CSD 2230HUMAN COMMUNICATION

DISORDERS

Topic 5Hearing Disorders and Hearing

LossIntroduction to SoundTypes of Hearing Loss

Sound System

Source Any vibrating object

Medium Any gas, liquid or

solid

Receiver anything designed to

detect the vibrations within the medium originating from the source

A Common Sound System

Illustration of the distribution of molecules surrounding a source in an instant in time

Condensation and Rarefaction

Bands of condensation and rarefaction emanating from a sound source

Propagation of a Disturbance Through a

Medium

Notice that as time goes on, molecules farther from the source become affected by the disturbance.

Important Physical Characteristics of Sound

Frequency

Rate of pressure change as a function of time

Measured as cycles/sec or Hertz

The primary determiner of pitch

Intensity

Magnitude of the pressure change

Measured as the decibel (dB)

The primary determiner of loudness

Frequency and Intensity

Sounds a and c share the same frequency and sounds b and c share the same intensity

Loudness and Intensity

Here are some common sounds and their decibel equivalents

The Hearing System

Basic schematic diagram of the entire auditory system

Putting It All Together….

Types of Hearing Impairment

A loss of sensitivity

Auditory nervous system

pathology

Important Terms

ü Time of onset

Congenital: present at birth Acquired: obtained after

birth Adventitious: acquired after

birth

Important Terms

ü Time Course

Acute: sudden onset/short duration

Chronic: long duration Sudden: rapid onset Gradual: changes slowly over

time

Important Terms

ü Time Course

Temporary: limited duration Permanent: irreversible Progressive: advancing Fluctuating: changes in degree

over time

Important Terms

ü Number of Ears Involved

Unilateral: Just one

Bilateral: Both

Hearing Sensitivity Loss§ “The ear is not as sensitive as

normal in detecting sound”

Types:

Conductive Sensorineural Mixed

Conductive Hearing Loss

n “Caused by an abnormal reduction or attenuation of sound as it travels from the outer ear to the cochlea”

Sensorineural Hearing Loss

n “Caused by a failure in the cochlea to transduce the sound from the middle ear to neural impulses in the VIII Nerve.”

Sensorineural Hearing Loss

n Implications include:

A reduction in the sensitivity of the receptor cells in the cochlea

A reduction in the frequency resolving power of the cochlea

A reduction in the dynamic range of the system

Mixed Hearing Loss

n “A loss with both a conductive and sensorineural component.”

Types of Hearing Impairment

A loss of sensitivity

Auditory nervous system pathology

Auditory Nervous System Impairment

§ Causes:

Disease Disordered auditory nervous

system development

Auditory Nervous System Impairment

§ Kinds:

Retrocochlear disorders Central auditory processing

disorders

Auditory Nervous System Impairment

§ Auditory Characteristics:

Reduced ability to understand speech in a noise background

Problems understanding speech with reduced redundancy

Problems with localization and lateralization

Problems processing normal or altered temporal cues

Auditory Pathologies

Outer and middle ear disordersConductive pathologies

Cochlear disordersSensorineural pathologies

Central auditory disordersCentral auditory pathologies

Outer and Middle Ear Disorders

Structural defects due to embryologic malformations

Structural changes secondary to infection or trauma

Outer Ear Disorders

Microtia and atresia

Microtia

n “an abnormal smallness of the

auricle”

Atresia

n “the absence of an opening of the external canal”

Outer Ear Disorders

Microtia and atresia

Impacted cerumen

Perforation of the tympanic membrane

Outer Ear Disorders

Microtia and atresia Impacted cerumen Perforation of the tympanic

membrane Other

Middle Ear Disorders

Otitis Media Most common cause of transient conductive hearing loss in children

Inflamation of the middle ear

Caused by eustachian tube failure

Ways to Classify Otitis Media

With or without effusion Fluid type

Serous Suppurative Mucoid

Ways to Classify Otitis Media

With or without effusion Fluid type Duration

Acute Chronic Subacute Persistent Recurrent

Otitis Media Facts 76-95% of all kids will have one episode of OM by age 6 Prevalence is highest during the first two years of life 50% of all kids with one episode before their first

birthday will have 6 or more bouts within two years Most episodes occur in winter and spring Risk factors

Cleft palate Down syndrome Native Americans Urban poor Day care Secondhand smoke

Middle Ear Disorders Otitis media Otosclerosis

Otosclerosis

n “a bone disorder that affects the stapes and the bony labyrinth of the inner ear. The disease process is characterized by resorption of bone and new spongy formation around the stapes and oval window”

Otosclerosis Facts:

Hereditary Women are more likely

to develop the disorder

Usually bilateral

progressive

Middle Ear Disorders Otitis media Otosclerosis Cholesteatoma

Cholesteatoman “an epithelial

pocket that forms on the tympanic membrane. Once the pocket forms, the normal shedding of epithelium results in growth of the tumor”

Middle Ear Disorders Otitis media Otosclerosis Cholesteatoma Other

Physical trauma Barotrauma Middle ear tumors

Glomus tumor

Cochlear Disorders Syndromes and inherited disorders

Syndromic disorders Nonsyndromal disorders

Syndromes and Inherited Disorders Resulting in Sensorineural Hearing Loss

Types of Nonsyndromic Disorders

Dominant Dominant

progressive Dominant

progressive with adult onset

Recessive hereditary SNHL

X-linked

Cochlear Disorders

Syndromes and inherited disorders Noise induced hearing loss

Noise Induced Hearing Loss

n The degree of SNHL depends on

The intensity of the noise

The spectral composition of the

noise

The duration of exposure

Individual susceptibility

OSHA Damage Risk Criteria

Cochlear Disorders

Syndromes and inherited disorders Noise induced hearing loss Other trauma Infections

Infections Congenital

Cytomegalovirus HIV Rubella Syphilis Toxoplasmosis

Infections Acquired

Herpes Zooster Oticus (Chicken Pox) Mumps Syphilis

Cochlear Disorders

Syndromes and inherited disorders Noise induced hearing loss Other trauma Infections Ototoxicity

Ototoxicity Some antibiotics that are often ototoxic:

Amikacin Dihydrostreptomycin Garamycin Gentamicin Kanamycin Neomycin Netilmicin Streptomycin Tobramycin Viomycin

Ototoxicity Chemotherapy

Carboplatin Cisplatin

Drugs that cause reversible hearing loss Quinine Salicylates (aspirin) Loop diuretics

Drugs that may be harmful during pregnancy Accutane Dilantin Quinine Thalidomide

Cochlear Disorders

Syndromes and inherited disorders Noise induced hearing loss Other trauma Infections Ototoxicity Meniere’s Disease

Meniere’s Disease

Symptoms Tinnitus Vertigo Unilateral

sensorineural hearing loss

Cochlear Disorders

Syndromes and inherited disorders Noise induced hearing loss Other trauma Infections Ototoxicity Meniere’s Disease Presbycusis

Central Auditory Disorders

VIII Nerve tumors Other diseases of the VIII Nerve Neural disorders

Cochlear neuritis Diabetes mellitus

Brain Stem disorders Infarcts Gliomas Multiple sclerosis

Temporal Lobe disorders