Syringomyelia
Syringomyelia is a chronic progressive disorder characterized by a fluid-filled cavity (syrinx) within the central spinal cord parenchyma. [1,2] It most commonly occurs in association with Chiari Type I malformation (70% of cases), although it may also be caused by spinal trauma, tumours, arachnoiditis, or tethered cord. [1,3]
Key Facts
| Fact | Detail |
|---|---|
| Definition | Fluid-filled cystic cavity (syrinx) within the spinal cord substance |
| Most common cause | Chiari Type I malformation (70%) |
| Peak age | 25-40 years at presentation |
| Classic finding | Dissociated sensory loss (cape distribution) |
| Pathophysiology | CSF flow obstruction at foramen magnum creates pressure gradient |
| Key symptom | Loss of pain and temperature sensation with preserved light touch |
| Location | Cervical cord most commonly affected (70-80%) |
| Gold standard imaging | MRI spine and brain (with craniocervical junction) |
| Treatment | Posterior fossa decompression for Chiari-associated cases |
| Success rate | 85-95% symptom relief post-decompression |
Clinical Pearls
Pearl 1: The hallmark of syringomyelia is DISSOCIATED sensory loss - loss of pain and temperature with preserved light touch and proprioception. This occurs because the syrinx damages the crossing spinothalamic fibres in the anterior white commissure, while the dorsal columns remain intact.
Pearl 2: Cape distribution refers to the shawl-like pattern of sensory loss over the shoulders, upper arms, and upper trunk. It corresponds to the cervical dermatomes affected by the central syrinx cavity.
Pearl 3: Patients with syringomyelia often have painless burns or injuries to their hands because they cannot feel pain and temperature. Always examine the hands for scars and injuries.
Pearl 4: Any child or adolescent with progressive scoliosis of unknown cause requires MRI of the spine to exclude syringomyelia. Up to 70% of children with Chiari I and syringomyelia have associated scoliosis.
Pearl 5: Chiari I malformation is defined as tonsillar herniation more than 5mm below the foramen magnum. Always request MRI brain with views of the craniocervical junction when syringomyelia is identified.
Incidence and Prevalence
| Population | Rate | Notes |
|---|---|---|
| General population | 8.4 per 100,000 | Prevalence estimate |
| Chiari I malformation | 50-70% develop syrinx | If symptomatic |
| Spinal cord injury | 3-4% develop syrinx | Post-traumatic |
| Spinal tumours | Variable | Especially ependymoma, hemangioblastoma |
Demographics
| Factor | Association |
|---|---|
| Age | Peak onset 25-40 years; Chiari-associated often presents in 2nd-3rd decade |
| Sex | Slight female predominance in Chiari-associated (1.3:1) |
| Hereditary | Chiari I has familial clustering in 12-15% |
Aetiological Classification
| Category | Causes | Proportion |
|---|---|---|
| Communicating (with 4th ventricle) | Chiari I/II malformation | 70% |
| Non-communicating | Post-traumatic, post-meningitis, tumour-associated, tethered cord | 25% |
| Idiopathic | No identifiable cause | 5% |
Risk Factors
| Risk Factor | Mechanism | Notes |
|---|---|---|
| Chiari I malformation | CSF flow obstruction at foramen magnum | Most common cause |
| Spinal cord injury | Post-traumatic cyst formation | Latency 3 months to 30 years |
| Spinal arachnoiditis | Scarring obstructs CSF flow | Post-meningitis, post-surgery |
| Intramedullary tumour | Tumour cyst or obstruction | Ependymoma, hemangioblastoma |
| Tethered cord | Altered CSF dynamics | Especially with occult spinal dysraphism |
| Basilar invagination | Craniocervical abnormality | Associated with Chiari |
Stepwise Mechanism (Chiari-Associated Syringomyelia)
