By: Dr Zaid Matti
Musculoskeletal Medicine Specialist
Incidental Syrinx: What Does It Mean When Found on a Spine MRI?
In today’s world, advanced MRI scans are often used to investigate back pain, injuries, or other spine-related symptoms. Sometimes, these scans reveal unexpected findings — one of which is called a syrinx. When this happens, many patients (and even some referring clinicians) are left wondering: what does this mean? Should we worry? Is treatment needed?
As a specialist in musculoskeletal and regenerative medicine, I often encounter this scenario. Let’s explore what an incidental syrinx means, particularly when found in the cervicothoracic or thoracic spine — regions where it often appears unintentionally during routine imaging.
What is a Syrinx?
A syrinx is a fluid-filled cavity that develops inside the spinal cord. You may also hear terms like syringomyelia (when it’s in the spinal cord) or syringobulbia (if it involves the brainstem). These cavities contain cerebrospinal fluid (CSF), which normally flows around the brain and spinal cord.
In many cases, when a syrinx is found incidentally — meaning the patient was scanned for another reason — it is very small and may have no impact on health or function.
Why Does a Syrinx Form?
There are multiple reasons why a syrinx may develop:
- Changes in CSF flow dynamics — sometimes from congenital conditions like Chiari malformation.
- Old injuries — including trauma to the spine, even years earlier.
- Degenerative spinal disease — which may subtly alter how spinal fluid moves.
- Inflammation or scarring — occasionally from prior infections or inflammation.
- Tumours — very rarely, but important to rule out.
- Idiopathic — meaning no clear cause is ever found.
In many patients, no significant underlying problem is identified, especially when the syrinx is small and stable.
How Common is an Incidental Syrinx?
Incidental syrinxes are not rare. Research shows they may appear in up to 1–2% of spinal MRIs. With modern, high-resolution scanners, we are detecting small syrinxes more frequently than ever before.
Fortunately, most of these are tiny (often just 2–3 millimetres), remain stable, and do not cause symptoms.
When Should We Be Concerned?
While most incidental syrinxes are harmless, certain features may warrant closer attention:
| Feature | Why It Matters |
|---|---|
| Size larger than 5 mm | May carry a higher risk of progression. |
| Symptoms present | Any weakness, numbness, or balance issues require evaluation. |
| Associated conditions | Chiari malformation, tethered cord, or spinal tumours may need treatment. |
If any of these are present, further evaluation — often by a neurosurgeon — may be recommended.
What Are the Symptoms If It Becomes Problematic?
When a syrinx becomes large enough, it may interfere with spinal cord function. Symptoms may include:
- Numbness, particularly involving the shoulders, arms, or hands (sometimes described as “cape-like”).
- Muscle weakness, stiffness, or spasticity.
- Problems with balance or walking.
- Bowel or bladder difficulties.
- In rare cases, chronic neuropathic pain.
However, it’s important to emphasize again: most incidental syrinxes never cause any of these symptoms.
What Tests Are Done After Finding a Syrinx?
When a syrinx is found, your specialist will usually:
- Review the MRI in detail to assess its size, shape, and location.
- Perform a careful neurological examination.
- Review your medical history for past injuries, infections, or symptoms.
- Occasionally order additional scans, such as:
- MRI of the brain to check for Chiari malformation.
- Cine MRI (a specialized study of CSF flow).
- Full-spine MRI if needed.
In most incidental cases, further testing is minimal, especially when no concerning symptoms are present.
How Are Incidental Syrinxes Managed?
In the majority of cases:
- No immediate treatment is required.
- Observation and monitoring with periodic MRI scans may be recommended.
- In many patients, one or two follow-up scans spaced months or years apart are enough to confirm that the syrinx is stable.
If the syrinx grows, becomes symptomatic, or is associated with an underlying condition, then referral to a neurosurgeon may be necessary. Treatment options could include surgical decompression, shunting, or addressing the underlying cause.
Should I Be Worried?
In my professional opinion, if you have been told that you have an incidental syrinx, the most important point is this:
Most small syrinxes are stable, harmless, and never require surgery or intervention.
With appropriate follow-up and expert monitoring, your care team can ensure that any changes are identified early, but most patients live completely normal lives without any problems from these findings.
Final Thoughts
The discovery of a syrinx on MRI can understandably create anxiety. However, with careful evaluation and follow-up, most patients can be reassured that:
- The syrinx is unlikely to cause harm.
- Monitoring is straightforward.
- Neurosurgical intervention is rarely needed for small, asymptomatic syrinxes.