Chiari Malformation Decompression


The cerebellum is the portion of the brain located low down at the back of the head. It has two small areas at the bottom called the cerebellar ‘tonsils’. Normally, the cerebellum (and nearby brainstem) sits entirely within the skull.

In Chiari Malformations, there is a descent of the cerebellar tonsils (and sometimes the brain stem) through the hole on the base of the skull (the foramen magnum) and into the spinal canal. In other words, there is a herniation of the brain into the spinal canal.


Asymptomatic Chiari I Malformations do not require any treatment.
Chiari malformations causing only headaches are initially treated with analgesia for pain control.

Surgery is reserved for patients with headaches which do not settle with analgesic medications, significant other symptoms, or the development of abnormal findings on neurological examination. The surgical procedure of choice is a posterior fossa (or Chiari) decompression


A Chiari decompression is a specific type of craniotomy designed to make more room for the herniated cerebellum, and to relieve pressure on the brain. It also may permit restoration of the normal flow of cerebrospinal fluid (CSF) round the brain and sometimes results in an improvement in any associated hydrocephalus, hydromyelia, or syringmyelia.


Modern neurosurgery is generally fairly safe, but serious complications can always occur. In order to reduce the risks associated with your surgery, it is important for your surgeon and anaesthetist to be aware of certain health problems and medications.
It is important that you tell your surgeon if you have:

  • Blood clotting or bleeding problems
  • Ever had blood clots in your legs (DVT or deep venous thrombosis) or lungs (pulmonary emboli), or if anyone else in your family has
  • Been taking aspirin, warfarin, or anything else (even some herbal supplements) that might thin your blood
  • High blood pressure
  • Any allergies or reactions to medications or tapes
  • Excessive scarring (keloid) or poor healing after surgery
  • Any other health problems

You should tell your anaesthetist if you have:

  • Heart problems or chest pain
  • Respiratory (breathing) problems
  • Diabetes
  • High blood pressure
  • Previous problems with anaesthesia

Your surgeon and/or anaesthetist may order several additional tests before surgery, including:

  • Blood tests (for anaemia, blood clotting problems etc.)
  • ECG (to examine your heart electrical activity)
  • Chest X-ray


If you are a smoker it is imperative that you stop 3 or 4 weeks before surgery, and should not resume smoking for at least a few months afterwards (but preferably never!).
It is important that you stop certain drugs before surgery, especially ones that thin your blood. If you are taking aspirin, warfarin, or other blood-thinning agents (including herbal products) it is very important that you contact us two weeks before your admission so that we can discuss stopping them with you. If you are taking warfarin we may need to admit you earlier but each case varies, so it is important that you phone and we can discuss the plan for you.


As with all types of surgery, there is a risk of complications, and the likelihood of these will depend upon a number of individual factors. You should discuss your specific circumstances with your neurosurgeon.
Whilst the majority of patients will not have any complications, there is a small risk of problems. In general the risks of surgery include, but are not limited to:

  • Stroke or haemorrhage
  • Quadriplegia (paralysis of the arms and legs)
  • Infection
  • Meningitis (this may be due to infection, but is more commonly a chemical or ‘aseptic’ meningitis which settles with time and steroid medication)
  • Seizures
  • Impaired speech (dysarthria)
  • Memory loss
  • Cognitive impairment (problems with your thinking)
  • Swallowing impairment
  • Balance problems
  • Hydrocephalus (fluid build-up within the head necessitating a shunt)
  • Numbness of the skin around the scalp incision
  • Headaches (these usually settle after a couple of weeks following surgery, but may last longer)
  • Cosmetic issues (your scar will extend a few cm below your hairline)
  • Death


  • Significant scarring (‘keloid’)
  • Wound breakdown
  • Drug allergies
  • DVT (‘economy class syndrome’)
  • Pulmonary embolism (blood clot in lungs)
  • Chest and urinary tract infections
  • Pressure injuries to nerves in arms and legs
  • Eye or teeth injuries
  • Myocardial infarction (‘heart attack’)
  • Stroke
  • Loss of life
  • Other rare complications


  • Before Surgery

    Prior to your surgery you may have undergone a chlorhexidine (antiseptic) shampoo as well as a steretactic MRI scan. You will not eat or drink anything for 6-8 hours before your operation.

