Routine use of FLAIR-negative MRI in the treatment of unknown onset stroke.

BACKGROUND: Treatment of FLAIR-negative stroke in patients presenting in an unknown time window has been shown to be safe and effective. However, implementation can be challenging due to the need for hyper-acute MRI screening. The purpose of this study was to review the routine application of this practice outside of a clinical trial. METHODS: Patients presenting from 3/1/16 to 8/22/18 in a time window <4.5 h from symptom discovery but >4.5 h from last known normal were included if they had a hyper-acute MRI performed. Quantitative assessment based on the MR WITNESS trial and qualitative assessment based on the WAKE-UP trial were used to grade the FLAIR images. The MR WITNESS trial used a quantitative assessment of FLAIR change where the fractional increase in signal change had to be <1.15, whereas the WAKE-UP trial used a visual assessment requiring the absence of marked FLAIR signal changes. RESULTS: During the study period, 136 stroke patients presented and were imaged in the specified time window. Of these, 17 (12.5%) received IV tPA. Three patients had hemorrhage on 24-h MRI follow up; none had an increase in NIHSS ≥4. Of the 119 patients who were screened but not treated, 18 (15%) were eligible based on FLAIR quantitative assessment and 55 (46%) were eligible based on qualitative assessment. In all cases where patients were not treated, there was an identifiable exclusion based on trial criteria. During the study period, IV tPA utilization was increased by 5.6% due to screening and treating patients with unknown onset stroke. CONCLUSIONS: Screening stroke patients in an unknown time window with MRI is practical in a real-world setting and increases IV tPA utilization.

MRI-based thrombolytic therapy in patients with acute ischemic stroke presenting with a low NIHSS.

OBJECTIVE: Treatment of patients with stroke presenting with minor deficits remains controversial, and the recent Potential of rtPA for Ischemic Strokes with Mild Symptoms (PRISMS) trial, which randomized patients to thrombolysis vs aspirin, did not show benefit. We studied the safety and efficacy of thrombolysis in a population of patients with acute stroke presenting with low NIH Stroke Scale (NIHSS) scores screened using MRI. METHODS: The NIH Natural History of Stroke database was reviewed from January 2006 to December 2016 to identify all patients with an initial NIHSS score ≤5 who received thrombolysis within 4.5 hours of symptom onset after being screened with MRI. The 24-hour postthrombolysis MRIs were reviewed for hemorrhagic transformation. Primary outcomes were symptomatic intracranial hemorrhage (sICH) and favorable 90-day outcome modified Rankin Scale score 0-1. Subgroup analysis was performed on patients who would have been eligible for the PRISMS trial, which enrolled patients with a nondisabling neurologic deficit. RESULTS: A total of 121 patients were included in the study with a median age of 65 and an NIHSS score of 3; 63% were women. The rate of any hemorrhagic transformation was 13%, with 11% of them being limited to petechial hemorrhage. The rate of sICH was <1%. Sixty-six patients had 90-day outcome data; of those, 74% had a favorable outcome. For the subgroup of 81 PRISMS-eligible patients, none experienced sICH. Fifty of these patients had 90-day outcome data; of these, 84% had a favorable outcome. CONCLUSIONS: Thrombolytic therapy was safe in our patients with stroke with minor deficits who were initially evaluated by MRI. Future studies of this population may benefit from MRI selection. CLASSIFICATION OF EVIDENCE: This study provides Class IV evidence that for patients with acute ischemic stroke and NIHSS ≤5 screened with MRI, IV tissue plasminogen activator is safe.