Table of ContentsView AllTable of ContentsAnatomyFunctionAssociated ConditionsRehabilitation

Table of ContentsView All

View All

Table of Contents

Anatomy

Function

Associated Conditions

Rehabilitation

Thestapediusmuscle is a muscle within the ear that stabilizes thestapes boneof the inner ear. It’s the smallest skeletal muscle in the body and plays an important role in hearing. This article will discuss the stapedius muscle’s anatomy, location, associated conditions, and treatment.

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Person with noise sensitivity troubled by hyper-acute hearing in bed at night

Shaped like a sickle, the stapedius muscle is often described as the smallest skeletal muscle in the human body. However, some sources suggest its average size may be larger than the often-cited 1 millimeter length.

A 2018 paper describing dissections and inspections of the inner ear and stapedius muscle published in theIndian Journal of Otolaryngology Head Neck Surgeryputs the measurement at between 9 and 11 millimeters. ​​The tendon, which is attached to the handle end of the sickle-shaped muscle, measures about 2 millimeters in length.

Location

The stapedius muscle is located inside the ear cavity, specifically inside the tympanic cavity, in themiddle portion of the ear. In a healthy hearing canal, the tympanic cavity is filled with air.

The muscle extends from the back portion of the stapes bone, with the thinnest part of the muscle connecting to the neck of the stapes. It emerges from a small opening of the pyramidal eminence, which is a hollow part of the tympanic cavity wall. The stapedial tendon attaches to the bottom portion of the stapedius muscle.

Two arteries supply blood to this small muscle:

Thefacial nerve, also called the seventh crainial nerve, supplies nerves to the stapedius muscle.

Anatomical Variations

In rare cases, a person can be born without a stapedius muscle or tendon. This may cause issues with hearing, such as hearing loss.

The small stapedius muscle plays a crucial role in your ability to hear. Its main function is to stabilize the stapes bone, the smallest bone in your body. The middle ear’s job is to facilitate the movement of sound waves from the outer ear to the inner ear.

This chain of events is set in motion as you hear sounds. Sound waves stimulateinner earreceptors that send signals to your brain. Your brain stem then sends an alert to your middle ear, telling your stapedius muscle to contract.

As sound waves pass through the middle ear’s threeossicles, the stapes bone hits the oval window, the part of the ear that delineates the middle and inner ear. When the stapes bone activates the oval window, fluid inside the inner ear begins to move, which starts the sound processing process.

By stabilizing the stapes, the stapedius dampens sound vibrations that eventually make their way to the inner ear.Think of the stapedius muscle as a sort of volume control mechanism. Without it, loud sounds could easily damage your inner ear.

This reflex to protect your hearing is part of the acoustic middle ear reflex, an involuntary reflex. Healthcare providers cantest your acoustic middle ear reflexusing certain tools, and the results can provide valuable information about your hearing health.

It’s not a fail-proof mechanism, though. You’re probably aware that you can experiencehearing losswhen hearing sudden loud sounds. The stapedius muscle and acoustic middle ear reflex have their limitations. Loud noises can still cause inner ear damage.

Issues with the stapedius muscle can cause problems with hearing.

For example, paralysis of the muscle prevents sound dampening. People with stapedius muscle paralysis have what’s known ashyperacusis, which makes things sound much louder than they are. It’s also known as sound sensitivity.

If you have hyperacusis, you may be less tolerant of certain sounds than others, like running water, vehicle noises, or paper shuffling.

This kind of paralysis can happen because of facial nerve damage.Bell’s palsyis an example of a condition that can cause hyperacusis. Other conditions that can cause this kind of sound sensitivity include:

Additionally, some conditions are associated with hearing hypersensitivity but aren’t necessarily the cause of it. These include:

You can also experience idiopathic middle ear contractions. Idiopathic means there’s no known medical cause. For example, some people may occasionally hear sounds like fluttering or clicking inside their ears. Some experts believe some of these sounds result from the stapedius muscle contracting when it shouldn’t.

Obstructions in the ear that impact sound transmission and stapedius muscle contraction can affect your acoustic reflex. Other things that can affect the acoustic reflex include:

While there’s no cure for hyperacusis, treating the underlying issue may help. For instance, if you’re taking medications that are causing ear damage, stopping the drug may prevent further damage.

