Chiari malformation 

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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 people will have a type 1 Chiari malformation, which is 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.

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

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

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. 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.

When symptoms do develop, they may include:

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 functions, and sometimes leads to paralysis.

Surgical treatments involve treating the underlying cause – in other words, operating on the Chairi malformation or treating hydrocephalus – or releasing the fluid using a system of drainage tubes and valves (see the "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 occurred 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. This procedure is known as a spinal laminectomy.

Other treatment options include:

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

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 infections
  • impaired speech
  • memory loss or problems with thinking
  • problems swallowing
  • balance problems
  • hydrocephalus
  • seizures (although these are rare)
  • a risk to life

Sometimes, surgery leads to no improvement or symptoms getting worse.

Page last reviewed: 23/07/2014

Next review due: 23/07/2016


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The 20 comments posted are personal views. Any information they give has not been checked and may not be accurate.

Olivecharlotte said on 29 October 2014

Hi everyone, I am Johanna. I was diagnosed with Arnold Chiari malformation 1 in 2002. I was having severe pressure headaches (prior that that many migraines), pressure in my ears, pain in my neck and shoulder, lost my vision in one eye for a few hours, lost my hearing for three months. I had decompression surgery in 2002. It was a painful surgery but worth it. My symptoms almost all went away. No headaches - great. Now in 2014 I am heaving some issues again. I am getting headaches when storms come in. I live in Florida. The worse thing in the pressure in my ears. But now I am also very fatigued. I am having some testing done again and will let you know how things turn out. To all of you Chiarians, I say one day at a time is all we can do. Treasure the days you feel OK.

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Amaya LH said on 19 September 2014

Hey, I'm Amaya. Im currently 15 years old. I was diagnosed with Chiari 1 malformation when i was 13. When I was 13 I was washing my hair when all of the sudden my legs went weak, I started getting nauseous, my eyes went black, and I heard a ringing in my ears. I passed out and my parents rushed me to the E.R. The doctors waved it off as just regular fainting. However, five months after that incident the same thing happened but was much worse. I was out for 1 minute. That's when my parents decided I need to see a neurologist. Multiple MRI's and CAT scans were done and that's when I found out I have Chiari. I have a plethora of days where I feel like I'm going to pass out (including today), some days I have passed out. I also looked up some symptoms and noticed I have more than I thought. For example, depression, sleeping problems, numbness, dizziness. I'm thinking about getting decompression surgery because it has gradually gotten worse. I just wanted to share my Chiari story for anyone who needs it. Stay strong.

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ricki l said on 24 August 2014

Hello my name is Ricki I am a 49 year old woman I have just been diagnosed with chiari 1. I have 8 or 9 cyst in my neck and my arms go numb at night what ever side I'am sleeping on, I have tinnitus ringing in the ears non stop with pain,blurred vision off an on, nerve pain from head to toe, I am agitated most of the time , I had a really bad headache so I went and laid down fell asleep for a few hours when I woke up I had a bubble like mushy spot on my head where it hurt worst. It felt like them packs of mayonnaise you get from the fast food stores mushy . I called for my husband to come se it he didn't know what it was as soon as I stood up it went away. No doctor could tell me what it was .Has anybody here ever had that happen ? I wondered if its from the fluid build up on the brain from the chairi 1? thank you for listening hope to get an answer best wishes to all..ricki

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Labsnark said on 11 July 2014

I just wanted to submit my experience of Type 1 Chiari, just in case it helps anyone else.

Before March last year, I'd had no significant symptoms of my condition, but I made the mistake of leaning over a farm gate, putting pressure onto my abdomen and, therefore, my head. Several minutes of throbbing pain followed, during which I seriously thought I was going to die. I immediately went from a being a fit 47 year old, who was running 3 miles off-road, three times a week, and karate twice a week, into a couch potato who was permanently tired, suffering headaches and having to sleep most afternoons.

Long story short, I was diagnosed with type 1 Chiari. I could no longer run without pain, and was seriously considering insisting on surgery just to restore some form of normality. My running appeared to jolt my head, which in turn made the condition worse. My neurosurgeon told me that there was no connection between my running and the pain I suffered when doing it; this, however, directly contradicted what I experienced on several previous occasions when I had attempted to run.

Eventually, I decided that I had had enough, and that I was going to run and suffer the consequences, even if that meant risking worsening the condition. After four runs over two weeks, I found the symptoms were actually reducing in severity.

