Mya Care Blogger 22 May 2024

Chiari malformation is a group of conditions that affect the brain and spinal cord. All the types stem from a congenital structural defect in the floor of the skull and the base of the cerebellum, the part of the brain that controls balance and coordination. This defect can cause a range of symptoms and complications.

Chiari malformations are relatively rare, estimated to affect 0.5-3.5% of the population. They are more common in women than men, with a diagnosis frequently occurring in early adulthood.

This article aims to address the causes of Chiari malformation, its symptoms, diagnosis, available treatment options, and the latest research on treating these congenital malformations.

What is Chiari Malformation?

The brain sits within the skull, a protective bony structure. At the base of the skull is an opening called the foramen magnum. This opening allows the spinal cord to connect with the brainstem, a vital part of the brain. The cerebellum, responsible for coordination and balance, sits just above the foramen magnum.[1]

Chiari malformation occurs when the lower part of the cerebellum, called the cerebellar tonsils, protrudes downward through the foramen magnum. This protrusion can cause compression on the affected areas and fluid-filled cavities to develop in the brain (hydrocephalus) and spinal cord (syringomyelia). The build-up of cerebrospinal fluid can lead to neurological symptoms.[2]

A small posterior fossa (the cavity near the skull's base containing the brain stem and cerebellum) might cause the developing brain to suffer from compression in Chiari malformation.

There are several types of Chiari Malformation[3]:

  • Chiari I: The most common type, affecting 0.5% to 3.5% of the population. In this type, the cerebellar tonsils extend down to the foramen magnum while the brainstem stays in its normal position.
  • Chiari II: This type is less common than Chiari I and often occurs with myelomeningocele, a type of spina bifida. In Chiari II, the cerebellar tonsils and lower part of the brainstem protrude into the foramen magnum. This type is sometimes known as Arnold-Chiari malformation.
  • Chiari III: A rare and severe type where the cerebellum (with or without the brainstem) protrude through an abnormal opening in the back of the skull. This can cause severe neurological problems, including life-threatening complications.
  • Chiari IV: Now considered an obsolete term, Chiari IV malformation initially represented a rare variant with severe cerebellar hypoplasia (underdevelopment). However, due to the difficulty distinguishing it from other types and overlapping features, it has been reclassified as Chiari II with severe cerebellar hypoplasia or primary cerebellar agenesis (complete absence of the cerebellum).

What Causes Chiari Malformations?

The exact cause of Chiari malformation is not fully understood. An assortment of genetic and environmental factors influences its development in utero.

Some possible mechanisms that may contribute to the development of Chiari malformation include[4]:

  • Genetics: There is evidence that Chiari malformation may run in families, indicating a genetic element to the condition. There is a link between the underdevelopment of the posterior fossa and gene mutations on chromosomes 1 and 22. Various hereditary disorders are associated with Chiari malformation, including Albright hereditary osteodystrophy (pseudohypoparathyroidism), Goldenhar syndrome, achondroplasia, and Hajdu-Cheney syndrome.
  • Developmental issues: Problems during embryonic development, such as incomplete closure of the neural tube, may lead to Chiari malformation.
  • Connective tissue disorders: Some connective tissue disorders, such as Ehlers-Danlos syndrome, have been linked to Chiari malformation.
  • Environmental influences: Exposure to certain toxins or infections during pregnancy may increase the risk of Chiari malformation. Folate supplementation during pregnancy may lower the risk, suggesting that deficiency may elevate it.

Conditions like tumors, cysts, hematomas, hydrocephalus, and intracranial hypertension can cause Chiari malformations in those affected. Leakage or drainage of cerebrospinal fluid from medical procedures can also contribute to an acquired Chiari malformation.

Recognizing the Symptoms

The symptoms of Chiari malformation can differ according to the severity of the condition and the type of malformation. Some people may not experience any symptoms, while others may have severe manifestations that significantly influence their daily lives. The severity of a Chiari malformation may not necessarily correlate with the length of herniation of cerebellar tonsils.