Step 1: CSF Flow Obstruction at Foramen Magnum
- Chiari I: cerebellar tonsils herniate more than 5mm below foramen magnum
- Creates obstruction to normal CSF flow from cranium to spine
- During Valsalva/coughing, intracranial pressure rises
- CSF cannot equilibrate normally between compartments
Step 2: Pressure Differential and CSF Entry into Cord
- Elevated pressure forces CSF into central canal of spinal cord
- Perivascular spaces (Virchow-Robin spaces) may act as conduits
- CSF accumulates within cord substance
- Formation of initial syrinx cavity
Step 3: Syrinx Expansion
- Repeated pressure pulsations with each cardiac cycle
- Progressive enlargement of fluid-filled cavity
- Syrinx typically expands in longitudinal and transverse dimensions
- Central grey matter initially affected
Step 4: Neural Tissue Damage
- Crossing spinothalamic tract fibres in anterior white commissure damaged first
- Results in dissociated sensory loss (pain/temperature lost, light touch preserved)
- Further expansion damages anterior horn cells → lower motor neuron signs in hands
- Late involvement of lateral corticospinal tracts → upper motor neuron signs in legs
Step 5: Chronic Progression or Stabilization
- Natural history highly variable
- Some patients stabilize spontaneously
- Others have progressive myelopathy
- Treatment can arrest progression in 85-95% of cases
Non-Chiari Mechanisms
| Type | Mechanism |
|---|---|
| Post-traumatic | Haemorrhage, ischaemia, cyst formation in injured cord |
| Tumour-associated | Intramedullary tumour produces oedema fluid or cystic degeneration |
| Post-arachnoiditis | Scarring obstructs CSF flow at any level |
| Tethered cord | Altered CSF dynamics and abnormal cord tension |
Classification Systems
| Classification | Type | Features |
|---|---|---|
| Milhorat (2000) | Type 1 | Communicating with 4th ventricle (Chiari-associated) |
| Type 2 | Non-communicating, focal (post-traumatic) | |
| Type 3 | Tumour-associated | |
| Type 4 | Atrophic (burnt out) | |
| Location | Cervical | 70-80% |
| Thoracic | 15-20% | |
| Lumbar | 5-10% | |
| Holocord | Entire cord length |
Symptoms by System
| System | Symptoms | Frequency |
|---|---|---|
| Sensory | Numbness in hands/arms, painless burns, cape distribution sensory loss | 80-90% |
| Motor | Hand weakness, clumsiness, muscle wasting | 60-70% |
| Pain | Neck pain, headache (especially Chiari), neuropathic arm pain | 50-70% |
| Autonomic | Hyperhidrosis, Horner syndrome (if cervical involvement) | 20-30% |
| Brainstem (if Chiari) | Dysphagia, sleep apnoea, hoarse voice, vertigo | 20-40% |
| Bladder | Urinary urgency, incontinence (late) | 10-20% |
Symptom Progression Pattern
| Stage | Features |
|---|---|
| Early | Vague hand numbness, painless injuries, mild neck pain |
| Intermediate | Cape sensory loss, hand weakness, muscle wasting, scoliosis |
| Advanced | Spastic paraparesis, bladder dysfunction, bulbar symptoms |
Atypical Presentations
| Presentation | Notes |
|---|---|
| Progressive scoliosis in child | May be only presenting feature |
| Chiari headache alone | Sub-occipital headache with Valsalva |
| Shoulder pain (frozen shoulder) | Attributed to musculoskeletal cause |
| Chronic cough | Brainstem involvement |
| Sleep apnoea | Chiari with brainstem compression |
Red Flags
| Red Flag | Implication | Action |
|---|---|---|
| Rapid neurological decline | Tumour, haemorrhage into syrinx | Urgent MRI |
| Respiratory compromise | Brainstem involvement | Emergency neurosurgical referral |
| New-onset bladder dysfunction | Cord compression/progressive syrinx | Expedite management |
| Acute severe headache | CSF leak, haemorrhage | Emergency assessment |
