Is CT Scan a Safer Alternative to MRI When You Have Tinnitus?

Hi there,

MRIs are very loud, and I'm afraid it will make my hearing loss or tinnitus worse.

But if my ENT wants to look for acoustic neuroma or other brain related issues, is a CT scan good enough alternative?

And what about MRI with contrast? I've read gadolinium is controversial - it can get permanently stuck in your brain tissue? Or is that nonsense?

I'd appreciate a round up of various imaging technologies when it comes to tinnitus and hearing loss.

 

Hello @Barbara777. I could probably write an entire book chapter and still not do justice to your excellent question. Anyway here just are the highlights as I see it ...

First, I think that in general too many scans (MRI and CT) are ordered as part of a tinnitus work-up. I know of one clinician who will not treat a person who presents with tinnitus unless he or she has had an MRI. And I am sure that clinician is not alone in his opinion.

So let me offer my thoughts about the indications for a scan and then give you the rationale behind my preference.

The reason these scans are ordered are to look for an acoustic neuroma (also called vestibular schwannoma). Acoustic neuromas are benign (non-cancerous) growths located along the auditory nerve in the region of the CPA (cerebello-pontine angle). These tumors are slow-growing and relatively rare, the incidence being roughly 1 in 100,000. Bilateral (both sides) acoustic neuromas are even rarer and are almost always associated with a genetic disorder called NFII (neurofibromatosis type 2). I mention this fact because bilateral tinnitus is almost never the presenting symptom of NFII. In other words, if you have NFII, you will have been diagnosed long before you develop tinnitus. What this means is that in my opinion bilateral tinnitus in and of itself is not an indication for a scan to rule out acoustic neuroma. There are a few exceptions, but they go beyond the scope of this site.

With that said, it has been my practice to order scans to look for acoustic neuromas in tinnitus patients only if the tinnitus is unilateral or markedly asymmetrical and unexplained. Another indication might be an unexplained markedly asymmetrical audiogram. So what would be an example of unilateral tinnitus that is not unexplained? I recall seeing a left-handed gentleman with unilateral right-sided tinnitus. He mentioned that he was an avid hunter. Well, if you are shooting a rifle left-handed, your left ear is tucked into your shoulder while your right ear is open to the barrel of the rifle. His tinnitus began after a hunting trip, and given that history I saw no reason to order a scan in spite of the fact that his tinnitus was unilateral.

OK. We have touched on indications. So which scan to order CT or MRI? Well, CT scans are better (i.e., more sensitive) for certain indications, and MRI scans for others. With respect to the brain, CT is generally better in determining the nature of a stroke, while MRI is generally better for soft tissue lesions like acoustic neuromas. Gadolinium is a contrast agent used in MRI to increase the sensitivity for picking up small lesions that might otherwise be missed. And the earlier you identify an acoustic neuroma, the more treatment options are available. As you have read, the use of gadolinium can be problematic in that it can result in renal failure in folks who are predisposed. Also, small amounts of gadolinium have been reported to remain in the brain, although the significance of this finding is unknown.

MRI does not use radiation, while CT does - and in high enough doses radiation can cause cancer. But MRI uses very strong magnets, which can become problematic with certain types of implants and clips. MRI machines are also LOUD, so well-fitting earplugs as essential in that regard.

OK, where does that leave us? As I see it, if your doctor is concerned about the possibility of an acoustic neuroma, it makes no sense to look for one using a study that is not optimally sensitive, or it will miss small lesions. So unless there are contraindications or concerns, the study for your doctor to order would be an "MRI of the brain and IACs (internal auditory canals) with and without gadolinium to rule out CPA (cerebello-pontine angle) lesion, etc." What contraindications or concerns? Well that is why a detailed discussion with your doctor is definitely warranted before going ahead. There is a lot to weigh, and your doctor will be in the best position to help you decide.

Probably too much information to wade through, which is why the very last three sentences in the above paragraph are key.

Now just imagine how awful it would be had I written that book chapter instead of just posting some highlights in response to your question!

Hope this helps more than frustrates or confuses.

All the best with it.

Stephen M. Nagler, M.D.