Multi-Contrast High-Resolution Magnetic Resonance Findings of Spontaneous and Unruptured Intracranial Vertebral Artery Dissection: Qualitative and Quantitative Analysis According to Stages.

BACKGROUND: Although high-resolution magnetic resonance imaging (HR-MRI) has been used as a strong imaging method for diagnosing intracranial vertebral artery dissection (IVAD), the diagnosis is sometimes challenging because a dissection has geometric changes in the natural course. The radiologic features may change or disappear over time, which makes the diagnosis confusing. Our study was to present radiological findings according to the stages in spontaneous and unruptured, IVAD on 3T HR-MRI and to guide the age estimation of IVAD with the distinguishing findings according to the stages.

METHODS: From January 2011 to July 2014, the 41 vertebral arteries (M:F = 18:12; age range 32-67 years) were retrospectively enrolled. Spontaneous, unruptured IVAD was diagnosed if it had a clear onset based on clinical and radiological findings. The stages were classified as acute (0-3 days), early subacute (3-10 days), late subacute (10-60 days) and chronic stage (>60 days; recovery and non-recovery groups) according to the time intervals from symptom onset, based on the prior published studies. HR-MR findings were assessed and compared in the intimal flap, double lumen, aneurysmal dilatation (maximal outer diameter, maximal wall thickness, wall thickness index and remodeling index), intramural hematoma (relative signal intensity) and vessel wall enhancement according to the stages with qualitative and quantitative methods. Two radiologists analyzed the HR-MR findings with consensus reading.

RESULTS: IVAD was classified into acute (n = 6), early subacute (n = 8), late subacute (n = 16) and chronic (n = 11) stages. HR-MR dissection findings such as intimal flap, double lumen, aneurysmal dilatation and intramural hematoma significantly decreased from the earlier stages to the chronic stage (p < 0.05). The quantitative indices in aneurysmal dilatation and the relative signal intensity of intramural hematoma showed significant higher values in the earlier stages followed by a significant decrease in the chronic stage recovery group (p < 0.05). The degree of vessel wall enhancement was higher in the earlier stage and decreased in the chronic stage (p < 0.05), but mild vessel wall enhancement was identified 900 days after symptom onset.

CONCLUSION: The 3T HR-MRI reveals the vessel wall characteristics and provides distinguishing findings between earlier stages and the chronic stage in spontaneous and unruptured IVAD. Characterization of these radiological findings according to stages may assist with the age estimation of the dissection and may help to understand IVAD as a whole.