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What Is a Chiari Malformation? All You Need to Know

The headaches and neck pain got worse over time.  The dizziness made simple tasks challenging.  Medications and physical therapy did not help.  Your doctor is concerned and thinks you may have a Chiari Malformation.  What is a Chiari Malformation (CM)? What are the different types of Chiari Malformations? What are the symptoms of a Chiari Malformation? What are the causes of a Chiari Malformation? What are the common treatments for Chiari Malformations? How is it diagnosed? What other conditions are associated with Chiari Malformations?  Let’s dig in.


Chiari Malformation is a medical condition where a part of the brain bulges through a normal opening at the base of the skull.  Under normal circumstances, the brain is not intended to descend or bulge through this opening.  This creates additional pressure on the delicate brain tissue which can cause multiple symptoms.

What Is a Chiari Malformation (CM)? chiari malformation

Chiari Malformation Is a medical condition where a part of the brain at the back of the skull abnormally descends through an opening in the skull.  It is named after Dr. Hans Chiari who was an Austrian pathologist who in the late 1880’s studied deformities of the brain.

The brain is a large structure divided into different parts that reside within the skull.  Important parts of the brain called the Cerebellum and Brainstem sit at the base of the skull.  The Foramen Magnum is a large hole at the base of the skull that allows the brain to join the spinal canal.  The Cerebellum and Brainstem under normal conditions sit above the boney opening at the base of the brain (Foramen Magnum).

In Chiari Malformations the Cerebellum and Brainstem move below the level of Foreman Magnum putting pressure on the lower parts of the brain (1).  It can also affect the flow of spinal fluid around the brain and spinal cord.

Chiari Malformation can occur when the opening at the base of the skull is not large enough or when there is abnormal pressure in the brain pushing it downward.

Chiari Malformations are categorized into 4 major types based upon anatomical abnormality and whether congential defects are present (2).

Chiari Type 1 Malformation

This malformation occurs during fetal development and is characterized by downward movement of the Cerebellum beneath the boney opening at the base of the skull (Foramen Magnum).  It is typically 4 mm.  Why is this important?

It can block the flow of spinal fluid between the spinal canal and brain leading to an increase in pressure.  It can also put pressure on the lower portion of the brain with varying symptoms.  Chiari Type 1 Malformation is typically associated hydrosyringomyelia which is a fluid-filled cyst within the spinal cord.

Chiari Type II Malformation

In Chiari Type II Malformation a greater amount of tissue extends down into the spinal canal compared to Chiari Type 1.  It is usually associated with a myelomeningocele which is a form of Spina Bifida.  This is a condition where the spinal canal and the backbone do not close before birth.

Chiari Type III Malformation

This is the most severe form of Chiari Malformation.  A significant amount of the brain is pushed through the opening at the base of the skull. This form of CM is diagnosed at birth or with ultrasound during pregnancy.

Chiari Type IV Malformation

Type IV is rare and involves an incomplete or underdeveloped Cerebellum.  This is also referred to as Cerebellar Hypoplasia.  In this type of CM the cerebellum is in its normal position in relation to the Foramen Magnum but parts of it are missing.

Symptoms of Chiari Malformation

Many people with Chiari Malformation have no signs or symptoms (3).  Symptoms can change depending upon the amount of brain and nerve compression and increase in cerebral spinal fluid pressure.  The downward displaced Cerebellum and Brainstem restrict the flow of cerebral spinal fluid from the brain into the spinal cord.  Accordingly, it backs up with increased pressure within the skull.  Abnormal pressure is also applied to the Cerebellum and Brainstem.  The Cerebellum controls the coordination of movement.  You know the wonderful coordination that is involved with walking, talking, dancing, and running. The Brainstem on the other hand controls many basic life functions such as heart rate, blood pressure, breathing, and level of consciousness.

Symptoms may include:

  • Headache
  • Neck Pain
  • Dizziness
  • Ringing in the ears (tinnitus)
  • Arm and Leg weakness and numbness
  • Difficulty with swallowing
  • Breathing problems
  • Problems with hand coordination
  • Nausea and Vomiting
  • Balance problems

Symptoms of Chiari Malformation Type I

In Chiari Malformation Type 1 symptoms typically occur in late childhood or early adulthood. Headaches are the classic symptom for Chiari Malformation.  They are typically in the back of the head and brought on by coughing or sneezing.  A patient may also experience any of the symptoms listed above including headache and balance problems.