The most common type of Chiari malformation is type 1. This type is usually present at birth yet may not cause symptoms until later in life. Some common Chiari malformation type 1 symptoms include:

  • Headaches, especially at the back of the head
  • Neck pain
  • Dizziness or vertigo
  • Balance problems
  • Numbness or tingling in the hands or feet
  • Difficulty swallowing and breathing
  • Vision problems
  • Ringing in the ears (tinnitus)
  • Muscle weakness
  • Sleep apnea
  • Scoliosis (excessive curvature of the spine)

Most of the symptoms occur due to disruptions in the cerebellum, brainstem, and spinal cord.

Chiari type 2 and 3 symptoms can include those seen in Chiari I, along with nystagmus (involuntary eye movements).

Muscle weakness can lead to additional symptoms such as difficulty with fine motor control, reduced bladder control, and digestive issues.

Chiari malformation symptoms in adults and children are similar.

What are the Complications?

Chiari malformation is associated with various conditions and complications that may improve with sufficient treatment.

Some of the most common complications include improper spinal development and fusing of the top cervical vertebrae with the base of the skull.[5]

Other possible complications include:

  • Hydrocephalus: Hydrocephalus is a condition with cerebrospinal fluid accumulation in the brain, leading to increased pressure. The fluid buildup causes symptoms such as headaches, nausea, and vision problems.
  • Spina bifida: Spina bifida is a birth defect that causes the spinal cord to develop incorrectly. It is often associated with Chiari malformation, and it can cause paralysis, bladder and bowel problems, and other complications.
  • Syringomyelia: Syringomyelia is a condition where a fluid-filled cyst forms in the spinal cord. Common symptoms include pain, weakness, and numbness in the arms and legs.
  • Tethered cord syndrome: Tethered cord syndrome is a congenital defect where the spinal cord is abnormally attached to the surrounding tissue, such as the skin in the back.[6] This can lead to manifestations of pain, numbness, weakness in the legs, and bladder and bowel problems.
  • Klippel-Feil deformity: This occurs when vertebrae in the spine of the neck fuse together during pregnancy, which can also cause malformation in the cervical spine.


If you suspect you may be experiencing Chiari malformation symptoms, seeking medical attention is crucial.

For Chiari malformation type I, a healthcare provider will likely begin the diagnostic process by conducting a thorough physical examination to assess your symptoms and medical history. An MRI imaging test provides a clearer picture of the structural abnormalities in the brain and spinal cord. It also helps to confirm the diagnosis, often during adolescence or adulthood.

Chiari malformation type II and III tend to show on neonatal ultrasound scans during pregnancy or shortly after birth. An MRI or CT scan may help to confirm the diagnosis at a later stage.

These imaging tests play a vital role in confirming the diagnosis of Chiari malformation. An MRI can provide detailed brain and spinal cord images, allowing healthcare professionals to identify a herniation or compression of the cerebellar tonsils in the foramen magnum. Moreover, it can help determine the severity of the condition and detect the presence of other related complications, such as hydrocephalus (abnormal accumulation of cerebrospinal fluid in the brain) or syringomyelia (formation of fluid-filled cysts within the spinal cord).

In some cases, additional tests may be necessary to evaluate potential complications or related conditions further. This could include a lumbar puncture (spinal tap) to measure cerebrospinal fluid pressure or specialized neurophysiological tests to assess nerve function.


The treatment for Chiari malformation relies on the condition’s severity and any complications. In some cases, no treatment may be necessary, and the condition can be monitored over time. However, if symptoms are severe or there are complications, treatment options may include:


Pain relievers and anti-inflammatory medications may help manage symptoms such as headaches and neck pain. In some instances, your doctor may also prescribe medications to help with other symptoms, such as sleep apnea or muscle weakness.

