Audiology Chapter 9 - Middle Ear - TCU Burger

Embryology of the Middle Ear

Development of the Middle Ear in relationship to gestation

What 4 objective tests are going to give us insights to the status of the middle ear?

Acoustic reflex testing (tells us about the muscle in the middle ear reacting appropriately)

Tympanometry (good to investigate for a type B, such as fluid or an infection)

Classic air or bone conduction testing

OAE - depends on the middle ear to carry information to the cochlea

malleus and incus are developing

4 weeks

Oval window formed

6 weeks

Ossicles become differentiated and still flexiable

12 weeks

Ossicles have fully formed

16 weeks… this is when we think that a baby can hear in utero

Ossification process is completing

21-24 weeks

Middle ears main job

to be a literal mechanical bridge (ossicles), taking acoustic energy to mechanical so that we can hear sound

The middle ear is a mechanical energy

Explain the process of middle ear

what door is to the inner ear

the oval window

Eustachian tube

ventilation/pressure equalizer

Impedance matching in middle ear

Transferring from air to fluid, it needs a boost towards the inner ear space… meets the difference, prevents loss of sound energy done through a bigger tympanic membrane than oval window, 1.3 to 1 ratio of the malleus, malleus moves a bit more than the incus 

Oval window stimulation

Stapes steps up and pushes fluid

Pressure equalization

The eustachian tube balances pressure so that the tympanic membrane can vibrate effectively.

Describe the general dimensions of the middle ear space.

What is the maximum conductive hearing loss (MCHL) that middle ear disorders generally do not exceed?

65 dBHL. Maximum conductive hearing loss

Will a conductive hearing loss (CHL) affect or change bone-conduction results?

No, not directly. (Though the sensorineural component may be exaggerated in mixed losses by bone conduction artifacts if the middle ear space is affected).

What is Otitis Media (OM)? What does it usually cause when it is present?

Infection in the mucous-membrane lining of the middle ear, the most common disorder of the middle ear space. A conductive HL.

What percentage of children in the USA will have OM before the age of 2 years?

70%.

What is the most frequent medical occurrence, second only to the common cold?

Otitis Media (OM).

Which two US racial/ethnic groups have a higher propensity for OM?

Eskimo and Native Americans.

How does OM access the middle ear space?

Access is gained up from the Eustachian tube (ET) in the nasopharynx region.

When the ET does not equalize pressure, which tympanogram type is often seen?

Type C tympanogram (negative pressure).

What is Suppurative OM?

Middle ear space is filled with pus (suppuration) and blood, causing TM redness, swelling, and possible rupture.

Superficial cells break down, the lining in the middle ear space is more sensitive, and the brewing will break through the mucosal lining and infect other parts, such as the mastoid, and even rupture the eardrum.

Starts with negativ epressure, brewing in the ear, eustachian tube doesn’t work…

What are the typical audiometric findings for Suppurative OM (or Mucoid OM)?

Type B (with normal ECV), Conductive hearing loss (flat to reverse slope), Excellent WDS( the +40bB allows them to hear fine because of a Conductive HL). Normal hearing and Conductive HL will always have excellent WDS… because the issue is louder , Absent ART (ipsi/contra), Absent OAE.

What is Serous OM?

Non-infected fluid in the middle ear space, often resulting from a continuing vacuum ("milking" of normal fluids).

Watery fluid… mass of the middle ear system… not infected, just fluid in the middle ear space

What are the typical audiometric findings for Serous OM?

Type B (with normal ECV), Conductive hearing loss (sloped configuration, due to mass), Excellent WDS, Absent ART (ipsi/contra), Absent OAE. More in the high frequency 

What is Mucous (Mucoid) OM?

Infected fluid in the middle ear space, often called "Glue ear," where long-standing secretions become dense.

Mucosal lining… inside of mouth, inside of middle ear… like glue is green and long-standing infections/secretion, can create scarring, will be a max conductive hearing loss

What is Tympanosclerosis?

TM scarring and calcium deposits that may be caused by long-standing mucous OM.

