Rapid development of a de novo vertebral artery dissecting aneurysm after contralateral vertebral artery occlusion: illustrative case.

backgroundDeveloping a de novo vertebral artery (VA) dissecting aneurysm (VADA) after occlusion of the contralateral VA due to VADA is rare. The underlying mechanism and optimal treatment strategy remain unclear. OBSERVATIONS: A 52-year-old male presented with headache and was diagnosed with a right VADA that had progressed to complete arterial occlusion. Imaging at that time demonstrated no abnormality in the left VA. Six weeks later, the patient developed recurrent symptoms, and follow-up imaging revealed a newly formed left VADA. Because the posterior inferior cerebellar artery originated adjacent to the lesion and the contralateral VA was already occluded, stent-assisted coiling (SAC) was performed to preserve the parent artery. The patient was discharged without neurological deficit, and 1-year follow-up angiography demonstrated patency of the left VA and no recurrence. A review of the literature identified 10 previously reported cases; earlier cases were often managed conservatively and were associated with poor outcomes, whereas more recent cases treated with SAC demonstrated favorable outcomes. LESSONS: De novo VADA may develop rapidly after contralateral VA occlusion, likely due to altered hemodynamic stress. Thus, careful vascular surveillance is essential. When parent artery occlusion is not feasible, reconstructive endovascular strategies such as SAC may provide an effective flow-preserving treatment option. https://thejns.org/doi/10.3171/CASE26231.