Otitis Externa – Causes, Symptoms, Diagnosis, Treatment

Causes of Otitis Externa

Pseudomonas aeruginosa and Staphylococcus aureus are the most common pathogens involved in otitis externa. Otitis externa can also occur as a polymicrobial infection, and rarely, it may result from a fungal infection such as Candida or Aspergillus. Various factors can predispose patients to the development of OE. Swimming is one of the most common risk factors, and it increases the risk five times when compared to non-swimmers. Other risk factors include [1]:

• Humidity
• Trauma or external devices (cotton swabs, earplugs, hearing aids)
• Dermatologic conditions such as eczema and psoriasis
• The narrow external ear canal
• Ear canal obstruction (cerumen obstruction, foreign body)
• Radiotherapy or chemotherapy
• Stress

These Are Associated Causes May include

• Decreased immunity due to human immunodeficiency virus (HIV), diabetes, and other immuno-deficiencies
• Genetic predisposition
• Mucins which include abnormalities of this gene expression, especially upregulation of MUC5B
• Anatomic abnormalities of the palate and tensor veli palatini
• Ciliary dysfunction
• Cochlear implants
• Vitamin A deficiency
• Bacterial pathogens, Streptococcus pneumoniae, Haemophilus influenza, and Moraxella (Branhamella) catarrhalis, are responsible for more than 95%
• Viral pathogens such as respiratory syncytial virus, influenza virus, parainfluenza virus, rhinovirus, and adenovirus
• Allergies
• Lack of breastfeeding
• Passive smoke exposure
• Daycare attendance
• Lower socioeconomic status
• Family history of recurrent AOM in parents or siblings

Risk factors for ear infections include

• Age – Children between the ages of 6 months and 2 years are more susceptible to ear infections because of the size and shape of their eustachian tubes and because their immune systems are still developing.
• Group child care – Children cared for in group settings are more likely to get colds and ear infections than are children who stay home. The children in group settings are exposed to more infections, such as the common cold.
• Infant feeding – Babies who drink from a bottle, especially while lying down, tend to have more ear infections than do babies who are breast-fed.
• Seasonal factors – Ear infections are most common during the fall and winter. People with seasonal allergies may have a greater risk of ear infections when pollen counts are high.
• Poor air quality – Exposure to tobacco smoke or high levels of air pollution can increase the risk of ear infections.
• Alaska Native heritage – Ear infections are more common among Alaska Natives.
• Cleft palate – Differences in the bone structure and muscles in children who have cleft palates may make it more difficult for the eustachian tube to drain.

Symptoms of Otitis Externa

The primary symptom of acute otitis externa is ear pain; other possible symptoms include fever, reduced hearing during periods of illness, tenderness on a touch of the skin above the ear, purulent discharge from the ears, irritability, and diarrhea (in infants). Since an episode of otitis media is usually precipitated by an upper respiratory tract infection (URTI), there are often accompanying symptoms like a cough and nasal discharge.^[rx] One might also experience a feeling of fullness in the ear.

The typical signs to watch for include

• Tugging or pulling at the ear(s)
• Loss of appetite
• Unsettledness and crying
• Trouble sleeping
• High fever
• Discharge from the ears
• Problems with balance
• Trouble hearing, especially soft sounds or when being spoken to from behind

Infants and children may have one or more of the following symptoms

• crying
• irritability
• sleeplessness
• pulling on the ears
• ear pain
• a headache
• neck pain
• a feeling of fullness in the ear
• fluid drainage from the ear
• a fever
• vomiting
• diarrhea
• irritability
• a lack of balance
• hearing loss

Common signs and symptoms in adults include

• Ear pain
• Drainage of fluid from the ear
• Trouble hearing

Diagnosis of Otitis Externa

Otitis externa is diagnosed clinically via objective findings on physical exam (otoscopy) combined with the patient’s history and presenting signs and symptoms. Several diagnostic tools are available such as a pneumatic otoscope, tympanometry, and acoustic reflectometry to aid in the diagnosis of otitis media. Pneumatic otoscopy is the most reliable and has a higher sensitivity and specificity as compared to plain otoscopy, though tympanometry and other modalities can facilitate diagnosis if pneumatic otoscopy is unavailable.

