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1.3.2 Conduction vs. Sensoneural Deafnness
Causes and Corrections
• Conductive hearing problems are those that disrupt the conduction of sound through the outer and middle ear.
Conductive Hearing Loss
• Affects hearing before the sound reaches the cochlea and the nerve receptors of the inner ear.
The Good News
• Conduction deafness is often temporary or curable
Causes of Conduction Deafness
• Otitis Media• Middle ear infection• Chronic suppurative otitis media –
1.Peferation of the tympanic membrane
2. Bacterial infection
l
“Glue Ear” Collection of fluid in the middle ear - (otitis media with effusion)
• Thick, sticky fluid collects behind the eardrum. • The fluid blocks the middle part of the ear and
can cause impaired hearing.• It usually affects children.
Interventions for “Glue Ear”
• Antibiotics• Ear Tubes (grommet)
Cerumen
• Ear Wax
Blockage of the outer ear, usually by wax.
Otosclerosis
• Ossicles of the middle ear harden and become less able to vibrate.
Otosclerosis
• Approximately one-third of all persons with impaired hearing have this condition.
• Hereditary• Damage to the ossicles, e.g. by serious infection or
head injury. • Perforated (pierced) eardrum, which can be caused
by an untreated ear infection (chronic suppurative otitis media), head injury or a blow to the ear, or from poking something in your ear.
Interventions
• Hearing aids -usually effective for conductive hearing loss.
http://www.nlm.nih.gov/medlineplus/ency/imagepages/8685.htm
Interventions
• Stapedectomy - top part of the stapes is removed. A laser beam is used to create a small hole in the footplate and a metal tube is inserted. A wire attached to the tube connects to the incus and transmits vibrations to the inner ear.
Sensorineural deafness
• Sensorineural deafness is decreased hearing or hearing loss that occurs from damage to the inner ear, the auditory nerve, or the brain.
• Sensorineural hearing loss is most often due to a loss of hair cells (sensory receptors in the inner ear).
• Sensorineural deafness can be present at birth (congenital), or it can develop later in life
• (SNHL) accounts for about 90% of all hearing loss
• Found in 23% of population older than 65 years of age
Causes of Sensorineural Deafness
• Presbycusis - hearing loss that gradually occurs in most individuals as they grow older
Presbycusis
• Aging
• Loud noises (acoustic trauma)-
http://www.healthpractical.com/tag/great-stressors
Duration
• The period of time the sound continues to exist.
• “Exposure to sound levels of 85 decibels, the equivalent of a lawn mower or food blender, may cause permanent hearing loss if endured for 8 hours per day for a prolonged period”
Healthy Cochlea
The cilia ( sensory hairs) appear normal
Damaged Cochlea
Loss of cilia as a result of Noise
Occupational Risk
• Some jobs carry a high risk for hearing loss, such as:
• Airline ground maintenance • Construction • Farming • Jobs involving loud music or machinery
Interventions:
• Hearing aid • Hearing aids will not restore normal hearing
or eliminate background noise. • Amplfies sound• Adjusting to a hearing aid is a gradual process
that involves learning to listen in a variety of environments and becoming accustomed to hearing different sounds.
Prevention
http://www.rainbowsafety.co.uk/warning-noise-levels--wear-ear-protection-sign-map-43-1438
Cochlear Implants
• Auditory understanding of the environment and helps in understanding speech.
• Does not reinstate or generate normal hearing.
• Compensates for damaged or non-working parts of the inner ear.
• Surgically implanted under the skin behind the ear, this device is made of four basic parts:
• microphone picks up sound from the environment
• speech processor translates the sounds picked up by the microphone into signals
• transmitter and receiver/stimulator receive these signals and convert them into electric impulses
• electrodes send these impulses to the brain.
Cholesteatoma
• Benign skin growth in the middle ear, causing deafness and vertigo
Intervention
• surgical removal of the cyst.
Acoustic neuroma
• A benign (non-cancerous) tumor affecting the auditory nerve
http://med.mui.ac.ir/slide/clinical/ent/AcousticNeuroma.jpg
Intervention
• Radiosurgery The use of ionizing radiation, either from an external source such as an x-ray machine or from an implant, to destroy cancerous or other diseased tissue.
http://www.health.wvu.edu/services/neurosurgery/gamma-knife/images/header.jpg
Tinnitus
• Ringing in the ears • Most tinnitus comes from damage to the
microscopic endings of the hearing nerve in the inner ear.
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