Effect of coil packing proximal to the dilated segment on postoperative medullary infarction and prognosis following internal trapping for ruptured vertebral artery dissection

Introduction: Medullary infarction is an important complication of internal trapping for vertebral artery dissection. This study investigated risk factors for medullary infarction following internal trapping of ruptured vertebral artery dissection.

Methods: We retrospectively studied 26 patients with ruptured vertebral artery dissection who underwent endovascular treatment and postoperative magnetic resonance imaging between April 2001 and March 2013. Clinical and radiological findings were analyzed to identify factors associated with postoperative medullary infarction.

Results: Ten of the 26 patients (38%) showed postoperative lateral medullary infarction on magnetic resonance imaging. Multivariate logistic regression analysis revealed that medullary infarction was independently associated with poor clinical outcome (odds ratio (OR) 17.01; 95% confidence interval (CI) 1.68-436.81; p=0.032). Univariate analysis identified vertebral artery dissection on the right side and longer length of the entire trapped area as risk factors for postoperative medullary infarction. When the trapped area was divided into three segments (dilated, distal, and proximal segments), proximal segment length, but not dilated segment length, was significantly associated with medullary infarction (OR 1.55 for a 1-mm increase in proximal segment length; 95% CI 1.15-2.63; p=0.027). Receiver operating characteristic analysis showed that proximal segment length offered a good predictor of the risk of postoperative medullary infarction, with a cut-off value of 5.8 mm (sensitivity 100%; specificity 82.3%).

Conclusions: Longer length of the trapped area, specifically the segment proximal to the dilated portion, is associated with a higher incidence of medullary infarction following internal trapping, indicating that this complication may be avoidable.