Chiari Malformation Surgery

Surgery may relieve those with severe symptoms or complications. The most common surgical procedure for Chiari malformation is a decompression craniotomy or posterior fossa decompression. In this procedure, the surgeon removes a small portion of the skull to alleviate pressure on the cerebellum and spinal cord.

If required, the surgeon may need to remove a small section of the vertebra to assist the spinal cord. This procedure is called a cervical laminectomy.

They may also perform electrocautery, which is the use of heat to shrink the cerebellar tonsils and create more space in the foramen magnum.[7]

During this surgery, a surgeon may lift the dura matter that covers the brain to reach the affected area. Some surgeons perform duraplasty to repair the dura during surgery, while others perform less invasive procedures that bypass the dura matter altogether.[8]

It is crucial to consult with a qualified healthcare professional on the risks and benefits of surgery before the procedure and to plan properly.

Potential risks and complications associated with Chiari malformation surgery include[9]:

  • Infection
  • Leakage of cerebrospinal fluid
  • Pseudomeningocele
  • Chiari malformation recurrence
  • Damage to surrounding structures

An infection may require further antibiotic treatment. The remaining complications may necessitate additional surgeries to correct or a shunt to drain excess fluids.

The patient stays in the hospital for a few days after the procedure. The hospital stay duration varies based on the outcome. It is typically advisable to avoid strenuous physical activities and heavy lifting for a certain period after surgery to allow for proper healing.

Instructions on caring for surgical incisions include keeping them clean and dry to prevent infection. Prescription medications help the patient to manage post-operative pain. Following the recommended dosage and informing your healthcare provider of any symptoms or adverse effects you experience is vital. Scheduled appointments are necessary to monitor healing and minimize complications.

Complementary Therapies

In addition to surgery, some people may find relief from complementary therapies such as physical therapy, acupuncture, and chiropractic care. These therapies can help manage pain, improve mobility, and promote well-being.

Prognosis and Life Expectancy

The prognosis for Chiari malformation is dependent on the severity of the condition and the presence of any complications.[10]

In most cases, people with Chiari malformation type I and II, with proper treatment and management, can expect to live with an average life expectancy. However, it is important to continue monitoring the condition and seeking treatment for any new or worsening symptoms.

Those with type III and more severe forms may not survive infancy.

Living with Chiari Malformation

Living with Chiari malformation can be challenging. However, there are provisions that can assist with symptom management and improve your quality of life.

Some tips for living with Chiari malformation include:

  • Avoid activities that put pressure on the head and neck, such as contact sports or heavy lifting.
  • Practice good posture to avoid straining the neck.
  • Get enough rest and manage stress levels.
  • Eat a healthy diet and stay hydrated.
  • Seeking support from friends, family, and support groups.
  • Educating yourself about the condition and staying informed about the latest research and treatment developments.

If you or a loved one has been diagnosed with Chiari malformation, staying informed about the latest research and treatment developments is important. Talk to your doctor about any new treatment options that may be available and how they may benefit you.

Latest Research and Treatment Developments

Research into Chiari malformation continues to progress, offering hope for a better understanding and improved treatment approaches. Scientists are investigating the genetic causes[11] and progression of Chiari malformations, striving to develop more refined diagnostic tools and explore non-invasive treatment possibilities.

One focus area is the advancement of minimally invasive surgical procedures[12], which offer the potential for reduced risks and faster recovery times.

In recent studies, stem cell therapy has shown promise in animal models of spina bifida[13]. It successfully alleviates pain in patients with syringomyelia (fluid-filled cavities in the spinal cord)[14].

The future may hold exciting possibilities, such as personalized medicine, where treatments cater to individual needs based on genetics and other unique factors.


Chiari malformation is a complex condition that can cause various symptoms and complications. Proper treatment and management can lessen symptom severity and enhance the patient’s quality of life. By understanding Chiari malformation's causes, symptoms, and treatment options, those affected can actively manage their ailment and lead fulfilling lives.

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