Hearing Ipmairment

"The problems of deafness are deeper and more complex, if not more important, than those of blindness. Deafness is a much worse misfortune. For it means the loss of the most vital stimulus-- the sound of the voice that brings language, sets thoughts astir and keeps us in the intellectual company of man." 1 (emphasis added)

"…after a lifetime in silence and darkness that to be deaf is a greater affliction than to be blind... Hearing is the soul of knowledge and information of a high order. To be cut off from hearing is to be isolated indeeed  (emphasis added) Blindness cuts you off from things. But deafness cuts you off from people.

The Ability to Switch Off Most of us only have the opportunity to experience blindness, albeit temporarily, when we close our eyes. This enables us to appreciate in a very limited way what it must be like to lose our eyesight. And as with so many things in life, it is often only by losing something important that we can appreciate what it really means to us. So perhaps this ability to temporarily switch off our eyesight is the reason why so many people will rank vision above their hearing: they've had the opportunity to experience what they'd be missing.

If we could switch off our hearing temporarily – as we can our eyesight – it would very quickly give us an insight into what our hearing actually does for us. But because our ears are always open, our hearing forms a seamless connection to the world around us, and we are therefore prone to take it for granted. It would therefore be useful to remind ourselves what our hearing does for us.

Hearing in our life..! Communication and inter-action (Acquisition of normal language & speech skills). Receiving incoming messages as a listener. Helps to monitor once own speech as a speaker & speech of others as listener. Awareness and safety (Life Saving Signals). Enjoyment and emotions (Aural Recreation).

FUNCTIONS OF HUMAN EAR The human ear has TWO functions 1. Hearing – The human ear helps us in awareness, identification, discrimination and comprehension of sound stimuli. 2. Balancing - The semicircular canals help us maintaining the balance.

Parts of the Ear The human ear has three main parts Outer Ear Middle Ear Inner Ear

The outer ear The outer ear includes: auricle (cartilage covered by skin placed on opposite sides of the head) auditory canal (also called the ear canal) eardrum outer layer (also called the tympanic membrane)

Outer Ear Sound entering the outer ear travels through the middle ear and causes the eardrum and ossicles in the middle ear to vibrate. As it travels, it amplifies (becomes louder) and changes from air to liquid.

The Middle Ear The middle ear includes: Eardrum Cavity (also called the tympanic cavity) Ossicles (3 tiny bones that are attached) Malleus (or hammer) – long handle attached to the eardrum Incus (or anvil) – the bridge bone between the malleus and the stapes Stapes (or stirrup) – the footplate; the smallest bone in the body

The Inner Ear The inner ear includes: Oval window – connects the middle ear with the inner ear Semicircular ducts – filled with fluid; attached to cochlea and nerves; send information on balance and head position to the brain Cochlea – spiral-shaped organ of hearing; transforms sound into signals that get sent to the brain Auditory tube – drains fluid from the middle ear into the throat behind the nose

The Inner Ear cont… When the stapes moves, it pushes the oval window, which then moves the cochlea. The cochlea takes the fluid vibration of sounds from the surrounding semicircular ducts and translates them into signals that are sent to the brain by nerves like the vestibular nerve and cochlear nerve.

How Do We Hear? The brain and auditory system work together to control how we hear and how we balance ourselves.  The human ear is a complex organ and many scientists consider hearing to be the most complex of the human senses. Sound can be detected whether a person is on land, underwater or in the air.  Hearing is our ability to perceive sound by detecting vibrations that travel through our ears.  The main purpose of the ear is to turn sound waves from the air into electrical signals that are interpreted by the brain.

How Do We Hear? Cont… Sound: Rapid Air Waves Through the Ear Sound travels through the auricle and the auditory canal, a short tube that ends at the eardrum. Sound entering the outer ear travels through the middle ear and causes the eardrum and ossicles in the middle ear to vibrate.  As it travels, it amplifies (gets louder) and changes from air to liquid.   When the stapes moves, it pushes the oval window, which then moves the cochlea.  The cochlea takes the fluid vibration of sounds from the surrounding semicircular ducts, translates them into signals sent to the brain by nerves like the vestibular nerve and cochlear nerve. The brain translates the information into recognizable sound patterns. It is a complex process but it occurs in a split- second of time. 

How Do We Hear? Cont… Vocalized and Non-Vocalized Sound The human ear can detect different tones and loudness levels, which can help a person determine the direction of something (locate where the sound comes from), and helps to pick out specific sounds despite lots of background noise. Specifically, when someone is speaking, the sounds may be vocalized or non-vocalized.   Vocalized Sound: Vowels Vocalized sounds require a combination of air passing through the vocal cords and mouth shapes. When a person is speaking, the vocal cords are in vibration.  There is no closure of the throat or mouth with these sounds.  And, in almost all languages, words must contain at least one vowel.

