Hello. Sorry to hear this. Your father should see a neurosurgeon. 98% blockage is significant and the best treatment to treat this is by a surgical procedure called as carotid endarterectomy. This procedure has the best efficacy in preventing future paralytic stroke and death. However, this benefit of this procedure is to be weighed against the potential risks of surgery. His other medical problems like diabetes, blood pressure, heart disease etc should be controlled adequately with medications to prevent future stroke. Wishing him a speedy recovery.