Med Term Ch 17: the ears

middle ear infection and AOM

Dr. Harris explains to Sara why the structure of the eustachian tube and its connection to the nasopharynx causes the middle ear to be prone to infection; the medical term that describes infection (-itis) of the middle (media) ear (ot/o) is *otitis media*. Although adults suffer occasional ear infections—just as Sara is now—*acute otitis media* (AOM) is usually thought of as a common childhood disease associated with colds, sore throats, and blockage of the eustachian tube. Of sudden onset and short duration, AOM is caused by a variety of bacteria. Acute otitis media is characterized by a sense of fullness in the ear, diminished hearing, pain, and fever.

audiometry

Dr. Harris uses audiometry as his method for measuring (-metry) hearing (audi/o) acuity and to help establish the degree and severity of Sara's hearing loss. An audiometer is an electric device used to measure (-meter) the sensitivity of hearing by delivering a series of acoustic tones that range from very low to very high frequencies. To do this, Dr. Harris asks Sara to signal when she hears a tone and in which ear; her hearing (audi/o) function results are then plotted on a graph or record (-gram) called an audiogram.

acoustic neuroma

Finally, acoustic neuroma is a benign tumor (-oma) that develops from the acoustic nerve (neur/o) and grows in the auditory canal (acous/o means hearing; -tic means pertaining to). The presence of the tumor may cause tinnitus, vertigo, and progressive hearing loss. The tumor is removed either by surgical incision or by radiosurgery—the use of x-ray beams to destroy the growth.

hearing impairment

If no growths or obstructions are evident, what is causing Sara's hearing loss? Hearing loss can range from difficulty perceiving certain words or tones to a total loss of hearing, or deafness. If deafness is congenital and profound, it can greatly influence the development of speech and conceptual thinking. Conductive hearing loss is caused by conditions that interfere with the collection and transmission of sound waves through the outer and middle ear. These conditions include accumulation of cerumen in the auditory canal, the presence of a foreign body in the ear, and diseases of the middle ear.

middle ear structures

The *tympanic membrane, or eardrum* (tympan/o, myring/o), is a shiny, oval, semitransparent membrane that lies at the end of the external auditory canal and at the entry to the middle ear. Within the middle ear cavity are three small bones, or *ossicles (ossicul/o): the malleus, incus, and stapes* (staped/o)—so named because they resemble a hammer, an anvil, and stirrups, respectively. They are attached to, or articulate with, one another. The "handle" of the malleus is connected to the tympanic membrane. The footplate of the stapes, when it moves, touches the oval window, which leads to the inner ear. The *auditory, or eustachian*, tube is another structure of the ear that joins the nasopharynx with the middle ear cavity. The eustachian tube (represented by the combining form salping/o) provides for an equalization of air pressure between the middle ear and the external atmosphere.

cochlear implant

The cochlear implant is a device now available for use by those with profound hearing loss. It is surgically implanted and converts the spoken word to electrical impulses and bypasses the damaged cochlea to stimulate the auditory nerve.

equilibrium

The structures of the ear involved in maintaining equilibrium are found in the vestibule and the semicircular canals. Sensitive hair cells and fluid within these structures allow detection of changes in the position of the head. Movement of the hair cells within the macula generates nerve impulses, which communicate through the brain to the body's muscles and provide for the recovery of balance.

auditory/audiologist

The term auditory means pertaining to hearing. An audiologist is a specialist (-ist) in the study (log/o) of diseases and treatment of hearing (audi/o) disorders.

tuning fork

The tuning fork is used to measure the efficacy of sound conduction through Sara's ear and helps to distinguish between conductive and sensorineural hearing loss. The *Weber tuning fork test*, in which the tuning fork is placed on the midline of the skull, assesses bone conduction of sound. In the *Rinne tuning fork test*, the tuning fork is placed alternately near the auditory canal and behind the ear on the mastoid bone. This technique helps to assess both air and bone conduction of sound.

PE tube

This device may be used to treat recurrent episodes of acute otitis media

otoscopy

A variety of techniques can help detect hearing loss. Screening of auditory function begins with a physical examination of the ear. As we have seen, Dr. Harris has already used otoscopy—the inspection (-scopy) of the structures of the ear (ot/o) canal with a handheld, lighted magnifying device called an otoscope. A pneumatic attachment to the otoscope allows evaluation of the eardrum's mobility.

cholesteatoma

An example of an obstruction would be a *cholesteatoma*, a cystic mass of the middle ear composed of epithelial cells, *sebum*, and cholesterol. The mass may occur as a congenital defect but most often is a complication of chronic otitis media. Surgical removal of the cholesteatoma is required to prevent damage to the middle ear structures caused by enzymes produced by the mass.

Sensorineural hearing loss/presbycusis

But these causes have been ruled out in Sara's case. Sensorineural hearing loss is caused by disease of, or trauma to, the structures of the inner ear or the nerve pathways leading to the brain. Degenerative changes in the inner ear, associated with old age (presby/o), can also result in hearing (-cusis, -acusis) impairment—a condition known as presbycusis.