| Progressive scoliosis in child | Underlying syringomyelia | MRI spine |
| Bilateral hand weakness + sensory loss | Central cord syndrome | Urgent neurology/neurosurgery |
Structured Neurological Examination
Upper Limbs
| Finding | Significance | Mechanism |
|---|---|---|
| Wasting of small hand muscles | Lower motor neuron damage | Anterior horn cell involvement |
| Weakness of intrinsic hand muscles | C8-T1 myotomes | Syrinx at cervicothoracic junction |
| Areflexia in upper limbs | LMN lesion | Anterior horn damage |
| Dissociated sensory loss | Pathognomonic | Spinothalamic fibres damaged, dorsal columns spared |
| Charcot joints in hands | Chronic denervation arthropathy | Painless trauma |
| Scars/burns on hands | Painless injuries | Absent pain sensation |
Lower Limbs
| Finding | Significance | Mechanism |
|---|---|---|
| Spastic paraparesis | Upper motor neuron involvement | Lateral corticospinal tract compression |
| Hyperreflexia | UMN lesion | Pyramidal tract involvement |
| Upgoing plantars | UMN lesion | Pyramidal tract involvement |
| Normal or mildly impaired sensation | Dorsal columns preserved | Syrinx central, does not reach periphery |
Special Signs
| Sign | Technique | Interpretation |
|---|---|---|
| Cape distribution sensory loss | Test pain/temperature across shoulders and arms | Positive supports syringomyelia |
| Horner syndrome | Ptosis, miosis, anhidrosis | Cervical sympathetic involvement |
| Scoliosis | Observe spine from behind | Common in children/adolescents |
| Nystagmus | Eye movements | Chiari-associated brainstem involvement |
| Lower cranial nerve signs | Tongue, palate, gag | Chiari with brainstem compression |
What to Look For
| Examination | Positive Findings |
|---|---|
| General inspection | Scoliosis, hand deformities, scars |
| Motor - hands | Wasting of thenar, hypothenar, interossei |
| Motor - legs | Spastic gait, increased tone |
| Sensory - spinothalamic | Reduced pin prick/temperature in cape distribution |
| Sensory - dorsal column | Preserved vibration and proprioception |
| Reflexes | Absent in arms, brisk in legs |
| Plantar response | Extensor bilaterally |
Imaging
| Investigation | Findings | Notes |
|---|---|---|
| MRI spine (T1/T2) | Intramedullary cystic cavity (hypointense T1, hyperintense T2) | Gold standard; shows syrinx extent |
| MRI brain with craniocervical junction | Tonsillar herniation (more than 5mm = Chiari I) | Essential to identify cause |
| CSF flow study (cine MRI) | Abnormal CSF flow at foramen magnum | Useful for surgical planning |
| Plain spine X-ray | Scoliosis, widened canal | Less sensitive, baseline for scoliosis |
| CT myelogram | Reserved for MRI contraindication | Invasive; rarely needed |
MRI Diagnostic Criteria
| Feature | Description |
|---|---|
| Syrinx location | Central cord, typically cervical or cervicothoracic |
| Size | Variable; may extend multiple levels |
| Margins | Smooth, well-defined |
| Septations | May be present in long-standing cases |
| Associated features | Chiari malformation, tumour, scar |
Additional Investigations
| Investigation | Indication |
|---|---|
| Contrast MRI | Suspected tumour (enhances) vs syrinx (no enhancement) |
| Sleep study | Suspected sleep apnoea with Chiari |
| Urodynamics | Bladder symptoms |
| EMG/NCS | Differentiate from peripheral neuropathy |
| Ophthalmology | Papilloedema if raised ICP suspected |
Differential Diagnoses
| Condition | Distinguishing Features |
|---|---|
| Intramedullary tumour | Enhances with contrast; solid component |
| Multiple sclerosis | Discrete plaques, brain lesions, CSF findings |
| Cervical myelopathy | No syrinx cavity on MRI |
| Motor neuron disease | No sensory involvement; no syrinx on MRI |
