Abstract
BACKGROUND: The reported actual risk of rupture for vertebral artery dissection (VAD) in patients presenting with headache is very low, ranging from 0.4% to 1.0%. The authors report a case in which the dissection site dilated rapidly within several hours after the dissection occurred resulting in subarachnoid hemorrhage (SAH). OBSERVATIONS: A 49-year-old healthy man who had participated in a marathon noticed a headache while running. Magnetic resonance imaging (MRI) performed 2 days later revealed no findings suspicious for right VAD, but a string sign was observed in the left side, suggesting left VAD. Three hours following MRI, he developed severe headaches and became unconscious at home, prompting emergency services to rush him to the hospital. A computed tomography scan showed diffuse SAH and a rapidly enlarged aneurysmal dilatation in the right vertebral artery. He underwent endovascular internal trapping to prevent rebleeding. He was discharged without any neurological symptoms. No recurrence or new dissection occurred after 2 years of follow-up. LESSONS: Even in the absence of typical imaging findings, strict management, such as blood pressure control, is required when clinical findings strongly suggest VAD, and differentiation of VAD from primary headache is important. https://thejns.org/doi/10.3171/CASE24202.