  • Anaesthetic and Preparation

    A general anesthetic is given and a breathing (‘endotracheal’) tube is inserted. Intravenous antibiotics and dexamethasone (steroids which reduce some types of brain swelling and protect the brain and spinal cord from injury) are administered.
    You will be positioned face-down on the operating table. The frameless stereotactic navigation system is set up. Antibiotics are given, and compression devices are used on your calves to reduce the risk of blood clot formation in your legs (deep venous thrombosis).

    Some hair at the back of your head is shaved, and the skin is cleaned with antiseptic solution. Local anaesthetic and adrenaline are then injected into the proposed incision site.

  • Surgical Procedure

    A midline incision is made at the back of your head, and extends down to the upper part of your neck. The incision is typically 5 or 6cm in length. The muscles attaching to the back of your skull and spinal bones are elevated. A small window of bone ( measuring around 2.5cm diameter is then removed from the base of your skull using a fine high-speed drill. This is part of the occipital bone and adjoining foramen magnum. This gives the cerebellum more room, and decompresses the brainstem.

    Because the tonsillar herniation frequently extends through the spinal canal formed by the first neck bone (cervical vertebra, C1), the posterior arch of the C1 bone is also removed.

    In many cases the above maneuvers are enough and nothing further is required. In some situations, however, such as when there is a tight band of tissue constricting the lining of the brain (dura), or where it is thought that there is scarring (adhesions) around the cerebellum and brain stem, the dura is opened and a patulous graft of tissue is sewn in place to create more room. If adhesions are found, they may be divided.

    The incision is then closed with staples.


  1. Neurological Observation
    You will be transferred to the recovery room immediately after surgery, where you will wake up. The recovery room nurses will monitor you closely, particularly in relation to your level of consciousness, arm and leg strength, as well as breathing, blood pressure and heart rate.
  2. Once you are more awake and stable, you will be moved to the neurosurgical high dependency unit or a closely monitored bed on the neurosurgery ward, where your condition can be closely monitored for around 24hrs. These highly specialised areas provide ongoing close observation with highly-trained nursing care.
  3. The first 24 hours after surgery represents the period of highest risk for post-operative bleeding. Your blood pressure will be kept under control and your level of consciousness will be watched closely. When fully conscious and completely stable, you will be returned to your regular room.
  4. Postoperative Pain and Nausea
    A dull headache is common, and most patients experience significant neck pain and stiffness after a Chiari decompression. The neck pain is due to the surgical elevation of the muscles from the back of the spine, and may take a number of weeks (or even longer) to settle. Pain medication will be ordered. Nausea and vomiting may also occur, and these will be treated with medications.
  5. Incision care
    The incision will be covered with a dressing, and sometimes a crepe bandage. The wound is usually checked, cleaned and redressed 3 or 4 days after surgery. The staples are usually removed 7 or 8 days after surgery. The wound must be kept dry for the first 2 weeks following your operation.
  6. Fluid Replacement and Nutrition
    Intravenous fluids will be ordered during the early recovery period and continued until you are fully awake and tolerating a reasonable amount of liquid by mouth.
  7. Emotional changes

    Brain surgery is generally fairly stressful, both physically and psychologically. It is common to feel discouraged and tired for several days after surgery. This emotional let-down must not be permitted to obstruct the positive attitude essential to recovery and a return to fairly normal activity.

  8. Discharge

    The amount of time spent in the hospital may be different for each patient, but is usually 3-5 days.


