Syringomyelia
Fluid-filled cyst within the spinal cord causing progressive neurological deficits
ICD-10: G95.0 · systemic condition
Syringomyelia is the formation of a fluid-filled cavity (syrinx) within the central grey matter of the spinal cord. As the syrinx expands, it destroys crossing spinothalamic fibers (causing dissociated sensory loss — impaired pain and temperature sensation with preserved touch), anterior horn cells (causing hand wasting and weakness), and lateral corticospinal tracts (causing spasticity below the lesion). The condition is slowly progressive in most cases, although the rate of expansion is unpredictable. Chiari Type I malformation — downward displacement of the cerebellar tonsils through the foramen magnum — is the most common cause of syringomyelia, accounting for roughly half of cases. CSF flow obstruction at the foramen magnum creates abnormal pressure gradients within the spinal cord that drive fluid into the central canal. Other causes include spinal cord injury (post-traumatic syrinx), arachnoiditis, spinal tumors, and tethered cord syndrome. Idiopathic syringomyelia occurs without an identifiable cause. Treatment is directed at the underlying cause rather than the syrinx itself. Foramen magnum decompression for Chiari I malformation typically causes the syrinx to stabilize or regress. Direct syrinx drainage (syringosubarachnoid or syringoperitoneal shunting) is reserved for cases where addressing the primary cause is not possible or fails.
Anatomy & Pathology
The spinal cord's central canal is a tiny fluid-filled channel running its full length. A syrinx forms when CSF — driven by abnormal pressure dynamics or obstructed flow — accumulates within or adjacent to the central canal and expands outward. The syrinx disrupts the cord's internal architecture, particularly the decussating (crossing) pain and temperature fibers that travel through the center of the cord.
Symptoms
- Cape-like dissociated sensory loss — impaired pain and temperature sensation over shoulders and arms with preserved light touch
- Painless hand burns or injuries from loss of pain sensation (Charcot joints)
- Progressive hand weakness and intrinsic muscle wasting
- Spastic leg weakness and gait difficulty as corticospinal tracts are affected
- Neck or back pain, often worse with Valsalva, coughing, or straining
- Scoliosis (particularly in children, as cord dysfunction disrupts paraspinal muscle balance)
- Bladder dysfunction in advanced cases
Causes & Risk Factors
- Chiari I malformation with foramen magnum obstruction to CSF flow (most common, ~50%)
- Post-traumatic syrinx following spinal cord injury
- Arachnoiditis from surgery, infection, or subarachnoid hemorrhage creating CSF flow barriers
- Intramedullary or extramedullary spinal tumor obstructing CSF circulation
- Tethered cord syndrome creating traction forces on the spinal cord
Imaging Findings
Imaging studies are commonly used to identify findings associated with this condition. Results vary by individual; a qualified spine specialist interprets findings in the context of a full clinical evaluation.
MRI
- Elongated CSF-intensity (T1 low, T2 high) cavity within the central or eccentric portion of the spinal cord — signal follows CSF on all sequences
- Syrinx extent in vertebral levels: correlates with symptom distribution — a large cervicothoracic syrinx causes cape-like loss of pain and temperature sensation
- Cord atrophy surrounding the syrinx cavity in longstanding cases
- Associated Chiari I malformation: cerebellar tonsillar descent below the foramen magnum (greater than 5 mm) on sagittal MRI — present in up to 65% of syringomyelia cases
- Note: Phase-contrast MRI can assess CSF flow at the craniocervical junction — impaired flow supports Chiari-related syrinx etiology
CT Scan
- CT myelogram: intrathecal contrast fills the syrinx cavity in communicating types over delayed imaging (4–6 hours)
- Non-communicating syrinx does not fill with contrast on CT myelogram
- Craniocervical junction bony anatomy for Chiari surgical planning — occipital bone and C1 arch morphology
X-Ray
- Scoliosis is commonly associated with syringomyelia — a left thoracic curve in a child should prompt MRI to exclude syrinx
- Plain films not useful for syrinx diagnosis; MRI is required
- Bony craniocervical anomalies (basilar invagination, Klippel-Feil) may be visible and can coexist with syringomyelia
Who Is Commonly Affected
The following patterns are commonly associated with this condition based on published population studies. Individual presentation varies; these figures are informational only.
