Statement of Principles concerning arachnoid cyst (Reasonable Hypothesis) (No. 11 of 2025)

The central concept is the “reasonable hypothesis” standard, which governs claims under sections 120A of the VEA and 338 of the MRCA. The RMA determines whether sound medical-scientific evidence indicates that a particular kind of injury, disease, or death can be related to relevant service. Here, the RMA has found that arachnoid cyst and death from arachnoid cyst can be so related. The instrument then sets out the minimum factors that must exist for a reasonable hypothesis to be raised. Importantly, the factors are not exhaustive; they represent the threshold. A claimant must show at least one factor existed and that it is related to service.

Clinical onset and clinical worsening are distinct concepts. Clinical onset refers to the first manifestation of the condition that would lead a medical practitioner to diagnose it. Clinical worsening refers to a material deterioration in the condition after it has already been diagnosed or manifested. For clinical worsening factors, the instrument applies only where the cyst was suffered or contracted before or during (but did not arise out of) relevant service - that is, the person already had the cyst before the claimed service period or acquired it during service from a non-service cause. The wording at section 10(2) limits worsening claims to those where the cyst was “suffered or contracted before or during (but did not arise out of) the person’s relevant service.” This means if the cyst arose out of service, worsening is irrelevant; if it was pre-existing or coincidental, worsening from service-related factors may be compensable.

The definition of trauma is specific: “significant injury to the vertebral column, or injury to the spinal cord or spinal meninges as a result of external force, excluding surgical or therapeutic procedures.” This definition explicitly excludes iatrogenic causes from the trauma factor, though spinal surgery itself is a separate factor. External force includes blunt trauma, acceleration or deceleration forces, blast force, or a foreign body penetrating the spinal region. This is a narrower definition than everyday trauma; minor strains or sprains likely do not qualify.

The exclusion of arachnoid cyst associated with autosomal dominant polycystic kidney disease (ADPKD) reflects that such cysts have a different aetiology and are not considered service-related. The instrument also provides a note listing clinical manifestations of intracranial cysts (headache, cranial nerve dysfunction, nausea, vomiting, seizures) and spinal cysts (back pain, gait/balance problems, sphincter disturbance). Clinical worsening includes enlargement, rupture, or haemorrhage.

Terminal event is defined as the proximate or ultimate cause of death, including pneumonia, respiratory failure, cardiac arrest, circulatory failure, or cessation of brain function. This is relevant where death is contributed to by the arachnoid cyst but the immediate cause is a terminal event listed.

The instrument operates within the framework of the VEA and MRCA, which already have rules about standard of proof and onus of proof. The RMA’s determination does not decide individual claims; it merely sets the medical-scientific gateway. Claimants must still prove that the factor existed and was related to service.

The instrument directly affects veterans, members of the Peacekeeping Forces, and members of the Forces under the VEA, as well as members under the MRCA, who have or have had arachnoid cyst and who are making a claim for compensation or treatment in respect of that condition. It also affects their dependants in death claims. Specifically, “relevant service” means operational service, peacekeeping service, hazardous service, or British nuclear test defence service under the VEA, or warlike or non-warlike service under the MRCA. This covers most Australian Defence Force members who have rendered service that triggers the VEA or MRCA compensation regimes. It does not cover peacetime service that is not classified as operational, hazardous, peacekeeping, or British nuclear test defence under the VEA; those members would fall under the MRCA for warlike/non-warlike service or possibly under other schemes.

The instrument also affects decision-makers at the Department of Veterans’ Affairs (DVA), the Veterans’ Review Board (VRB), and the Administrative Appeals Tribunal (AAT), who must apply these factors when determining whether a reasonable hypothesis is raised. Medical practitioners providing reports for claims need to understand the specific definitions (e.g., concussion, moderate to severe TBI, trauma) and the temporal windows. Legal practitioners representing claimants must identify which factor applies and ensure the evidence addresses the timing and relationship to service.

Indirectly, the instrument affects the broader veteran community and medical professionals who treat arachnoid cyst. Because the instrument sets an evidentiary threshold, it may influence clinical practice: for example, doctors may document head injuries or surgeries more carefully if they know the patient is a veteran. Conversely, the instrument’s narrow definitions may limit the ability of some claimants to succeed, particularly where the cyst is asymptomatic or discovered incidentally, as clinical onset would be difficult to pinpoint.

