Ear Infections - Introduction

Introduction

The ear is the organ of hearing and balance. It has three parts: the outer, middle, and inner ear.

• The outer ear collects sound waves, which move through the ear canal to the tympanic membrane, commonly called the eardrum.
• The tympanic membrane, or ear drum, is lined with mucus. When incoming sound waves strike this membrane, it vibrates like a drum, and converts the sound waves into mechanical energy.
• This energy echoes through the middle ear. The middle ear is a complex structure filled with air and made of tiny bones. These bones vibrate to the rhythm of the eardrum and pass the sound waves on to the inner ear.
• The inner ear is filled with fluid. Here, hair-like structures stimulate nerves to change sound waves into electrochemical impulses that are carried to the brain, which senses these impulses as sounds.
• The inner ear also contains three semi-circular canals that function as the body's gyroscope, regulating balance.
• The Eustachian tube, an important structure in the ear, runs from the middle ear to the passages behind the nose and the upper part of the throat. This tube helps equalizes the air pressure in the middle ear to the outside air pressure. Problems here are primary factors in most cases of ear infection.

Ear Infections (Otitis Media) in Children

Acute Otitis Media (AOM). An inflammation in the middle ear is known as "otitis media." AOM is a middle ear infection caused by bacteria that traveled to middle ear from fluid build-up in the Eustachian tube. AOM may develop during or after a cold or the flu.

• Middle ear infections are extremely common in children, but are infrequent in adults.
• In children, ear infections often recur, particularly if they first develop in early infancy.

Otitis Media with Effusion (OME). This condition occurs when fluid, called an effusion, becomes trapped behind the eardrum in one or both ears, even when there is no infection. In chronic and severe cases, the fluid is very sticky and is commonly called "glue ear."

• It is usually not painful. Sometimes the only clue that it is present is a feeling of stuffiness in the ears, which can feel like "being under water."
• It may impair children's hearing.
• Children who are susceptible to OME can have frequent episodes for more than half of their first 3 years of life.
• Most episodes will resolve within 3 months, but 30 - 40% percent of children may have recurrent episodes. Only 5 - 10% of episodes last longer than 1 year.

Review Date: 03/02/2006
Reviewed By: Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital