CAUSES OF HEARING IMPAIRMENT TOPIC 2 CAUSES OF HEARING IMPAIRMENT

Outer and Middle Ear Disorders Structural defects due to embryologic malformations Structural changes secondary to infection or trauma OUTER AND MIDDLE EAR DISORDERS These pathologies are commonly of two types - structural defects due to embryologic malformations - structural changes secondary to infection or trauma

Outer Ear Disorders Microtia and atresia • microtia and atresia--these are the most common congenital malformations of the auricle (pinna) and the external canal.

“an abnormal smallness of the auricle” Microtia “an abnormal smallness of the auricle”

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

Outer Ear Disorders Microtia and atresia Impacted cerumen Perforation of the tympanic membrane • Impacted Cerumen--very common cause of temporary conductive HL. Very treatable and preventable. HL that results is flat, conductive, and of varying degree.

Perforation of the TM • Perforation of the tympanic membrane--These usually occur either by trauma or secondary to OM. An example of the audiogram illustrating the flat, mild, conductive hearing loss that can occur with a perforated tympanic membrane

Outer Ear Disorders Microtia and atresia Impacted cerumen Perforation of the tympanic membrane Other • Other disorders of the outer ear---there are others, but not common and usually don’t affect hearing unless the auditory meatus is blocked

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 • Otitis Media--the most common cause of transient conductive HL in kids. OM is an inflammation of the middle ear. Caused by eustachian tube malfunction. When it is accompanied by middle ear effusion (fluid) it often causes a conductive HL.

Otitis Media Three examples of the usual characteristics of a conductive hearing loss arising from otitis media Ways to classify OM: - OM w/out effusion - fluid types: - duration:

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 76-95% of all kids will have one episode of OM by age 6. Prevalence is highest during the first 2 years, then declines after that. 50% of all kids with one episode before their first birthday will have 6 or more bouts within 2 years. Most episodes occur in winter and spring. Some populations are more prone to OM--kids with cleft palate or other craniofacial anomalies, Down syndrome, Native Americans, urban poor, day care kids, kids exposed to secondhand smoke.

Middle Ear Disorders Otitis media Otosclerosis

Otosclerosis “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--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

Cholesteatoma “an epithelial pocket that forms on the tympanic membrane. Once the pocket forms, the normal shedding of epithelium results in growth of the tumor” • Cholesteatoma--usually a secondary condition to OM. A cholesteatoma is an epithelial pocket that forms on the tympanic membrane. Once the pocket forms, the normal shedding of epithelium results in growth of the cholesteatoma, or tumor, which is capable of reabsorbing adjacent bone

Middle Ear Disorders Otitis media Otosclerosis Cholesteatoma Other Physical trauma • Other middle ear disorders - physical trauma - barotrauma - Middle ear tumors

Physical Trauma of the Middle Ear Here’s an example of an audiogram resulting from disarticulation of the ossicular chain

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 - syndromic disorders: occurring as part of a constellation of other medical and physical disorders that occur together. - nonsyndromic disorders: autosomal recessive or dominant genetic conditions in which there is no other significant feature besides HL

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 HL---very common cause of SNHL in adults. Right up there with presbycusis. This can happen with a one-time exposure to a very loud sound or long-time exposure to constant, softer sounds.

Noise Induced Hearing Loss The degree of SNHL depends on The intensity of the noise The spectral composition of the noise The duration of exposure Individual susceptibility Effects of noise are cumulative. How damaging sounds are to the cochlear are dependent on - the intensity of the sound. - the spectral composition of the sound - duration of exposure - individual susceptibility

OSHA Damage Risk Criteria

Noise Induced SNHL Noise notch Cummulative Progressive

Cochlear Disorders Syndromes and inherited disorders Noise induced hearing loss Other trauma Infections • Other trauma--physical trauma that causes a fracture of the temporal bone and leakage of endolymph.

Infections Congenital Cytomegalovirus HIV Rubella Syphilis Toxoplasmosis • Infections--we discussed congenital infections most commonly associated with SNHL that included: - cytomegalovirus - HIV - rubella - syphilis - toxoplasmosis

Infections Acquired Herpes Zooster Oticus (Chicken Pox) Mumps Syphilis Acquired infections: can be caused by viral or bacterial infections--and by fungi Some common acquired viral infections that can cause HL - Herpes Zoster Oticus--caused by a virus that also causes chicken pox. - Mumps----HL is rare but can occur related to encephalitis. - syphilis--occurs in the secondary or tertiary stage of the disease.

Cochlear Disorders Syndromes and inherited disorders Noise induced hearing loss Other trauma Infections Ototoxicity • Ototoxicity--certain drugs and chemicals are toxic to the cochlea

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 Thalidomide

Cochlear Disorders Syndromes and inherited disorders Noise induced hearing loss Other trauma Infections Ototoxicity Meniere’s Disease • Meniere’s Disease--endolymphatic hydrops. Triad of symptoms includes tinnitus, vertigo, and SNHL.

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 • Presbycusis--decline in thresholds due to aging. The leading contributor to HL in adults. Estimates are that 25-40% of those over 65 have this.

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 CNS DISORDERS The nature of the HL that accompanies CANS disorders vary as a function of location of the lesion--more peripheral, more apparent. Disruption in speech perception also gets more subtle as the lesion becomes more central. • VIII N. Tumors • Other tumors, cysts, and aneurysms can affect the VIII nerve and the cerebellopontine angle. • Neural disorders: - cochlear neuritis-- - diabetes mellitus • Brain Stem Disorders--these include infarcts, gliomas (fast growing tumors), and multiple sclerosis. • Temporal-Lobe Disorder