Endovascular treatment for posterior inferior cerebellar artery aneurysm with vertebral artery stenosis: The critical role of diagnosing osteophyte compression.

Background: Vertebral artery (VA) stenosis can be caused by several factors, including arteriosclerosis, arterial dissection, and mechanical compression. Symptomatic vertebrobasilar insufficiency caused by VA stenosis due to mechanical compression associated with head rotation is well-known as Bow Hunter's syndrome. However, an accurate diagnosis of asymptomatic osteophyte compression-induced nonrotational VA stenosis is difficult. We report a case of left posterior inferior cerebellar artery aneurysm with severe left VA stenosis, treated with stent-assisted coil embolization following appropriate diagnosis. Case Description: A 72-year-old female patient was found to have severe asymptomatic VA stenosis at the V2 segment (C4-5 level of the cervical spine) on cerebral angiography. Osteophyte compression-induced VA stenosis was suspected, which was confirmed by cone-beam computed tomography. The VA stenosis improved by flexing the neck and fixing the head position, following which the endovascular treatment was successfully completed. Conclusion: The site of the VA stenosis is critical in determining the etiology. Atherosclerotic VA stenosis often occurs at the origin of the artery or V4 segment, whereas bony compression-induced stenosis is more likely to occur at the V2 segment. Diagnosis and appropriate management of VA stenosis is based on determining the site.