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Myringotomy
Drainage of the middle ear cavity

The build up of fluid in the ear from infections has been known for at least 2500 years and has been described since the time of Hippocrates, the father of medicine. Fluid in the middle ear cavity may hamper conduction of sound, leading to partial deafness. Drainage of the ear cavity through an incision made in the ear drum (myringotomy) was first described in the 18th century as a means to cure deafness.

Anatomy and Physiology

  • The external auditory meatus (ear canal) develops as an ingrowth from the side of the face. The middle ear cavity develops as an outgrowth from the back of the throat (Figure 1). This connection from the middle ear to the throat remains as the Eustachian tube. The junction of the external ear canal and the middle ear cavity forms the tympanic membrane (ear drum)
Figure 1 - The tympanic membrane (ear drum) forms from an ingrowth from the skin of the face and an outgrowth from the throat starting as small buds and progressing towards each other. The facial ingrowth forms the external auditory meatus (canal) and the throat outgrowth forms the Eustachian tube. © T. Graves.
  • The middle ear is a very small cavity - 15 mm in width and height and 5 mm deep (Figure 2). Its function is to amplify and conduct sound waves from the external ear canal through the ear drum to the inner ear and then to the brain
Figure 2 - Anatomy of the ear. © T. Graves.
  • The middle ear contains 3 small bones called ossicles, which join with each other in a chain bridging from the ear drum to the inner ear on the inside wall of the cavity. The individual bones are named for their shape (in Latin) - malleus (hammer), incus (anvil) and stapes (stirrup). These bones serve to amplify the sound
  • The tympanic membrane is about 9mm x 9mm in size and about 0.075 mm thick. It vibrates to sound waves from the outside
  • The Eustachian tube is a connection from the front wall of the middle ear cavity to the nasopharynx (back of the throat). It is about 4 cm (1.75 inches) long. Its function is to equalize pressures on both sides of the ear drum and to drain any secretions from the middle ear. Swallowing opens up the tube and lets air from the throat reach the middle ear
  • The inner wall of the middle ear is close to the inner ear and brain as well as large blood vessels to the brain. Infections of the middle ear cavity can spread towards the brain and cause meningitis, an infection of the covering of the brain

Pathology

  • Inflammation of the middle ear cavity is called otitis media. It may be associated with fluid in the cavity. This is the leading cause of hearing loss in children
  • The most common cause is obstruction of the Eustachian tube, preventing drainage of the middle ear. This may be due to allergy or throat infection (sinusitis, tonsillitis, adenoids). This causes swelling of the throat and obstruction of the tube
  • Nasopharyngeal tumors must be suspected in adults
  • Trauma causing fractures to the temporal bone or base of skull can also cause obstruction of the Eustacian tube
  • Muscles in the throat of children with cleft palates (split upper lip and adjacent bone) that usually keep the Eustachian tube open may not function properly causing blockage of the tube

    Clinical Features

  • Otitis media may cause pain with a sensation of fullness of the ear
  • There may be a history of a respiratory infection a few days before onset of otitis media
  • Hearing may be impaired on the side of an otitis media because of the dampening of sound conduction in the middle ear
  • Patients may also suffer from a low grade fever

    Clinical Examination

  • Otoscopy is viewing of the tympanic membrane using a special short, lighted tube that is placed in the external ear canal. This may reveal the eardrum to be discolored and distended with fluid (sometimes a fluid level or bubbles may be seen) or contracted due to the vacuum from the Eustachian tube being blocked
  • Pneumatic otoscopy is an additional procedure in which air is blown through the otoscope to visualize movement of the eardrum. With the presence of fluid in the middle ear, the ear drum does not move as much as seen normally
  • A similar test is impedance tympanometry. A continuous vibration is delivered to the eardrum via the sealed tip of a special instrument and the reflection of this vibration is measured. A dampening of the vibration is characteristic of middle ear fluid
  • A tuning fork may be used to localize the ear with the greatest loss of hearing. It can also be used to confirm the diagnosis of deafness due to failure of sound to pass through the middle ear
  • The nose and throat are examined for any source of obstruction of the Eustachian tube especially in adults, where the cause of obstruction may be a tumor. This may be performed by use of a small mirror through the mouth to visualize the back of the throat (indirect pharyngoscopy), or by a flexible camera scope through the mouth (direct pharyngoscopy). The sinuses may also be visualized through this scope

    Treatment

  • Initial management of otitis media with effusion is usually not surgery
    1. Decongestants and antihistamines are prescribed for allergic swelling
    2. Antibiotics may be prescribed for swelling from an infection
  • Patient may be asked to perform the Valsalva maneuver. This consists of attempting to forcibly breathe out the nose with the nose and mouth closed. This causes the Eustachian tube to open and blows air into the tube to help drainage
  • In cases of chronic tonsillitis or adenoids these may need to be removed
  • A tumor is treated by surgery and/or radiation (X-ray therapy)

Indications for Surgery

  • Surgery may be necessary for recurrent attacks of otitis media. These attacks may cause permanent damage to the conducting ossicles of the middle ear
  • Otitis media that is resistant to non-surgical treatments
  • Retracted tympanic membrane due to persistent poor function of the Eustachian tube
  • Surgery is also recommended for children with cleft palate due to a known anatomic defect in drainage of the Eustachian tube predisposing them to recurrent infection

Surgery

  • Myringotomy may be performed without anesthesia as an office procedure in adults and cooperative older children. Sometimes a local anesthetic may be swabbed over the surface of the eardrum if necessary. In small children it may have to be done under general anesthesia to prevent movement
  • The eardrum is visualized with an otoscope. A small stab incision is made in the lower part of the drum (Figure 2A). Care is taken to avoid injuring the malleus, the ossicle lying against the eardrum). Fluid is drained through this incision. (Figure 2B) The incision usually heals by itself
Figure 2a - A small incision is made in the tympanic membrane being sure to avoid the ossicles. © T. GravesFigure 2b - Pus behind the membrane is removed by gentle suction. © T. Graves
  • In cases where the fluid is thick and does not drain easily or where prolonged drainage is required, a small tube (called a grommet) is inserted into this incision. (Figure 2C,D) This is a hollow tube, which serves to keep the incision open for continued drainage
Figure 2c - A small tube (grommet) is inserted into the incision. © T. Graves Figure 2d - The tube remains and allows continued drainage of the middle ear infection. © T. Graves
  • This grommet usually spontaneously extrudes itself after a few months or can be easily removed
  • Cotton may be placed in the ear canal to absorb drainage. The drainage may be tinged with blood for a few days

Complications

  • Tympanosclerosis - scarring of the tympanic membrane
  • Perforation of the tympanic membrane after the extrusion of the tube
  • Injury to the conducting bones (ossicles) in the ear may cause permanent hearing deficit
  • Injury to nerve tissue near the inner wall of the middle ear cavity

Care After Discharge

  • A child can eat whatever is tolerated and fluids should be encouraged
  • Children are encouraged to rest for the first day. Adults can usually resume normal activities
  • Pain is usually controlled with mild pain medication
  • If there is fluid in the ear, eardrops may be prescribed to prevent blockage of the grommet
  • The ear should be kept dry for the first two weeks. When bathing a cotton ball with petroleum jelly (Vaseline) may be placed in the ear. For swimming, a special earplug may be fitted to keep the ear dry
  • If there is persistent drainage from the ear for over a few days or if there is fever, chills, pain or irritability, the surgeon should be called