MRI Indications and Protocol
- CT-negative with persistent pain or neurological symptoms
- High clinical suspicion for cord or ligamentous injury
- Obtain within 48–72 hours if cord injury is suspected
- STIR and fat-saturated T2 are most sensitive for acute ligamentous disruption
- Flexion-extension radiographs are contraindicated acutely
Ligament-by-Ligament MRI Findings
| Ligament | Anatomy | MRI Findings | Clinical Significance |
|---|---|---|---|
| Apical ligament | Tip of dens → basion | Small midline structure; loss of signal or discontinuity; best on sagittal fat-sat T2 | Weak structure; injury usually concurrent with alar or TAL disruption |
| Cruciate ligament | Vertical limb: C2 body → occiput; horizontal limb = TAL | TAL best on axial T2; vertical bands on sagittal T2/STIR | TAL is the critical horizontal component; vertical limb injury = severe craniocervical injury |
| Transverse atlantal ligament (TAL) | Anchors dens to C1 lateral masses; horizontal limb of cruciate | T2/STIR hyperintensity or discontinuity at attachment; ADI >3 mm adult (>5 mm child) | Critical stability structure; rupture → atlantoaxial instability; associated with Jefferson burst type III |
| Alar ligaments | Bilateral: dens → occipital condyles | STIR asymmetric signal/disruption; loss of taut low-signal band | Limit rotation and lateral flexion; bilateral injury → craniocervical instability |
| Posterior ligamentous complex (PLC) | Supraspinous + interspinous + ligamentum flavum + facet capsules | T2/STIR hyperintensity in interspinous space; facet capsule disruption; CT: widened interspinous distance, perched/jumped facets | Primary restraint to flexion; disruption = instability; AO Spine morphology modifier |
| Posterior longitudinal ligament (PLL) | Posterior vertebral bodies C2–sacrum | T2 hyperintensity/discontinuity posterior to vertebral bodies; associated anterior cord edema | Disruption in flexion injuries; increases risk of posterior disc herniation and cord compression |
| Anterior longitudinal ligament (ALL) | Anterior vertebral bodies | T2 hyperintensity anterior to vertebral body; prevertebral hematoma | Disrupted in hyperextension injuries; less critical than PLC for stability |
Instability Criteria
Radiographic instability is indicated by either of the following on imaging:
- Horizontal displacement >3.5 mm between adjacent vertebrae
- Angulation >11° between adjacent vertebrae
STIR MRI is the most sensitive sequence for acute ligamentous disruption. Flexion-extension radiographs must not be performed in the acute setting. ADI >3 mm in adults or >5 mm in children indicates TAL insufficiency and should prompt urgent spine surgery consultation.
Reporting Checklist — Cervical Ligamentous Injury
- MRI indication: CT-negative with symptoms / high clinical suspicion / cord injury evaluation
- Sequences obtained: STIR / fat-sat T2 / T1 / other
- Apical ligament: intact / disrupted / indeterminate
- Cruciate ligament — TAL: intact / disrupted / indeterminate; ADI: ___ mm
- Cruciate ligament — vertical limb: intact / disrupted
- Alar ligaments: intact bilaterally / asymmetric signal / disrupted (side: ___)
- Posterior ligamentous complex: intact / disrupted (interspinous signal / facet capsule disruption / CT correlation)
- PLL: intact / disrupted; anterior cord signal change: present / absent
- ALL: intact / disrupted; prevertebral hematoma: present / absent
- Instability criteria met: horizontal displacement ___ mm / angulation ___ ° (threshold: >3.5 mm or >11°)
- Cord signal: normal / T2 hyperintensity (level: ___); hemorrhage: present / absent
- Overall assessment: stable / potentially unstable / unstable — spine surgery consultation recommended
Reference
RadioGraphics 2015: Cervical Spine Ligamentous Injury.