The exclusion of ADPKD-associated cysts means that a subset of claimants with a genetic predisposition will not be able to rely on this SOP, though they might still claim under another condition (e.g., ADPKD itself). The instrument’s application date is 28 January 2025, and it repeals the 2015 SOP. Claims made after that date are determined under the new instrument. For claims already determined, the repeal does not reopen them unless they are still under review or appeal.

The instrument does not impose duties directly on individuals; rather, it defines the rights of claimants to have their claim assessed against these factors. The key right is the right to have a reasonable hypothesis raised when at least one factor exists and is related to service. This right is conditional on the person having relevant service and satisfying the evidentiary requirements.

The RMA has a duty under the VEA to determine Statements of Principles based on sound medical-scientific evidence. The instrument itself notes that the RMA is of the view that there is such evidence for arachnoid cyst. Once made, the SOP has binding effect on decision-makers in the compensation system. Under section 120A(3) of the VEA, the Repatriation Medical Authority’s determination is conclusive as to whether a reasonable hypothesis is raised; decision-makers cannot depart from it. So the instrument creates a de facto duty for decision-makers to apply these factors.

For claimants, there is a duty to adduce evidence that a factor exists and that it is related to service. The instrument sets out minimum factors, but the claimant must still prove the underlying facts. For example, if factor 9.1 (concussion within 12 months before clinical onset of cranial arachnoid cyst) is relied upon, the claimant must show they had a concussion (likely defined by the RMA in another SOP for concussion, or per general usage) within 12 months of the first symptoms that would lead to diagnosis, and that the concussion was related to service. Similarly, for factor 9.4 (trauma in the region before clinical onset of spinal arachnoid cyst), the trauma must meet the definition in the dictionary (significant injury to vertebral column or injury to cord/meninges from external force, excluding surgery). The claimant must also show temporal sequence.

The instrument also creates a right for claimants to rely on the “inability to obtain appropriate clinical management” factor (9.14) for clinical worsening. This factor is not time-bound and does not require a specific medical event; it requires evidence that the person could not obtain appropriate management for the cyst (e.g., due to service-related reasons such as remote posting, lack of specialist access) and that this led to worsening. This factor is broad and could be contentious; the RMA has not defined “appropriate clinical management,” leaving it to medical evidence.

For the worsening factors, section 10(2) limits the right to those whose cyst was suffered or contracted before or during (but not arising out of) relevant service. This means that if the cyst arose out of service, the person’s right to claim ongoing worsening may be more straightforward (though worsening is still compensable if it is a natural progression). The instrument protects against double-counting: if the cyst itself is already accepted as service-related, the worsening factor is still relevant but the condition is already covered.

This instrument contains no penalty provisions. As a Statement of Principles, it is not a penal instrument. However, it operates within a compensation scheme that has its own enforcement mechanisms. False or misleading statements in a claim for compensation under the VEA or MRCA can attract criminal penalties under the Criminal Code (e.g., fraud offences under section 134.1 or 135.1 of the Criminal Code 1995). The instrument itself does not create any offences; it is purely evidentiary.

Enforcement of the SOP is indirect. If a claimant raises a reasonable hypothesis based on a factor that did not actually exist, and the decision-maker accepts it without proper scrutiny, that may lead to incorrect payment. The DVA has internal review mechanisms and the power to recover overpayments (under Part VII of the VEA). The VRB and AAT can set aside decisions that misapply the SOP. The Commonwealth Ombudsman can investigate systemic issues. But there are no penalties specific to this instrument.

From a compliance perspective, the burden falls on claimants and their representatives to ensure the evidence matches the factors. Medical practitioners who provide reports that are knowingly false could face professional sanctions or criminal liability, but again, that arises under other laws.

The instrument is made under subsection 196B(2) of the VEA, and it applies to claims under section 120A of the VEA and section 338 of the MRCA. Those sections require the relevant decision-making body to determine whether a reasonable hypothesis exists connecting the injury or disease with service. The SOP is conclusive as to what factors are sufficient. So this instrument overrides any inconsistent medical opinion or tribunal precedent on the question of what can raise a hypothesis for arachnoid cyst.

