Follow-Up Diffusion-Weighted Image Reveals Delayed Appearance of Ischemic Lesions in Suspected Transient Ischemic Attack

Introduction: In patients suspected of transient ischemic attack (TIA), it is not uncommon to find no lesion on the diffusion-weighted image (DWI) on admission but a delayed appearance on the follow-up DWI. Methods: Enrolled patients met the following criteria: (1) MRI performed within 24 hours of onset and seven days after admission; (2) National Institutes of Health Stroke Scale (NIHSS) score ≦4 on admission; (3) pre-stroke modified Rankin scale (mRS) score of 0-1. Patients were divided as follows: no lesion on the first DWI and a new lesion on the second DWI (delayed-specified ischemic stroke; DSIS); and no lesion on either the first or second DWI (well-screened TIA; WSTIA). We compared both groups regarding the clinical background and the outcome at three months. Results: We identified 144 cases (male 70%; median age 64 years; DSIS, n=34) between October 2012 and March 2019. DSIS was older (71 vs. 60 years, p=0.006) and had a higher NIHSS score on admission (1 vs. 0, p=0.041), a higher rate of large vessel occlusion (LVO) (17% vs. 2%, p=0.008), and symptom duration over one hour (82% vs. 64%, p=0.041). A favorable outcome mRS score of 0-1 at three months was less frequent in DSIS (85% vs. 96%, p=0.004). Age/10 (OR 1.62, 95%CI 1.17-2.24; p=0.004) and LVO (OR 10.84, 95%CI 1.87-63.06; p=0.008) were independent factors for DSIS. Conclusions: In suspected TIA with age or LVO but no lesion in the initial DWI, the second DWI should be considered to identify the delayed appearance of an ischemic stroke.