Chronic Suppurative Otitis Media (CSOM)
UpToDate Literature review current through: Nov 2014
INTRODUCTION — Chronic suppurative otitis media (CSOM) is the most common childhood infectious disease worldwide and is the most common cause of hearing impairment in the developing world, although it is infrequently seen in the developed world . It is characterized by drainage from the middle ear for at least two weeks and is associated with a tympanic membrane (TM) perforation that is usually painless [2,3]. The otorrhea may be persistent or intermittent. CSOM is usually preceded by an episode of acute infection.
The epidemiology, pathogenesis, clinical features, diagnosis, and management of CSOM are reviewed here. Acute otitis media (AOM) and otitis media with effusion in children and acute and chronic otitis media in adults are reviewed separately.
EPIDEMIOLOGY — CSOM is uncommon in the developed world, with an prevalence of less than 1 percent in the United States , for example, but is seen more frequently in the developing world, with an prevalence ranging from 6 to 46 percent in other geographic areas and populations [4-6]. One theory regarding the higher prevalence in developing countries is that the cost of treatment is prohibitive. In a Nigerian study, the cost of CSOM treatment per patient per year amounted to more than the national monthly minimum wage . Public education and awareness in developing countries are also an issue. In one study of 203 mothers of children with CSOM living in two slums in Bangladesh, 65 percent were aware of the disease and sequelae, but only 40 percent had knowledge about the treatment .
CSOM typically occurs in the young child. About 60 percent of children were affected by 6 months of age in a Nigerian study , 18 months of age in a study from the Solomon Islands , and 24 months of age in an Ethiopian study . The mean age of onset of CSOM was about 11 months in a prospective two-year study of 465 children aged zero to four years in an Inuit population in Greenland . In contrast, a South Indian study found that preschool children (age 2 to 5 years) were equally as likely as school-age children (age 6 to 10 years) to be affected by the disease .
Most studies have found that males and females are equally affected, although some have found a male predominance [10-12]. In one study, the "simple form" occurred in both sexes equally, but the cholesteatomatous form was more common among males .
In nearly all studies, a unilateral preponderance is not seen. The reported frequency of bilateral disease ranges from 27 to 55 percent [5,8].
Risk factors — An increased incidence of CSOM is seen in children with a history of multiple episodes of acute otitis media (AOM) [14,15], early otitis media (defined as otitis media occurring in the first few months of life) , and chronic secretory otitis media . Risk factors for CSOM represent a combination of common risk factors for AOM as well as factors associated with low socioeconomic status and inadequate healthcare . These include:
●Living in crowded conditions [14,15]
●Living in a large family [6,14,15]
●Daycare attendance [6,14,15]
●Low parental education level [14,19]
●Poor nutrition and lower levels of zinc, selenium, calcium, and vitamin A [5,10,20,21]
●Passive smoke exposure 
●History of tympanostomy tubes 
●Frequent upper respiratory tract infections [6,10,14] and nasopharyngitis 
●Infectious and chronic diseases, such as measles, human immunodeficiency virus (HIV) infection, tuberculosis, diabetes, and cancer [5,10,22]
●Other comorbid conditions, such as cleft lip/palate, Down syndrome, cri du chat syndrome, choanal atresia, and microcephaly [12,14]
●Unhygienic practices, such as bathing in contaminated ponds and rivers, unsterile ear piercing, and cleaning ears with cotton buds [8,12]
While there are many environmental and social risk factors for CSOM, the rate of CSOM has not changed in countries, such as Greenland, despite many changes in social conditions . A genetic predilection is also suspected to play a role. This is suggested by the increased risk of CSOM seen in the Inuit of Alaska, Canada, and Greenland, Australian Aborigines, and certain Native Americans (particularly the Apache and Navajo) [6,18].
Family history may also play a role in AOM and CSOM. A family history of otitis media increased the risk of CSOM . Maternal history of otorrhea  and CSOM  are risk factors for development of CSOM in children.
PATHOGENESIS — CSOM generally results from an acute ear infection that is not diagnosed promptly or is inadequately treated. Infrequently it can result from chronic otitis media with effusion. CSOM can occur in a patient with a previously intact tympanic membrane (TM) or a TM with a preexisting perforation or tympanostomy tube. There are also reports of CSOM following traumatic perforations . Suppuration can also occur after tympanostomy tube placement.
Some have proposed that CSOM is, at least in part, the result of chronic Eustachian tube dysfunction (ETD) and resulting histologic changes in the middle ear, coupled with a nasopharyngeal reservoir of pathogens [3,24]. However, in one series, there was no correlation between cultures from the external auditory canal (EAC) or middle ear and nasopharyngeal cultures, indicating the nasopharynx does not serve as a reservoir for the bacteria causing CSOM . A suggested alternative is that the nasopharyngeal bacteria may contribute to the initial acute otitis media (AOM) preceding CSOM, but bacteria from the EAC enter the middle ear through the perforated TM as the infection becomes chronic, leading to a secondary infection and chronic drainage . Contaminated water may also play a role in the pathogenesis of CSOM. Swimming or bathing in unclean water can lead to middle-ear contamination with bacteria when a TM perforation exists [3,18].
