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Diffusion-perfusion MRI characterization of post-recanalization hyperperfusion in humans
C S Kidwell1, J L Saver, J Mattiello
1UCLA Stroke Center, UCLA Medical Center, Los Angeles, CA 90095, USA. ckidwell@ucla.edu
Background:
Animal and human studies have demonstrated that postischemic hyperperfusion may occur both early and late timepoints following acute cerebral ischemia.
Objective:
To use diffusion-perfusion MRI to characterize hyperperfusion in humans following intra-arterial thrombolysis.
Methods:
MRI were performed before treatment, several hours following vessel recanalization, and at day 7 in patients successfully recanalized with intra-arterial thrombolytics.
Results:
Hyperperfusion was visualized in 5 of 12 patients within several hours after recanalization (mean volume, 18 mL; range, 7 to 40 mL), and in 6 of 11 patients at day 7 (mean volume, 28 mL; range, 4 to 45 mL). Within the core region of hyperperfusion, mean cerebral blood flow was 2.1 times greater than in the contralateral homologous region at the early time point, and 3.1 times greater at day 7. Seventy-nine percent of voxels with hyperperfusion at day 7 demonstrated infarction at day 7, whereas only 36% of voxels (within the initial hypoperfusion region) not showing hyperperfusion at day 7 demonstrated infarction at day 7. Mean pretreatment apparent diffusion coefficient (ADC) and perfusion values were more impaired in voxels that subsequently developed hyperperfusion compared with other at-risk voxels (all p values < 0.0001). There were no significant differences in the degree of clinical improvement in patients with regions of hyperperfusion versus those without, although sample size limited power to detect group differences.
Conclusions:
Postischemic hyperperfusion, visualized with perfusion MRI in humans following recanalization by intra-arterial thrombolytic therapy, occurred in about 40% of patients within hours and in about 50% of patients at day 7. Hyperperfusion developed mainly in regions that went on to infarction. Compared with other abnormal regions, tissues that developed postischemic hyperperfusion had greater bioenergetic compromise in pretreatment apparent diffusion coefficient values and greater impairment in pretreatment blood flow measures.
Insights
Post-stroke hyperperfusion, identified by diffusion-perfusion MRI after intra-arterial thrombolysis, occurred in about half of patients. This hyperperfusion often developed in brain regions that ultimately showed infarction.
Area of Science:
- Neuroimaging
- Cerebrovascular Diseases
- Interventional Neurology
Background:
- Post-ischemic hyperperfusion is a known phenomenon in both animal and human studies following acute cerebral ischemia.
- This hyperperfusion can manifest at both early and late time points after the initial ischemic event.
Purpose of the Study:
- To characterize post-thrombolysis hyperperfusion in human patients using diffusion-perfusion MRI.
- To investigate the temporal patterns and characteristics of hyperperfusion following intra-arterial thrombolysis for acute cerebral ischemia.
Main Methods:
- Diffusion-perfusion MRI scans were acquired before treatment, several hours post-recanalization, and at day 7 in patients who underwent successful intra-arterial thrombolysis.
- Analysis focused on identifying and quantifying regions of hyperperfusion and comparing them with surrounding tissues and contralateral homologous regions.
Main Results:
- Hyperperfusion was observed in approximately 40% of patients within hours and 50% by day 7 after recanalization.
- Regions of hyperperfusion showed significantly increased cerebral blood flow (2.1x early, 3.1x late) compared to contralateral regions.
- Tissues developing hyperperfusion exhibited greater pretreatment impairment in apparent diffusion coefficient (ADC) and blood flow measures, and were more likely to infarct by day 7.
Conclusions:
- Post-thrombolysis hyperperfusion is detectable with perfusion MRI in humans, occurring in a significant portion of patients.
- Hyperperfusion predominantly develops in brain areas that subsequently infarct, suggesting a link to severe ischemic injury.
- Pretreatment imaging markers indicate that tissues destined for hyperperfusion experience profound bioenergetic compromise.