Insane in the (Tympanic) Membrane

TM anatomy!

Here’s a picture of my left tympanic membrane (TM).

Try to identify the following structures and quadrants before clicking on the answer. 

• Structures:
  • Umbo
  • Manubrium
  • Short process of the malleus
  • Pars tensa
  • Pars flaccida
• Quadrants:
  • Anterior superior
  • Anterior inferior
  • Posterior superior
  • Posterior inferior

The TM itself is divided into the pars tensa, which makes up the majority of the TM, and the pars flaccida. The pars flaccida may be the first place that bulging of the TM is seen due to increased pressure in the middle ear space. The pars flaccida is where movement is most readily appreciated when evaluating TM mobility with pneumatic otoscopy. 

The manubrium (Latin: handle) is the part of the malleus (Latin: hammer) that connects to the TM. The umbo (Latin: shield boss) is the most depressed part of the TM.

Note that the manubrium faces anteriorly. We know the pictured TM is on the left because the manubrium is pointing leftwards. 

Use the manubrium to divide the TM into quadrants, which can help us localize lesions on the TM, describe sites of perforation, etc. All we have to remember is that the manubrium points anteriorly in order to orient ourselves. Note that a normal light reflex typically appears in the anterior inferior (AI) quadrant.

OME vs AOM

Otitis media with effusion (OME) and acute otitis media (AOM) are not the same thing, and it’s important to recognize the difference for diagnosis and management. 

• OME = presence of middle ear effusion without signs of acute infection
• AOM = acute infection of middle ear fluid

The differences between OME and AOM can be subtle, but one key distinction is the presence of bulging (a hallmark of acute inflammation), which is a characteristic of AOM and not OME. 

• Key point: Clinicians should not diagnose AOM in children who do not have middle ear effusion (Grade B recommendation from the 2013 AAP guideline on the diagnosis and management of AOM)

Check out the following algorithm: 

• Mnemonic: Remember “COMA” for middle ear effusions: abnormal Color, Opacification, decreased Mobility, and Air-fluid levels 

OME often follows AOM. In fact, following AOM, 50% of children have evidence of OME after 1 month, 20% at 2 months, and 10% at 3 months. OME occurrence after AOM does not indicate antibiotic failure. Kids with OME lasting >3 months should be referred for a hearing test. 

Quiz Time!

Put your knowledge to the test by looking at the TMs below. Picture A is normal, but the remaining pictures are not. 

1. Describe each TM in terms of anatomy, color, opacification, air-fluid levels, peripheral blood vessels, bulging, etc.
2. Do you think the diagnosis is OME or AOM?

Take-home points!

• OME and AOM are distinct, clinical diagnoses.
• Bulging of the TM is a feature of AOM, not OME. 
• A middle ear effusion is characterized by a TM with abnormal color, opacification not due to scarring, decreased mobility, and/or air-fluid levels. 
• Clinicians should not diagnose AOM in children who do not have middle ear effusion.