The Chiari I malformation (CM-I) is an uncommon congenital (present at birth) deformity of the lower compartment of the cranium called the posterior fossa that results in crowding of the brainstem and cerebellum. The lower part of the cerebellum, known as the cerebellar tonsils, protrudes down the opening at the base of the skull (known as the foramen magnum) and into the spinal canal. This results in tissue compression and decreased spinal fluid flow. Although the Chiari (pronounced kee-ar'-ee) I malformation can cause problems in childhood, many people do not develop symptoms until adulthood.

The Chiari I malformation is more common in women than in men though the exact cause is still unknown. People with CM-I may develop symptoms in their 20’s or 30’s, although they can develop sooner or later than this. Multiple symptoms are possible. Among the most common are headache, dizziness, blurred vision, neck pain, weakness, numbness, or tingling the arms, nausea, and problems swallowing.

Symptoms from the CM-I often develop in a slow and insidious manner. They are often vague and progress over a number of years. Many persons have symptoms for years before they are properly diagnosed. About 1 out of 4 patients develop symptoms after a mild or moderate trauma. Examples include falling off a trampoline, falling off a porch, or a blow to the back of the head.

Symptoms

Headache

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

The headache is often made worse by straining activities (known as valsalva maneuvers) such as coughing, sneezing, or even laughing or singing. Some patients report feeling as though “my head will explode” or “my head will pop off”. Bending forward, or looking up can worsen the headache. When the headache is intense, some patients note dizziness, blurring of vision, nausea, or a feeling of a “mental fog”.

Visual Symptoms

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

Dizziness & Auditory Symptoms

Dizziness is frequently seen in persons with CM-I. It is usually intermittent, often worse with the headache, and more noticeable when changing position. A sensation of spinning (vertigo), ringing in the ears (tinnitus), poor balance (disequilibrium), and decrease or loss of hearing may also occur.

Difficulty Swallowing & Hoarseness

People with CM-I may develop difficulty swallowing (dysphagia), either with liquids or solid foods, or a feeling of “catching” in the throat when attempting to swallow. The progression of this symptom may be rapid and result in aspiration (inhaling fluid or food products into the lungs). Change in voice character and timber is a common complaint. Hoarseness is often noted first by a family member or friend. Some persons report inability to modulate voice when singing or speaking loudly.

Pain

Persons 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. It is usually present or worse on one side. Along with pain, some patients experience weakness of the hand or arm, or difficulty with fine movements of the fingers. If syringomyelia is present, the pain may be more widespread.

Numbness

Tingling, numbness or 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. These symptoms are usually more noticeable if a person has a syrinx.

Problems Walking

Problems walking may be described as unsteadiness or listing to one side. Persons may report falling, or bumping into walls or doors. Infrequently, persons may present with spasticity (stiffness) of the legs. These symptoms occur more commonly with syringomyelia.

Respiratory, Heart, and Abdominal Symptoms

Effects of the CM-I on the respiratory and heart centers 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.

General & Cognitive Symptoms

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

Other Possible Conditions

It is important to note that other conditions can result in symptoms similar to that of the Chiari I malformation. Other conditions that should be considered include:

1. Migraine
   

2. Cluster headache
   

3. Rebound headache
   

4. Pseudotumor cerebri
   

5. Occipital neuralgia
   

6. Post-concussion syndrome
   

7. Hydrocephalus
   

8. Multiple sclerosis
   

9. Chronic fatigue syndrome
   

10. Fibromyalgia
    

11. Sleep apnea
    

12. Spinal fluid leak
    

13. Cervical disc degeneration
    

14. Psychiatric disease
    

Evaluation & Management

To learn about the evaluation and management of Chiari I malformation and syringomyelia, please visit the Treatment page.