Thank you for posting on the ANA Forums!
Your husband has probably already seen the ENT since you posted this, and you probably already know the answer to your question. If so, please update us on what you found out.
I am not a physician, so I can only guess at what the radiologist wrote. But when his conclusion reads, "Left Cochlear enhancement which may reflect a small underlying schwannoma versus inflammation," the way I interpret it in my non-clinical understanding is that the radiologist saw something quite small in or around the left cochlear, and it is possible that it is a small acoustic neuroma (also known as vestibular schwannoma) as opposed to simply inflammation in the cochlear.
Again, that is my guess, and I'm not clinically trained, so take it with a grain of salt, as they say.
Acoustic neuromas when they are very small are often difficult to see on the MRI. They can appear like a swelling from an inflammation. The good news is that, if it IS an acoustic neuroma, it sounds like it may be very small -- which would give your husband plenty of time to decide what treatment method he wants.
Please update us with the latest!