Chiari malformation 

  • Overview


A Chiari malformation (sometimes called an Arnold Chiari) means that the lower parts of your brain have been pushed downwards towards your spinal cord, so they are below the entrance to your skull.

Most patients will have a type 1 Chiari malformation, the least serious form of the disease. This is where the lowest part of the back of the brain (the cerebellar tonsils) drops down into the top of the spinal canal. 

Type 2 and 3 Chiari malformations are less common and more serious. They are associated with spina bifida (a birth defect involving problems with the development of the spine) and adults will also have hydrocephalus (a build-up of fluid in the brain). 

The rest of this page focuses on the most common type, type 1 Chiari malformations.

How a type 1 Chiari happens

Usually, the lower parts of the brain are contained in a space within the skull, above the level of the foramen magnum (opening at the base of the skull). If you have a type 1 Chiari malformation, these brain parts are pushed downwards because they are too big for the skull.

When parts of the brain are pushed out of the skull towards the spinal cord, this can:

  • cause pressure at the base of the brain
  • block the flow of cerebrospinal fluid (CSF) to and from the brain

CSF is a clear fluid that surrounds and protects the brain and spine, and also carries nutrients to the brain and removes waste.

Is it hereditary?

Chiari malformation can sometimes run in families, and it's possible that some children born with this disorder may have inherited a faulty gene that caused problems with their skull development in the womb. Researchers are currently trying to find the gene or genes that are responsible.

However, try not to worry – the risk of passing a Chiari malformation on to your child is very small, and even if children do inherit it, most will not develop symptoms.

What are the symptoms?

Many people with a type 1 Chiari malformation will not have any symptoms, or they do not develop symptoms until later in life.

When symptoms do develop, they may include:

  • headaches, usually at the back of the head – these are brought on, or made worse by, exercise, straining, laughing or bending over
  • neck pain
  • dizziness and balance problems
  • numbness or tingling in the arms or legs
  • blurred vision and involuntary movement of the eyes (nystagmus)
  • swallowing problems
  • hearing loss and tinnitus
  • feeling sick and vomiting
  • insomnia
  • depression

Syrinxes and syringomyelia 

Many people with a type 1 Chiari malformation will develop a condition called syringomyelia, where a tube-shaped cavity forms within their spinal cord and fills with fluid.

This fluid-filled cavity, known as a syrinx, can expand and elongate over time, pressing on, and damaging, the spinal cord. It can cause pain, numbness, weakness, stiffness and problems with bladder or bowel function, and sometimes leads to paralysis.

Surgical treatments involve treating the underlying cause – in other words, operating on the Chiari malformation or treating hydrocephalus – or releasing the fluid using a system of drainage tubes and valves (see 'Treatment' section below).

Reducing the fluid in a syrinx can stop symptoms getting worse and can sometimes improve them.

How common is it?

In the past, it was estimated that Chiari malformations occured in about 1 in 1,000 births. However, the increased use of diagnostic imaging has shown that they may be much more common.

How is it diagnosed?

Sometimes, Chiari malformations are discovered by chance after a magnetic resonance imaging brain scan (MRI scan) is done to investigate a different condition.

If you see your GP with symptoms suggesting you may have a Chiari malformation, they should arrange for you to have an MRI scan to confirm this diagnosis. A brain scan will show up any abnormalities in the structure of your brain and spine.

How is it treated?

The symptoms caused by a type 1 Chiari malformation can usually be managed with medication. For example, painkillers can help relieve any headaches and neck pain.

You may need decompression surgery to reduce the pressure at the base of your brain. The surgeon will make an incision at the back of your head and remove a small piece of bone from the base of your skull. This will widen the space in the foramen magnum (opening to the skull). They may also remove a small piece of bone from the top of your spine, to relieve the pressure on your brain and allow CSF to flow normally.

Other treatment options include:

Most people who have surgery find that their symptoms improve afterwards. It should also prevent existing symptoms from worsening.

However, as with all types of surgery there is a small risk of complications, which you should discuss with your neurosurgeon.

Possible risks of decompression surgery include:

  • stroke or haemorrhage (bleeding)
  • paralysis of the arms and legs
  • meningitis or other infection
  • impaired speech
  • memory loss or problems with thinking
  • swallowing impairment
  • balance problems
  • hydrocephalus
  • seizures (although these are rare)
  • a risk to life

Sometimes, surgery leads to no improvement or even worsening of symptoms.

