What is Syringomyelia
Syringomyelia is a rare disorder characterized by a fluid-filled cavity (cyst) that forms within the spinal cord parenchyma, resulting in progressive myelopathy and neurological deterioration. 1
Definition and Pathophysiology
Syringomyelia should be distinguished from related conditions:
- True syringomyelia: A fluid-filled cavity within the spinal cord related to either cerebrospinal fluid (CSF) flow disturbances, spinal cord tethering, or an intramedullary tumor 2
- Hydromyelia: Abnormal dilatation of the central canal, also called "slit-like syrinx" 1
- Not syringomyelia: Glioependymal cysts, myelomalacias, or cystic tumors should be excluded from this diagnosis 2
The prevailing pathophysiological mechanism involves disturbances in CSF flow in the subarachnoid spaces that disrupt flow velocity, leading to abnormal intramedullary pulse pressure and syrinx formation 1. This unified model explains most cases regardless of etiology 3.
Classification by Etiology
Syringomyelia is classified based on anatomical features and pathogenesis 1:
1. Foraminal Syringomyelia (Most Common)
- Related to craniocervical junction abnormalities
- Chiari I malformation accounts for the majority of cases (543 of 604 patients in one large series) 2
- Other posterior fossa pathologies 4
2. Non-Foraminal Syringomyelia
- Spinal arachnopathies causing CSF flow obstruction (most common in this category: 533 patients) 2
- Post-traumatic (severe spinal trauma) 5
- Infection or inflammation causing arachnoiditis 1
3. Tumor-Associated Syringomyelia
- Associated with intramedullary tumors (152 patients in one series) 2
- Typically resolves spontaneously after tumor resection 1
4. Tethered Cord-Related
- Tethered cord syndromes (69 patients) 2
5. "Idiopathic" Syringomyelia
- A progressively shrinking category as advanced imaging uncovers occult substrates 3
- In reality, 91-95% have identifiable causes when systematically investigated 3
Clinical Presentation
Symptoms typically develop during the third or fourth decade of life 1, presenting with:
- Paralysis and motor weakness
- Sensory loss (particularly pain and temperature sensation in affected regions) 5
- Chronic neuropathic pain (often the main long-lasting symptom) 1
- Muscular atrophy in affected regions 5
The natural history is one of gradual, stepwise neurological deterioration extending over many years 1. If left untreated surgically, most symptomatic patients experience progressive neurologic deficits that may lead to severe paraplegia and chronic neuropathic pain 5.
Diagnostic Approach
Diagnosis is based on magnetic resonance imaging (MRI) 1, which should include:
- Morphological sequences: T1-weighted, T2-weighted, FLAIR, T2*, contrast-enhanced T1 1
- Dynamic MRI: CISS and cine-MR sequences with careful study of CSF velocity 1
- Additional neuroradiologic studies to reveal the underlying cause 2
Epidemiology
Based on the North Western Italy Registry 6:
- Syringomyelia prevalence: 4.84 per 100,000
- Syringomyelia incidence: 0.82 per 100,000
- Female predominance (292 of 436 patients)
Clinical Significance
Syringomyelia is a severe disease with high impact on quality of life 1. The condition requires:
- Prompt treatment without delay for evolutive (progressive) syringomyelia 1
- No evidence supports surgery for incidental asymptomatic syringomyelia or hydromyelia 1
- Multidisciplinary approach including neurosurgery, neurology, neuroradiology, and pain management 1
Important Caveat
The diagnosis of syringomyelia should be reserved for patients with a fluid-filled cavity demonstrably related to CSF flow disturbance, spinal cord tethering, or intramedullary tumor. When such a relationship cannot be established, the diagnosis should be withheld pending further investigation 2.