Initial magnetic resonance imaging/magnetic resonance angiography may miss intracranial artery dissection in young adults with stroke: the role of subsequent imaging.

INTRODUCTION: Intracranial artery dissection (IAD) is an important cause of ischaemic stroke in young adults; however, its diagnosis at initial presentation remains challenging. We aimed to determine how often initial magnetic resonance imaging (MRI)/magnetic resonance angiography (MRA) and subsequent imaging identified IAD, and to clarify the timing of IAD diagnosis. METHODS: We performed a secondary analysis of a prospective, multicentre registry of 275 adults aged 18-50 years admitted with acute ischaemic stroke within 14 days of onset. All patients underwent MRI/MRA at admission, followed by scheduled follow-up MRI/MRA 7 days later. Vessel wall MRI (VW-MRI), digital subtraction angiography (DSA) and computed tomography angiography (CTA) were performed when clinically indicated. The proportion of patients in whom each examination identified IAD and the time to diagnosis were assessed. RESULTS: IAD was diagnosed in 53 patients. Initial MRI/MRA identified IAD in only 9 (17%; 95% CI, 8-30). The median time to diagnosis was 5 days after admission; 77% had been diagnosed by Day 7, and the latest diagnosis was made on Day 35. Among patients who underwent each examination, the observed diagnostic yield was 38 of 45 for VW-MRI (84%; 95% CI, 71-94), 41 of 53 for follow-up MRI/MRA (77%; 95% CI, 64-88), 15 of 30 for DSA (50%; 95% CI, 31-69) and 7 of 34 for CTA (21%; 95% CI, 9-38). CONCLUSION: Among young adults with ischaemic stroke who ultimately met the imaging criteria for IAD, initial MRI/MRA alone was insufficient to establish the diagnosis in most cases. Repeated and multimodal imaging contributed to the diagnosis of IAD.