Arachnoid Cyst


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.



Arachnoid cysts are cerebrospinal fluid filled cysts arising from the arachnoid membrane of the brain or spinal cord. Generally congenital they are often incidentally found when imaging the brain for an unrelated reason.

In most cases arachnoid cysts are asymptomatic. If symptoms occur they are usually non-specific and related to raised intracranial pressure. Symptoms can include headaches, seizures, visual disturbance, lethargy, behavioural changes, developmental delay, weakness, tingling in extremities or hormonal abnormalities. 

Pre-referral investigations

  • MRI brain (see link below for Medicare details) required prior to referral
    • Please include the report and radiology service’s contact details
  • If unable to perform MRI, please arrange a CT scan
    • Include the report and radiology service’s contact details in the referral
  • Neurological exam including Glasgow Coma Score, pupil reaction, limb tone, power and reflexes.

Pre-referral management

  • Nil

When to refer

  • If signs of raised intracranial pressure or concerning symptoms please refer directly to the nearest Emergency Department without waiting for imaging
  • If cyst found incidentally and child is asymptomatic, repeat MRI in 6-12 months. Only refer to the Neurosurgery Department if concerned.

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
  • Urgent referrals (less than seven days) go to the PCH Referral Office. Please call Perth Children’s Hospital Switch on 6456 2222 to discuss referral with the relevant speciality. 

Essential information to include in your referral

  • MRI report and contact details of the radiology department
  • Comprehensive neurological exam
  • Relevant history
  • Patient demographics including next of kin contact details. 

Useful resources


  1. National Institutes of Health. (2020, April 16). Arachnoid Cysts. Retrieved February 21, 2021, from Genetic and Rare Diseases Information Center:
  2. St Vincent's Private Hospital Melbourne. (2021). Arachnoid Cyst. Retrieved February 21, 2021, from St Vincent's Private Hospital Melbourne:

Reviewer/Team: Dr Sharon Lee and Dr Simon Williams - Neurology Department, PCH 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.

Referring service