What is the clinical significance and recommended management of a slight thickening of the transverse ligament of the atlas on imaging?

Clinical Significance and Management of Slight Transverse Ligament Thickening

Slight thickening of the transverse ligament on imaging is most commonly a nonspecific finding that does not indicate instability or require intervention, but must be interpreted in the clinical context of trauma history, neurological examination, and associated imaging findings to determine if it represents true ligamentous injury versus normal anatomical variation. 1

Understanding the Clinical Context

The transverse ligament is the primary stabilizing structure of the atlantoaxial joint, and its integrity determines whether surgical fusion is necessary. 2 However, imaging findings must be carefully interpreted:

• MRI has a false-positive rate of 25-40% for soft tissue injuries, meaning many apparent abnormalities do not reflect true instability. 1
• Established criteria for distinguishing significant from inconsequential MRI abnormalities do not exist. 1
• The range of normal anatomical variations has only become apparent as MRI has become established, and distinctions between "lesion" and "variation" are blurred. 1

Diagnostic Algorithm for Interpretation

Step 1: Assess the Clinical Scenario

In trauma patients:

• If there is neurological deficit referable to the spinal cord, MRI is the gold standard and ligamentous findings should be taken seriously. 1
• If the patient is neurologically intact with negative CT, purely ligamentous cervical spine injuries are exceptionally rare (0.1-0.7% of blunt trauma victims). 1

In non-trauma patients:

• Slight thickening may represent chronic degenerative changes, anatomical variation, or prior subclinical injury. 3

Step 2: Evaluate MRI Signal Characteristics

Through-and-through tears indicate definite mechanical failure and require surgical consideration. 1

Simple high signal on T2-weighted images (like slight thickening) is considered ambiguous or suspicious, not definitive for instability. 1

• Hypointense signal on T2 with associated hyperintense signal may indicate chronic changes or granulation tissue. 4
• These less specific findings must be incorporated with clinical findings, evidence of subluxation, mechanism of injury, and likelihood of successful compliance with conservative treatment. 1

Step 3: Look for Associated Instability Markers

Check for atlantoaxial subluxation or dislocation on CT or flexion-extension views:

• Atlantodental interval >3mm in adults or >5mm in children suggests instability. 2
• Presence of atlantoaxial facet dislocation indicates true instability requiring intervention. 4

Evaluate for associated fractures:

• Fractures of C-1 or C-2 with an intact transverse ligament typically heal without instability. 2
• CT has near 100% sensitivity for detecting bony injuries. 1

Step 4: Correlate with Neurological Examination

If neurologically intact with no evidence of subluxation, slight thickening alone does not warrant intervention. 1

If myelopathy is present (gait instability, hyperreflexia, Hoffman's sign, bowel/bladder dysfunction), the finding becomes clinically significant regardless of degree of thickening. 5

Management Recommendations

For Trauma Patients with Slight Thickening:

If CT shows no fracture or subluxation and patient is neurologically intact:

• The transverse ligament thickening is likely a false-positive finding. 1
• Clinical clearance can proceed without prolonged immobilization. 1
• Only 3.9% of obtunded trauma patients with normal CT have true ligamentous injury on MRI, and these patients are typically severely traumatized with profound disability. 1

If subluxation is present or neurological deficit exists:

• Surgical fusion should be considered as the remaining ligaments are inadequate to maintain stability after transverse ligament failure. 2
• Internal fixation is required for atlantoaxial instability associated with transverse ligament rupture or laxity. 2

For Non-Trauma Patients:

Slight thickening without instability or neurological symptoms requires no intervention. 6

Follow-up imaging is only indicated if:

• New neurological symptoms develop (neck pain with radiculopathy, myelopathy). 5
• Progressive instability is suspected based on clinical examination. 6

Critical Pitfalls to Avoid

Do not immobilize patients for weeks based solely on MRI findings of slight ligamentous thickening without evidence of instability. Over 90% of patients with stable cervical spines may be subjected to unnecessary immobilization if all MRI abnormalities are treated as significant. 1

Do not order flexion-extension radiographs acutely. These studies are inadequate 28-97% of the time due to limited motion and are potentially dangerous. 7

Do not assume all MRI ligamentous abnormalities require surgery. Only 5.7% of MRI-detected ligamentous injuries in one series required surgical fusion, and both were visible on CT. 1

Recognize that postmortem data shows MRI demonstrates lesions within ligaments with high sensitivity, but many do not reflect instability. 1