Background and PurposezzIntracranial atherosclerotic stenosis (ICAS) is considered as a major cause of stroke. The carotid intima-media thickness (CIMT), which accurately reflects the burden of generalized atherosclerosis, is also associated with stroke. The aim of this study was to determine the association between the CIMT and ICAS responses to medical treatment. MethodszzThis study constituted part of the “Trial of cilostazol in symptomatic intracranial arterial stenosis”-2 that evaluated the ICAS response after randomized antiplatelet treatment. Magnetic resonance angiography and CIMT measurement were performed at baseline and after 7 months of treatment. CIMT was measured using semiautomated software, and was presented as maximum (CIMT-max) and average (CIMT-ave) values. The change in CIMT was compared relative to the ICAS response (i.e., progression, no-change, and regression). Ordinal logistic regression and analysis of covariance (ANCOVA) were used to analyze the association between the responses. ResultszzAmong the 101 enrolled patients, 85 underwent follow-up CIMT measurement. CIMT increased most in the ICAS progression group (CIMT-max: 0.09±0.23, CIMT-ave: 0.04±0.12), and to a lesser degree in the no-change group (CIMT-max: 0.02±0.16, CIMT-ave: 0.02±0.11), but decreased in patients with ICAS regression (CIMT-max: -0.04±0.11, CIMT-ave: -0.03±0.07; CIMT-max: p=0.010, CIMT-ave: p=0.015). Ordinal logistic regression analysis demonstrated that the change in CIMT-max was independently associated with the ICAS response (p=0.032). However, the ANCOVA revealed that the reverse was not true, in that the ICAS response was not independently associated with the change in CIMT after adjusting for confounding factors. ConclusionszzThe ICAS response may be associated with the CIMT response to medical treatment.