International Stroke Conference
Deepak Gulati, MD
During one of the first symposium sessions on day one at ISC 2018 in Los Angeles, speakers discussed a few interesting topics, including the role of MR imaging and high resolution MR (vessel wall) imaging in acute stroke.
The first presentation was on “MRI Guided Treatment of Patients With Resolved or Minimal Symptoms” by Dr. Richard Leigh from NINDS. There are always few cases in daily practice when there is a diagnostic dilemma, whether it is a stroke mimic or making treatment decisions for patients with high risk of bleeding or an unclear time window. When performed as first modality in the setting of acute stroke, MRI can provide additional information in patients with resolving or resolved NIHSS or where the risk/benefit of thrombolysis is in debate. MRI could also identify blood flow abnormalities that are concerning for clinical decline and prevent treatment of patients with a high burden or worrisome pattern of microbleeds. However, there are practical difficulties in performing DWI-MRI in a timely manner, including scheduling issues, the patient’s condition, pacemaker, patient movements, etc., even though it has been reported that 11% of hospitals with MRI on site had performed MRI on any stroke patient within 6 hours of onset. MRI rapid stroke protocol usually takes approximately 8 minutes.
The next presentation was on “MRI of the Vessel Wall in Acute Stroke Patients” by Dr. Tanya Turan from the Medical University of South Carolina. High resolution MR could provide additional information in the evaluation of high-risk atherosclerotic lesion and diagnosis of non-atherosclerotic vasculopathy, and to evaluate the impact of acute stroke treatments on vessel wall. With help finding vessel wall enhancement on high resolution MR vessel wall imaging, it could be possible to differentiate conditions like intracranial atherosclerosis, vasculitis or RCVS. There is an ongoing multicenter and observational study — MOTIVE (MRI for Observing Thrombectomy-induced Vascular Effects) — to look at the changes in large intracranial arteries after mechanical thrombectomy related to thrombectomy devices. There have been studies suggesting that endothelial injury is more with vessel wall contact devices (e.g. Stent retriever) when compared to the aspiration technique. More research is still needed to understand the spectrum of morphological changes and the duration of those changes on high resolution MR vessel wall imaging.
Another interesting topic was “The Window to Treatment for Patients With Unwitnessed Onset” by Dr. Amie Hsia from MedStar Washington Hospital Center. It was focused on challenges to apply emerging evidence from recent endovascular trials. In an unwitnessed stroke, FLAIR signal intensity ratio <1.15 is shown in few studies to have high predictive value for early time window and to assist in IVtpa decision-making. Recent endovascular trials have different imaging inclusion/exclusion criteria. The DEFUSE 3 trial was based on perfusion mismatch, whereas the DAWN trial was based on clinical core mismatch. There are still some challenges to apply DAWN and DEFUSE 3 inclusion/exclusion criteria to few subsets of patients in our daily clinical practice. Dr. Marc Ribo from Spain said, “Perfusion scan provides more information in selection of patients, but non-contrast CT Head should be enough to treat patients for mechanical thrombectomy based on ASPECTS score.” The subgroup analysis from recent endovascular trials (DEFUSE 3 and DAWN) will hopefully guide us in better management of unwitnessed or wake up strokes.
The last presentation was on “Emerging Applications of MRI in Stroke Treatment” by Dr. Jochen Fiebach from Charite Medical University Germany. MRI could provide additional information to guide the management of patients with unknown symptoms onset. MRI could also be helpful in illustrating pathophysiology with new techniques including perfusion imaging with time shift analysis or bold delay or oxygen extraction fraction. There is a recent trial, WAKE-UP, which is a European multicenter investigator-initiated randomized placebo-controlled clinical trial of MRI-based thrombolysis in acute stroke patients with unknown time of symptom onset. The trial enrolled 1377 patients and was stopped following a decision by the steering committee. The results of the WAKE-UP trial will likely be announced at the European Stroke Organization Conference in 2018.
Overall, there appears to be increasing need to perform MRI in an acute setting to guide comprehensive stroke management.