How Do We Hear? Cont… Non-Vocalized Sound: Consonants Non-vocalized sounds are created strictly from mouth shapes. Lipreading is the process of visually detecting non-vocalized sounds.  When a person is speaking, the quietest sounds are those that are actually easier to detect visually.  When a person can see someone speak, they can understand him or her better. This combination of seeing what is heard contributes to a better sense of understanding.

How Do We Hear? Auditory Pathways The auditory pathways begin in the nerve fibers in the inner ear, where sound waves get converted into nerve impulses. These impulses then travel via the auditory nerve to the highest cerebral levels in the cortex of the brain.

Hearing Impairment ? ? ? Also called as Hearing Loss Definition 1.Hearing impairment may be defined as inability of a person to perform day to day communication with or without amplification. 2. According to PWD (Persons With Disability- Equal opportunities, protection of rights & full participation ) Act 1995 Hearing disability means loss of 60 decibels or more in the better ear in the conversational range of frequencies.

HEARING IMPAIRMENT

How we hear (a) Pinna (b) Ear canal (c) Eardrum (d) 3 smallest bones in the body (e) Cochlea (f) Auditory nerve

Onset of hearing loss Site of lesion Degree of hearing loss The hearing loss can be classified on the following basis: Onset of hearing loss Site of lesion Degree of hearing loss

Depending on the age of onset: Hearing loss/deafness in early childhood/since birth {Prelingual deafness} … Severe Speech & Language Deficits Deafness Acquired after speech & language development {Post-lingual Deafness} … Deterioration in speech because of difficulty in monitoring one’s own speech.

Depending on the site of lesion: Conductive hearing loss Sensori - neural hearing loss Mixed hearing loss Auditory processing disorder

Depending on the degree of hearing loss (ASHA) 0-15 Normal Hearing 16-25 Minimal hearing loss 26-40 Mild hearing loss 41-55 Moderate hearing loss 56-70 Moderately severe hearing loss 71-90 Severe hearing loss >90 Profound hearing loss

How we hear

TYPES OF HEARING IMPAIRMENT

Types of Hearing Impairment A loss of sensitivity Auditory nervous system pathology Hearing impairments are of two major types: • A loss of sensitivity--Characterized by a reduction in the sensitivity of the auditory system so that sounds need to be louder to be perceived. • Auditory nervous system pathology--May or may not include a change in sensitivity and results in reduced ability to hear suprathreshold sounds (ie. Speech) properly.

Important Terms Time of onset Congenital: present at birth Acquired: obtained after birth Adventitious: acquired after birth Other ways to describe a hearing loss: Time of onset: - congenital--present at birth - acquired--obtained after birth - adventitious---acquired after birth

Important Terms Time Course Acute: sudden onset/short duration Chronic: long duration Sudden: rapid onset Gradual: changes slowly over time Time course: - acute---of sudden onset and short duration - chronic---of long duration - sudden--rapid onset - gradual--changing slowly over time

Important Terms Time Course Temporary: limited duration Permanent: irreversible Progressive: advancing Fluctuating: changes in degree over time - temporary---limited duration - permanent---irreversible - progressive--advancing - fluctuating---changes in degree over time

Number of Ears Involved Important Terms Number of Ears Involved Unilateral: Just one Bilateral: Both Number of ears involved: - unilateral - bilateral

Hearing Sensitivity Loss “The ear is not as sensitive as normal in detecting sound” Types: Conductive Sensorineural Mixed HEARING SENSITIVITY LOSS

Conductive Hearing Loss “Caused by an abnormal reduction or attenuation of sound as it travels from the outer ear to the cochlea” • Conductive HL: caused by an abnormal reduction or attenuation of sound as it travels from the outer ear to the cochlea.

Conductive Hearing Loss Conductive hearing loss is characterized by an obstruction to air conduction that prevents the proper transmission of sound waves through the external auditory canal and/or the middle ear. It is marked by an almost equal loss of all frequencies. The auricle (pinna), external acoustic canal, tympanic membrane, or bones of the middle ear may be dysfunctional. Conductive hearing loss may be congenital or caused by trauma, severe otitis media, otosclerosis, or atresia of the ear canal. Some conductive hearing loss can be treated surgically with tympanoplasty or stapedectomy, and the use of hearing aids and assistive listening devices may also be beneficial.

