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Arnold Chiari Malformation: Types, Causes, Symptoms and Treatment

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When the skull is smaller than usual  or misshapen , it presses on the brain and forces it downwards into the spinal canal  is known as a Chiari malformation. It typically affects the region of the brain called the cerebellum, which is responsible for controlling balance. 

In most cases of Chiari malformation, it is present at birth. However, in some types , the symptoms develop later in childhood. Based on the severity, the patient may need regular monitoring. 

The blog explains the Chiari malformation, its types, causes, symptoms, and various treatment options. 

What is Arnold-Chiari malformation?

In the 1980s, Hans Chiari, an Austrian pathologist, first described this brain abnormality. Therefore, the condition was named after him. 

Chiari malformation type 1 occurs when a section of the skull having a part of the cerebellum (brain) is deformed or is too small, thus crowding or putting pressure on the brain. The lower part of cerebellum is displaced into the upper spinal canal.

Chiari malformation type 2 is nearly always linked to a form of spina bifida known as myelomeningocele.

As mentioned, the disorder is most often genetic. It can cause neurological symptoms, including loss of balance. 

It is also known as Arnold-Chiari malformation, hindbrain herniation, and tonsillar ectopia.

What are the types of Arnold Chiari Malformation?

Experts have noted four types of Chiari malformation. They are as mentioned below:

  • Chiari Type 1: the most common form of Chiari malformation in children. Patients with this disorder do not show symptoms or develop symptoms during adolescence or adulthood. It affects the lower part of the cerebellum and not the brain stem. The cerebellum enters into a hole at the base of the brain known as the foramen magnum. Usually, the spinal cord passes through this passage. It is often accidentally found during the diagnosis of other health conditions.
  • Chiari Type 2 : typically develops in patients with severe Spina Bifida, known as myelomeningocele. It occurs in utero when the spinal cord and backbone do not correctly close before the child’s birth. Surgery is necessary soon after birth to close the spinal cord and the backbone, and the chances of paralysis are high. Chiari type 2 affects both the cerebellar and brain stem tissues, Chiari Type 2 is also known as classic Chiari Malformation or Arnold-Chiari malformation. 
  • Chiari Malformation Type 3: It is rare and severe form of  a Chiari malformation. In this, the cerebellum or the brain stem enters the spinal cord through an opening in the back of the skull – known as the foramen magnum. The abnormality leads to swelling at the back of the skull, known as encephalocele. Type 3 causes life-threatening complications and neurological symptoms, including learning delays and seizures. Patients with Chiari malformation type 3 may also suffer from hydrocephalus – the accumulation of cerebrospinal fluid in the brain. Typically, doctors diagnose this form of Chiari malformation during pregnancy through ultrasound or at birth.
  • Chiari malformation type 4: A rarity where the cerebellum is underdeveloped or certain parts are missing. However, the spinal cord and the skull are exposed . This type is severe and causes  fatality. 
  • Chiari malformation type 0: This form is controversial to some experts as there is little to no protrusion of the cerebellum into the foramen magnum. It is the rarest form of Chiari malformation. However, doctors may find significant crowding, causing abnormal cerebrospinal fluid flow at the base of the skull. 

What are the causes of Chiari malformation?

Several causes lead to Chiari malformation. Some of them are as follows:

  • Structural defect: It occurs when the baby is developing in the uterus. Certain researchers believe that when the skull is smaller than the standard size can lead to crowding and increased pressure on the brain, thus pushing the tissues through the foramen magnum, where the brain and the spinal cord meet. 
  • Genetics: A family history of Chiari malformation can increase the risk of a person developing the same,  as it may be inherited. 
  • Lack of nutrients: Some experts believe that lack of some nutrients during pregnancy may also play a crucial role.
  • Infections and high fever: During pregnancy, if the pregnant woman develops an infection or high fever, it may affect fetal development. 
  • Exposure to toxic chemicals: illegal substances, alcohol, and toxic chemical are harmful during  fetal development.
  • Other factors: Chiari malformations are mostly present at birth, and symptoms often develop later in life. 

In some cases of Chiari Malformation, it can occur due to accidents or infections where the spinal fluid is drained out, known as secondary Chiari malformation. 

What are the symptoms of Chiari malformation?

Every person’s symptoms vary from each other. Some may experience mild symptoms, while others develop severe symptoms. Some symptoms present at birth, while others may appear in late childhood or adulthood. Some of the common symptoms are as follows:

  • Headache: It is a common symptom. Headache may start or worsen after the person coughs, sneezes, or strains, often developing at the back of the head. However, the ache may spread to the neck and shoulder. Patients describe the pain as throbbing, stabbing, or sharp.
  • Balance and movement issues: Chiari malformation may cause weakness in the muscles, lack of coordination, and numbness in the limbs, causing a lack of fine motor skills. It can also result in dizziness, vertigo, and balance issues. 
  • Issues in hearing and vision: Some patients experience buzzing or ringing sounds in the ear and have trouble hearing. They also experience double vision, blurred vision, abnormal eye movements, and sensitivity to light. 
  • Problems with eating, drinking and speaking: Swallowing becomes difficult. Some babies with Chiari malformation may experience vomiting, gagging, or drooling, in addition to difficulty eating and may struggle to put on weight for proper development. 
  • Scoliosis: Curvature of the spine, known as scoliosis, is seen in some people with Chiari malformation.
  • Sleep-related issues: Patients may also experience insomnia due to headaches, while others may also experience sleep apnea.
  • Problems with bladder and bowel: Chiari malformation may also cause bladder and bowel control issues.
  • Other symptoms: Chronic fatigue, palpitations, fainting spells, and tingling or burning sensations in the fingers, toes, or lips are some of the other symptoms.

