Clinical Recognition of Syringomyelia
Syringomyelia should be suspected in any patient presenting with dissociated sensory loss (impaired pain and temperature sensation with preserved proprioception and vibration), particularly when accompanied by segmental dysesthetic burning pain and progressive motor weakness in the upper extremities. 1, 2
Classic Sensory Presentation
The hallmark clinical feature is dissociated sensory loss in a "cape-like" or segmental distribution:
- Loss of pain and temperature sensation while proprioception and vibration remain intact 2, 3
- Dysesthetic burning pain described as "cold burning pain" that is segmental and corresponds to the level of spinal cord involvement 1
- Hyperesthesia and allodynia are common, with exaggerated pain responses to normally non-painful stimuli 1
- The sensory loss typically affects the upper extremities and trunk in a suspended pattern (sparing distal extremities initially) 2, 3
Motor Findings
Progressive motor deficits develop over years with characteristic patterns:
- Weakness and muscular atrophy most pronounced in small hand muscles and muscles innervated by C5-T1 roots 4
- Reduced or absent reflexes in affected segments due to anterior horn cell involvement 3
- Chronic neurogenic changes on EMG with sparse fibrillation potentials and reduced motor unit recruitment, particularly in hypothenar muscles 4
- Progressive paraplegia may develop if untreated 3
Associated Clinical Features
When headache accompanies syringomyelia, evaluate for Chiari malformation first, as this is the most common form of syringomyelia and the likely source of cephalic symptoms rather than the syrinx itself 5. Do not assume a thoracic syrinx is causing headache—look for alternative explanations including Chiari malformation, CSF leak, or cervicogenic features 5.
Additional features include:
- Autonomic dysfunction from thoracic cord sympathetic disruption, potentially causing syncope 5
- Scoliosis may be present, particularly in long-standing cases 2
- Neuropathic pain is often the main long-lasting symptom requiring dedicated management 2
Temporal Pattern
- Symptoms typically develop during the third or fourth decades of life 2
- Natural history shows gradual, stepwise neurological deterioration extending over many years 2
- Progression is from minor sensory changes to weakness, wasting, and in syringobulbia cases, respiratory compromise 6
Diagnostic Confirmation
MRI is essential for diagnosis and should include:
- Excellent morphological sequences (T1, T2, FLAIR, T2*, enhanced T1) 2
- Dynamic MRI with careful study of CSF velocity (CISS, cine-MR sequences) 2
- Evaluation of the craniocervical junction for Chiari malformation 2, 6
Electrophysiologic Findings
When electrodiagnostic studies are performed:
- Reduced hypothenar compound muscle action potential amplitude is the most common nerve conduction abnormality 4
- Ulnar and median nerve SEPs are usually normal in the presence of dissociated sensory loss 4
- SEPs become abnormal when all sensory modalities are impaired 4
- Tibial nerve SEPs are frequently abnormal and correlate with impaired proprioception in lower extremities 4
Critical Pitfall
The most important clinical pitfall is delayed diagnosis due to the insidious, stepwise progression. In the pre-MRI era, syringomyelia often presented late as a crippling disorder 7. Today's challenge is recognizing early, less pronounced deficits and understanding when surgical intervention is warranted 7. Symptomatic evolutive syringomyelia should be treated without delay due to its severe impact on quality of life, but there is no evidence for surgery in incidental asymptomatic cases 2.