The mastoid process is the bulge bit behind the styloid process, the styloid process is separate and so I’m not sure exactly what the radiologist is talking about, I think you have to presume it’s probably compression of the IJV by the styloid…
@Hamela - There is also two styloid processes in each wrist which is why your report specified mastoid styloid process(es) as that indicates it’s the skull based styloids not those in the wrists.