Section 11 of the instrument provides that if a factor refers to an injury or disease covered by another SOP, then the factors in that other SOP apply. For example, factor 9.2 requires “moderate to severe traumatic brain injury.” If a person has that injury, they must also satisfy the SOP for moderate to severe traumatic brain injury (if one exists) to establish that the injury itself is related to service. This creates a cascading evidentiary chain: the arachnoid cyst SOP points to the TBI SOP, which may point to other conditions. This can increase the overall compliance burden on claimants, as they may need to prove multiple conditions are service-related.

The instrument also interacts with the VEA’s standard of proof provisions. For operational service (under VEA), the standard is reasonable hypothesis (beneficial). For non-operational service under VEA or MRCA, the standard may be reasonable satisfaction (balance of probabilities). The SOP applies to both, but the application of the factors may be interpreted differently depending on the standard. However, the instrument does not address this nuance; it simply states the factors that must exist before a reasonable hypothesis can be said to be raised. For non-operational service, the decision-maker still uses the SOP to determine if the hypothesis is reasonable, then applies the balance of probabilities to whether the factor actually existed.

The instrument repeals the previous SOP (No. 91 of 2015). Claims determined before 28 January 2025 are unaffected, but any claim not finally determined must be decided under the new instrument. This creates a cutoff; claimants who would have succeeded under the old factors but not under the new ones may have an incentive to expedite their claims before commencement, but the instrument applies from its commencement date.

The definition of trauma excludes surgical or therapeutic procedures. That means factor 9.4 (trauma in region) cannot be satisfied by a medical intervention, but factor 9.6 (spinal surgery) covers that scenario separately. Similarly, intrathecal catheter placement or dural puncture is a separate factor. This indicates careful delineation between different aetiologies. The instrument also excludes arachnoid cysts associated with ADPKD, affirming that genetic conditions are not considered service-related unless a separate SOP deals with ADPKD.

The instrument repeals and replaces the Statement of Principles concerning arachnoid cyst (No. 91 of 2015). No other amendment history is provided in the text. The 2015 SOP was made under the same subsection 196B(2) and dealt with the same condition. The new instrument updates the factors and definitions. Without access to the 2015 SOP, we cannot detail specific changes, but the current instrument adds factors such as “having intrathecal catheter placement, including lumboperitoneal shunt and spinal anaesthesia, or inadvertent dural puncture” (factor 9.10) and “having a myelogram” (factor 9.11) which may not have been in the 2015 version. Also, the 2015 SOP may have had different temporal windows. The current instrument has a 12-month window for concussion before onset (factor 9.1), which is relatively long; previously it may have been shorter.

The exclusion of ADPKD-associated cysts is new or retained; not verifiable without the old instrument. The note on clinical worsening including enlargement, rupture, or haemorrhage may have been added for clarity. The definition of trauma in the dictionary may be more precise than before.

The instrument was made on 17 December 2024 and commences on 28 January 2025, giving a six-week lead time for stakeholders to adjust. The repeal of the 2015 SOP is automatic upon commencement.

The instrument contains no references to any court or tribunal cases. However, Statements of Principles are regularly challenged in the AAT and Federal Court on grounds of jurisdictional error, failure to apply correct test, or that the factor does not reflect sound medical-scientific evidence. For arachnoid cyst specifically, there have likely been cases under both the 2015 SOP and earlier ones. Without specific mention, we cannot cite them. Generally, the AAT has considered the meaning of “reasonable hypothesis” and the weight to be given to the SOP. The Federal Court has emphasised that the RMA has a wide discretion and courts will not substitute their own medical judgment (e.g., Repatriation Commission v Bendy [1989] FCA 527, but not cited here). The instrument’s factors may be litigated if a claimant argues that the factor list is incomplete or that a particular factor was misinterpreted.

