The ivy sign as a radiological marker for follow-up of postoperative cerebral perfusion status in adult moyamoya disease

OBJECTIVE Little is known about the relationship between postoperative changes in cerebral perfusion and the ivy sign representing leptomeningeal collateral burden in moyamoya disease (MMD). This study aimed to investigate the usefulness of the ivy sign in evaluating cerebral perfusion status following bypass surgery in patients with adult MMD. METHODS Two hundred thirty-three hemispheres in 192 patients with adult MMD undergoing combined bypass between 2010 and 2018 were retrospectively enrolled. The ivy sign was represented as the ivy score on FLAIR MRI in each territory of the anterior, middle, and posterior cerebral arteries. Ivy scores, as well as clinical and hemodynamic states on SPECT, were semiquantitatively compared both preoperatively and at 6 months after surgery. RESULTS Clinical status improved at 6 months after surgery (p < 0.01). On average, ivy scores in whole and individual territories were decreased at 6 months (all p values < 0.01). Cerebral blood flow (CBF) postoperatively improved in three individual vascular territories (all p values ≤ 0.03) except for the posterior cerebral artery territory (PCAt), and cerebrovascular reserve (CVR) improved in those areas (all p values ≤ 0.04) except for the PCAt. Postoperative changes in ivy scores and CBF were inversely correlated in all territories (p ≤ 0.02), except for the PCAt. Furthermore, changes in ivy scores and CVR were only correlated in the posterior half of the middle cerebral artery territory (p = 0.01). CONCLUSIONS The ivy sign was significantly decreased after bypass surgery, which was well correlated with postoperative hemodynamic improvement in the anterior circulation territories. The ivy sign is believed to be a useful radiological marker for postoperative follow-up of cerebral perfusion status.