Objective: Crossed cerebellar diaschisis (CCD) after ischemic stroke plays an important role in the evaluation of neurological function and clinical outcome. The aim of this study was to investigate the value of magnetic resonance (MR) intravoxel incoherent motion (IVIM) quantitative parameters in detecting CCD after subacute ischemic stroke.

Methods: The medical records of 56 patients with subacute ischemic stroke were collected and analyzed retrospectively from January 2015 to December 2017. Of 56 patients, 39 patients met the criteria of case selection. All patients underwent routine MR imaging (MRI), IVIM sequence on 3.0T MR and three-dimensional arterial spin labeling (ASL). The cerebral blood flow (CBF) and asymmetric index (AI) of CBF (AI_CBF) of bilateral cerebellar hemisphere were detected on ASL perfusion MRI. AI_CBF > 10% was considered as CCD positive. The IVIM derived parameters (D , D﹡, f and ADC ) and the corresponding asymmetric indexes (AI_D , AI_D﹡, AI_f and AI_ADC ) were measured. Paired t test was used to compare the differences in parameters of cerebellar hemispheres. Pearson correlation analysis was used to evaluate the correlation between IVIM parameters values and CBF. Receiver operating characteristics (ROC) curve was used to evaluate the diagnostic accuracy of the statistical significant IVIM parameters in detecting CCD.

Results: Among 39 patients, 15 (38.5%) were CCD positive and 24 (61.5%) were CCD negative. The National Institute of Health Stroke Scale (NIHSS) scores at admission and discharge of the CCD positive group were higher than those of the CCD negative group (P > 0.05). The values of D﹡ and f of the CCD positive group showed statistically significant differences between the bilateral cerebellar hemispheres (P < 0.001), and the D﹡ values of the healthy side decreased compared with the affected side, while the f values increased. There was a positive correlation between AI_D﹡ and AI_CBF (r = 0.502，P = 0.001), and a negative correlation between AI_f and AI_CBF (r = －0.347，P = 0.003). The parameters AI_D﹡ and AI_f showed high accuracy for detecting CCD with the areas under the curve of 0.744 and 0.717, respectively.

Conclusion: IVIM-derived quantitative parameters are useful to detect CCD after supratentorial ischemic stroke.