Gain – the amount of dB that the sound has been increased.
Gain control – a device which allows the gain to be adjusted (such as volume control or potentiometer).
Gain reduction – used in multi-channel hearing aids to automatically lower the gain in a specific channel in order to control feedback.
Glue ear: most common in children where there is fluid collection behind the ear drum. Otitis media (Latin) is inflammation of the middle ear, or a middle ear infection. It occurs in the area between the tympanic membrane and the inner ear, including a duct known as the eustachian tube. It is one of the two most common causes of an earache – the other being otitis externa. Diseases other than ear infections can also cause ear pain, including cancers of any structure that shares nerve supply with the ear and shingles which can lead to herpes zoster oticus. Though painful, otitis media is not threatening and usually heals on its own within 2–6 weeks. Signs and symptoms
When the middle ear becomes acutely infected, pressure builds up behind the eardrum (tympanic membrane), frequently causing intense pain. It may result in bullous myringitis (myring means “eardrum”), which means that the tympanic membrane is blistered and inflamed.
In severe or untreated cases, the tympanic membrane may rupture, allowing the pus in the middle ear space to drain into the ear canal. If there is enough of it, this drainage may be obvious. Even though the rupture of the tympanic membrane suggests a highly painful and traumatic process, it is almost always associated with the dramatic relief of pressure and pain. In a simple case of acute otitis media in an otherwise healthy person, the body’s defenses are likely to resolve the infection and the ear drum nearly always heals.
Instead of the infection and eardrum perforation resolving, however, drainage from the middle ear can become a chronic condition. As long as there is active middle ear infection, the eardrum will not heal. The World Health Organization defines chronic suppurative otitis media (CSOM) as “a stage of ear disease in which there is chronic infection of the middle ear cleft, a non-intact tympanic membrane (i.e. perforated eardrum) and discharge (otorrhoea), for at least the preceding two weeks” (WHO 1998). (Notice WHO’s use of the term serous to denote a bacterial process, whereas the same term is generally used by ear physicians in the United States to denote simple fluid collection within the middle ear behind an intact eardrum. Chronic otitis media is the term used by most ear physicians worldwide to describe a chronically infected middle ear with eardrum perforation.)
Otitis media is most commonly caused by infection with viral, bacterial, or fungal pathogens. The most common bacterial pathogen is Streptococcus pneumoniae. Others include Pseudomonas aeruginosa, nontypeable Haemophilus influenzae, and Moraxella catarrhalis. Among older adolescents and young adults, the most common cause of ear infections is Haemophilus influenzae. Viruses such as respiratory syncytial virus (RSV) and those that cause the common cold may also result in otitis media by damaging the normal defenses of the epithelial cells in the upper respiratory tract.
A major risk factor for developing otitis media is Eustachian tube dysfunction, which leads to the ineffective clearing of bacteria from the middle ear.
The role of the anti-H. influenzae vaccine that children are regularly given is to prevent invasive disease such as meningitis and pneumonia. This vaccine is active only against strains of serotype b, which has been found to cause meningitis and pneumonia in children under five years, with children between 4 and 18 months the most susceptible. Isolates of serotype b rarely cause otitis media.
Susceptibility is heritable, though the specific genetic markers are still under investigation. Casselbrant et al. found in 2009 that the “best-supported linkage regions may contain susceptibility genes that influence the risk for recurrent/persistent OM. Plausible candidates in 17q12 include AP2B1, CCL5, and a cluster of other CCL genes, and in 10q22.3, SFTPA2.”
Typically, acute otitis media follows a cold: after a few days of a stuffy nose, the ear becomes involved and can cause severe pain. The pain will usually settle within a day or two, but can last over a week. Sometimes the ear drum ruptures, discharging pus from the ear, but the ruptured drum will usually heal rapidly.
Pathophyisiology progression of acute otitis media: the tissues surrounding the Eustachian tube swell due to an upper respiratory infection, allergies, or dysfunction of the tubes. The Eustachian tube remains blocked most of the time. The air present in the middle ear is slowly absorbed into the surrounding tissues. A strong negative pressure creates a vacuum in the middle ear, and eventually the vacuum reaches a point where fluid from the surrounding tissues accumulates in the middle ear. This is seen as a progression from a Type A tympanogram to a Type C to a Type B tympanogram. The fluid may become infected. It has been found that dormant bacteria behind the tympanic membrane (eardrum) multiply when the conditions are ideal, infecting the middle ear fluid.