What is a Cholesteatoma?

A pseudotumor of extra skin (keratin, squamous epithelium, fats) in the middle ear, often associated with a foul-smelling discharge (otorrhea).

If TM gets sucked in with negative pressure, it can create a tumor… usually just a sack that is stinky and has stuff in it… The treatment is for the physician to remove it. It can cause a conductive hearing loss when you have it, but the surgeon takes them out… 

What is Otosclerosis?

Formation of a new growth of spongy bone (otospongiosis), typically over the stapedial footplate, causing stapes fixation.

70% hereditary, Schwartze sign, rosy glow from the refraction of the prominotory… originates in the bony labyrinth of inner ear… bluish cast to the whites of their eyes

What are the typical audiometric findings for Otosclerosis?

Type As , Conductive hearing loss, Carhart notch by BONE, Reverse sloped configuration (early stiffness), Absent ART (ipsi/contra), Absent OAE.

What is a Patulous Eustachian Tube (PET)?

The ET is chronically open, often causing autophony (own voice perceived as louder). (Audiometric: Type A, hearing not affected).

What surgical intervention is used to provide artificial ventilation to the middle ear?

Pressure-Equalization (PE) Tubes, often placed via a Myringotomy.

What type of tympanogram does a patent PE tube create?

Type B with a large Equivalent Ear Canal Volume (ECV).

What surgical procedure involves scraping away the infected bone of the mastoid?

Mastoidectomy.

What is a general term for the surgical reconstruction of the middle ear system?

Tympanoplasty.

What is the most simple form of tympanoplasty, involving repair of the TM?

Myringoplasty. Usually, where we repair the tympanic membrane.

What is the surgical treatment for Otosclerosis?

Stapedectomy (removal of the stapes from the oval window).

What is the mode of energy transmission through the middle ear?

Mechanical Energy.

List the path of mechanical energy transmission from the TM to the inner ear.

Displacement of tympanic membrane… malleus… incus.. stapes.. oval window 

What are the three primary functions of the middle ear?

Impedance matching (1.3:1 ratio), Oval window stimulation, and Pressure equalization (via the Eustachian tube).

What is the primary function of the Eustachian Tube (ET)?

Pressure equalization—it likes the air pressure to be the same on both sides of the TM.

What muscle provides a protective function by reducing the amplitude of vibration to the cochlea?

Stapedius muscle. (Innervated by the Facial [VIIth] nerve).

Which muscle pulls the TM back and makes it tense?

Tensor Tympani muscle. (Innervated by the Trigeminal [Vth] nerve).

Describe the general dimensions of the middle ear space.

ear space.An oval, air-filled area about 2cm^2 in area, roughly 1/2 inch in height and width, and 1/4 inch in depth.

What covers the entire middle ear area?

Mucous Membrane.

What structures form the roof and floor of the middle ear?

Roof: Bone that separates the brain. Floor: Jugular bulb.

What non-auditory structure passes through a protrusion of the medial wall of the middle ear?

The Fallopian Canal, which contains a portion of the Facial (VIIth) nerve.

What part of the Facial (VIIth) nerve gives sensation information for the anterior 2/3 of the tongue?

Chorda Tympani nerve.

Who is otitis media more present in?

Men/males

When do we think a baby can hear in utero?

16 weeks

What is primarily a childhood disease but can happen in adulthood?

Otitis media

Why shouldn’t you put a baby to bed with a bottle?

Goes through the eustachian tube, rotten teeth, and choking 

Acute Suppurative OM

Symptoms develop rapidly including, swelling, redness and bleeding… puss fluid, gross

Chronic suppurative OM

Long standing condition

Treatment for OM

PE tubes, antibiotics, decongestants, myringotomy in inferior posterior region of TM,

Mastoiditis

Infection of the mastoid from chronic OM… increases for meningitis, less common now due to antibiotics.

Mastoidectomy

Surgical procedure where the bone of the mastoid is scraped away until the infection is gone.

Manubrium

is embedded into TM, you can see when doing otocspocy

What two windows does the promontory have?

Oval window and round window