Biofilms have also been implicated in the pathogenesis of CSOM. The role of biofilms in patients with cholesteatoma is better defined, but there is some evidence that biofilms also play a role in CSOM. In several small studies, biofilms were detected in 14 to 92 percent of patients with CSOM [26-30]. Biofilms may account for some of the difficulty in treating CSOM, since they are difficult to eradicate.
Organisms — In studies from the 1980s, Pseudomonas and Proteus were the most common microbial isolates in patients with CSOM [10,31]. However, the incidence of community-acquired methicillin-resistant Staphylococcus aureus (MRSA) has increased over the years and is now the most common isolate reported, followed by methicillin-sensitive S. aureus (MSSA) [32-34]. In addition, increasing numbers of patients have anaerobic bacteria as part of the microbiology in CSOM, with Peptostreptococcus, Fusobacterium, Prevotella, and Porphyromonas being the most common anaerobic isolates . Fungi are also identified in cultures from patients with CSOM .
Bacteriology in patients with CSOM and cholesteatoma may be different. In one series of 119 children with CSOM, those with cholesteatoma were 30 times more likely to have mixed infections compared with patients with noncholesteatomatous CSOM . Among 368 patients (adults and children) with CSOM, those with cholesteatoma were more likely to have S. aureus than Pseudomonas, while those patients with no cholesteatoma had the reverse .
Role of immune system — Interferon-gamma (IFN-gamma) has been shown to have immunoregulatory properties in otitis media with effusion, and it may play a similar role in CSOM. Middle-ear secretions were collected and examined in 358 children with CSOM . The children were then treated and followed for nine months. IFN-gamma concentrations were significantly lower in the 61 percent of children in whom CSOM resolved compared with the 39 percent of children who had persistent drainage (mean IFN-gamma concentration 27.2 versus 73.1 pg/mL, respectively). Levels of IFN-gamma also inversely correlated with concentrations of immunoglobulin G (IgG), IgE, and IgA in the fluid.
Immunoglobulin levels were below normal in 3 of 69 (4.3 percent) of patients with CSOM in one series, suggesting a defect in humoral immunity in a small subset of patients . Additional factors that may impact the ability to clear an infection include the high rate of biofilm formation seen in patients with CSOM compared with chronic otitis media with effusion in one series  and decreased ciliary beat frequency in the middle ear in another series .
Environmental allergies may be more common in patients with CSOM. Positive allergy testing to perennial aeroallergens was seen in 16 of 20 (80 percent) patients with CSOM compared with 8 of 17 (47 percent) patients with AOM and 5 of 15 (33 percent) controls without otitis media . IgE was elevated in the serum and middle-ear secretions of these patients, with an increased ratio of middle ear to serum levels in patients with CSOM compared with those with AOM.
CLINICAL PRESENTATION — The most common presenting complaint is hearing loss, followed by ear discharge [5,12]. The definition of "chronic" in the entity of CSOM is somewhat controversial, although the most common suggested cutoff for duration of suppuration is six weeks (range, two weeks to three months) . The otorrhea may be persistent or intermittent. Patients do not typically complain of ear pain. Any report of fever, dizziness, or pain should alert the clinician to consider complications of CSOM. Most patients have had the disease for over six years before seeking medical care (range 0 to 20 years) [11,12]. One study found that 52.8 percent of their patients had ear discharge for more than a year. In another series, 73 percent of patients had recurrent disease, while 27 percent had continuous disease .
Hearing loss — Hearing loss (threshold of hearing >25 dB) occurs in about 50 to 60 percent of patients with CSOM [8,22,44]. It is moderate to severe in up to two-thirds of patients [5,13,44-46], with an average hearing threshold of 40 dB in one series of 115 patients with CSOM . Conductive hearing loss is more common than sensorineural hearing loss [44,47], and patients appear to have greater hearing loss in the low frequencies  and increase bone conduction thresholds in most series [49-51]. Hearing loss may occur in the contralateral ear despite lack of evidence of bilateral disease . Longer duration of otorrhea is associated with greater degree of hearing loss , and lower socioeconomic status, but not age of onset or number of episodes, is associated with an increased risk of hearing loss . The site of the perforation corresponded to degree of hearing loss, with posterior perforations having greater decibel level loss, probably as a result of loss of protection of the round window membrane from impinging sound pressure waves . In many series, the hearing loss is strictly a result of middle-ear pathology in most cases of CSOM and the inner ear is typically not affected [49,52,53]. However, others have found that mixed hearing loss (conductive and sensorineural) is common .