Conductive Hearing Loss An audiogram of a bilateral conductive hearing loss

Conductive Hearing Loss Differences in the air-bone gap across different types of hearing loss

Sensorineural Hearing Loss “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: caused by a failure in the cochlea to transduce the sound from the middle ear (mechanical movement) to neural impulses in the VIII N. This results in a number of changes in cochlear processing including:

Sensorineural Hearing Loss 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 - 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

Sensorineural hearing loss occurs when the sensory receptors of the inner ear are dysfunctional. Sensorineural deafness is a lack of sound perception caused by a defect in the cochlea and/or the auditory division of the vestibulocochlear nerve. This type of hearing loss is more common than conductive hearing loss and is typically irreversible. It tends to be unevenly distributed, with greater loss at higher frequencies. Sensorineural hearing loss may result from congenital malformation of the inner ear, intense noise, trauma, viral infections, ototoxic drugs (e.g., cisplatin, salicylates, loop diuretics), fractures of the temporal bone, meningitis, ménière's disease, cochlear otosclerosis, aging (i.e., presbycusis), or genetic predisposition, either alone or in combination with environmental factors.

Many patients with sensorineural hearing loss can be habilitated or rehabilitated with the use of hearing aids. Patients with profound bilateral sensorineural hearing loss (e.g., at least 90 dB) who derive no benefit from conventional hearing aids may be appropriate candidates for the cochlear implant device, which bypasses the damaged structures of the cochlea and stimulates the function of the auditory nerve.

Sensorineural Hearing Loss An audiogram of a bilateral sensorineural hearing loss

Sensorineural Hearing Loss Differences in the air-bone gap across different types of hearing loss

Mixed Hearing Loss “A loss with both a conductive and sensorineural component.” • Mixed hearing loss: A loss with both a conductive and SN component.

Individuals with mixed hearing loss have both conductive and sensory dysfunction. Mixed hearing loss is due to disorders that can affect the middle and inner ear simultaneously, such as otosclerosis involving the ossicles and the cochlea, head trauma, middle ear tumors, and some inner ear malformations. Trauma resulting in temporal bone fractures may be associated with conductive, sensorineural, and mixed hearing loss.

Mixed Hearing Loss An audiogram of a bilateral mixed hearing loss

Mixed Hearing Loss Differences in the air-bone gap across different types of hearing loss

Auditory Processing Disorder (APD) is a deficit in neural processing of auditory stimuli that is not due to higher order language, cognitive, or related factors. However, APD may lead to or be associated with difficulties in higher order language, learning, and communication functions. This type of auditory problem affects more complex auditory processes, such as understanding speech when there is background noise. The results of hearing sensitivity and physiological tests, such as otoacoustic emissions (OAE) and auditory brainstem response (ABR) are normal in children with a central auditory disorder.

Types of Hearing Impairment A loss of sensitivity Auditory nervous system pathology

Auditory Nervous System Impairment Causes: Disease Disordered auditory nervous system development Caused by disease or disordered auditory nervous system development in children.

Auditory Nervous System Impairment Kinds: Retrocochlear disorders Central auditory processing disorders We tend to divide these impairments into two groups, depending on the nature of the underlying disorder. - retrocochlear disorder--when an impairment is caused by an active, measurable disease process (tumor) or from damage due to trauma or stroke. These are structural lesions of the nervous system. - CAPD--when an impairment is due to developmental disorder or delay or from diffuse changes (aging). These are functional lesions of the nervous system.

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

Degree of hearing loss Deaf/Deafness refers to a person who has a profound hearing loss and uses sign language. Hard of hearing refers to a person with a hearing loss who relies on residual hearing to communicate through speaking and lip-reading. Hearing impaired is a general term used to describe any deviation from normal hearing, whether permanent or fluctuating, and ranging from mild hearing loss to profound deafness. Residual hearing refers to the hearing that remains after a person has experienced a hearing loss. It is suggested that greater the hearing loss, the lesser the residual hearing.

Conductive hearing loss is characterized by an obstruction to air conduction that prevents the proper transmission of sound waves through the external auditory canal and/or the middle ear. It is marked by an almost equal loss of all frequencies. The auricle (pinna), external acoustic canal, tympanic membrane, or bones of the middle ear may be dysfunctional. Conductive hearing loss may be congenital or caused by trauma, severe otitis media, otosclerosis, neoplasms, or atresia of the ear canal. Some conductive hearing loss can be treated surgically with tympanoplasty or stapedectomy, and the use of hearing aids and assistive listening devices may also be beneficial