Air conduction
sound waves move through the air in the external auditory canal, hit the tympanic membrane (TM) and cause the tympanic membrane to move.
- 3 bones in the middle ear (the malleus, the incus, and the stapes) are connected to the TM. When the TM moves, it is transmitted to the bone...
air conduction sound waves move through the air in the external auditory canal
hit the tympanic membrane tm and cause the tympanic membrane to move 3 bones in the middle ear the malleus
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Air conduction - sound waves move through the air in the external auditory canal, hit the
tympanic membrane (TM) and cause the tympanic membrane to move.
- 3 bones in the middle ear (the malleus, the incus, and the stapes) are connected to
the TM. When the TM moves, it is transmitted to the bones. These movements cause
pressure waves in the fluid-filled inner ear.
- The cochlea in the inner ear is surrounded by fluid and contains multiple small hairs.
Pressure waves in the fluid cause the hairs to move stimulating the auditory nerve.
Different frequencies of noises stimulate different hairs on the cochlea, which translate
to the sensation of sounds of different pitch.
Bone conduction - occurs when a sound wave or other source of vibration causes the
bones of the skull to vibrate. These vibrations are transmitted to the fluid surrounding
the cochlea and hearing results.
2 types of hearing loss - Conductive, sensorineural
conductive hearing loss - - results from physical problems with the movement of the
sound wave through the ear
a. obstructed external ear canal - cerumen build-up, hematoma, or foreign body
b. perforated tympanic membrane - caused by direct trauma such as a finger or cotton
swab, otitis media, or explosions
c. dislocated ossicle (malleus, incus, or stapes) - usually from trauma to the ear
d. serous otitis media - middle ear infection
e. otitis externa - infection of the ear canal that causes it to swell
sensorineural hearing loss - - causes are from damage to the hair cells or nerves that
sense sound waves.
a. acoustic trauma - prolonged exposure to loud noises causes the hair cells on the
cochlea to become less sensitive.
b. barotrauma (pressure trauma) or ear squeeze - usually in divers
c. head trauma - A fracture of the temporal bone can disrupt the nerves of the auditory
system
d. ototoxic drugs - Certain drugs can affect hearing by damaging the nerves involved in
hearing. Usually this occurs when large or toxic doses are used but may also occur with
lower doses. Examples include:
i. antibiotics including aminoglycosides (gentamicin, vancomycin), erythromycins, and
minocycline
ii. diuretics including furosemide and ethacrynic acid
iii. salicylates (aspirin) and nonsteroidal anti-inflammatories (NSAIDs) such as
ibuprofen and naproxen
iv. antineoplastics (cancer drugs)
e. vascular diseases including sickle cell disease, diabetes, leukemia, polycythemia,
and diseases in which excessive blood clotting occurs.
, f. children and adults with kidney problems are more susceptible to sensorineural
hearing loss.
g. Meniere's disease - A disease that affects hearing and balance and is usually
associated with tinnitus. It has a gradual onset and often progresses to deafness and
severe vertigo. The cause is unknown.
h. acoustic neuroma - A tumor in the auditory nerve. Usually associated with ringing in
the ears.
i. infections - mumps, measles, influenza, herpes, mono, syphilis, meningitis
j. aging
Tinnitus - - not a disease, but rather a symptom, a marker for other conditions
- of the 10% of pts with some type of ear problem, 85% have tinnitus
- perception of sound in absence of an acoustic stimulus
- mb buzzing, ringing, roaring, whistling, hissing or more complex sounds
- mb intermittent, continuous, pulsatile
History:
may be a sx of nearly all ear problems - noise exposure, head trauma, hearing
problems, dizziness, loss of balance, recent dental problems, bruxism, stress, ototoxic
med., smoking, caffeine
Physical Exam:
cranial N function and hearing
carotid artery bruits? HTN? recent dental work? signs of bruxism? myofascial spasms?
paraspinal and SCM muscles, TMJ
Tinnitus etiology - Outer ear: cerumen or foreign objects in external ear canal, external
ear canal tumors, TM
perforations, and cholesteatoma
Middle ear: otosclerosis, ossicular chain discontinuity, ossicular chain fixation, and
ossicular necrosis
Inner ear: cochlear hydrops, cochlear otosclerosis, perilymph fistulas, noise damage,
congenital malformations, vestibular schwannomas, presbycusis, allergic
reactions, bacterial infections, viral infections, ototoxic medications or chemical agents,
meningiomas, and atrophy
Systemic: hyperlipidemia, allergies, diabetes, hypertension, hypotension, syphilis, and
cardiovascular, endocrine, and metabolic diseases
Tinnitus secondary to temporomandibular joint (TMJ) disorders, cervical injuries,
obesity, menses, stress, dietary deficiencies, and intake of stimulants such as
nicotine and caffeine have been noted by tinnitus patients.
Subjective tinnitus - audible only to pt. - may be neurological, vascular, Musculo-skeletal
or idiopathic, emotional - what do you not want to hear?
pathophysiology of irreversible tinnitus suggests damage to the fine hair cells of the
inner ear causes them to remain in a constant state of irritation. Thus, stimulation of
aeroacoustics impulses is random and spontaneous Vs. a direct consequence of sound
waves. The random impulses are interpreted as noise, usually perceived as high
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