Symptoms of Chiari Malformation Type II

In CM Type II a larger amount of the brain extends through the Foramen Magnum into the spinal canal. Increased pressure is applied to the brain resulting in varying symptoms.
What is unique about CM Type II is its association with a form of spina bifida.  Spinal Bifida is a birth defect in which the spinal column does not form properly.  It has many different forms and presentations. Symptoms of CM Type II typically appear during childhood and typically are caused by problems associated with Spina Bifida.  These include:

Involuntary rapid eye movements

Irregular breathing

Loss of arm and leg strength.

Symptoms of Chiari Malformation Type III

Symptoms of this severe and rare condition appear at birth or in infancy. They can cause life-threatening complications.  They can also be associated with severe neurologic conditions such as seizures and delayed growth.

Causes of Chiari Malformation

Chiari Malformations are complex with different types with varying symptoms depending upon the severity of the injury.  In general, there are two principal causes of Chiari Malformations:


Otherwise known as a birth defect, these involve structural defects in the brain and spinal cord during pregnancy.


Unlike congenital causes of Chiari Malformation, these typically occur later in life.  They may be due to traumatic injury, disease, or infection.   Illness or trauma may cause an increase in the pressure within the skull.  The skull is a boney structure that is not pliable or expandable.  The opening at the base is the only outlet.  Increased pressure within the brain therefore can put downward pressure on the brain.

Common Treatments for Chiari Malformation

Chiari Malformations are classified into four major groups based upon type and severity of tissue injury.  Type 1 and 2 Chiari Malformations are the most common.  Treatment is dependent upon the type of the malformation, its severity, the amount of tissue involvement, and symptoms.


Most patients with Chiari 1 Malformation do not have symptoms or functional limitations and therefore only require regular follow-up with their providers.  Period imaging may be required along with medications to address pain and headache.


There are several surgical options depending upon the type of CM, its severity and associated problems.  The most common surgery is called posterior fossa decompression.  It involves removing a portion of the bone at the base of the skull.   The surgery creates more space for the brain.  It doing so reduces the amount of pressure on the brain and can improve spinal fluid flow. The intended goal is to improve symptoms and function.

Diagnosis and Examination

Many patients with Chiari malformation have NO symptoms and their malformation is only discovered during the evaluation and treatment of another disorder.

There are a number of tests that can help diagnose and determine the severity of the malformation. The most common includes:

Magnetic Resonance Imaging (MRI)

A powerful imaging tool that uses a strong magnetic field, magnetic field gradient, and radio waves to create 3-D images of the body. The brain, Cerebellum, Brainstem, and spinal fluid are easily visualized and evaluated.

Computed Tomography Scan (CT)

Another powerful imaging tool that uses x-ray.  Multiple x-rays are taken at different angles to provide detailed imaging.

Sleep Study

A dedicated study where your breathing, snoring, level of oxygenation, and seizure activity is closely monitored and recorded.  Lack of breathing called apnea is also evaluated.

Swallowing Study

A specialized x-ray procedure that watches the swallowing process to determine if any lower brain dysfunction is present.


Other Conditions Associated with Chiari Malformations

Chiari Malformation is a collection of conditions characterized by abnormal bulging or descent of the cerebellum and or brain stem through a boney opening at the base of the skull called the foramen magnum.  There are other conditions associated with Chiari malformations which include:

Tethered Cord Syndrome

Tethered cord syndrome is a group of neurologic disorders that occur as a result of chronic traction on the spinal cord due to it’s being “tethered” or held by various structures.

Spinal Curve

Spinal curvature is common and may involve curving of the spine to the right or left which is called Scoliosis.  Another form is where one is abnormally bent forward which is called Kyphosis.  There may also be rotational curving of the spine which is called Rotatory Scoliosis.