Children younger than seven are much more prone to otitis media due to shorter Eustachian tubes, which are at a more horizontal angle than in the adult ear. They also have not developed the same resistance to viruses and bacteria as adults. Numerous studies have correlated the incidence in children with various factors such as nursing in infancy, bottle feeding when supine, parental smoking, diet, allergies, and automobile emissions; but the most obvious weakness of such studies is the inability to control the variable of exposure to viral agents during the studiesBreastfeeding for the first twelve months of life is associated with a reduction in the number, and duration of all OM infections. Pacifier use has been associated with more frequent episodes of AOM.
Acute otitis media is usually diagnosed via visualization of the tympanic membrane in combination with the appropriate clinical history. The use of a monocular otoscope and perhaps a tympanometer may not be able to distinguish bacterial versus viral etiology, especially if the canal is small and there is wax in the ear that obscures a clear view of the eardrum. Also, an upset child’s crying can cause the eardrum to look inflamed due to distension of the small blood vessels on it, mimicking the redness associated with otitis media.
The occurrence, duration, or severity of symptoms is not predictive of an ear infection in the absence of examination of the eardrum.
Otitis media has many degrees of severity, and various names are used to describe each. The terminology is sometimes confusing because of multiple terms being used to describe the same condition. A common misconception with ear infection is that sufferers think that a symptom is itchy ear. Although sufferers may feel discomfort, an itchy ear is not a symptom of ear infection.
Acute otitis media
Acute otitis media (AOM) is most often purely viral and self-limited, as it usually accompanies viral URI (upper respiratory infection). There is congestion of the ears and perhaps mild discomfort and popping, but the symptoms resolve with the underlying URI. If the middle ear, which is normally sterile, becomes contaminated with bacteria, pus and pressure in the middle ear can result, and this is called acute bacterial otitis media. Viral acute otitis media can lead to bacterial otitis media in a very short time, especially in children, but it usually does not. The individual with bacterial acute otitis media has the classic “earache”, pain that is more severe and continuous and is often accompanied by fever of 102 °F (39 °C) or more Bacterial cases may result in perforation of the ear drum, infection of the mastoid space (mastoiditis) and in very rare cases further spread to cause bacterial meningitis.
1st phase – exudative inflammation lasting 1–2 days, fever, rigors, meningism (occasionally in children), severe pain (worse at night), muffled noise in ear, deafness, sensitive mastoid process, ringing in ears (tinnitus)
2nd phase – resistance and demarcation lasting 3–8 days. Pus and middle ear exudate discharge spontaneously and afterwards pain and fever begin to decrease. This phase can be shortened with topical therapy.
3rd phase – healing phase lasting 2–4 weeks. Aural discharge dries up and hearing becomes normal.
Otitis media with effusion
Otitis media with effusion (OME), also called serous or secretory otitis media (SOM), is simply a collection of fluid that occurs within the middle ear space as a result of the negative pressure produced by altered Eustachian tube function. This can occur purely from a viral URI, with no pain or bacterial infection, or it can precede and/or follow acute bacterial otitis media. Fluid in the middle ear sometimes causes conductive hearing impairment, but only when it interferes with the normal vibration of the eardrum by sound waves. Over weeks and months, middle ear fluid can become very thick and glue-like (thus the name glue ear), which increases the likelihood of its causing conductive hearing impairment. Early-onset OME is associated with feeding while lying down and early entry into group child care, parental smoking, too short a period of breastfeeding and greater amounts of time spent in group child care increased the duration of OME in the first two years of life.
Chronic suppurative otitis media involves a perforation (hole) in the tympanic membrane and active bacterial infection within the middle ear space for several weeks or more. There may be enough pus that it drains to the outside of the ear (otorrhea), or the purulence may be minimal enough to only be seen on examination using a binocular microscope. This disease is much more common in persons with poor Eustachian tube function. Hearing impairment often accompanies this disease.
Adhesive otitis media has occurred when a thin retracted ear drum becomes sucked into the middle ear space and stuck, i.e. adherent, to the ossicles and other bones of the middle ear.
Pneumococcal conjugate vaccines when given during infancy decrease rates of acute otitis media by 6–7% and if implemented broadly would have a significant public health benefit. Evidence does not support zinc supplementation as an effort to reduce otitis rates except maybe in those with severe malnutrition such as marasmus. Long term antibiotics, while they decrease rates of infection during treatment, have an unknown effect on long term outcomes such as hearing loss. Certain factors such as season, allergy predisposition and presence of older siblings are known to be determinants of recurrent otitis media and persistent middle ear effusions (MEE). Previous history of recurrence, environmental exposure to tobacco smoke, use of daycare, and lack of breastfeeding have all been associated with increased risk of OM development, recurrence, and persistent MEE. Breastfeeding can reduce the rates of OM from 19% to 6% in children that were breastfed for at least one year. Reduction of risk factors in combination with medicinal or surgical methods are necessary to reduce the recurrence of OM and prevent persistent MEE.
