Abstract WMP48: Usefulness of High-Resolution MRI in the Investigation of Intracranial Stenosis

Objective: High-resolution dark-blood MRI (HR-MRI) is recently applied for investigation of intracranial stenosis. We aim to study the usefulness of HR-MRI in a group of stroke patients with intracranial stenosis detected on TOF-MRA. Methods: Consecutive patients with ischemic stroke or TIA presented to a teaching hospital in Singapore were recruited into a long-term follow-up study and underwent MRI of the brain including TOF-MRA with a 3T scanner at the convalescent stage. Symptomatic intracranial stenoses >/=50% were further investigated with T2 and T1 3-dimentional HR-MRI, and post-contrast T1 HR-MRI were also performed in subjects with normal renal function. Additional scan times required for HR-MRI were 6’22” for each of the non-contrast sequences and 4’33” for the post-contrast sequence. Findings: 35 stroke patients underwent study MRI at a mean of 123 days after stroke onset, and 12 were found to have symptomatic stenoses on TOF-MRA. 2 of them did not reveal any obvious disease on HR-MRI, while intracranial stenoses were confirmed in 10 patients (mean age: 57 years, 8 were male). Distributions include 7 with M1 stenosis/occlusion, 1 with tandem petrous ICA and M1 stenoses, 1 with cavernous ICA stenosis and 1 with petrous ICA stenosis. HR-MRI were not evaluable in one patient with M1 stenosis due to movement artifacts, and for the distal petrous ICA stenosis in the patient with tandem stenoses due to susceptibility artifact from the paranasal sinus. For the remaining 9 symptomatic stenoses, HR-MRI provided additional information with better definition of the distribution and extent of plaques in all cases, reclassification of total occlusion to severe stenosis in 3 cases, demonstration of significant plaque enhancement in 5 of 6 cases when gadolinium was given, and detection of plaque in the asymptomatic contralateral artery in 4 cases. Conclusion: HR-MRI is a promising technique that can reveal potentially useful information in the majority of patients with stroke due to intracranial stenosis. However, further technological advance to overcome the current limitations of long acquisition time and restricted brain coverage is required before adoption of this technique into routine clinical practice.