If a significant pre-operative neurologic deficit remains after surgery, a period of rehabilitation is often necessary to maximise your improvement. Otherwise you are likely to be discharged home. The vast majority of patients undergoing a Chiari decompression are able to be discharged directly home.
Your GP should check your wounds 4 days after discharge. We will advise you when to have your staples removed at your GP’s surgery or by the Precision Neurosurgery Practice Nurse (this is usually 7-8 days after surgery). You should not sign or witness any legal documents until you have been seen by your GP. You will need to take it easy for 6-8 weeks.

You should try to do around an hour of gentle exercise, such as walking, every day. You will be reviewed after 6-8 weeks by your neurosurgeon. You should not drive a motor vehicle, operate heavy machinery, or return to work until your neurosurgeon gives you the go ahead.


Your neurosurgeon will review you 7-8 weeks after discharge, but will see you sooner if there are any problems. You will need to see your GP frequently during that time, so that your wound can be monitored for signs of infection, and your medications can be adjusted.
Before returning to see your neurosurgeon, a CT scan or MRI may be arranged. Blood tests may also be organized. This will depend upon your specific circumstances.

You should keep in contact with the Precision Neurosurgery Registered Nurse, and relay any concerns to her.


Your Neurosurgeon and/or the Precision Neurosurgery Registered Nurse will give you specific advice which should be followed.
You are encouraged to set a flexible plan for your recovery, and should work slowly and steadily to increase your physical and mental tolerance.

During the first week at home, you should relax and just move around at will. Lifting anything over 2-3kg is discouraged for the first two or three months.

Your dressing will be changed a few days after surgery, and can be removed a week or so later. Once the dressing is no longer required, you can wear a clean hat or scarf until your hair has re-grown. The staples are generally removed at 7-8 days post-op.

You can shower and gently wash your hair with shampoo, but you should keep your wound dry for the first 2 weeks after surgery. The best way to do this is to wear a shower cap. Avoid hair products such as mousse or gels, as well as hair colourants and perms for at least 2 months after surgery.

Walking is the best exercise to undertake after brain surgery. Commence a walking program your second week home and increase the time and distance as each week passes. Aim for 1-2 hours per day on flat ground after two months.

You should avoid riding bicycles or running for at least two months. Other activities should be discussed with your neurosurgeon or the Precision Neurosurgery Registered Nurse.

You can resume sexual activity when you feel comfortable, but this should not be too vigorous for the first month or so after surgery.

Driving should be discussed with your neurosurgeon, as these guidelines vary from State to State, as well as from patient to patient.


The following are common problems encountered by many patients, and usually do not mean anything serious is wrong:

  • Headaches: these are usually present daily to some degree, and may persist for a number of weeks. They will change in their location, character and severity as the bone heals and the scalp nerves regenerate.
  • Neck pain: this is the most common and bothersome symptom after a Chiari decompression. It usually responds to anti-inflammatory medications and small doses of muscle relaxants, and tends to settle with time. Some gentle physiotherapy commencing 4-6 weeks after surgery may be beneficial.
  • Numbness: this is common, and arises because the skin nerves have been cut. The area of numbness usually decreases over weeks to months, but sometimes does not disappear completely.
  • Concentration: this is usually impaired for weeks to months after craniotomy. It is common to find difficulty focusing on tasks, you may need to re-read information in order to retain it. These symptoms tend to get better with time.
  • Emotional instability (lability): you may experience irritability, depression, crying spells, anxiety, and sensitivity to noise or people in crowded places. Try to relax and take it easy. Spend more quiet time. If you have major problems with these symptoms and cannot relax, call us and we will arrange for you to see a Clinical Psychologist to receive some strategies to do so.
  • Tiredness and fatigue: these are very common, and gradually improve. Once you commence a regular walking program, you will start to feel more energy.

It is common for it to take up to 3 months before you feel “well” again. Have plenty of rest during the day and eat healthy foods. Do not drink more than a small amount of alcohol during this time. Get up at your regular time and get plenty of sleep. Your internal clock would have been severely deranged during your hospitalisation, and it takes some time to return to normal.