Hyrdocephalus is a medical condition characterized by an excessive buildup of cerebral spinal fluid in the brain. If left untreated the condition can become life threatening.  This can occur with CM as it blocks the flow of cerebral spinal fluid which then backs up into the brain.


This is a medical condition characterized by a fluid-filled cyst within the spinal cord.  It is oftentimes called a Syrinx.  If expanding, the Syrinx can damage the spinal cord and compromise the nerves, and transmitted information from the brain to the rest of the body.

Treating Chiari Malformations and Associated Symptoms

Many patients with Chiari Malformations have no signs or symptoms. The list of symptoms associated with Chiari Malformation is extensive.   Oftentimes the symptoms are not unique to Chiari Malformations.  For example, neck pain is a common complaint but can arise from a number of different clinical conditions other than CM.  So too with headaches.  It is critical that a thorough and extensive evaluation be completed.  Evaluation of all possible sources of a given complaint must be examined.

Many of these symptoms associated with Chiari Malformations and how they are interrelated is poorly understood by many medical providers.  What is worse is many are simply not interested nor have sufficient time to put together all the pieces. All too often patients with headache, neck pain and other mild neurologic symptoms are dismissed as drug seekers or as having emotional and psychological issues.

At the Centeno-Schultz Clinic we are experts in the evaluation and treatment of neck and head pain.  At a new patient evaluation time is dedicated to reviewing past medical history, current symptoms, alleviating and aggravating factors, current radiographic imaging in addition to performing a thorough evaluation.  Rather than treat symptoms we focus on establishing an accurate diagnosis so that a successful treatment plan can be developed.  Patients with Chiari type 1 Malformations for example may have neck pain for reasons other than the CM.  Neck pain can arise from many different sources including:

To learn more about the Craniocervical instability please click on the link below

In Conclusion

Under normal circumstances, the Cerebellum and Brainstem reside at the base of the skull.

Chiari Malformation is a medical condition where a part of the brain bulges through a normal opening at the base of the skull.  This boney opening is called the Foramen Magnum.

This creates abnormal pressure on the lower brain, restricts spinal fluid flow, and causes a variety of symptoms.

Chiari Malformations are categorized into four major types based upon the anatomical abnormality and whether birth defects are present.

Many patients with Chiari Malformations have NO signs or symptoms.

Symptoms of Chiari Malformations include:

  • Headaches
  • Neck Pain
  • Dizziness
  • Ringing in the ears
  • Arm and leg weakness

Chiari Malformations can be due to birth defects or secondary causes such as trauma, disease, or infection.

Treatment of Chiari Malformations depends upon the type of malformation, the severity of tissue injury, and symptoms. Most patients with Chiari Type 1 Malformation do not have symptoms or limitations.

Other conditions associated with Chiari Malformations include Tethered Cord, Spinal Curve, Hydrocephalus, and Syrinx.

There are many causes of neck and headache other CM.  Not all headaches and neck pain in patients with CM type 1 are due to malformation.  The upper cervical spine is complex and requires a dedicated and compassionate team of experts to clearly establish an accurate diagnosis.

If you or a loved one have ongoing neck, headache, and dizziness that has not responded to conservative treatment, please schedule a telephone candidacy discussion with a board-certified, fellowship-trained physician. At the Centeno-Schultz Clinic, we are experts in the evaluation and treatment of upper neck injuries.  From the comfort of your home or office learn what treatment options are available for you.

1.Fernández AA, Guerrero AI, Martínez MI, et al. Malformations of the craniocervical junction (Chiari type I and syringomyelia: classification, diagnosis and treatment). BMC Musculoskelet Disord. 2009;10 Suppl 1(Suppl 1):S1. Published 2009 Dec 17. doi:10.1186/1471-2474-10-S1-S1

2.Shah AH, Dhar A, Elsanafiry MSM, Goel A. Chiari malformation: Has the dilemma ended?. J Craniovertebr Junction Spine. 2017;8(4):297-304. doi:10.4103/jcvjs.JCVJS_138_17

3.Abd-El-Barr MM, Strong CI, Groff MW. Chiari malformations: diagnosis, treatments and failures. J Neurosurg Sci. 2014 Dec;58(4):215-21. PMID: 25418275.