Abstract
BACKGROUND: The management of large thrombosed unruptured vertebral artery (VA) aneurysms is complex and remains a significant clinical challenge. OBSERVATIONS: A 46-year-old man presented with a headache and was diagnosed with a thrombosed 28-mm aneurysm in the right VA. The initial treatment with a Pipeline flow diverter stent was followed by parent artery occlusion with coils after the aneurysm had enlarged to 40 mm. Subsequently, the patient experienced cardiopulmonary arrest owing to brainstem compression-induced respiratory failure. A surgical approach involving a thrombectomy via a lateral suboccipital craniotomy was used, resulting in significant clinical improvement. The patient was eventually transferred to a rehabilitation facility with a modified Rankin Scale score of 1 and continued to recover with time. LESSONS: Although endovascular treatments are less invasive, they may be insufficient in cases with significant mass effects. Direct surgical intervention, including thrombectomy and coagulation of the vasa vasorum, can be an effective strategy to reduce the mass effect and halt aneurysm growth. Timely surgical intervention before the onset of severe symptoms is recommended to optimize outcomes. https://thejns.org/doi/10.3171/CASE25383.