  • Increasing headache which is unrelieved by pain medication
  • Fever (high temperature) or chills
  • Swelling or infection of the wound (redness, increasing pain or tenderness)
  • Leakage of fluid from the wound, or any opening in the wound after the staples have been removed
  • Fitting (seizures) or fainting spells
  • Abnormal sensations or movements in your face, arms or legs
  • Weakness or numbness
  • Drowsiness
  • Problems with balance or walking
  • Nausea or vomiting
  • Pain in the calf muscles or chest
  • Shortness of breath
  • Any other concerns


Private patients undergoing surgery will generally have some out-of-pocket expenses.
A quotation for surgery will be issued, however this is an estimate only. The final amount charged may vary with the eventual procedure undertaken, operative findings, technical issues etc. Patients are advised to consult with their Private Health Insurance provider and Medicare to determine the extent of out-of-pocket expenses.

Separate accounts will be rendered by the anaesthetist and sometimes the assistant, and hospital bed excess charges may apply. Medical expenses may be tax deductible (you should ask your accountant).

You should fully understand the costs involved with surgery before going ahead, and should discuss any queries with your surgeon.


You will be asked to sign a consent form before surgery. This form confirms that you understand all of the treatment options, as well as the risks and potential benefits of surgery. If you are unsure, you should ask for further information and only sign the form when you are completely satisfied.


  • What happens at the time of your admission?

    Patients are usually admitted to hospital either the day before, or on the morning of surgery. In situations where a number of investigations (scans etc) or consultations are needed you may be admitted a couple of days before surgery. On admission you will be assessed by a physician and a nurse. Blood tests and sometimes an ECG are done to make sure you are fit for surgery. You will also meet the anaesthetist at some stage before your operation.

  • I’ve been told I’ll need a Stealth or Brainlab Scan. What is this?

    A stealth scan is frequently used by neurosurgeons to help them pinpoint the exact location of a tumour, blood clot, or specific area in the brain. This makes your surgery safer.

    Either the day before or on the morning of surgery you will undergo a brain scan, either a CT or an MRI. This information is loaded into a computer in the operating theatre in order to generate an exact three-dimensional image of your head and brain which can be closely correlated with your real brain during surgery.

    Small round surface markers called ‘fiducials’ are stuck to the forehead and scalp. It will be necessary to shave a small amount of hair to ensure that the fiducials make proper contact with the skin and don’t fall off. The markers stay in place until surgery where they are ‘seen’ by the computer. It is important you do not pick the fiducials off or wash your hair before surgery, as they are likely to fall off.

  • How long will surgery take?

    Surgery usually takes 1-2 hours. The exact time depends upon a number of technical factors. You will usually be in the recovery room for an hour or so immediately after you wake up, and in total you will be away from the ward for at least a few hours.

  • How to I get my life back to ‘normal’ after surgery?

    You can gently wash your hair around two weeks after surgery. It is recommended that you use a gentle shampoo for this. It is advised that you avoid hair dyes and perms for a couple of months as these may irritate the incision.

    You are advised to avoid flying for at least two weeks after your operation, due to the possibility that changes in cabin pressure may cause problems if you have some air left in your head after surgery. You must obtain clearance from your neurosurgeon before flying.

    You can resume light work around the house and a gentle exercise program as soon as you feel fit. How quickly you can return to work will depend upon the nature of your job, and it is best to discuss this with your neurosurgeon.

    It is safe to resume sexual activities once you feel capable.

    Drinking a small amount of alcohol is safe, but you may be more susceptible to the mind-altering effects of alcohol after brain surgery, and it is recommended that you only have one or two standard drinks per day for the first few months after your operation.


The main aim of surgery is to prevent ongoing deterioration.
Most patients (around 80%) experience a significant improvement in their headaches and/or neck pain after surgery.