When headaches or other types of pain are the primary symptom, pain medication may be recommended.

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 (known as 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 (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 tissue harvested from another part of the body.

The doctor also may 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 a patient has fluid in the brain (hydrocephalus). If a patient has a syrinx or hydrocephalus, he or she may need a tube (shunt) to drain the excess fluid.

The surgery involves risks, including the possibility of infection, fluid in your brain, cerebrospinal fluid leakage or problems with wound healing. Patients should discuss the pros and cons with their doctor when deciding whether surgery is the most appropriate alternative.

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, patients will need regular follow-up examinations with their doctor, including periodic imaging tests to assess the outcome of surgery and the flow of cerebrospinal fluid.