Chiari Malformations


These guidelines have been produced to guide clinical decision making for general practitioners (GPs). They are not strict protocols. Clinical common-sense should be applied at all times. These clinical guidelines should never be relied on as a substitute for proper assessment with respect to the particular circumstances of each case and the needs of each patient. Clinicians should also consider the local skill level available and their local area policies before following any guideline.

If there is evidence of raised intercranial pressure including a reduced Glasgow Coma Score, uneven or non-reactive pupils or reduced power, send to the nearest Emergency Department immediately.


A Chiari malformation is where the cerebellar tonsils extend past the level of the foramen magnum into the cervical spinal canal. Type I malformations are often incidental findings during imaging for unrelated reasons. Patients’ symptoms vary from:

  • asymptomatic (generally no intervention required)
  • headaches (on coughing or laughing)
  • central sleep apnoea
  • upper and lower limb symptoms of syringomyelia.

Type II (Arnold Chiari) malformations are generally associated with myelomeningocele and are usually diagnosed prenatally or shortly after birth.

Pre-referral investigations

  • MRI brain required prior to referral
  • Please include the report and contact details of the radiology clinic (see link below for Medicare details)
  • If unable to perform MRI please arrange a CT scan and include report, contact details of the radiology clinic and the reason for performing a CT scan instead of MRI.
  • Relevant history and neurological exam (headaches with laughing or coughing, sleep apnoea, Upper and lower limb exam).

Pre-referral management

No pre-referral management necessary.

When to refer

  • If signs of raised intracranial pressure or concerning symptoms please refer directly to ED without waiting for imaging.  
  • Chiari 1 malformation (5mm or more) in a patient who is symptomatic should be referred to the neurosurgery department. If possible arrange a spinal MRI looking for a syringomyelia. Including the results with in the referral.
  • Type 2 (Arnold Chiari) malformations are usually associated with spinal dysraphism and may require a combined approach.  Consider referring to the spinal rehabilitation team if there are other concerns.

How to refer

  • Routine non-urgent referrals from a GP or a Consultant should go to the Central Referral Service
  • Routine non-urgent referrals from a nurse practitioner, non-medical referrers or private hospitals go to the PCH Referral Office.

Essential information to include in your referral

  • MRI report and contact details of the radiology clinic
  • Neurological exam results
  • Medical and surgical history
  • Patient demographics including next of kin contact details. 

Useful resources 


  1. American Association of Neurological Surgeons. (Undated ). Chiari Malformation. Retrieved February 6, 2021, from American Association of Neurological Surgeons:
  2. St Vincent's Private Hospital Melbourne. (2021). Arnold-Chiari Malformations. Retrieved February 21, 2021, from St Vincent's Private Hospital Melbourne:

Reviewer/Team: Dr Sharon Lee and Dr Simon Williams - Neurology Last reviewed: Apr 2020

Review date: Apr 2023
Endorsed by:
CPAC Date:  May 2021

This document can be made available in alternative formats on request for a person with a disability.