What is myringitis?

Updated: Oct 19, 2018
  • Author: John Schweinfurth, MD; Chief Editor: Arlen D Meyers, MD, MBA  more...
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Answer

The extremely thin and delicate tympanic membrane (TM) is the first component of the middle ear conductive system. The TM is easily traumatized, and diseases of the TM deprive patients of their ability to work and to enjoy life.

Myringitis, or inflammation of the TM, may be accompanied by hearing impairment and a sensation of congestion and earache. After 3 weeks, acute myringitis becomes subacute and, within 3 months, chronic.

The TM lies across the end of the external auditory canal (EAC) and looks like a flattened cone with its apex pointed inward as seen in the image below. The diameter of the TM is about 8-10 millimeters. Its outer surface is slightly concave.

Tympanic membrane (TM) as continuation of the uppe Tympanic membrane (TM) as continuation of the upper wall of external auditory canal (EAC) with angle of incline up to 45 degrees on the border between middle ear and the EAC.

The edge of the membrane is thickened and attached to a groove in an incomplete ring of bone, the tympanic annulus, which almost encircles it and holds the membrane in place as seen in the image below.

Normal tympanic membrane. Pars tensa (PT), pars fl Normal tympanic membrane. Pars tensa (PT), pars flaccida (PF), light reflex (LR), fibrous ring (FR), umbo (Um), handle of malleus (HM), lateral process of malleus (Lpm), anterior plica (AP), posterior plica (PP).

In newborns, the angle of incline of the TM is more than 30° relative to the horizontal plane. In addition, the TM in newborns is thicker than in adults; consequently, in the newborn, examining the TM is sometimes difficult.

The uppermost small area of the membrane, where the ring is open, is under no tension; this part is known as the pars flaccida. The majority of the membrane is tightly stretched; this is called the pars tensa. The loose part of the TM, or the pars flaccida, borders on the pars tensa from above and is considerably smaller, about one-eighth the size of the pars tensa. See the image below.

Mirror display of a tympanic membrane surface on t Mirror display of a tympanic membrane surface on the polymeric masc from external acoustical canal of healthy man. Masc of tympanic membrane surface (MtmS).

The physiologic function of the TM involves conduction of sound to the middle ear through a system of small bones, the ossicles. The surface of the TM is approximately 25 times larger than that of the stapes footplate, with the resulting amplification of sound to 45 decibels, or 27 times ambient volume levels. At the same time, the TM forms a safe shield with the round window of the labyrinth against direct sound waves. This window is necessary for movement of the liquid in the cochlea, providing for transmission of the sound to the acoustic receptors in the organ of Corti. In addition, the TM protects the gentle mucosa of the middle ear from the external environment.


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