Sound therapy may also help improve sound tolerance.In this therapy, you wear a noise-generating device that produces barely audible white noise. It retrains the brain to accept sounds you hear throughout the day.

Summary

The stapedius muscle is a small muscle located inside the middle ear. It helps stabilize the stapes bone and is involved in regulating sound and protecting your inner ear from damage due to loud sounds.

8 SourcesVerywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Prasad KC, Azeem Mohiyuddin SM, Anjali PK, et al.Microsurgical anatomy of stapedius muscle: anatomy revisited, redefined with potential impact in surgeries.Indian J Otolaryngol Head Neck Surg. 2019;71(1):14-18. doi:10.1007/s12070-018-1510-5Behera SK.Congenital absence of stapedius muscle and tendon: rare finding in two cases.Indian Journal of Otology. 2017;23(1): 43-45. doi:10.4103/0971-7749.199511Johns Hopkins Medicine.How the ear works.NYU Langone Health.Diagnosing facial nerve paralysis.National Institute on Deafness and Other Communication Disorders.Noise-induced hearing loss.American Academy of Otolaryngology–Head and Neck Surgery Foundation.Hyperacusis.ENT & Audiology News.Middle ear muscle disorders: Presentation, diagnosis and management.Open Access Guide to Audiology and Hearing Aids for Otolaryngologists.Acoustic (stapedius) reflexes

8 Sources

Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Prasad KC, Azeem Mohiyuddin SM, Anjali PK, et al.Microsurgical anatomy of stapedius muscle: anatomy revisited, redefined with potential impact in surgeries.Indian J Otolaryngol Head Neck Surg. 2019;71(1):14-18. doi:10.1007/s12070-018-1510-5Behera SK.Congenital absence of stapedius muscle and tendon: rare finding in two cases.Indian Journal of Otology. 2017;23(1): 43-45. doi:10.4103/0971-7749.199511Johns Hopkins Medicine.How the ear works.NYU Langone Health.Diagnosing facial nerve paralysis.National Institute on Deafness and Other Communication Disorders.Noise-induced hearing loss.American Academy of Otolaryngology–Head and Neck Surgery Foundation.Hyperacusis.ENT & Audiology News.Middle ear muscle disorders: Presentation, diagnosis and management.Open Access Guide to Audiology and Hearing Aids for Otolaryngologists.Acoustic (stapedius) reflexes

Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.

Prasad KC, Azeem Mohiyuddin SM, Anjali PK, et al.Microsurgical anatomy of stapedius muscle: anatomy revisited, redefined with potential impact in surgeries.Indian J Otolaryngol Head Neck Surg. 2019;71(1):14-18. doi:10.1007/s12070-018-1510-5Behera SK.Congenital absence of stapedius muscle and tendon: rare finding in two cases.Indian Journal of Otology. 2017;23(1): 43-45. doi:10.4103/0971-7749.199511Johns Hopkins Medicine.How the ear works.NYU Langone Health.Diagnosing facial nerve paralysis.National Institute on Deafness and Other Communication Disorders.Noise-induced hearing loss.American Academy of Otolaryngology–Head and Neck Surgery Foundation.Hyperacusis.ENT & Audiology News.Middle ear muscle disorders: Presentation, diagnosis and management.Open Access Guide to Audiology and Hearing Aids for Otolaryngologists.Acoustic (stapedius) reflexes

Prasad KC, Azeem Mohiyuddin SM, Anjali PK, et al.Microsurgical anatomy of stapedius muscle: anatomy revisited, redefined with potential impact in surgeries.Indian J Otolaryngol Head Neck Surg. 2019;71(1):14-18. doi:10.1007/s12070-018-1510-5

Behera SK.Congenital absence of stapedius muscle and tendon: rare finding in two cases.Indian Journal of Otology. 2017;23(1): 43-45. doi:10.4103/0971-7749.199511

Johns Hopkins Medicine.How the ear works.

NYU Langone Health.Diagnosing facial nerve paralysis.

National Institute on Deafness and Other Communication Disorders.Noise-induced hearing loss.

American Academy of Otolaryngology–Head and Neck Surgery Foundation.Hyperacusis.

ENT & Audiology News.Middle ear muscle disorders: Presentation, diagnosis and management.

Open Access Guide to Audiology and Hearing Aids for Otolaryngologists.Acoustic (stapedius) reflexes

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