Pathogenesis and clinical presentation
Post-traumatic syringomyelia has a delayed onset. The pathological cavity (syrinx) does not form immediately at the time of injury, but develops some time later in the area of the previous spinal cord trauma.
The primary clinical challenge is that the resulting cyst tends to expand. This process leads to progressive compression of the surrounding intact spinal cord tissues. Consequently, the patient experiences a progressive decline in residual neurological function. When such life-threatening conditions develop, conservative therapy is ineffective, and the patient may require surgical drainage of the syringomyelic cavity.
Diagnostic Imaging of Syringomyelia
Magnetic resonance imaging (MRI) is the primary method for detecting post-traumatic syringomyelia.
On T2-weighted images (T2WI), specialists evaluate the site of prior injury. Two main projections are used for comprehensive visualization:
- Sagittal projection allows assessment of the longitudinal extent of the syringomyelic cavity along the spinal cord.
- Axial projection provides a cross-sectional view of the cavity and the degree of compression exerted on the remaining spinal cord pathways.
Associated Injuries: Brachial Plexus Avulsion
Patients with spinal trauma and polytrauma frequently present with concomitant injuries, notably brachial plexus injury (brachial plexus injury).
Anatomically, the plexus is formed by the lower four cervical spinal nerves (C5–C8) and the first thoracic nerve (Th1/T1). The etiopathogenesis involves avulsion (avulsion) of the nerve roots from the spinal cord due to a closed traction force. This force is initially applied to the shoulder and subsequently transmitted to the spinal cord.
Injury Statistics:
- 75% of cases involve severe root avulsion directly from the spinal cord.
- 25% of cases involve isolated injury to the distal divisions of the plexus.
Important diagnostic nuance: brachial plexus avulsion can be accompanied by diffuse spinal cord edema, which is well visualized on sagittal T2WI (due to multilevel root avulsion). This diffuse edema should not be mistaken for a direct spinal cord injury directly related to a cervical spine fracture. Furthermore, complete nerve root avulsion typically results in a dural tear (dural tear), ultimately leading to the formation of a traumatic meningocele.
For diagnosing root avulsion, MRI has virtually replaced CT myelography. Currently, heavily T2-weighted 3D myelographic sequences (heavily T2-weighted 3D myelography sequences) are utilized. These allow the radiologist to select the optimal slice orientation to examine the intradural segments of the nerve roots in detail.
Clinico-Radiological Correlation and Complete Transections
Correlation between clinical findings and MRI data is crucial. If a patient presents with clear clinical signs of a brachial plexus injury, but the intradural nerve roots appear intact (undamaged) on MRI, this directly indicates that the injury site is located more distally—typically in the infraclavicular region (infraclavicular region).
Fracture-dislocation with complete spinal cord transection (Fracture-Dislocation With Cord Transection) represents another severe injury pattern. Sagittal projections using the STIR (short tau inversion recovery) sequence are employed for its evaluation on MRI scans.
A gradient echo sequence (gradient echo sequence) is used to detect associated hemorrhage. This sequence visualizes the presence of blood significantly better than any other. In such trauma, blood typically accumulates within the diastasis (gap)—directly at the site of complete transverse transection (transection) of the spinal cord.
Briefly: answers to topical questions
What specific neurological syndromes and symptoms develop in a patient with an enlarging syringomyelic cavity?
Enlargement of the syringomyelic cavity can lead to compression of spinal cord structures, resulting in impaired residual neurological function. Specific neurological syndromes and symptoms associated with the progression of a syringomyelic cavity are not detailed in the provided source.
In other literature sources, syringomyelia is cited as a potential cause or associated condition for:
- neurogenic/neuromuscular scoliosis;
- neurogenic trophic ulcers.
However, a direct causal link between these conditions and the enlargement of the syringomyelic cavity specifically is not stated in the sources.
The rule of intact roots: "If clinical signs are present but root structures appear intact on MRI, look for a distal lesion (below the clavicle)."
Class and exam questions
Which MRI sequence best visualizes hemorrhage in spinal cord transection?
The presence of blood is significantly better visualized on gradient echo sequences, where it appears within the diastasis at the site of transection.
What can spinal cord edema mimic in brachial plexus root avulsion?
Diffuse edema resulting from multilevel nerve root avulsion is frequently mistaken for direct spinal cord injury caused by cervical spine fractures.
Which imaging modality has replaced CT myelography in nerve root injuries?
CT myelography has been almost entirely replaced by MRI utilizing heavily T2-weighted 3D myelographic sequences.
What else to study on this topic
- Mechanisms of delayed pathological cavity formation in the spinal cord
- Surgical drainage techniques for syringomyelic cysts
- Traumatic meningocele: pathogenesis of dural tears
- Optimizing 3D MRI sequences for evaluating intradural roots
- Differential diagnosis of distal and proximal brachial plexus injuries
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