Because brain surgery is as complex as, well, brain surgery.
Even in cases where it’s super clear what should/should not be there, it’s very easy to mess something up and leave the patient permanently disabled, or worse, brain-dead.
Add in the complexity that ADHD is not an easily identifiable and useless tumor, but a problem in the otherwise working neurons, and you get a recipe for disaster if you tried to fix it through surgery.
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