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Audiology

Terms in this set (45)

Role of the outer and middle ear
The outer ear gathers sound waves and funnels them through the external auditory meatus (canal) The middle ear carries vibrations from the outer ear to the inner ear by transferring the sound energy from the air in the outer ear to the fluids of the inner ear Role of the pinna (auricle) specifically in reference to localization. Aids in the human ability to localize the sources of sounds that come from in front of, behind, below, and above the head. Helps to funnel sounds directed to it from the surrounding air into the opening of the EAC
Length of adult EAC
2.5 cm (adults)
What is cerumen?
Cerumen is ear wax that is formed in the cartilaginous auditory canal, cerumen should be removed if it blocks hearing, or a doctor notices that it should be removed. Objects entering the ear canal can cause injury and pushing cerumen farther into the ear canal can be damaging.
The angle of EAC in adults vs. children
Infants and small children -- EAC angled downward and at a more acute angle
Why is the TM located where it is?
Protected from trauma & Kept at constant temperature and humidity levelsBorder between outer/middle ear and middle/inner ear
Three layers
Outer layer: viewed from the EAC. Middle layer- tough, fibrous, connective tissue which contributes most to the TM's ability to vibrate with impinging sound waves. Inner layer- lined with mucous membrane
How much movement of the TM is required to obtain a threshold response in a normal-hearing individual?
Movement of one-billionth of a centimeter is sufficient to produce a threshold response in normal hearing individuals in the 800 to 6000 Hz range
Point of greatest retraction of the TM
Umbo
How to perform otoscopy
​​1.Visualize entire auricle for any abnormalities 2.Sit at the same level as the patient 3.Pull up and back on the pinna.Don't be shy.... Pull!!!!! 4.Hold the otoscope like you are holding a writing utensil. MAKE SURE TO USE YOUR PINKY TO BRACE AGAINST THE HEAD 5.Slowly insert the otoscope -- visualizing the all parts of the EAC and TM 6.Observe any abnormalities in the EAC/TM. Note the color, translucency, and position of the TM. Identify pars tensa, cone of light, handle and short process of the malleus, and the pars flaccida
First mobile link in the chain of auditory events
Tympanic membrane
Type of HL associated with disorders of the outer, middle, inner ear
Outer Ear: conductive hearing loss, Middle Ear: Conductive, Inner Ear: Sensorineural Hearing Loss
Do all abnormalities of the outer ear result in hearing loss?
Some abnormalities of the outer ear do not result in hearing loss
What is atresia? With what disorders/syndromes is it usually present? What type of AC transducers might you use for an individual with atresia? What type of HL will be present?
In some patients, the cartilaginous portion, the bony portion, or the entirety of the external auditory canal has never formed at all. Such congenital abnormalities may occur in one or both ears. This lack of canalization is called otic atresia and can occur in the EAC either in isolation or in combination with other anomalies.One inherited condition, Treacher Collins syndrome, involves the facial bones, especially the cheek and lower jaw; the auricle; and congenital atresia of the EAC. Not all closures of the external auditory canal are congenital; some may occur as the result of trauma or burns In cases of atresia of the canal, the hearing loss is directly related to the area and the amount of occlusion. The loss may be mild if only the cartilaginous area is involved, and certainly can be more severe if the bony canal is occluded.
Conductive hearing loss:
bone transducer
Microtia (don't need to memorize all the grades)
At times, one or both ears may be of very small size
Anotia
Absence of the pinna
What type of HL might we see with collapsed ear canals? What type of AC transducers might you use?
Conductive hearing loss: interferes with/blocks the normal sound vibrations transmitted through the outer ear. AC transducer: foam inserts because it would pry open the collapsed ear canal
What is external otitis? What type of individuals commonly develop this infection?
An infection that occurs in the skin of the external auditory canal. The condition is often referred to as swimmer's ear because it frequently develops in people who have had water trapped in their ears. External otitis is quite common in tropical areas
Why is the EAC heavily susceptible to infection?
It's a cul-de-sac that is lined with skin, the only such structure in the human body, which makes it particularly susceptible to infection. It is an almost ideal environment for the development of bacterial growth because the skin is thin and the area is dark, warm, and moist. Part of its natural defense is cerumen, which contains certain bacterial destroying enzymes and tends to reject the absorption of water.
What are exostoses?What type of individuals commonly develop this condition?
The outward projections for the surfaces of bone, sometimes seen in the ears of people who have done a great deal of swimming in cold water.
How can the TM develop a perforation? Do traumatic perfs or perfs due to disease heal better? Why? Do perfs in inferior or superior portion of the TM heal faster? Why?
The tympanic membrane can become perforated in several ways; Excessive pressure buildup during a middle-ear disorder may cause rupturing of the membrane. Sometimes, in response to infection, usually in the middle ear, the membrane may become necrosed (dead) and perforate. A frequent cause of perforation is direct trauma from a pointed object such as a cotton swab or hairpin. This may happen if patients are attempting to cleanse their own ears and either misjudge the length of the EAC or are jarred or startled while probing in it.
