Behind the ear drum lies a hollow air-filled cavity known as the middle ear. It is shaped somewhat like a box and has six walls. Within it lies the auditory ossicles (middle ear bones) which transmits vibrations from the ear drum caused by sound to the hearing apparatus in the inner ear.
A hollow cavity connects the middle ear to the the area between the nasal cavity and the throat (nasopharynx). This cavity, known as the eustachian tube, allows air to enter the middle ear and equalizes the pressure on either side of the eardrum. However, it can also serve as an entry point for microorganisms which can then cause an infection of the middle ear.
What is otitis media?
Otitis media is the term for inflammation of the middle ear often associated with an infection. While most cases are seen in infants and children, otitis media can occur in any age group. The immature immune system, shorter and less developed eustachian tube and frequency of adenoiditis (infected adenoids) is the reason why otitis media is more frequently seen in children. Otitis media may arise sporadically, often with an upper respiratory tract infection, but may be recurrent or persistent if there is underlying anatomical abnormalities or pathology in the outer ear, middle ear, eustachian tube and/or nasopharynx.
Types of Otitis Media
Acute Otitis Media
An inflammation of the nose and throat with an upper respiratory tract infection may also involve the eustachian tube. The walls of the tube swell and the cavity is blocked to a large degree or completely. This allows for fluid to accumulate within the middle ear. Acute otitis media (AOM) is most commonly due to a viral infection although a bacterial infection may also be responsible. Often, the bacterial infection arises secondary to a viral upper respiratory tract infection. Acute otitis media tends to present with intense symptoms which can resolve on its own within a few days. However, treatment may be necessary particularly in bacterial infections.
Otitis Media with Effusion
Once the infection resolves in acute otitis media, the fluid that accumulates within the middle ear (effusion) should gradually drain out of the ear. Sometimes this does not occur and the fluid remains trapped within the middle ear despite the lack of an infection and associated symptoms. It is then known as otitis media with effusion (OME). This can persist for weeks or even months and slowly the fluid becomes thick and sticky, hence the term ‘glue ear’. This types of otitis media is also known as secretory otitis media. The function of the auditory ossicles (middle ear bones) may be affected to varying degrees which is evident as diminished hearing or even a loss of hearing (conductive).
Chronic otitis media
The middle ear, while separated from the outer ear by the eardrum, needs to have a clear channel of communication with the nasopharynx via the eustachian tube. This not only allows the ear pressure to equalize on either side of the eardrum but any fluid from the middle ear can drain out into the nasopharynx. Chronic otitis media (COM) tends to arise with other conditions or abnormalities of the middle or outer ear that predisposes the ear to recurrent infections. This may be seen with a chronic disturbance of the eustachian tube or a perforated eardrum although there may be other underlying conditions or risk factors. Chronic otitis media may be silent (asymptomatic) for long periods of time, with symptoms only noticed during an acute exacerbation and infection. In chronic suppurative otitis, the infection is ongoing for weeks and can cause significant damage of the middle ear.
Causes of Otitis Media
Inflammation in the middle ear is almost always due to an infection. The most common acute infections are viral in origin and linked to an upper respiratory tract. It may be caused by :
- Respiratory syncytial virus (RSV)
- Influenza viruses
- Parainfluenza viruses
Bacterial infections tend to arise as a superimposed infection following a viral upper respiratory tract infection. It may also arise without a preceding viral infection particularly with a perforated eardrum. Some of the bacteria more frequently involved includes :
- Streptococcus pneumoniae
- Haemophilus influenzae
- Moraxella catarrhalis
In infants under 6 weeks or age, other gram-negative bacilli may be a more likely cause of otitis media. With chronic suppurative otitis media, the more commonly seen bacteria include P.aeruginosa, S.aureus, Corynebacterium species, and Klebsiella pneumoniae.
Other conditions may be non-infectious in nature and cause localized inflammation and increase the chances of an infection setting in. These conditions and risk factors include :
- Family history, although this may be more likely associated with environmental factors.
- Allergic conditions particularly allergic rhinitis and asthma.
- Recurrent tonsillitis/adenoiditis
- Anatomical abnormalities of the eustachian tube, nasopharynx or outer and middle ear.
- Trauma resulting in a perforated eardrum.
- Immune deficiency seen with HIV, uncontrolled diabetes and related conditions. This also applies to the immature immune system of newborns and infants.
- Cigarette smoking and passive smoking
- Gastroesophageal reflux particularly in infants who are bottle-fed
- Crowding in day care centers or living quarters
Signs and Symptoms of Otitis Media
The clinical presentation of otitis media may vary in acute and chronic forms. The typical symptoms seen with acute otitis media or acute flareups of chronic otitis media includes :
- Ear pain
- Red bulging eardrum
- Difficulty hearing
- Poor balance
The signs and symptoms of a upper respiratory tract infection may also be present and this includes :
- Runny nose and sneezing
- Nasal congestion
- Sore throat
Since otitis media is more frequently seen in infants and children, parents and caregivers need to take note of the following :
- Constantly interfering with ear
- Irritable and crying frequently for no apparent reason
- Loss of appetite
- Unusual sleeping patterns
Vomiting and diarrhea are also frequently seen with acute otitis media in infants and children.
Chronic suppurative otitis media is often associated with a perforation of the eardrum. A foul smelling, purulent ear discharge may therefore also be evident. There may be the development of a polyp which can even protrude through the eardrum. If a cholesteatoma develops, there is the likelihood of other severe complications which may contribute to the overall clinical presentation.