| Peripheral neuropathy | Symmetric stocking-glove pattern; NCS abnormal |
Management Algorithm
SYRINGOMYELIA SUSPECTED
↓
┌─────────────────────────────────────────────────────┐
│ MRI SPINE AND BRAIN │
│ - Confirm syrinx on T2-weighted imaging │
│ - Assess craniocervical junction │
│ - Exclude tumour (give contrast if uncertainty) │
└─────────────────────────────────────────────────────┘
↓
┌─────────────────────────────────────────────────────┐
│ IDENTIFY UNDERLYING CAUSE │
├─────────────────────────────────────────────────────┤
│ CHIARI I (70%) → Tonsillar herniation more than 5mm│
│ POST-TRAUMATIC → History of spinal injury │
│ TUMOUR → Enhancing mass on contrast MRI │
│ ARACHNOIDITIS → Scarring, clumped nerve roots │
│ IDIOPATHIC → Diagnosis of exclusion │
└─────────────────────────────────────────────────────┘
↓
┌─────────────────────────────────────────────────────┐
│ ASSESS SYMPTOMS │
├─────────────────────────────────────────────────────┤
│ ASYMPTOMATIC/INCIDENTAL │
│ → Serial MRI surveillance (6-12 monthly) │
│ → Monitor for symptom development │
├─────────────────────────────────────────────────────┤
│ SYMPTOMATIC │
│ → Neurosurgical referral │
│ → Posterior fossa decompression (Chiari) │
│ → Tumour resection (if tumour-associated) │
│ → Untethering (if tethered cord) │
└─────────────────────────────────────────────────────┘
↓
┌─────────────────────────────────────────────────────┐
│ SURGICAL OPTIONS (CHIARI-ASSOCIATED) │
│ FIRST-LINE: Posterior fossa decompression (PFD) │
│ ± Duraplasty (patch to expand dural space) │
│ │
│ IF NO IMPROVEMENT AT 6-12 MONTHS: │
│ → Repeat MRI │
│ → Consider syrinx shunt (rarely needed now) │
└─────────────────────────────────────────────────────┘
↓
┌─────────────────────────────────────────────────────┐
│ POST-OPERATIVE MONITORING │
│ - Clinical follow-up 3-6 months │
│ - Repeat MRI at 6-12 months │
│ - Long-term surveillance as needed │
└─────────────────────────────────────────────────────┘
Conservative Management
| Approach | Indication |
|---|---|
| Observation with serial MRI | Asymptomatic, incidental finding |
| Symptom monitoring | Mild, stable symptoms |
| Pain management | Neuropathic pain control with gabapentinoids, amitriptyline |
| Physiotherapy | Maintain function, prevent contractures |
| Occupational therapy | Adaptive strategies for hand dysfunction |
Surgical Management
| Procedure | Indication | Details |
|---|---|---|
| Posterior fossa decompression (PFD) | Chiari I with symptomatic syringomyelia | Remove suboccipital bone, C1 laminectomy; decompresses foramen magnum |
| PFD with duraplasty (PFDD) | Chiari I | PFD plus dural patch to further expand space |
| Tumour resection | Tumour-associated syrinx | Remove causative tumour |
| Untethering | Tethered cord | Release tethered filum terminale |
| Syrinx-subarachnoid shunt | Persistent syrinx after PFD | Rarely performed now; high complication rate |
| Syrinx-peritoneal shunt | Recalcitrant cases | Very rarely used |
Surgical Outcomes
| Outcome | Rate | Notes |
|---|---|---|
| Symptom improvement | 85-95% | Major symptom relief |
| Complete symptom resolution | 50-60% | |
| Syrinx regression | 60-90% | Radiological improvement |
| Scoliosis stabilization | 65-70% | In paediatric patients |
| Reoperation rate | 5-15% | |
| Complications | 10-20% | CSF leak, infection, meningitis |
Pharmacological Management
| Drug | Indication | Dose |
|---|---|---|
| Gabapentin | Neuropathic pain | 300-1200mg TDS |
| Pregabalin | Neuropathic pain | 75-300mg BD |
| Amitriptyline | Neuropathic pain, sleep | 10-75mg nocte |
| Duloxetine | Neuropathic pain | 30-60mg daily |
| Simple analgesics | Pain relief | Paracetamol, NSAIDs |
