BIO Pathophysiology Ear Hearing Impairment Disorders Hearing

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BIO Pathophysiology Ear Hearing Impairment Disorders Hearing Powered By Docstoc
					1   BIO 240
    Pathophysiology I
    Altered Senses
    Chapter 46
    Dr. Brian Sailer
2   Ear
    • External ear - protection and access to sound
    • Middle ear - transmit sound energy from air to fluids of middle ear
       – Ossicles - malleus, incus, stapes
    • Inner ear - oval window, cochlea, semicircular canals
       – Actual hearing - sound impusles to nervous impulses
       – Balance and equilibrium
    • Balance - equilibrium - semicircular canals and vestibule
    • Vertigo - common symptom of vestibular disorders
        – Sense of motion wo/ movement or exaggerated sense

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6   Hearing Impairment Disorders
    • Conductive hearing impairment - when sound cannot reach cochlea
        – Decreased sound sensitivity
        – Obstruction, mass loading, stiffness effect, discontinuity
    • Loss due to cerumen impaction and foreign body occlusion
        – Cerumen impaction most common

7   Hearing Impairment Disorders
    • Otosclerosis - progressive conductive sensoineural or mixed hearing impairment
        –   Often caused by stapedial fixation
        –   Bony lesions on ossicles - decrease sound transmission
        –   Usually familial
        –   Also due to pregnancy, viral infection, measles
        –   Surgical repair

8   Hearing Impairment Disorders
    • Sensorineural hearing impairment
        –   Hearing mechanism disturbed in inner ear
        –   Either cochlea or vestibulocochlear nerve
        –   Multiple causes
        –   Loss by ototoxic medications
        –   Loss by trauma
        –   Presbycusis
        –   Meniere disease




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9    Sensorineural hearing impairment

     • Ototoxic medications - aminoglycoside antibiotics, salicylates, quinine, antimalarials, chemo
       drugs
         – Affect hair cells of cochlea
         – Normally after removal of drug
     • Trauma - common - repeated lound sound
         – Multiple causes - all over 85 dB
         – Severe cases - damage to organ of Corti
         – Two phases:
              • Temporary threshold shift
              • Permanent with no return after temporary shift

10   Sensorineural hearing impairment

     • Presbycusis - sensorineural hearing loss in elderly
         – Gradual onset - bilateral - high pitches affected
         – Can progress to other tones
         – Four categories:
              •   Sensory
              •   Neural
              •   Metabolic
              •   Mechanical

11   Sensorineural hearing impairment

     • Meniere Disease - excessive endolymph in membranous labyrinth
         –   Scala media distends and membrane ruptures
         –   Neural ends organs in cochlea degenerate
         –   Allergies, infections, head trauma, metabolic disorders, stress
         –   Tinnitus, fluctuating hearing loss, vertigo, sensation of ear fullness

12   Otitis Media
     •   Inflammation of middle ear
     •   Common cause - misfunction of Eustachian tube - presence of effusion
     •   Viral or bacterial infection
     •   Acute - sudden onset associated with RTI
     •   Chronic - > 12 wks
         – Irreversible damage results
         – Normally develops from unresolved acute

13   Vision
     • Review eye structures and visual pathways on own
     • General manifestations of visual impairment
         – Any time during life
         – Affect daily living




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          – Clues: squinting, closing one eye, tilting of head, redness of eye, excessive tearing, eye rubbing, floaters,
            headaches, eye pain

14   Errors of refraction
     • Normally need a clear image focused on retina for good vision
          – Brain can’t correct an unsharp image
     •   Myopia - eye elongated, images focuses in front of retina - nearsightedness
     •   Hyperopis - eye shorter than normal - focuses behind retina - farsightedness
     •   Presbyopia - loss of accommodative capacity
     •   Astigmatism - irregularity in curvature of cornea or lens

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16   Age-Related Disorders
     • Strabismus - squint or cross-eyedness
          – Lack of fusion of the eyes
          – Eyes appear misaligned
          – Treated with occlusion therapy
     • Amblyopia - poor vision with optical correction
          – Altered visual development - normal nerve pathways
     • Cataracts - clouding or change in opacity of lens
          – Painless blurring of visual and loss of sight
          – Many causes

17   Retinopathy
     • Retinal detachment - spontaneous or secondary to trauma
          – Eye tumors, myopia, cataract extraction
          – Allows vitreous fluid behind retina - detachment progresses
          – Progressive loss of vision

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19   Retinopathy
     • Diabetic retinopathy - disease of vasculature of retina
          – Lack of O2 and nutrients cause hypoxia & ischemia
          – Two categories:
              • Non-proliferative - retinal veins dilated - microaneurysms develop
              • Proliferative - production of abnormal, new blood vessels caused by ischemia
          – Symptoms: blurred, darkened and distorted vision
              • Fluctuate in severity

20   Retinopathy
     • Age related macular degeneration
          – Leading cause of permanent vision loss
          – Unknown cause - progressive bilateral macular deterioration with central vision loss
          – Two subgroups:
              • Dry (atrophic) - most common
                  – Degeneration of outer retina, pigmented layer and choroids
                  – Cellualar debris accumulates under retina
              • Wet (exudative) - more rapid loss
                  – Severe visual disruption
                  – Collection of subretinal fluid causes retinal detachment




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21   Glaucoma
     • Increased intraocular pressure with progressive loss of vision
     • Decreased retinal blood flow
        – Retinal degeneration and loss of vision
     • Open angle - bilateral and genetic
        – Insidious onset - gradual peripheral vision loss
     • Closed angle - abnormality of angle between pupil and lateral cornea
        – Narrow angle blocks aqueous humor outflow when pupil is dilated
        – Rapid - emergency

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23   Visual Field Deficits
     • Caused by changes in eye itself or ..
        – Tumors, vascular lesions, demyelinating lesion, visual cortex problems
     • Not always total vision loss
     • Monocular field loss - disease of retina or optic nerve
     • Bilateral - hemianopsia (loss of 1/2 of each visual field)
24   Smell and Taste
     • Senses that allow separation of noxious and lethal agents from desirable
     • Olfactory disorders - loss or reduction to distortions and olfactory hallucinations
     • Common - diminished from smoking and congestion
        – Also - head trauma, tumors, aneurysms, epilepsy, psychiatric disorders
     • Gustatory senses decreased by…
        – Smoking, dryness of tongue, medications, flu like illnesses, lesions on thalamus




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