Hi, this is Dr Sathya. Thanks for your question and I will try my best to help you.
If the carotid artery blockage (or stenosis) is total (that is 100% blockage) then carotid surgery is not recommended.
If there is a major or severe stenosis but no total blockage (stenosis is between 79% and 99%) then carotid surgery is recommended irrespective of whether the patient has had mini stroke or strokes.
If there is a moderate stenosis (blockage between around 50% and 79%) then carotid surgery is recommended - only if there is a history of mini stroke or stroke, but not otherwise.
If the stenosis is mild (blockage less than 50%) then surgery is not recommended, irrespective of whether patient has a history of mini stroke or stroke or not.
So up to about 50% of the stenosis or blockage is acceptable and doesn't require any surgery irrespective of whether there is a history of any mini stroke or stroke or not, and up to about 70% stenosis or blockage is acceptable before surgery provided there is no history of any mini strokes or strokes.
Please ask me if there are any further questions.
Thanks for the waiting!
All the best!
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