Inspection of the eardrum may sometimes demonstrate subtle movements due to contraction of the tensor tympani (Cohen and Perez, 2003). 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|
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 ! 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 idea: one might be able to measure "thresholds" for the air puff stimulus, using similar methodology to blink reflexes, and thus develop a better method of diagnosing TT myoclonus.
There should not be movement of the palate in the stapedius myoclonus syndrome, as the stapedius does not insert onto the eardrum but rather onto the stapes.
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, in this case.
|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). He 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.
Treatment of TT myoclonus.
Treatment of these muscle spasm syndromes is usually just reassurance. Surgery to cut the muscle should be effective. Other methods include medications to reduce nerve or muscle irritibility. A recent report suggested using Botox (Liu et al, 2011), but it would seem difficult to us to administer it to this tiny muscle.
- Bance M, Makki FM, Garland P, Alian WA, van Wijhe RG, Savage J.Effects of tensor tympani muscle contraction on the middle ear and markers of a contracted muscle. Laryngoscope. 2012 Nov 20. doi: 10.1002/lary.23711.
- Levine, R. A. (2006). "Typewriter tinnitus: a carbamazepine-responsive syndrome related to auditory nerve vascular compression." ORL J Otorhinolaryngol Relat Spec 68(1): 43-6; discussion 46-7.
- Liu HB, Fan JP, Lin SZ, Zhao SW, Lin Z. Botox transient treatment of tinnitus due to stapedius myoclonus: case report. Clin Neurol Neurosurg. 2011 Jan;113(1):57-8. Epub 2010 Aug 25.
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