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Introduction
The tensor tympani muscle is the largest muscle within the middle ear. It is innervated by the mandibular division of the trigeminal nerve. Its fibres originate from the cartilaginous wall of the eustachian tube and the greater wing of the sphenoid. The tendon of the tensor tympani muscle arises from the cochleariform process and inserts into the medial surface of the handle of the malleus. Under contraction, the tensor tympani muscle pulls the malleus and the tympanic membrane medially, increasing the stiffness of the tympano-ossicular system. Although its action is largely understood, the audiometric effects of this contractile activity have been documented in very few papers.1-3
In this report, the authors describe an unusual case of bilateral voluntary contraction of the tensor tympani muscle, and discuss its functional repercussion on sound conduction.
Case report
A 27-year-old Caucasian man presented to our ENT department complaining of bilateral tinnitus that was voluntarily evoked. The tinnitus was defined as a cracking sound. The patient had no history of otological disease.
Otoscopy was normal, but the patient was found to be able to contract his tensor tympani muscle voluntarily. During rapid contractions, the handle of the malleus and the tympanic membrane were medially displaced, repeatedly, at a maximum rate of 3-4 times per second, always under voluntary control. Contraction was observed in both ears simultaneously; the patient could not move each muscle individually. Fibre-optic nasopharyngoscopy showed no signs of synchronous palatal movement.
The patient reported that he could sustain the contraction for longer periods, up to 30 seconds. He reported that this caused a marked reduction in hearing capacity, including hearing of the human voice. After 2 or 3 maximal sustained contractions, a period of 3-5 minutes of rest was necessary to resume contractions. A short video-otoscopy recording demonstrating the voluntary contraction of the tensor tympani muscle is available on The Journal of Laryngology & Otology website (Appendix 1).
Audiograms were performed under conditions of rest and maximal contraction of the tensor tympani muscle (Figure 1). During contraction, a marked reduction in air conduction was observed, particularly at low frequencies, with air-bone gaps of 35 and 30 dB at frequencies of 250 and 500 Hz respectively. No...