I stutter. I have had multiple MRIs and CAT scans, EEGs. Nothing remarkable to be seen. Ever.  One doctor said the area speech is "made" was a little small but did not differ greatly enough from many scans he'd seen over years of his career so nothing at all to indicate a structural issue being the cause.  Sibling who does not stutter had similar findings on MRI fwiw. We had an older relative who stuttered.