For example, the definition of trauma may be contested: what constitutes “significant injury to the vertebral column”? Could mild compression fracture qualify? The dictionary says “significant injury,” which imports a threshold. Uncertainty around “significant” invites litigation. Similarly, “moderate to severe traumatic brain injury” is not defined here; it would need to be determined by reference to other SOPs or clinical guidelines. The temporal windows (e.g., “within the 12 months before clinical onset”) may be disputed if onset is gradual or if there are multiple possible onset dates.

The exclusion of ADPKD-associated cysts might be challenged as irrational, but the RMA has medical-scientific basis for it. The litigation history of SOPs generally shows that the RMA is given broad deference, but there have been successful challenges where the SOP failed to include a clearly relevant factor. However, no such history is in the source.

Several aspects of this instrument could cause difficulty for unwary claimants or representatives.

First, the definition of trauma excludes surgical or therapeutic procedures. Many people might assume that a spinal surgery constitutes trauma, but the instrument deliberately separates trauma (external force) from surgery (which is a separate factor). If a claimant tries to use factor 9.4 after a discectomy, it will fail because the surgery is not trauma. They must instead use factor 9.6 (spinal surgery). Similarly, if someone had an epidural that caused a dural puncture, that is covered by factor 9.10 (intrathecal catheter placement or inadvertent dural puncture), not trauma.

Second, the temporal windows differ between onset and worsening. For trauma, the window for onset is “before clinical onset” (no stated limit for spinal trauma, but for cranial concussion it is 12 months, and for moderate-severe TBI no specified limit other than “before clinical onset” could be any time). For worsening, trauma and surgery have a strict 3-month window. A claimant who had a back injury 6 months before their spinal cyst worsened cannot rely on factor 9.5; they would need to show the injury itself caused the onset (if they had no prior diagnosis) or rely on another factor. The causal link must be proximate.

Third, the factor 9.14 “inability to obtain appropriate clinical management” is a catch-all that seems generous but is vague. It requires both inability to obtain management and a causal link to worsening. If the person simply chose not to seek treatment, that likely does not qualify. The inability must be due to something related to service (e.g., remote posting, delay due to DVA administrative issues). This factor could be difficult to prove without evidence of attempts to obtain care and failure.

Fourth, the exclusion of arachnoid cysts associated with ADPKD. If a person has ADPKD, any arachnoid cyst they have will not be covered by this SOP even if other factors exist. They would need to claim under the SOP for ADPKD (if any) or on a different basis. Many people may not know that their arachnoid cyst is linked to ADPKD.

Fifth, the definition of terminal event for death claims is broad but does not include all possible immediate causes of death. If a person dies from anaphylaxis or myocardial infarction, those are not listed; the list is inclusive but suggests the terminal event must be one of the specified types or something analogous. This could be contentious.

Sixth, the worsening factors apply only where the cyst was suffered or contracted before or during (but not arising out of) relevant service. This limits the scope. If a person’s cyst arose out of service, they can claim for the condition itself, but worsening factors may still be used if the worsening is not part of the natural progression but caused by a new service-related factor. However, section 10(2) states the clinical worsening aspects apply only to material contribution/aggravation where the cyst was not service-related originally. This could create a situation where a service-caused cyst is worsened by another service factor; does the claimant need to prove worsening separately? The wording seems to say the worsening factors are only available for pre-existing cysts not arising out of service. That is a trap: if the cyst is already accepted as service-related, the claimant cannot rely on a worsening factor later because the cyst arose out of service. But they could still claim deterioration as part of the natural progression of the accepted condition. The SOP’s factors for worsening would be redundant for service-caused cysts.

Seventh, the factor requiring “concussion within the 12 months before clinical onset” may be difficult to prove if the concussion was mild and not documented. Also, “moderate to severe traumatic brain injury” is not defined in this SOP, so it must be determined by reference to medical standards (Glasgow Coma Scale, etc.). The burden is on the claimant.

Eighth, the instrument applies to claims under both VEA and MRCA, but the definitions of relevant service differ slightly. For VEA, it includes British nuclear test defence service; for MRCA, warlike and non-warlike. But only VEA includes British nuclear test defence service. So a person who served in that capacity cannot rely on MRCA.

