What treatment for occluded left vertebral artery in the brain?

Monitor, aspirin. If the artery is completely occluded, there is likely no medication or surgery that is needed. Reopening a totally occluded artery can actually cause injury to the brain. You should be evaluated by a neurologist to evaluate why the occlusion happened, such as whether there is a clotting disorder. Sometimes blood thinners such as daily Aspirin are needed to prevent further occlusions.
Antiplatelet meds. First, why is artery occluded? Could be due to local thrombosis, but could also be due to traumatic or spontaneous dissection. Secondly, are there risks for stoke such as diabetes, hypertension, high cholesterol/triglycerides, high homocysteine? Talk with your doctor re prevention, perhaps clopidogrel, aggrenox. Many areas need to be addressed.