Hard hearing

Hard hearing

Anatomy of the ear
Auditory pathway
1. Efferent Cochlear (Olivocochlear) Bundle
  1. is a crossed and uncrossed tract that arises from the superior olivary nucleus and projects to the hair cells of the organ of Corti. suppresses auditory nerve activity when stimulated
Physiology of hearing
1. Impedance matching
  1. Sound waves traveling through air must be converted into pressure waves in fluid.
    1. The acoustic impedance of fluid is much greater than that of air.
      1. The combination of the tympanic membrane and ossicles act as an impedance matching device in order to transfer the same frequency as the original sound waves.
2. Auditory transduction
  1. The hair cells are fixed tightly in the reticular lamina. The reticular lamina is supported by the rods of corti which are attached tightly to the basilar membrane
    1. When vibrating, the rods of corti, the basilar membrane and reticular lamina move as a rigid unit.
      1. Upward (or downward) movement of the basilar membrane rocks the reticular lamina upward and inward (or downward and outward) toward the modiolus.
        Hair cells bend toward the longer ones ➝ rapid movement of K+ from the surrounding Scala media fluid into the stereocilia ➝ Excitation
symptomatology
1. Ear pain causes
  1. Ear infection... Air pressure changes... Wax build up...Strep throat... Foreign object inside ear... Shampoo trapped in ear...Toothache
2. Light headedness vs Vertigo
3. Tinnitus
  1. Subjective:
    1. High pitched...Continuous or intermittent... In the affected ear... Only you hear it
    2. Objective:
      1. Heard by the examiner... Blood vessel or middle ear bone condition
  2. Causes
    1. Age...Loud noise... Wax blockage... Head & neck injuries... Meniere’s disease
Ear examination
1. Tuning fork ( rinne and weber )
2. Otoscope
3. Pure tone Audiometry
Choleosteatoma and aural polyp
1. What causes a cholesteatoma?
  1. Injury to the eardrum... Chronic middle ear infections... Eustachian tube dysfunction
2. Definition of aural polyp
  1. a growth in the outside (external) ear canal or middle ear. It may be attached to the eardrum (tympanic membrane), or it may grow from the middle ear space.
chronic suppurative otitis media (CSOM)
1. Causes:
  1. Acute otitis media cause persistent perforation. Ascending infection via Eustachian tube. Persistent mucoid otorrhea.
2. Types:
  1. Tubotympanic... Atticoantral
Otitis Media: Management and surgery
1. Ibuprofen or acetaminophen Topical benzocaine over 2
  1. High dose amoxicillin
  2. Tympanostomy Tubes
2. Gentamicin, Neomycin
Prognosis and complications of otitis media
1. Prognosis
  1. The severity of the symptoms and the age of the patient determines the likelihood of success of antibiotic treatment. Acute otitis media in children below the age of 2 has a poor prognosis. It is associated with an increased number of recurrences of acute otitis media, as well as the development of otitis media with effusion 6 months later in 35% of children. Acute otitis media in older age groups usually resolves on its own without antibiotic treatment.
2. Complications
  1. There are many complications of otitis media. They are classified as those that occur outside of the brain (extracranial) and those that occur within the brain (intracranial). These complications are extremely rare and usually occur in very young children, or those with serious medical conditions. Extracranial complications occur most commonly, and include mastoiditis, cholesteatoma and otitis media with perforation. Intracranial complications are less common, and include meningitis, brain abscess and lateral sinus thrombosis. In Australia, approximately 60% of extracranial and intracranial complications of otitis media occur in children.

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