Ninth, the SOP does not specify what constitutes “clinical onset” for an asymptomatic cyst found incidentally on imaging. The note says most arachnoid cysts are asymptomatic. If a cyst is discovered on MRI for another reason, clinical onset may be the date of the imaging. But if the person later becomes symptomatic, the clinical worsening factors might apply, but the onset factor must be satisfied before that date. This can lead to disputes.

For a legal practitioner representing a veteran with arachnoid cyst, the first step is to identify whether the claim is for onset of the cyst or for worsening of a pre-existing cyst, and whether it is cranial or spinal. Then review the list of factors in section 9. The claim must fail if none of the factors can be established on the evidence. If one or more factors are plausible, gather medical evidence that addresses each element: (1) existence of the factor (e.g., documented concussion, surgery records, infection history); (2) temporal relationship (within the specified windows); (3) the definitional requirements (e.g., trauma must meet the dictionary definition; infection must be of the types listed); (4) relationship to service (the factor must itself be related to relevant service). For example, if relying on factor 9.1 (concussion within 12 months before clinical onset of cranial cyst), the practitioner must obtain evidence of the concussion diagnosis (medical records) and evidence of the clinical onset of the cyst (first symptom or imaging). Then show the concussion was related to service (e.g., occurred during a training accident). The timeline is critical; if the concussion occurred 13 months before onset, it fails unless other factors apply.

For clinical worsening claims, first confirm that the cyst was not caused by service. That is, the person had the cyst before the claimed period or acquired it during service from a non-service cause. Then select a worsening factor with a 3-month window (or per other timeframes) before the worsening event. The definition of clinical worsening in the note includes enlargement, rupture, or haemorrhage, but the SOP does not require those specific events; “clinical worsening” is generally a material deterioration in symptoms. The factor “inability to obtain appropriate clinical management” has no timeframe, but it must cause the worsening.

Practitioners should check the definitions carefully: trauma excludes surgery, but surgery is a separate factor. For spinal cysts, intrathecal catheter placement includes epidural anaesthesia and inadvertent dural puncture; myelogram is also a factor. For cranial cysts, cranial surgery is a factor. Infections must be bacterial brain/spinal cord infection, meningitis (bacterial, viral, fungal), cranial/spinal tuberculosis, or neurosyphilis. Subarachnoid haemorrhage and spinal adhesive arachnoiditis are included. Malignant neoplasm with meningeal infiltration must be within 1 year before onset or worsening.

If a factor is itself a disease or injury covered by another SOP (e.g., moderate to severe traumatic brain injury, infection), the practitioner must also address that SOP. This means the 2-step analysis: first, ensure the factor exists (e.g., TBI), then ensure the factor is related to service under the TBI SOP. This may require separate expert evidence.

The instrument does not address the standard of proof; that is in the VEA/MRCA. For operational service, the claimant only needs to raise a reasonable hypothesis; for non-operational, the claim must be decided to the reasonable satisfaction of the decision-maker. However, the SOP itself is mandatory for the hypothesis test: if the factors are met and related to service, the hypothesis is reasonable. If not met, it is not reasonable.

For death claims, establish that the person had arachnoid cyst and that it contributed to a terminal event listed (pneumonia, respiratory failure, cardiac arrest, circulatory failure, cessation of brain function). The terminal event must be proximately or ultimately caused by the cyst.

Practitioners should document the chain: service records to show relevant service; medical records to show diagnosis of arachnoid cyst; evidence of the factor (e.g., medical report confirming TBI); evidence of relationship to service (e.g., incident report, deployment records). For worsening, show that the cyst was not service-related originally (e.g., discovered before service, or during service but not caused by service). If the cyst is symptomatic, clinical onset is easier to prove; for asymptomatic cysts, onset may be the date of imaging, which might be after service, complicating the claim.

Finally, consider the exclusion of ADPKD. If the person has ADPKD, the SOP cannot be used; they would need to claim the ADPKD as a separate condition or argue that the cyst is not related to ADPKD (if medical evidence supports that). The definition says arachnoid cyst “excludes arachnoid cyst associated with autosomal dominant polycystic kidney disease.” This means a medical opinion must confirm no association. If the association is uncertain, the SOP may still apply.