Inspection of the eardrum may sometimes demonstrate subtle movements due to contraction of the tensor tympani (Cohen and Perez, 2003). As Schwartze first described in 1864, tensor tympani myoclonus causes a thumping sound.
|Cartoon of the middle ear showing muscles that attach to ossicles (ear bones), and ear drum. The stapedius is attached to the stapes (of course -- horseshoe object above), while the tensor tympani is attached to the ear drum. While useful, be aware that there are multiple errors in this illustration from Loyola Medical School. With permission, from: http://www.meddean.luc.edu/lumen/meded/grossanatomy/dissector/mml/images/stap.jpg||Image showing middle ear and tensor tympani from Gray's anatomy http://upload.wikimedia.org/wikipedia/commons/2/24/Musculustensortympani.png|
The tensor tympani syndrome is common. It sometimes results in visible contractions of the ear drum, and sometimes even produces sounds audible to the examiner. Patients usually indicate that it makes a "thumping" noise -- like a tympani drum ! There have also been occasional reports of higher frequency sounds (Bento et al, 1998; Abdul-Baqi, 2004). The tensor tympani is contiguous with a palatal muscle, the tensor veli palatini. Thus contractions of the tensor tympani may also be accompanied by contraction of the palatal muscles. Both the TT an TVP are innervated by the 5th nerve.
The tensor tympani and stapedius muscles are part of protective reflexes. They reduce the amount of sound that gets into the inner ear. They are somewhat similar to the blink reflex. Thus they can be triggered by loud noise, and when they "go off", both ears can be involved. This is similar to the situation that occurs when one eye is irritated, and both eyes blink for hours.
Again like blinks, these protective reflexes can become more prominent when a person is under stress.
Stapedius myoclonus has been reported once in "benign fasciculation syndrome" (Brigo et al, 2013), basically a diagnosis where patients become "twitchy" without an identified cause. This information is not especially useful, but it does suggest the general idea that when muscles are more irritible, tinnitus can result.
There are several simple methods of diagnosing TT myoclonus. The easiest is to simply watch the ear drum with an otoscope. When the muscle contracts, the eardrum dimples.
A second easy method is to listen. One can often hear the tinnitus by putting ones ear next to the patients ear. It generally is not useful to use a stethescope.
Some practices such as the authors, Chicago Dizziness and Hearing, have the ability to make audio recordings using a microphone placed within the ear canal. This is probably the best way to document objective tinnitus. As TT myoclonus often can be elicited by a loud noise, an adaptation of this technique (not in use to the author's knowledge) would be to record just after a loud noise.
An impedance bridge (tympanometer) can document rhythmic changes in ear drum compliance. A long recording of ear drum compliance should be made with a tympanometer (a screener won't work here). According to Bance, tensor tympani function can be measured by detecting changes in middle ear impedence. They also noted that the most effective method of stimulating it are orbital puffs of air --i.e. the same as the stimuli that might elicit a blink ( Bance et al, 2012).
Audiology research project ideas: one might be able to measure "thresholds" for the air puff stimulus, or loud noises, using similar methodology to blink reflexes, and thus develop a better method of diagnosing TT myoclonus.
There should not be movement of the ear drum in the stapedius myoclonus syndrome, as the stapedius does not insert onto the eardrum but rather onto the stapes. The stapedius is innervated by the 7th nerve, and is therefore part of a different circuit than the tensor tympani (5th nerve).
In our experience (see recording below), the sound can be heard from the outside -- it is a high-pitched "tic". We were unable to hear with a stethescope however, possibly due to it's high pitch. There was no visible movement of the eardrum.
|Rhythmic changes in impedance of the middle ear. Each bump was correlated with a high-pitched "tic" that can be heard from the outside, due to stapedius myoclonus.|
Click below to play recording of stapedius myoclonus.
A similar clinical picture may be associated with "typewriter tinnitus" as described by Levine (2006). Levine attributed this type of tinnitus to irritibility of the 8th nerve. This tinnitus is intermittent and has a staccato quality ('like a typewriter in the background, pop corn, Morse code'). It is responsive to carbamazepine. In our view, this clinical picture would be difficult to distinguish from stapedius myoclonus without careful clinical examination. TT myoclonus should be associated with a visible displacement of the ear drum during the sound. Stapedius myoclonus should be audible to the examiner, also one should be able to record it from an external ear microphone and it should be higher pitched. We do not know of anyone who has reported this however.
Surgery to cut the muscle is effective, and is used as a last resort.
A recent report suggested using Botox to paralyze the muscles (Liu et al, 2011). Botox can be injected into the wall of the eustachian tube. Of course, the TT is a small muscle and thus only a small amount of Botox is needed (Botox, sold by Allergan, is extremely expensive). This treatment seems reasonable, except that one needs an individual to administer the Botox who has a very good understanding of the anatomy of the TT to administer the injection, and also Botox wears off in 3 months.
Treatment of these muscle spasm syndromes is usually reassurance. Tinnitus coping strategies of counselling, relaxation and anxiety reduction are standard practice. Hypnosis, sedatives, psychotherapy, acupuncture, biofeedback have been attempted -- as this type of tinnitus is somewhat related to stress, these strategies are sometimes helpful.
Medications can be tried to reduce nerve or muscle irritibility. These include muscle relaxants, carbamazepine and related medications for myoclonus (such as sodium valproate). While the logic of reducing muscle spasm through medication is reasonable, we ourselves have not had success. It seems to us that the TT muscle requires considerable local irritation to develop myoclonus, and medications that affect the whole body are unable to reduce such intense local spasms.
Although masking has been reported effective (East et al, 1987), it is difficult to see a reasonable rationale, and we suspect this is a placebo.
Pharyngeal muscle tone alteration, swallowing, Valsalva, and grommet insertion are not effective (Badia et al, 1994). We are similarly dubious that manual compression of the face as reported by Chan and Palaniappan (2010) has any general utility as it would seem to us that any relief would be necessarily brief.
What is needed is a method of selectively weakening these muscles through drops administered through a ventilation tube or grommet. Alternatively, a method of causing a longer paralysis of the TT than can be obtained using Botox.
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