Page last reviewed: 11/07/2012

Next review due: 11/07/2014


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The 12 comments posted are personal views. Any information they give has not been checked and may not be accurate.

lanehouserocks said on 11 April 2014

Hi Ouch21, I was also topd that no more could be done for me but after yet another MRI scan my neuro consultant at Poole Hospital refered me to a Consultant at the new Q E Hospital in Birmingham. He is fantastic and I am now on nis waiting list for Surgery. I don't live in Birmingham, I live in Dorset.
Hope this helps.

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Ouch21 said on 25 March 2014

I had my op 12 years ago followingdiscovery by my optician that ihad nystagmus.My condition deteriorated rapidlywith loss of coordination, numbness in arms, pains in arms and legs, headaches, and very poor sight due to the nystagmus. They said the decompression was sucessful but continued to be signed off work for a year due to the nystagmus and clumsyness not being improved. I continued to be referred to various consultants who were diammissive. I have started a course of botox as being treated as chronic migraine but the nystagmus is worse, I cant do simple chores luke ironing more than 3 items before I end up in pain and can no longer bake without use of gadgets.i amgaining weight as I cannot exercise ither than walking. My gp has agreed that I can be referred to another consultant in london but I have no idea where to go, ahe suggested I google to choose where to be referred to... terrified i'll be met by another consultant who says there's no more that can be done.Does anyone have any suggestions of hospitals to try?

Lea290884 - hope my lost hasn't deterred you, considering how things were before the op I am much improved a part from this blip, just make sure following op you have physio or exercises to help strengthen your neck again - I did not receive this and was sent home and told to take paracetemol if I was in pain. Everyone is diffwrent and recovers differently but after 5 days in hospital when home I would become exhausted by walking the shortest diatance so best to arrange for help from friends and family in advance. I hope it goes well, everyone seems positive about the outcome of having the surgery :)

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lea290884 said on 10 March 2014

Been offered the op for this, on tabs at the not working! Is the op as bad as am thinking? May sound daft I know, but I have young kids to run after. Got to be better then the bad head's right??

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dolly18 said on 18 February 2014

I had my operation 16th january '14 for my Chiari one and my results have been amazing. I had every single side affect with painkillers and other drugs not helping, had none stop headache for 2years+ but not had one since my operation. it took me 2years+ fighting to see the right person but finally did and had it done and my results are amazing. if anyone is thinking do i have this operation have it as soon as offered as i had to wait so long to see the right person i now have non-reversable nerve damage and now cant feel the different between hot and cold.

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Vijay79 said on 25 January 2014

This is a msg for Sarahlou79.
I had surgery almost 5 years and have pain my right arm. Can you tell me more about the pains you get etc?

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sarahlou79 said on 22 January 2014

hi, i had syringomyelia 19 years ago now. ive suffered with severe pain in my left arm and shoulder ever since.
just wondered if anyone else has experienced similar as my gp desnt seem to understand the condition no

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kimm81 said on 19 December 2013

Hi 21,the surgery will be performed if you fit two criteria,cough headache and a syrinx in the is free of charge.

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kimm81 said on 19 December 2013

And chiari one,it is rare actually

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kimm81 said on 19 December 2013

I recently attended the walk in centre.when asked my medical history i said i have chiari malformation and a cervical syrinx.the nurse didnt have a clue,i even had to spell it out! Maybe if medical staff were better trained i wouldn't have suffered for years before being diagnosed.i think the lack of knowledge about this condition is ridiculous

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21 said on 16 December 2013

I have a friend who is in need of the surgery :( I cant imagine how anyone with this deals with the pain!! I have been re-searching everything. I'm trying to find out locations as to where the surgery is performed? If there's any way to receive help towards the cost, life after surgery. Any knowledge would be greatly appreciated :) I want to do everything I can to help him!

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Chiari One said on 26 November 2013

I have also been decompressed if anyone has questions about this

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Chiari One said on 26 November 2013

Glad to see a Chiari article, thanks. Hope to see more improvements like experienced neurologists being more aware about it. It is uncommon but not rare. I have been living with it a while and am happy to try and answer any questions.

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MRI scan

An MRI scan uses strong magnetic fields and radio waves to produce detailed images of the inside of the body

Having an operation

If your GP has suggested you may need surgery, this guide is for you