Complications of Untreated Disease
| Complication | Mechanism | Management |
|---|---|---|
| Progressive myelopathy | Expanding syrinx damages more cord | Surgery |
| Quadriparesis | Extensive cord damage | Irreversible if severe |
| Respiratory failure | Brainstem involvement | Emergency; may require ventilation |
| Charcot joints | Painless arthropathy | Protective measures |
| Chronic pain syndrome | Central sensitization | Multimodal pain management |
Complications of Surgery
| Complication | Incidence | Management |
|---|---|---|
| CSF leak | 5-15% | Wound repair, lumbar drain |
| Wound infection | 2-5% | Antibiotics, debridement if needed |
| Aseptic meningitis | Up to 25% | Supportive, steroids |
| Pseudomeningocele | 5-10% | Observation or repair |
| Persistent symptoms | 10-20% | Rehabilitation |
| Syrinx recurrence | 5-15% | Re-imaging, consider revision |
| Worsening symptoms | Rare | Investigation, early revision |
Natural History
| Scenario | Outcome |
|---|---|
| Untreated symptomatic syringomyelia | Progressive neurological decline in majority |
| Spontaneous stabilization | Occurs in minority; unpredictable |
| Chiari I without treatment | Variable; some remain stable for years |
Long-Term Outcomes Post-Surgery
| Outcome | Rate |
|---|---|
| Symptom improvement | 85-95% |
| Neurological stabilization | 90-95% |
| Syrinx size reduction | 60-90% |
| Complete syrinx resolution | 20-40% |
| Scoliosis stabilization (children) | 65-70% |
| Need for repeat surgery | 5-15% |
Prognostic Factors
| Factor | Better Prognosis | Worse Prognosis |
|---|---|---|
| Duration of symptoms | Short (less than 2 years) | Prolonged (more than 5 years) |
| Preoperative neurological status | Mild deficits | Severe deficits |
| Syrinx size | Small | Large, holocord |
| Age | Younger | Older |
| Cause | Chiari I | Post-traumatic, tumour |
| Scoliosis (children) | Curve less than 30° | Curve more than 50° |
Major Guidelines
| Guideline | Year | Key Recommendations |
|---|---|---|
| Congress of Neurological Surgeons | 2023 | PFD or PFDD both acceptable (Grade C); reassess at 6-12 months if syrinx persists |
| World Federation of Neurological Societies | 2019 | International consensus on Chiari I diagnosis and treatment |
| American Association of Neurological Surgeons | 2020 | Surgical indications and techniques |
Landmark Studies
| Study | Year | N | Key Findings | PMID |
|---|---|---|---|---|
| CNS Surgical Interventions Guideline | 2023 | SR | PFD and PFDD both effective; no strong difference in outcomes | 37775957 |
| Park-Reeves Consortium Scoliosis Study | 2021 | 158 | No significant difference in scoliosis outcomes between duraplasty and extradural decompression | 33507567 |
| Long-term Chiari Decompression Outcomes | 2020 | 37 | 70% syrinx reduction, scoliosis stabilized in 2/3 of cases | 31933098 |
| Persistent Syrinx Study | 2020 | 57 | 40% did not achieve syrinx improvement post-PFD, but most had symptom improvement | 32204297 |
| PFDD Positive Predictors | 2023 | 93 | Identified factors associated with good surgical outcomes | 37190011 |
Evidence Levels
| Intervention | Evidence Level |
|---|---|
| PFD for Chiari-associated syringomyelia | Grade C (CNS guidelines) |
| Duraplasty vs no duraplasty | No definitive superiority; both acceptable |
| Syrinx shunting | Low; reserved for failures |
| Observation of asymptomatic syrinx | Expert consensus |
Simple Explanation
What is syringomyelia? Syringomyelia is a condition where a fluid-filled cyst (called a syrinx) develops inside your spinal cord. The spinal cord is the bundle of nerves that runs down your back and carries messages between your brain and body.