History and Physical

• Otitis externa is a clinical diagnosis; therefore, a complete history and physical examination are required. Physical examination should include evaluation of the auricle, assessment of surrounding skin and lymph nodes, and pneumatic otoscopy. Otoscopy will reveal an erythematous and edematous ear canal with associated debris (yellow, white, or gray). In some cases, the tympanic membrane is erythematous or partially visualized due to edema of the external auditory canal. Concomitant otitis media is suspected when there is evidence of an air-fluid level along the tympanic membrane (middle ear effusion). Its clinical presentation may vary depending on the stage or severity of the disease. Initially, patients with OE will complain of pruritus and ear pain that is usually worse with manipulation of the tragus, pinna, or both. Ear pain is often disproportionate to physical exam findings, and it is due to irritation of the highly sensitive periosteum underneath the thin dermis of the bony ear canal. It can also present with otorrhea, fullness sensation, and hearing loss.

Systemic symptoms such as fever greater than 101 F (38.3 C) and malaise suggest extension beyond the external ear canal.[rx]

• The otoscopic examination – should be the first and most convenient way of examining the ear and will yield the diagnosis to the experienced eye. In AOM the TM may be erythematous or normal, and there may be fluid in the middle ear space. In suppurative OM there will be obvious purulent fluid visible and a bulging TM. The external ear canal (EAC) may be somewhat edematous, though significant edema should alert the clinician to suspect otitis externa (outer ear infection, AOE), which may be treated differently. In the presence of EAC edema, it is paramount to visualize the TM to ensure it is intact. If there is an intact TM and a painful, erythematous EAC, to topical drops should be added to treat AOE. This can exist in conjunction with AOM or independent of it, so visualization of the middle ear is paramount. If there is a perforation of the TM then the EAC edema can be assumed to be reactive, and ototopical medication should be used, but an agent approved for use in the middle ear, such as ofloxacin, must be used, as other agents can be ototoxic.[rx][rx][rx]

Evaluation

The diagnosis of otitis media should always begin with a physical exam and the use of an otoscope, ideally a pneumatic otoscope.[rx][rx]

Laboratory Studies

• Laboratory evaluation is rarely necessary. A full sepsis workup in infants younger than 12 weeks with fever and no obvious source other than associated acute otitis media may necessary. Laboratory studies may be needed to confirm or exclude possible related systemic or congenital diseases.

Imaging Studies

Imaging studies are not indicated unless intra-temporal or intracranial complications are a concern.[rx][rx] When an otitis media complication is suspected, computed tomography of the temporal bones may identify mastoiditis, epidural abscess, sigmoid sinus thrombophlebitis, meningitis, brain abscess, subdural abscess, ossicular disease, and cholesteatoma.

• Magnetic resonance imaging – may identify fluid collections, especially in the middle ear collections.
• Tympanocentesis – Tympanocentesis may be used to determine the presence of middle ear fluid, followed by culture to identify pathogens – Tympanocentesis can improve diagnostic accuracy and guide treatment decisions but is reserved for extreme or refractory cases.[rx][rx]
• Tympanometry – During a tympanometry test, your child’s doctor uses a small instrument to measure the air pressure in your child’s ear and determine if the eardrum is ruptured.
• Reflectometry – During a reflectometry test, your child’s doctor uses a small instrument that makes a sound near your child’s ear. Your child’s doctor can determine if there’s fluid in the ear by listening to the sound reflected back from the ear.
• Acoustic reflectometry. This test measures how much sound is reflected back from the eardrum — an indirect measure of fluids in the middle ear. Normally, the eardrum absorbs most of the sound. However, the more pressure there is from fluid in the middle ear, the more sound the eardrum will reflect.

Other Tests

Tympanometry and acoustic reflectometry may also be used to evaluate for middle ear effusion.[rx]

• In more severe cases, such as those with associated hearing loss or high fever, audiometry, tympanogram, temporal bone CT and MRI can be used to assess for associated complications, such as mastoid effusion, subperiosteal abscess formation, bony destruction, venous thrombosis or meningitis.^[rx]
• Acute otitis media in children with moderate to severe bulging of the tympanic membrane or new onset of otorrhea (drainage) is not due to external otitis. Also, the diagnosis may be made in children who have mild bulging of the eardrum and recent onset of ear pain (less than 48 hours) or intense erythema (redness) of the eardrum.
  To confirm the diagnosis, middle-ear effusion and inflammation of the eardrum have to be identified; signs of these are fullness, bulging, cloudiness, and redness of the eardrum.^[rx]
• It is important to attempt to differentiate between acute otitis media and otitis media with effusion (OME), as antibiotics are not recommended for OME.^[rx] It has been suggested that bulging of the tympanic membrane is the best sign to differentiate AOM from OME, with a bulging of the membrane suggesting AOM rather than OME.^[rx]

