• Clinical science

Acute otitis media (Middle ear infection)

Abstract

Acute otitis media (AOM) is a viral or bacterial infection of the middle ear that is most commonly caused by Streptococcus pneumoniae. AOM is a common infection in children under the age of five years and it usually follows an upper respiratory tract (URT) infection. It is characterized by an acute onset of symptoms (e.g., otalgia, fever, anorexia) with signs of middle ear inflammation (e.g., bulging tympanic membrane, effusion). Mild unilateral infections can be managed without antibiotics, as they are often self-limiting. Bilateral AOM or severe symptoms are usually treated with oral amoxicillin. Tympanostomy and insertions of tympanostomy tubes is recommended in children with recurrent AOM. Complications are rare and occur mostly in immunosuppressed patients or in AOM due to highly virulent, drug-resistant bacteria. The most common complication is acute mastoiditis, but facial palsy, labyrinthitis, and in rare cases, even intracranial abscesses may also occur.

Epidemiology

  • Highest incidence between 6–24 months of age
    • ∼ 70% of children < 2 years old experience AOM at least once
    • Slightly higher incidence in boys
  • Immunization of infants against pneumococci has decreased the incidence of AOM
  • Most common cause of prescribing antibiotics in children < 5 years

References:[1][2]

Epidemiological data refers to the US, unless otherwise specified.

Etiology

Etiology

Risk Factors for AOM

  • Bottle feeding/formula feeding, inadequate breastfeeding
  • Pacifier use
  • Passive cigarette smoke
  • Children who attend day care centers
  • Poor socioeconomic status
  • Ethnicity: Native Americans have higher rates of acute and chronic ear infection compared to African Americans living in the same communities.

References:[1][3][4]

Pathophysiology

References:[1][2]

Clinical features

  • In infants
    • Irritability
    • Incessant crying
    • Refusal to feed (anorexia)
    • Repeatedly touching the affected ear
    • Fever and febrile seizures
    • Tender mastoid in late stages
  • In older children
    • Otalgia/earache, commonly with throbbing
    • Hearing loss in the affected ear
    • Fever
    • Tender mastoid in late stages

References:[1][2]

Diagnostics

  • Otoscopy: tympanic membrane (TM) evaluation
    • Early findings
      • Retracted and hypomobile
      • Loss of light reflex
    • Late findings
      • Cartwheel TM
      • Red bulging TM with loss of landmarks
      • Yellow spot on TM (antero-inferior quadrant of pars tensa) which indicates site of imminent rupture
      • If TM rupture → purulent/serosanguinous discharge in the external auditory canal
  • Tuning fork test: conductive hearing loss

References:[2][5]

Treatment

Ear drops are not effective in the treatment of otitis media and not every case of otitis media should be treated with antibiotics!

References:[2][6]

Complications

Complications are rare and are usually only seen in the following cases:

Intratemporal complications

Mastoiditis

  • Definition: inflammation of the mastoid air cells
  • Epidemiology: often occurs in children < 5 years
  • Pathophysiology: infection spreads from the middle ear cavity into the mastoid, which is a closed bony compartment → collection of pus under tension and hyperemic resorption of the bony walls → destruction of the air cells (coalescent mastoiditis) → mastoid becomes a pus-filled cavity (empyema mastoid)
  • Untreated, the pus may perforate through the bony walls and cause the following abscesses:
  • Clinical features
    • Persistence/recurrence of otalgia and fever after initial improvement
    • Ear discharge becomes profuse (discharge persisting > 3 weeks suggests mastoiditis).
    • Tender and edematous mastoid
    • Ear displaced laterally and forward
    • In advanced stages, the retroauricular sulcus is obliterated and the ear can be pushed forward.
  • Diagnostics
    • Otoscopy: The TM may be perforated.
    • First test: CT scan of the temporal bone
      • Opacification of the mastoid air cells
      • Erosion of the air cell walls
      • Pus in the mastoid cavity (areas of enhancement on CT)
    • X-ray of the mastoid
      • Early stage: The air cells appear cloudy and indistinct.
      • Advanced stage: A cavity can be seen in the mastoid.
  • Treatment

Labyrinthitis

Peripheral facial palsy

Petrositis

Intracranial complications (see extra information below)

Lateral/sigmoid sinus thrombosis

  • Etiology: Inflammatory destruction of the temporal bone overlying the dura → spread of inflammation and infection to the sinus → sinus thrombophlebitis → sinus thrombus formation
  • Clinical features:
    • Signs of raised ICP
    • Features of mastoiditis (see above)
  • Diagnostics
    • Contrast-enhanced CT scan
      • Shows a filling defect in the thrombosed venous sinus
      • Delta sign: triangular area with rim enhancement
    • Brain MRI
  • Treatment
    • IV antibiotics + mastoidectomy
    • Anticoagulant therapy: Only in cases where the thrombus is enlarging and involving the sagittal sinus

Otogenic meningitis

Otogenic abscess

  • Route of spread: direct spread of infection from the middle ear through the destroyed bone overlying the dura or through an emissary vein
  • Types
    • Epidural abscess
    • Subdural abscess
    • Cerebral abscess: The ipsilateral temporal lobe is the most common site (ipsilateral cerebellar abscess is second most common).
  • Clinical features
    • Persistent headache and otorrhea
    • Signs of raised ICP
    • Signs of meningeal irritation
    • Focal neurological deficits
  • Diagnostics: MRI/contrast-enhanced CT
  • Treatment: IV antibiotics + drainage + mastoidectomy

References:[7][8][9]

We list the most important complications. The selection is not exhaustive.