Completely blocked carotid

My mother (61yrs) was recently recommended surgery because her left internal carotid artery was 90% blocked, she has high blood pressure & diabetes (under control with medicine) and has smoked for most of her life. She had a transient ischemic attack about 5 yrs ago which she recovered completely. She has since been asymptomatic.  
Once surgery was attempted, it was discovered that it had become COMPLETELY blocked.
The doctor subsequently cleared out what he was able to in (what I would assume) would be the external carotid artery but was unable to clear out the INTERNAL CAROTID w/o risk of a major stroke.
Her right internal carotid artery is less than 50% occluded. She has yet to be discharged and I would like to know if anyone has any suggestions as to the prognosis or continued treatment options (perhaps even a 2nd opinion..??)

ANY INFO would be EXTREMELY appreciated!