Ct angio there is an incidental fenestration of the basilar artery the basilar artery appears otherwise intact should i worry about this? stroke/aneurysm possibility? had done due to finding on mri of a small hemangioma in temporal muscle?

This anomaly is considered somewhat rare and congenital. Usually there's no need for treatment or need to do followup studies of it but there is mention of increased predisposition to basilar artery aneurysm in the literature. If you're still concerned, consult a neurosurgeon for advice.

You describe a congenital vascular variation affecting the basilar artery. From your post, you do not describe presence of an aneurysm. Cannot comment about stroke risks without more of your medical history, but the described fenestration has little contributing impact to eventual stroke.