Peak Age Range
Chiari-associated syringomyelia: typically diagnosed in young to middle-aged adults (25–45 years); post-traumatic syringomyelia: develops months to decades after spinal cord injury
Gender Distribution
Roughly equal overall; Chiari I malformation (the most common associated cause) has slight female predominance
Estimated Prevalence
Estimated prevalence 8 per 100,000 in the general population; Chiari I malformation is identified in approximately 0.5–1% of individuals on brain/spine MRI, and up to 65% of symptomatic Chiari patients have a syrinx; post-traumatic syringomyelia occurs in approximately 20–30% of spinal cord injury patients
Treatment Options
Conservative
- MRI surveillance every 1–2 years for small, asymptomatic syrinx without neurological deficits
- Activity modification to avoid Valsalva-heavy activities that increase CSF pressure
- Physical and occupational therapy for hand weakness and gait dysfunction
Surgical
- Posterior fossa decompression (suboccipital craniectomy ± dural patch) for Chiari I — primary treatment that causes syrinx regression in 70–80% of cases
- Syringosubarachnoid shunting — direct drainage of syrinx fluid into the subarachnoid space for persistent or progressive syrinx after Chiari decompression
- Untethering surgery for tethered cord syndrome; spinal tumor resection; arachnoid lysis for arachnoiditis-related cases
When to see a spine specialist
Any patient with progressive unexplained hand weakness, loss of pain and temperature sensation, or new-onset scoliosis without a structural cause should have MRI of the entire spine and brain. Rapid neurological deterioration from syringomyelia warrants urgent neurosurgical evaluation. Annual MRI surveillance is appropriate for known syrinx with stable symptoms.
Specialists Who Treat Syringomyelia
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Questions to Ask Your Doctor
Bring these questions to your next appointment about syringomyelia.
- 1
What is causing my syrinx — Chiari malformation, spinal cord injury, tethered cord, arachnoiditis, or another cause — and does treating the underlying cause collapse the syrinx?
- 2
Is my syrinx progressing or stable, and does the size or progression rate correlate with my neurological symptoms?
- 3
If I have Chiari malformation, is foramen magnum decompression (posterior fossa craniectomy with duraplasty) the recommended treatment, and what is the expected syrinx regression rate?
- 4
What neurological symptoms should I monitor — progressive weakness, hand numbness, loss of pain/temperature sensation — that would indicate syrinx progression requiring urgent re-evaluation?
- 5
If no treatable underlying cause is found, what surgical options exist — syringopleural or syringosubarachnoid shunting — and what are the outcomes and risks?
Research Evidence
No studies reviewed yet for this condition. Check back soon — our evidence pipeline runs nightly.
Clinical Evidence
Frequently Asked Questions
If I have a Chiari malformation, will I definitely develop syringomyelia?
No. Chiari I malformation is a common incidental finding and the majority of patients never develop syringomyelia. The risk of syrinx is higher when tonsillar descent is greater, when the foramen magnum is more congested, and when symptoms such as occipital headache, Valsalva-exacerbated symptoms, or myelopathy are present. Patients with Chiari I and no syrinx and no symptoms can often be monitored without surgery.
Does treating the Chiari malformation cure the syrinx?
In most cases, posterior fossa decompression for Chiari I causes the syrinx to stabilize or shrink — typically over 6–18 months. Complete resolution occurs in 30–50% of cases; partial reduction in another 30–40%. Neurological improvement correlates with syrinx regression but is not guaranteed if cord injury was already significant. Persistent or growing syrinx after adequate Chiari decompression may require direct syrinx shunting.
Can syringomyelia cause scoliosis?
Yes. Syringomyelia is an important cause of scoliosis in children and should be suspected when scoliosis is found in a child under 10, when the curve is left-thoracic (atypical for idiopathic scoliosis), or when neurological findings are present. MRI of the entire spine is recommended for atypical scoliosis presentations before bracing or surgical planning, as undiagnosed and untreated syringomyelia can cause scoliosis to progress despite spinal instrumentation.