Objective

Intracranial atherosclerosis is highly associated with ischemic stroke, accounting for 8% to 10% of events in North America and even higher in Asia[1]. High-resolution magnetic resonance imaging (HR-MRI), particularly using a 3D variable-flip-angle turbo spin-echo method, has successfully been used to depict the intracranial vessel wall and atherosclerotic lesions [2,3]. This 3D method was recently optimized and now allows for whole-brain spatial coverage, superior signal suppression of cerebrospinal fluid, and isotropic 0.5-mm spatial resolution within a reasonable scan time of 7-8 minutes [4,5]. Our study aimed to evaluate the feasibility of using the new technique to evaluate the therapeutic efficacy of medical therapy on symptomatic atherosclerotic plaques in the middle cerebral artery.

Materials and methods

Sixteen patients who had recent clinical symptoms (transient ischemic attack or ischemic stroke within the last 2 weeks) caused by intracranial atherosclerotic stenosis >50% were recruited with informed consent. Exclusion criteria included: general contraindications to MRI or contrast agent; emergent interventional procedures performed or scheduled. Before initiation of medical therapy, imaging was conducted on a 3.0 Tesla scanner (Tim Trio, Siemens Medical Solution) with a 32-channel head coil. Patients underwent conventional brain MRA (T1-weighted, T2-weighted, T2 FLAIR as well as 3D TOF) followed by T1-weighted whole-brain 3D high-resolution MRI before and after Gadolinium injection. Statins therapy was then initiated in all subjects, and 94 days (range: 7 – 130 days) later, the same imaging protocol was repeate. And we calculated the plaque area (PA) and degree of stenosis before and after medical therapy. We used the chi-square test to compare the degree of stenosis between improved patient group and non-improved patient group before medical therapy, and t-test to compare the plaque area between pre-therapy and post-therapy respectively. The improvement in clinical symptoms in each subject was recorded.

Results

With the medical therapy, clinical symptoms of 10 patients were substantially improved as measured by mRS (4-5 pre-therapy vs 1-3 post-therapy), and their the plaque area were significantly reduced(PA=6.43±0.88（pre）；4.33±1.42（post）:P=0.001). In the remaining 6 patients, plaque area (PA=5.87±0.77（pre）；5.48±0.76（post）：P=0.:39) exhibited essentially no difference between pre- and post-therapy. Between the two groups, PA and degree of stenosis exhibited no significantly difference at the pre-therapy state.

Discussion and Conclusion

The small cohort study showed that the plaque area and degree of stenosis at the middle cerebral artery are significantly reduced in symptomatic patients who show symptom improvement by statin therapy but not changed in those who had no symptom improvement. This suggests that high-resolution MRI may be used to provide an imaging marker for treatment response to medical therapy. A larger cohort will be needed to systematically validate the clinical utility.

Acknowledgements

This work was funded by Whole Brain Vessel Wall Imaging in Stroke Patients: An International Multi-Center Registry(NO: NCT02923752)

References

[1] Turan TN et al Stroke 2009;40:2257. [2] Qiao Y et al. JMRI 2011;34:22. [3] van der Kolk AG et al. EurRadiol. 2013;23:2996. [4] Fan Z et al. MRM 2016; Feb 28.