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Chiari malformation

Learn more about the Chiari malformation — its causes, symptoms and treatments — as well as helpful resources to assist in your recovery.

What is the Chiari-1 malformation?

The Chiari malformation type I (sometimes called Chiari-1 malformation or CM-1) is an uncommon, complex, neurological abnormality that is present at birth. The abnormality involves the back of the brain (cerebellum) coming through the back of the skull. The pressure of this bulge can result in a variety of neurological symptoms, typically occurring when you are an adult, that can decrease your overall quality of life.

Although there is a form of Chiari malformation which occurs in children with meningomyelocele, the Chiari 1 malformation more frequently causes problems in adults.

Because each person can experience drastically different symptoms from another, it may be difficult for providers to diagnose Chiari malformations.

What causes the Chiari-1 malformation?

The exact cause is unknown. It is believed that in many, though not all, the condition develops during early embryonic development of the posterior fossa. In most persons affected, the posterior fossa is smaller than normal and causes crowding of the lower brainstem and a shift of the cerebellar tonsils downward into the former magnum.

Chiari-1 malformation symptoms

Symptoms often develop in a slow and subtle manner. Frequently, the symptoms are vague and progress over a number of years, with many experiencing symptoms for years before being properly diagnosed.

While you may develop symptoms in childhood, adolescence, middle age or even older, typically, symptoms begin developing around the time of your twenties or thirties. You may also develop symptoms after a mild or moderate trauma, such as falling off a trampoline or experiencing a blow to the back of the head.

The condition occurs more often in women than men, but there is no particular ethnic or geographic incidence of the disorder. While in some rare cases it can be passed down in families, a specific gene causing the malformation has not been identified.

Dizziness and auditory symptoms

Dizziness is usually intermittent, often worse with a headache, and more noticeable when changing positions. A sensation of spinning (vertigo), ringing in the ears (tinnitus), poor balance (disequilibrium) and decrease or loss of hearing may also occur.

General and cognitive symptoms

These include poor sleep (insomnia), fatigue and depression. Some note problems with memory, thinking, speech and difficulty with word finding. People may report the feeling of a "brain fog," with difficulty in thinking and concentration. Difficulty in finding the right word may also occur.


The most common symptom is a headache. It usually begins at the back of the head and radiates behind one or both eyes, to the top of the head or near the temples. The headache is often described as a pressure sensation but can be heavy, pounding, sharp or stabbing. For many, the pain varies between these and other sensations.

The headache is often made worse by straining activities, such as coughing, sneezing, or even laughing or singing. Bending forward or looking up can worsen the headache, and when it is particularly intense, you may experience dizziness, blurring of vision, nausea or mental fog.

Hoarseness and difficulty swallowing

Difficulty swallowing (dysphagia), either with liquids or solid foods, or a feeling of "catching" in the throat, can occur when attempting to swallow. The progression of dysphagia may be rapid and result in aspiration (inhaling fluid or food products into the lungs). Change in voice character and timber are also common complaints. Hoarseness is often noted first by a family member or friend, while some report the inability to modulate voice when singing or speaking loudly.


With Chiari-1 malformation, you may complain of neck or arm pain. Often the pain is worse with exertion, fatigue, or lifting. The pain may be dull and aching, or shooting and stabbing, and it is usually present or worse on one side. Along with pain, some experience weakness of the hand or arm, or difficulty with fine movements of the fingers.


Tingling, numbness or a "pins and needles” sensation often occur in the same areas as the pain. Numbness can progress over months to years, and involve the lower extremities and trunk.

Problems walking

Problems walking may be described as unsteadiness or listing to one side. You may report falling or bumping into walls or doors. Infrequently, patients may have spasticity (stiffness and jerkiness) of the legs.

Respiratory, heart and abdominal symptoms

Effects on the respiratory and cardiovascular systems can cause shortness of breath, chest pain, episodes of rapid heart rate (tachycardia), black out spells and hypertension. Abdominal symptoms may include nausea, abdominal pain or vomiting.

Visual symptoms

A variety of visual symptoms can occur, including double vision, decreased peripheral vision, seeing flickers of light, visual loss, blind spots, photophobia (sensitivity to bright lights), spasm of the eyelids (blepharospasm) and jerking of the eyes (nystagmus).

Diagnostic testing for Chiari-1 malformation

The first step in the diagnostic process is a thorough neurological evaluation. The evaluation assesses cognitive and cerebellar function, reflexes, sensory and motor skill and cranial nerve function.

If not already complete, labs and imaging studies will be performed to create an anatomical picture of the brain and cervical spine. These imaging studies may include magnetic resonance imaging (MRI) or CINE MRI flow analysis.

If Chiari-1 malformation is confirmed, your neurosurgeon will discuss the various treatment options available.

Treatments for Chiari-1 malformation

The number of people with the Chiari-1 malformation has been estimated to be one in 1,200, though it may actually be more common, as many with the condition have no symptoms and may not get tested.

Not everyone needs interventional treatment. When symptoms are mild, treatments such as relaxation, dietary recommendations, lifestyle changes and medications for headaches can be sufficient.

When symptoms do not respond to conservative treatments, surgery can be considered.

Surgery for Chiari malformation

The goal of Chiari malformation surgery, often called a posterior fossa decompression procedure, is to relieve the crowding at the bottom of the posterior fossa and upper cervical spinal canal. This surgery is done to reshape the opening at the base of the skull, thereby relieving pressure on the protruding brain tissue.

Your Chiari malformation surgeon will customize your particular procedure based on an analysis of the morphology (shape and form) of your skull, the effect on neurological tissues and any findings during surgery. The overwhelming majority of those who have the surgery experience relief within the first year.

Please note that we do not treat children younger than 16 years of age. For patients under the age of 16, please refer to these sites:

Chiari malformation surgery recovery

After surgery, some people have remarkable recoveries, while others show improvement but still have lingering problems. Recovery takes time and you should set realistic expectations for yourself. The reality is that you will experience some good days and some days when things seem achy or sore. This is normal. Slowly increasing activity, eating healthy, avoiding strenuous lifting, adhering to your doctor's instructions and maintaining a positive attitude are the best ways to allow your body to recover.

Concentrate and focus on the symptoms that have improved, instead of what symptoms remain. The goal is not to recover fully in the first two weeks, but to generally progress and recover over the months following surgery.

Your surgeon will work with you closely to help you understand what to do and not do after surgery, while you are in recovery.

Chiari malformation support resources

The support you receive from your family, friends and other sources is an important component of your treatment plan and recovery. Support services for if you are experiencing Chiari-1 malformation, syringomyelia and tethered cord syndrome are growing.

Many of these organizations offer information about support groups, message boards, chat rooms, patient stories and much more.

For more information about Chiari-1 malformation, its effects, how it affects children, among other topics, visit our frequently asked questions page or the Chiari Medicine blog.