In a spinal tap - say, prior to beginning a new treatment for multiple sclerosis - will cocaine from past use be detected? if so, for how long?

Cocaine detection: CSF is not routinely checked for cocaine. Usually doctors perform a urine test -that can extend back to 2 days if it was a 'one time' use. For chronic cocaine users though, it could be longer. So there are Qs such as how long you’ve been using, the average amount used each time, if you have any liver problems, and the type of test used. Generally docs are non-judgemental so hope you can go forward

Talk to your doctor: This is certainly not in my area of expertise. Generally, drug testing is done with urine or blood. I am concerned that you may be worried about some past behaviors - probably needlessly. It would be sad if this worry delayed your getting treated appropriately for your current condition. Have a frank discussion with your doctor. Start with "this is awkward for me to ask, but..." Good luck!

How much "past": If you have not used cocaine for days, it will not show up in any blood test.