I need to understand what it means if a ct scan of head shows opacification of the left mastoid air cells with most of these air cells sclerosed over?

Mastoiditis: These findings signify prior infection/inflammation of the mastoid which is part of the skull. This is almost always a result of old middle ear infections which often set off associated mastoiditis. I believe your findings show old burnt out mastoiditis, but an Otolaryngologist could evaluate you, look at your ct scan and advise you best.