Irrespective of the type or severity of the condition, the following are the symptoms in an infant:

  • Problems swallowing
  • Excessive drooling, gagging, or vomiting
  • Irritability while eating or feeding
  •  Breathing difficulties
  • Developmental delays 
  • Stiff neck
  • Problems gaining weight
  • Lack of arm strength 

If the infant is suffering from Chiari malformation type 2 with excess fluid in the brain, the following are some of the additional symptoms to look out for:

  • A large head
  • Vomiting
  • Seizures
  • Irritability 
  • Delay in development

If the symptoms are developed rapidly, they may require emergency treatment.

Who is at risk of developing Chiari malformation?

Chiari malformation affects anyone. However, women are more likely to develop this than men. Babies may be born with this condition, but it may not be discoverable until their teen years or adulthood. The disease is incurable, but the symptoms are manageable with constant monitoring, medications, and, sometimes, surgery.

Patients with other neurological and bone conditions also are at a higher risk of developing Chiari malformation. They include the following:

  • Myelomeningocele: A severe spina bifida where the spinal canal and backbone do not close before the baby’s birth.
  • Hydrocephalus: When there is an accumulation of excess fluid in the brain, mostly seen with Chiari malformation type 2 patients. 
  • Syringomyelia: Patients have a cyst in the spinal column  called a syrinx
  • Tethered cord syndrome: A disorder where the spinal cord gets attached to the spinal bone causing damage to the lower body. Patients with myelomeningocele are at higher risk of developing this syndrome.
  • Spinal curvature is a common condition among patients with Chiari malformation type 1. 

When to seek medical help?

If a person or a child experiences symptoms that can be associated with the disease, seeking medical evaluation is necessary. Sometimes symptoms are similar to other disorders, and only a medical practitioner can diagnose the condition correctly. 

How is Chiari malformation diagnosed ?

In most cases, Chiari malformation shows in prenatal scans. However, some patients are unaware of their condition as symptoms appear later in teens or adulthood. In such cases, the doctor performs physical checks, reviews medical history, and prescribes the following tests:

  • Magnetic resonance imaging (MRI): One of the standard diagnostic methods to detect Chiari malformation is MRI. 
  • Computerized tomography (CT) helps reveal brain tumours, brain damage, problems in the blood and bone vessels.
  • Cine MRI: It is similar to the traditional MRI, but it indicates or shows the flow pattern of cerebrospinal fluid around the base of the skull. 
  • X-ray: It helps detect any bone defects in the skull and neck region.

What are the treatment options for Chiari malformation?

Based on the severity of the symptoms, the doctor decides on a treatment plan. If the patient does not present any symptoms, regularly monitoring the patient’s health with various tests may help. With mild symptoms, including headaches and pain, pain medications may help. However, for severe cases, surgery may be required . The doctors perform the following surgeries to prevent future structural abnormalities and reduce the symptoms:

  • Posterior fossa decompression: It is the most common surgery that treats Chiari malformation. In this procedure, the doctor removes a part of the back of the skull called the posterior fossa. Thus, it provides more room and relieves the pressure on the brain.
  • Laminectomy: Based on the severity of the disease, the surgeon may decide to remove a tiny portion of the bone covering the spinal column. It helps restore cerebrospinal fluid flow and provides more space for the spinal cord.
  • Duraplasty is a decompression surgery where the doctor opens the dura – the membrane located outside the brain – and sews a patch to enlarge the membrane. This provides more room and relieves pressure on the brain.
  • Electrocautery: The surgeon sends a small amount of electricity to shrink the cerebellar tonsil – a small portion of the brain without causing neurological harm. The procedure creates more room for the cerebrospinal fluid to flow freely. 

What are the complications of Chiari malformation?

Chiari malformation may also cause severe health issues and delay in development. These health complications include: 

  • Hydrocephalus: A life-threatening condition where there is  excessive CSF build up in the brain as it does not effectively circulate . With an increase in the fluid build-up, the pressure in the brain also increases. Failure to treat the condition can be fatal. A shunt is placed to drain the fluid effectively. This is typically noticed in patients with Chiari malformation type 2.  
  • Spina bifida. A condition where the spinal cord or its covering is not fully developed, may happen in Chiari malformation. A part of the spinal cord is exposed, which may lead to serious conditions like paralysis. Usually, those with Chiari malformation type 2 have a form of spina bifida known as myelomeningocele.
  • Syringomyelia. In this condition, a few individuals having Chiari malformation also develop a condition known as syringomyelia, where a cyst (syrinx) or cavity forms within the spinal column.
  • Tethered cord syndrome. A condition in which the spinal cord gets attached to the spine causing it to stretch. This can result in serious muscle and nerve damage in the lower body.


Some patients with Chiari malformation live long lives with no to mild symptoms. However, there are others with severe symptoms causing nerve damage. The important thing is to be constantly monitored, administered medications, and, if required, undergo surgeries to relieve and prevent the symptoms from worsening. 

Frequently Asked Questions (FAQs)

Can Chiari malformation be prevented?

Chiari malformation cannot be prevented as it is due to genetic mutation. However, it can be detected during pregnancy through ultrasound.

Is Chiari malformation common?

Chiari malformation appears in nearly one out of every 1000 people. 

Can Chiari malformation be cured?

Unfortunately, there is no cure for Chiari malformation. However, with constant monitoring, medications, and sometimes surgery, the symptoms can be managed and prevented from worsening.

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