What roles do both muscles play in hyperacusis and tinnitus?

Both the stapedius and tensor tympani muscles play central roles in controlling sound transmission in the middle ear, and their dysfunction or hyperactivity can contribute to hyperacusis (increased sound sensitivity) and tinnitus (ringing or internal noises in the ear).

Role in Normal Hearing and Protection

• The stapedius muscle contracts reflexively in response to loud sounds through the acoustic reflex, pulling the stapes away from the oval window to reduce sound vibrations reaching the inner ear.
• The tensor tympani muscle, activated during startle reflexes and self-generated noises (e.g., chewing, speaking), pulls the tympanic membrane inward to dampen vibrations and protect the cochlea.
• Together, they form the middle ear muscle reflex system, stabilizing the ossicles and maintaining auditory balance under changing sound intensities.

Role in Hyperacusis

• Hyperacusis often develops when these muscles lose their ability to properly regulate sound transmission.
• Stapedius dysfunction (e.g., paralysis from facial nerve damage) prevents adequate damping of stapes vibration, so ordinary sounds are perceived as excessively loud or painful.
• Tensor tympani overactivity or hypersensitivity—often linked to Tensor Tympani Syndrome (TTS)—causes excessive or reflexive contraction in response to moderate sounds or even anticipation of noise, tightening the eardrum and creating a feeling of fullness, tension, or pain in the ear.
• Chronic muscle tension and abnormal reflex sensitivity can also trigger somatic hyperacusis, where non-auditory stimuli (like jaw movement or stress) amplify sound sensitivity.

Role in Tinnitus

• Middle ear myoclonus syndrome occurs when either or both muscles undergo rhythmic or spasmodic contractions, leading to objective tinnitus—perceived as clicking, fluttering, or buzzing sounds synchronized with muscle movement.
• Stapedius myoclonus can produce low-pitched buzzing, while tensor tympani spasms typically produce clicking or crackling sounds due to tympanic membrane movement.
• These involuntary contractions may result from stress, noise trauma, or neural hyperexcitability in the trigeminal or facial nerve pathways