Audiometry is done to determine

Hearing for specific frequencies

otosclerosis

Here is another example of an obstruction. Otosclerosis involves the excess formation of bony tissue in the middle ear—particularly at the labyrinth—that attaches to, and prevents movement of, the stapes. The ankylosis, or stiffening, of the stapes prevents it from transmitting sound vibrations to the inner ear, producing a conductive hearing loss. Surgically removing the stapes and replacing it with a prosthesis corrects the condition.

chronic otitis media

Myringotomy to ventilate the middle ear may be necessary in cases of

the process of hearing

Now let us look at the series of events involved in the process of hearing. Sound waves, conducted by air, enter the ear with the aid of the *auricle*. They are conducted along the *auditory meatus* to the *tympanic membrane* (tympan/o, myring/o), or eardrum. When the taut eardrum is struck by the sound waves, it begins to vibrate, moving the three small bones in the middle ear. The *ossicles* (ossicul/o) amplify the sound waves and conduct them through the *middle ear, to the oval window, and into the inner ear*. Sound is then picked up by the sensory hair cells of the *cochlea*, which produce impulses that are transmitted by the *auditory nerve fibers to the auditory cortex*.

treatment for otitis media

Recurrent bouts of infection and chronic inflammation can lead to the accumulation of fluid—serous or mucoid—in the middle ear, a condition known as *serous otitis media (SOM) or otitis media with effusion (OME)*. Obstruction or dysfunction of the eustachian tube and enlarged lymphoid tissue in the nasopharynx are among the causes of improper fluid drainage. Antibiotic therapy is used to treat acute and chronic otitis media. A *myringotomy*—surgical incision (-tomy) of the tympanum or eardrum (myring/o) to relieve the pressure and buildup of fluid—may be required for those who don't respond to antibiotic treatment. In this procedure, a *pressure-equalizing tube (PE tube)* is placed in the eardrum to provide ventilation.

serous otitis media

Recurrent bouts of infection and chronic inflammation can lead to the accumulation of fluid—serous or mucoid—in the middle ear, a condition known as:

disorders

The ability to hear can be compromised by a variety of diseases and disorders. These pathologic conditions are categorized by which area of the ear they affect: the external ear, the middle ear, or the inner ear. In this lesson, we'll focus on middle and inner ear disorders.

the ear

The ear (ot/o, aur/o, auricul/o) provides the dual function of sensing sound and serving as the organ of balance, or equilibrium. The ear is divided into three anatomic regions: the outer ear, the middle ear, and the inner ear. The combining forms for the process of hearing are acous/o, audi/o, and audit/o

inner ear structures

The inner ear is composed of a *bony labyrinth*, inside of which is a membranous labyrinth. The bony labyrinth consists of three parts: the *vestibule (vestibul/o), cochlea (cochle/o), and semicircular canals*. The membranous labyrinth contains a protein-rich fluid called *endolymph* and is surrounded (peri-) by the bony labyrinth that contains a clear liquid known as* perilymph*. The cochlea houses the *organ of Corti*, a sensitive receptor whose hair cells relay sound waves to auditory nerve fibers. These fibers then convey impulses to the auditory region of the cerebral cortex

outer ear structures

The outer ear consists of the *auricle* (auricul/o), or *pinna, and the external auditory meatus, or auditory canal* (also called the auditory tube). The auricle, a skin-covered cartilaginous flap, projects from the side of the head. The auditory meatus, the external portion, is a slender, one inch canal lined with glands that secrete a sticky substance called *cerumen*. Cerumen lubricates the ear and prevents the entry of foreign particles into the internal portions of the ear.

hearing

The suffix -cusis in the term presbycusis means

treatment methods

There are a number of treatment methods and assistive devices that can help correct or compensate for hearing loss. The proper treatment depends on the cause of the hearing loss. Conductive hearing loss caused by blockage, infection, or other disease may be managed with antibiotics or surgery. Use of a hearing aid may be indicated for both conductive and sensorineural hearing loss. In Sara's case, Dr. Harris believes that a hearing aid will help with Sara's presbycusis.

conductive

This type of hearing loss results from impairment of the middle ear ossicles and membranes that transmit sound waves into the cochlea

ankylosis

With otosclerosis, bone forms around the oval window, which causes a stiffening or fixation, known as _________, of the stapes bone.

Ménière's Disease

We learned in the previous lesson that Sara used to suffer from bouts of dizziness. Dr. Harris explained that what Sara had was Ménière's disease, which affects the *vestibular labyrinth*. The structures responsible for equilibrium and balance are housed in this labyrinth, contained in the inner ear. Ménière's disease can lead to profound hearing loss. The cause of the disease is unknown, but it results in an accumulation of *endolymph* in the membranous labyrinth. Ménière's disease is marked by *vertigo*, a sensation that the body is spinning or that objects are spinning around the body. *Tinnitus*, a subjective noise such as ringing, buzzing, whistling, or clicking—heard in the absence of sound—can also be a prominent feature of Ménière's disease. Various methods are used to treat this disorder, including tranquilizers, antihistamines, diuretics, and surgery to reduce the pressure of the endolymph on cochlear hair cells. It can also spontaneously go away, as Sara's did after about two years.