Cholesteatoma — Cholesteatoma should be considered when CSOM does not resolve with maximal medical treatment. It occurs in 1 to 18 percent of all patients with CSOM [4,8,13,55]. Cholesteatoma, in conjunction with CSOM, should be distinguished from isolated cholesteatoma, which can have a similar presentation, but is a distinct entity.
Physical exam findings — A large central perforation of the tympanic membrane (TM) is the most common and perforation of the posterosuperior quadrant is the least common [8,48]. Discharge can range from purulent to fetid to cheese-like, and can fill the ear canal. There is typically not significant edema of the external auditory canal. There may be granulation tissue present, but it should be distinguished from retraction-pocket cholesteatoma in which the granulation tissue occupies the pars flaccida of the TM. Middle-ear mucosa, when it is seen, can be polypoid or edematous and can appear pale, red, or may be normal.
DIAGNOSIS — The diagnosis of CSOM is based upon consistent clinical findings (eg, hearing loss, chronic ear discharge). Cultures are not required to make the diagnosis and are generally reserved for unresponsive disease. They should be obtained through the perforation or tympanostomy tube, since culture samples taken from the external auditory canal (EAC) may be unreliable or misleading . However, patients usually fail medical treatment for reasons other than microorganism resistance. Thus, alternative or additional diagnoses should be considered and a computed tomography (CT) scan of the temporal bones obtained to evaluate for cholesteatoma or other processes when a patient is unresponsive to appropriate medical treatment.
In one study, 110 patients with CSOM were randomized to culture-directed or broad-spectrum antimicrobial therapy . Culture-directed therapy for two weeks led to a dry ear in 95 percent of cases, whereas broad spectrum antibiotics resulted in a dry ear in 74 percent. However, this difference was not significant, suggesting that routine performance of cultures is not necessary. In addition, there is poor correlation between cultures taken from the EAC, which is how they are most often obtained, versus the middle ear. In one study, they correlated for Pseudomonas in 32 percent and anaerobes in 45 percent .
DIFFERENTIAL DIAGNOSIS — The most common and important condition in the differential diagnosis for CSOM is isolated cholesteatoma, particularly the acquired form, which can also present with hearing loss and/or chronic otorrhea. It can be difficult to distinguish the two entities, since cholesteatoma can also occur in conjunction with CSOM. Keratin debris seen on exam, as opposed to just purulence, and prolonged duration of suppuration both are suggestive of cholesteatoma. Symptoms such as dizziness or facial nerve weakness should also make one consider cholesteatoma. A careful physical exam along with computed tomography (CT) scanning of the temporal bones, which may reveal bone erosion or destruction, should identify cholesteatoma in most cases.
The differential diagnosis also includes acute and chronic otitis media. The perforated tympanic membrane (TM) is what distinguishes CSOM from both acute and otitis media with effusion, in which the ear drum is intact. Acute otitis media (AOM) can lead to TM perforation in some cases and may progress to CSOM. The duration of symptoms is the main differentiating factor between these two conditions.
CSOM can also occur in the presence of tympanostomy tubes, which is discussed in greater detail separately.
Other conditions to consider include:
●Foreign body, particularly in young children with chronic drainage.
●Petrous apicitis (petrositis, infection of the petrous bone and air cells), which generally presents with retro-orbital pain, cranial nerve six palsy, and ear drainage.
●Tuberculosis of the temporal bone, particularly in underdeveloped areas or among at-risk populations (eg, nursing home or prison contacts, poor healthcare), can present as painless otorrhea. Testing for tuberculosis can help differentiate this from CSOM.
●Langerhans cell histiocytosis. A CT scan will help differentiate this entity from CSOM.
●Malignancy (rare in pediatric populations). These patients usually present with pain. A CT scan will help differentiate this as well.
●Chronic suppurative otitis media (CSOM) is the most common childhood infectious disease worldwide and is the most common cause of hearing impairment in the developing world, although it is infrequently seen in the developed world.
●CSOM generally results from an acute ear infection that is not diagnosed promptly or is inadequately treated. The acute otitis media (AOM) then progresses to tympanic membrane (TM) perforation and subsequent contamination from dirty bathing water or possibly a nasopharyngeal reservoir.
●CSOM is characterized by hearing loss and drainage from the middle ear for at least two weeks that is associated with a TM perforation. The otorrhea can be recurrent or persistent. CSOM is usually painless.
●The diagnosis of CSOM is based upon consistent clinical findings (eg, hearing loss, chronic ear discharge). Cultures are not required to make the diagnosis and are generally reserved for unresponsive disease.
●The most common and important condition in the differential diagnosis for CSOM is isolated cholesteatoma, which can also present with hearing loss and/or chronic otorrhea. It can be difficult to distinguish the two entities, since cholesteatoma can also occur in conjunction with CSOM.