The following conditions come under the differential diagnosis of otitis media[rx][rx][rx]

• Cholesteatoma
• Fever in the Infant and Toddler
• Fever Without a Focus
• Hearing Impairment
• Pediatric Nasal Polyps
• Nasopharyngeal Cancer
• Otitis Externa
• Human Parainfluenza Viruses (HPIV) and Other Parainfluenza Viruses
• Passive Smoking and Lung Disease
• Pediatric Allergic Rhinitis
• Pediatric Bacterial Meningitis
• Pediatric Gastroesophageal Reflux
• Pediatric Haemophilus Influenzae Infection
• Pediatric HIV Infection
• Pediatric Mastoiditis
• Pediatric Pneumococcal Infections
• Primary Ciliary Dyskinesia
• Respiratory Syncytial Virus Infection
• Rhinovirus (RV) Infection (Common Cold)
• Teething

Treatment of Otitis Externa

Most patients diagnosed with otitis externa will receive outpatient management. The mainstay of uncomplicated otitis externa treatment usually involves topical antibiotic drops and pain control. Pain can be intense and severe; therefore, it should be managed appropriately. Acetaminophen or nonsteroidal anti-inflammatory drugs have been proven to be adequate for mild to moderate pain. Also, opioids (e.g., oxycodone or hydrocodone) are recommended for severe pain and should be prescribed in a limited amount since symptoms for uncomplicated OE should improve within 48 hours of initiating topical antibiotic therapy. If there is no improvement in pain within 48 to 72 hours, a reassessment by a primary care physician is strongly recommended.[rx]

In general, antibiotic otic drops are safe and well-tolerated. Its safety and efficacy compared to placebo have been proven with excellent results in randomized trials and meta-analyses. Some studies have shown that topical antibiotic drops containing steroids may decrease inflammation and secretions, and hasten pain relief.[rx][rx] Regardless of the topical antibiotic used, approximately 65% to 90% of cases will have a clinical resolution within 7 to 10 days.

Common topical antibiotics indicated for otitis externa include:

• Polymyxin B, neomycin, and hydrocortisone 3 to 4 drops to the affected ear four times a day
• Ofloxacin 5 drops to the affected ear twice daily
• Ciprofloxacin with hydrocortisone 3 drops to the affected ear twice daily

Patients with marked edema of the ear canal require placement of an ear wick (compressed hydro cellulose or ribbon gauze) to facilitate medication delivery and reduce ear canal edema.[rx] The wick is moistened with antibiotic drops and placed into the ear canal. The wick will usually fall out spontaneously, and if necessary, it should be removed by a clinician in approximately two to three days.

If perforation of the tympanic membrane is suspected, neomycin/polymyxin B/Hydrocortisone drops, alcohols, and ototoxic drops (aminoglycosides) should be avoided. Fluoroquinolones have no ototoxicity and are the only FDA-approved drug for middle ear use; therefore, they are recommended for the treatment of uncomplicated OE with associated tympanic membrane perforation.[rx]

It is of great importance to educate patients on how to properly administer otic drops and the significance of adherence to treatment. The patient should lie down with their affected side facing upward, apply two to five drops depending on the prescribed drug, and remain in that position for about 3 to 5 minutes. This will maximize treatment effectiveness. Patients should also be advised to avoid water exposure and to minimize manipulation or trauma to the ear.[rx]

Although not typically done in the primary care setting, aural toilet or cleansing of the external ear canal is recommended for the treatment of acute OE by the American Academy of Otorhinolaryngology. Gentle lavage or suctioning should be performed only if there is no evidence or suspicion of tympanic membrane perforation. Also, it should be avoided in patients with a history of diabetes because it can potentially induce malignant otitis externa.[rx]

Oral antibiotics have not been proven to be beneficial [rx], and its inappropriate use will increase the resistance among common otitis externa pathogens. The indications for oral antibiotics include:

• Patients with diabetes and increased morbidity
• Patients with HIV/AIDS
• Suspected malignant otitis externa
• Concomitant acute otitis media

Topical antifungal agents are not considered a first-line treatment for OE. They are only recommended if fungal etiology is suspected by otoscopic examination or culture results.[rx]

References