I am now back to running 4-5 off-road miles, four times a week. I don't get tired in the afternoon, and I'm as fit as I was before. I have to take great care not to lean over to pick up items, or to do anything that puts pressure on my brain, so the karate's finished for me. That aside, I'm in a far better place than I was twelve months ago.

It may be that my improvement was coincidental to running again, but it didn't feel like that. I feel like being fitter helps.

Good luck to all of you who get diagnosed and suffer like I did - hopefully there is light at the end of your tunnel as there was at the end of mine.

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Wends12 said on 01 July 2014

I don't normally respond on anything like this but you have very similar symptoms to mine. I was originally diagnosed with Chiari in 2010 when I had an MRI scan for a condition called Ankylosing Spondylitis. It is a type of inflammatory arthritis. I have pain in my back (lower mainly), hips and neck and the main recognising factor is the fact that is better when you move than when you sit down. So I find going to the cinema difficult, standing in 1 position, driving a car and anything that involves not moving, yet feel much better when moving around, walking, swimming etc.

My rheumatologist is puzzled to what extend of my pain is due to the AS or the Chiari ( I also have a syrinx). I am currently waiting for a date to have surgery to hopefully ease the symptoms of the Chiari, something I felt I had to risk as I also have the AS to contend with and couldn't see any light at the end of the tunnel for me if I didn't at least attempt to 'fix' one thing.

Not sure if this answers your query but might be worth looking in to - the NASS website is excellent and their volunteers are amazing if you phone them.

Out of interest - if anyone has had surgery how long did you have to wait???

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juliewad said on 24 June 2014

I've been recently diagnosed with CHIARI, after having several 'absences'. I am 54, and I have lived with all of the symptoms for 52 years, without being diagnosed. I am now getting increased pressure at the base of my skull and severe pain in my lower back. Please can anyone tell me if this is related to my CHIARI, as my GP just tells me to take analgesics. I can only sit for short periods of time, but I am still able to walk, run and stand without any pain. I would appreciate any information that I can pass on to my GP, or request a referal to another consultant?

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jonesylou said on 02 May 2014

i had the decompression surgery august 2012, i had to have a lumbar shunt fitted in nov 2012 due to having a build up of fluid and pressure making my symptoms worse. i had a revision of the shunt dec 2012 as it had twisted. i felt great for nearly 12 months when last oct (2013) i started having really bad headaches/pressure again. i have just had the shunt revised again now march 2014 and touch wood i feel great so far.

it took nearly 11 years to find out what was causing my headaches and loss of sensations as i already have back problems and they weren't sure if they were being made worse by the back problems i have.

my surgeons in stoke have been fantastic and i would recommend anyone to them they have supported me and listened to me when i knew i was bad and even said to me "well you know the symptoms and how bad things get so we trust u when you say its bad" unlike a very un-supportive gp i once saw.

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EmmaBro said on 21 April 2014

Where do I start... Began having a sore neck and headaches at 19 (I'm now 38) during my first pregnancy at 20 my headaches were intense.
I saw a chiropractor thinking I had damaged my shoulder and neck during exercise. My shoulder had by this stage began to droop forwards.
The headaches just continued, the neck and shoulder pain remained. During my 2nd pregnancy at 22 it was believed I was suffering carpol tunnel.
After my son was born I was referred to an Ortho Dr and physio. The Ortho dr did nerve conduction studies and carried out carpol tunnels ops on both hands. The physio's trying to tape my shoulder up and back kept failing . Everything kept getting worse, unequal pupils, flicks eyes , lb weakness . Wanting to drill a hole in my head to release the pressure. MRIs were done by the Ortho who failed to find anything . After a private scan revealed Chiari my NHS scans had disappeared!! Seen neurosurgeons who know nothing, seen specialists. One who offered surgery then decided against it. Took 9years to get diagnosed with Chiari and then began a new battle. 10 years on everyday is a headache developed more neuro conditions, need PCT Carers to help due to diminished quality of life. Too many symptoms to list, no life at 38 meeting suffers with far less symptoms thane getting treated whilst I'm left to get worse . Whilst no one wants to take responsibility for trying to help on anyway! Thank you Leicester, Birmingham & Nottingham.. Now facial dystonias & movement disorders are with me to due to nerve root compression but you've failed me all the way on all fronts. Including the carpol tunnel ops I later discovered I never needed as nerve conduction had in fact shown damage to be spinal nerve root compression therefore there were always going to be failed procedures.

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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