The tympanic membrane may also be perforated from sudden pressure in the external ear canal, as created by a hand clapped over the ear or an explosion. Rapid changes in external ear canal air pressure such as may be experienced in scuba diving, known as barotrauma, can also rupture the tympanic membrane. Because traumatic perforations alter what is essentially normal tissue, they tend to show spontaneous closure better than perforations resulting from disease. Perforations in the inferior portion of the tympanic membrane heal more rapidly than those in the superior portion because the normal epithelium migration is more active inferiorly. Placing a thin piece of cigarette paper over the perforation has encouraged the migration of tissue. Eustachian tube in children vs. adults
Children: horizontal and shorter, making the entrance of bacteria to the middle ear easier. The diameter of the tube is also smaller in children, thus making fluid drainage more difficult Adults: Enters the ear anteriorly at a 30 degree angle
Why must air pressure on both sides of the TM be equal?
The air pressure of the middle ear must match that of the external auditory canal to keep the pressure equal on both sides of the tympanic membrane to maximize its mobility and the passage of sound. The absorption of air by middle-ear tissues is the major reason for the need for a pressure-equalization system. The only way for this pressure equalization to be maintained is through the eustachian tube.
Smallest bone in the body
Stapes
To which window does the footplate of the stapes attach?
Footplate of the stapes occupies the space in the oval window
Purpose of ME muscles
ME muscles: Tensor Tympani and Stapedius, Contractions of these muscles serve as a protective function for the inner ear by stiffening the ossicular chain and attenuating loud, and potentially damaging, sounds that enter it. May also decrease loudness of sounds generated within the head (chewing or speaking)
Stapedius muscle:
responds to sound, Introduction of loud sounds in right ear causes both stapedius muscles to contract
Tensor Tympani muscle
responds to air in the EAC, changes in temp, or touch
In adults, the ET is normally kept closed by a spring mechanisms
Opened by action of four sets of muscles, Occurs during yawning, sneezing, swallowing, or when excessive air pressure is applied from the nose
What is otitis media (general) and why is it more common in children? Type of HL?
Otitis media is any infection of the mucous-membrane lining of the middle-ear cleft. Otitis media is more common in children than adults because their eustachian tubes are horizontal and shorter, making the entrance of bacteria to the middle ear easier. The diameter of the tube is also smaller in children, thus making fluid drainage more difficult. Causes conductive hearing loss
What is otosclerosis?
Disease of the bony labyrinth that causes a CHL (conductive hearing loss) when the new bone growth affects either the oval window or the round window. Affects the cochlea, SNHL or MHL occurs. Can be unilateral or bilateral Audiometric configuration ia generally flat, May have drop in BC thresholds at 2000 Hz (carhart's notch)
Vestibular mechanism includes which 3 systems?
Visual, proprioceptive, vestibular. Visual- provides direct information from surrounding objects on the orientation of the body. Proprioceptive- concerns somatosensory stimuli, received in tissue from supporting structures, such as the muscles and tendons of the body
Purpose of semi-circular canals? (Also: think about positioning/shape)
Arise from the utricle, They make a semicircular shape, Responsible for angular acceleration, Spinning in a circle
What is vertigo?
Loss of balance, spinning, When vestibular mechanisms become damaged or diseased
Fluid locations in the cochlea (endolymph/perilymph) and what fluids are high/low in (potassium/sodium)
Endolymph (apex, low frequencies)- high in potassium, low in sodium, Perilymph (base, high frequencies)- high in sodium, low in potassium
How many turns are in typical cochlea?
2.5
Stria Vascularis - Role?
Blood supply, nutrients and oxygen to the cochlea. It also produces endolymph, Blood supply and nerve supply enter the Organ of Corti by way of the modiolus, Modiolus is the central core of the cochlea around which it is wound (medial portion)
How many rows of OHCs and IHCs are in the cochlea?
On the fibrous basilar membrane are 3-5 parallel arrows of 12,000 to 15,000 outer hair cells and one row of 3,000 inner hair cells
Place Theory
Every tone that can be heard is assigned its own specific place within the cochlea. Think keys on the piano (specific pitch representation)
Location of frequencies in the cochlea (i.e., high frequencies in basal turn, low frequencies in apical turn)
Lowest frequencies to which the ear responds (about 20 Hz) are located at the atypical endSpacing between nerve fibers is not equal all along the vestibular mechanism
Fibers for frequencies between 2000 and 20,000 Hz (highest frequency to which the ear can response to AC sounds) lie from the midpoint off the BM to the basal end of the cochlea near the oval window. Fibers for frequencies < 2000 Hz are contained on the other half of the BM
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What did the discovery of OAEs (Otoacoustic Emissions) provide?
Discovered weak acoustic signal, probably generated by the motility of the OHC, Discovered the cochlea generates a sound of its own, Most common complaint from individuals with SNHL, Difficulty understanding speech (most common),
Presbycusis (general)
Age related hearing loss, causes alterations to the TM, ossicular chain, cochlear windows, central auditory system, general oxygen deficiency due to arteriosclerosis (thickening or hardening of membrane)
What is the Noise Notch?
Hearing poorest between 3000-6000 Hz recovering at 8000 Hz
What type of ear condition does Dr. Noud exhibit?
Tympanosclerosis
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