Nature & Etiology of Hearing Loss Flashcards
3-4 months- development
Babies will turn their head to sound & respond to their mothers voice more than anything else
6 months
infants can localize soft speech normal hearing babies at this age have better hearing than adults
air cionduction
when sound is carried through the medium of air:
sound that hit the TM –> causes ossicles to move –> causes fluids of the inner ear to move –> movement causes vibrations of the basilar membrane –> hair cells supplied by the acoustic nerve respond to the vibrations & carried to the brain via electric impulses
bone conduction
the larger bones of the skull conduct the sounds as well as the ossicles. the bones vibrate in response to airborne sound waves causing the inner ear fluids to vibrate
Risk factors for hearing loss
anatomic malformations in the face/ head/ neck, maternal history of alcohol/ drug use, certain maternal diseases like rubella or syphilis during pregnancy, genetic predispositions
Slight Hearing loss
16-25 dB HL
Mild Hearing Loss
26-40 dB HL
Moderate Hearing Loss
41-55 dB HL
Moderately Sever Hearing Loss
56-70 dB HL
Severe Hearing Loss
71-90 dB HL
Profound Hearing Loss
91+ dB HL
Deaf
Children/Adults cannot hear conversational speech under normal circumstances
Conductive Hearing Loss
- damage to the middle ear leading to impaired ability to conduct sound- pure conductive hearing loss means inner ear, acoustic nerve, and auditory centers of the brain are all working normally
- CONDUCTIVE HEARING LOSS IS NEVER PROFOUND EVEN WHEN OSSICLES ARE NOT WORKING BECAUSE SKULL BONES CAN STILL CONDUCT SOUND
- PEOPLE WITH CONDUCTIVE HEARING LOSS WILL TYPICALLY SPEAK SOFTLY BECAUSE THEY CAN HEAR THEMSELVES
Causes Conductive Hearing Loss
abnormalities in the EAM, TM, or ossicular chain in middle ear, birth defects, diseases, foreign bodies, bony growths, tumors, otosclerosis
Aural Atresia
external ear canal in completely closed. commonly associated with microtia which is a small/deformed pinna.
Stenosis
results in extremely narrow EAC- most sound waves will not strike the TM
External Otitis
infection of the skin of the external auditory canal which causes swelling, sound transmission is reduced
Otitis Media
aka middle ear effusion an ear infection if the middle ear often associated with upper respiratory infection and eustachian tube dysfunction
-typically causes a conductive hearing loss of 20-35 dB HL
Otosclerosis
condition characterized by new spongy growth in the stapes footplate causing the stapes to become rigid which means the footplate cannot go into the oval window enough to create necessary pressure waves
Carthart’s Notch
telltale sign of otosclerosis in an audiogram characterized by reduced bone-conduction sensitivity predominantly at 2000 Hz
Sensorineural Hearing Loss
damage to the hair cells of the cochlea (sensori) or the acoustic nerve (neutral) prevents the brain from receiving the neural impulses of the sound which causes PERMANENT damage because those pieces cannot be repaired
- People with this type of hearing loss will speak LOUDLY because there is air and bone conduction loss so they cannot hear themselves
- higher frequencies tend to be more effected than lower frequencies
STORCH
acronym for the major causes of hearing loss in fetuses
Syphilis
Toxoplamosis- disease transmitted through the placenta when mother contacts cat feces or raw eggs/meat
Rubella- German measles
Cytomegalovirus- herpes-type virus is the most common cause of viral hearing loss
Herpes Simplex- transmitted from mother to fetus
Acoustic Neuroma
tumor that can develop on the acoustic nerve and cause sensorineural hearing loss by slowing down nerve conduction of sound impulses to brain
Presbycusis
“old ears” sensorineural type hearing loss associated with normal aging
Meniere’s disease
disease that causes fluctuating hearing loss in normally typical adults
-caused by excessive endolymphic fluid pressure in the membranous labyrinth which causes Reissner’s membrane to become distended
Mixed Hearing Loss
the middle and the inner ear are not functioning properly caused by any combination of the sensorineural and conductive hearing losses
Central Auditory Processing
the effectiveness and efficiency with which the central nervous system processes auditory information
-difficulty taking spoken information and ad interpreting it to make it meaningful
Peripheral Hearing Problems
result from problems in the outer, middle, or inner ear (excluding the auditory nerve)
Central Auditory Disorders
refers to hearing losses due to disrupted sound transmission between the brainstem and the cerebrum as a result of damage/malformation
- the temporal cortex may receive incorrect information OR the person may process information incorrectly
Causes CAP disorders
tumors, TBI, HIV, asphyxia during birth, genetic disorders, infections like meningitis, metabolic disturbances, cerebrovascular disorders, drug/chemical induces disorders, Alzheimer’s disease, multiple sclerosis or other demyelinating diseases
Testing for CAPD
people with CAPD do not have significant peripheral hearing loss. they may do well on speech recognition tests in quiet environments and in pure tone audiometry
Dichotic testing
listener must decipher a a different message in each are presented simultaneously- CAPD patients will have a lot of difficulty with this
Retrocochlear Disorders
damage to the nerve fibers along the ascending auditory pathways from the internal auditory meatus to the cortex
- typically consist of pathology involving the cerebellopontine angle or cranial nerve VIII
- typically caused by unilateral tumors (acoustic neuromas) audiogram shows unilateral high frequency hearing loss
- typically accompanied by alterations in facial sensation and movement because of facial and trigeminal nerve involvement- possible headache in ear region