Oral and topical analgesics are effective to treat the pain caused by otitis media. Oral agents include ibuprofen, paracetamol (acetaminophen), and narcotics. Topical agents shown to be effective include antipyrine and benzocaine ear drops. Decongestants and antihistamines, either nasal or oral, are not recommended due to the lack of benefit and concerns regarding side effects.
Deferring the start of antibiotics in acute otitis media for one to three days if pain is manageable with the above measures is currently recommended as: two out of three children with acute otitis media resolve without antibiotic treatment, no adverse effect on long term outcomes have been found when treatment is withheld, antibiotics have significant rates of potential side effects, and a recent trial has found increased rates of recurrence of otitis in children (aged six months to two years) who were treated with amoxicillin.
The first line antibiotic treatment, if warranted, is amoxicillin. If there is resistance, then amoxicillin-clavulanate or another penicillin derivative plus beta lactamase inhibitor is second line. While less than 7 days of antibiotics have less side effects more than seven days appear to be more effective. Among short-course antibiotics, long-acting azithromycin was found more likely to be successful than short-acting alternatives.
In chronic cases with effusions, insertion of tympanostomy tube (also called a “grommet”) into the eardrum reduces recurrence rates in the 6 months after placementbut have little effect on long term hearing. Thus tubes are recommended in those who have more than 3 episodes of acute otitis media in 6 month or 4 in a year associated with an effusion.
Complementary and alternative medicine is not recommended for otitis media with effusion because there is no evidence of benefit. An osteopathic manipulation technique called the Galbreath technique was evaluated in one randomized controlled clinical trial; one reviewer concluded that it was promising, but a 2010 evidence report found the evidence inconclusive.
Acute bacterial otitis media can cause pain that leads to sleepless nights for both children and parents, can cause eardrum perforations, not all of which heal, and can spread to cause mastoiditis and/or meningitis, brain abscess, and even death if a severe infection goes untreated long enough. High fever can occur and can cause febrile seizures. Appropriate antibiotic administration prevents most such complications.
Children with recurrent episodes of acute otitis media and those suffering from otitis media with effusion or chronic otitis media, have higher risks of developing conductive and sensorineural hearing loss.
This hearing loss is mainly due to fluid in the middle ear or rupture of the tympanic membrane. Prolonged duration of otitis media is associated with ossicular complications, and together with persistent tympanic membrane perforation contributes to the severity of both the disease and the hearing loss. When a cholesteatoma or granulation tissue is present in the middle ear, the degree of hearing loss and ossicular destruction is even greater.
Periods of conductive hearing loss from otitis media may have a detrimental effect on speech development in children. Recent studies have also linked otitis media to educational problems, attention disorders, and problems with social adaptation. Furthermore it has been demonstrated that patients suffering from otitis media have more depression/anxiety-related disorders compared to individuals with normal hearing. Once the infections resolve and hearing thresholds return to normal, childhood otitis media may still cause minor and irreversible damage to the middle ear and cochlea.
Otitis media per 100,000 inhabitants in 2004.
Otitis media is very common in childhood, with the average toddler having two to three episodes a year, almost always accompanied by a viral upper respiratory infection (URI), mostly the common cold. The rhinoviruses (nose viruses) that cause the common cold infect the eustachian tube that goes from the back of the nose to the middle ear, causing swelling and compromise of pressure equalization, which is one of the normal functions of the tube. The other main function is the lateral drainage of fluids from tissues on either side of the skull. It has to be remembered that the eustachian tube is only the width of three to four hairs in places along its length. It also changes its anatomical and physiological appearance during the early growth period of the child. In the newborn the tube is horizontal making it more difficult to drain naturally, and the surface of the tube is 100% cartilage, with a lining of lymphatic tissue which is an extension of the adenoidal tissue from the back of the nose. As the early years pass by, the superior (upper) part of the tube ossifies to bone but the lower remains the same. The angle of the tubes changes and descends to roughly a 45 degree angle increasing the downward flow of fluids. Individuals with Down syndrome (DS) anatomically have more severe curves to their tubes, hence DS children tend to have more grommet operations than other children. In general, the more severe and prolonged the compromise of eustachian tube function, the more severe the consequences are to the middle ear and its delicate structures. If a person is born with poor eustachian tube function, this greatly increases the likelihood of more frequent and severe episodes of otitis media. Progression to chronic otitis media is much more common in this group of people, who often have a family history of middle ear pathology.