What causes it? Most commonly, it is caused by a condition called Chiari malformation, where part of the brain (the cerebellar tonsils) pushes down through the opening at the base of the skull. This blocks the normal flow of spinal fluid and forces it into the spinal cord. Other causes include:
- Previous spinal injury
- Spinal tumours
- Scarring after infection or surgery
What are the symptoms? The syrinx can damage nerves in your spinal cord, causing:
- Numbness, tingling, or loss of feeling in your hands and arms
- Weakness in your hands
- Burns or injuries you don't feel
- Neck and arm pain
- In some cases, stiffness or weakness in your legs
How is it diagnosed? The main test is an MRI scan, which shows the cyst inside your spinal cord. You may also need an MRI of your brain to check for Chiari malformation.
How is it treated?
- Observation: If you have no symptoms, we may simply monitor you with regular scans.
- Surgery: If you have symptoms, surgery can help. The most common operation is called posterior fossa decompression, which relieves pressure and allows spinal fluid to flow normally. Most people (85-95%) see improvement after surgery.
- Medications: For pain or discomfort, we can prescribe medicines to help.
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Milhorat TH, Chou MW, Trinidad EM, et al. Chiari I malformation redefined: clinical and radiographic findings for 364 symptomatic patients. Neurosurgery. 1999;44(5):1005-1017. doi:10.1097/00006123-199905000-00042. PMID: 10232534
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Heiss JD, Patronas N, DeVroom HL, et al. Elucidating the pathophysiology of syringomyelia. J Neurosurg. 1999;91(4):553-562. doi:10.3171/jns.1999.91.4.0553. PMID: 10507374
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Menezes AH. Primary craniovertebral anomalies and the hindbrain herniation syndrome (Chiari I): data base analysis. Pediatr Neurosurg. 1995;23(5):260-269. doi:10.1159/000120969. PMID: 8867521
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Common Exam Questions
| Question Type | Example |
|---|---|
| MCQ | A 32-year-old presents with bilateral hand weakness and loss of pain sensation over the shoulders. Light touch and vibration are intact. What is the most likely diagnosis? |
| SAQ | Describe the pathophysiology of syringomyelia associated with Chiari I malformation. |
| OSCE | Examine the upper limbs of this patient and describe your findings. |
| Viva | Discuss the surgical management options for syringomyelia and expected outcomes. |
High-Yield Viva Points
| Topic | Key Points |
|---|---|
| Clinical feature | Dissociated sensory loss: loss of pain/temperature, preservation of light touch/proprioception |
| Distribution | Cape distribution (shoulders, upper arms, upper trunk) |
| Mechanism | Syrinx damages crossing spinothalamic fibres in anterior white commissure |
| Chiari I definition | Tonsillar herniation more than 5mm below foramen magnum |
| Gold standard investigation | MRI spine and brain (including craniocervical junction) |
| Treatment | Posterior fossa decompression (± duraplasty) for Chiari-associated |
| Outcome | 85-95% symptom improvement post-surgery |
Common Mistakes
| Mistake | Correct Approach |
|---|---|
| Missing dissociated sensory loss | Always test pain/temperature AND light touch separately |
| Forgetting to request MRI brain | Always image brain for Chiari when syrinx found |
| Attributing hand symptoms to carpal tunnel | Cape distribution and dissociated loss points to syringomyelia |
| Not considering syringomyelia in scoliosis | MRI spine mandatory in any child with progressive scoliosis |
| Expecting syrinx to completely resolve | Many patients have radiological persistence but clinical improvement |
Examination Cheat Sheet
| Parameter | Key Information |
|---|---|
| Sensory pattern | Cape distribution; loss of pain/temperature |
| Preserved modalities | Light touch, vibration, proprioception |
| Upper limb signs | LMN: wasting, weakness, areflexia |
| Lower limb signs | UMN: spasticity, hyperreflexia, upgoing plantars |
| Chiari I definition | More than 5mm tonsillar herniation |
| Imaging modality | MRI spine and brain with craniocervical junction |
| Primary surgery | Posterior fossa decompression |
| Success rate | 85-95% symptom relief |