Mastoiditis is the inflammation of a portion of the temporal bone referred to as the mastoid air cells. The mastoid air cells are epithelium lined bone septations that are continuous with the middle ear cavity. As children are more susceptible to middle ear infections, they are at increased risk of developing acute mastoiditis when compared to adults. Most commonly, acute mastoiditis is a complication of acute otitis media. Although rare, other causes mastoiditis include infection of the mastoid air cells alone, referred to as incipient mastoiditis, and subacute middle ear infections, referred to as subacute mastoiditis.
With the advent of antibiotics, the development of acute mastoiditis and progression to dangerous sequela is unlikely. However, if left untreated, mastoiditis can result in life-threatening sequela, including meningitis, intracranial abscess, and venous sinus thrombosis. Despite advanced imaging techniques, antibiotics, and microsurgical procedures, the mortality of mastoiditis sequela in children remains 10%.
Mastoiditis can subdivide into three different categories based on the mechanism of infection, as detailed below:
Although mastoiditis can occur at any age, the majority of patients are less than two years of age, with a median age of 12 months. In the pre-antibiotic era, 20% of cases of acute otitis media were complicated by acute mastoiditis and frequently associated with severe intracranial complications.
With the advent of antibiotics, mastoidectomy, and PCV-7 by 2008, the incidence has fallen drastically. Specifically, before the antibiotic era, 5 to 10% of children with acute otitis media developed coalescent mastoiditis with a mortality rate of 2/100000 population. After antibiotics and pneumococcal vaccination (PCV-7), 0.002% of children with acute otitis media progress too acute coalescent mastoiditis with a mortality rate of less than 0.01 per 100000 population.
The majority of cases of mastoiditis result from the progression of acute otitis media. The ear subdivides into three cavities: the outer ear, middle ear, and inner ear. In particular, the middle ear cavity extends from the tympanic membrane to the cochlea and includes important structures such as the Malleus, Incus, Stapes, and Eustachian tube. The middle ear cavity is continuous with the lining of the mastoid air cells, which are a portion of the temporal bone.
The Eustachian tube is a connection from the middle ear to the oral cavity. It is responsible for draining fluid or air from the middle ear. If this tube becomes narrowed via inflammation or debris, it provides an opportunistic environment for pathogens to grow. This lining in the middle ear cavity, as mentioned above, is continuous with the lining of the mastoid air cells. In acute mastoiditis, the extension of the infection from the middle ear to the mastoid air cells can lead to bony septation erosion and coalescence of small air cells into larger ones full of pus referred to as acute coalescent mastoiditis. The pus filling this eroding cavity can extend via direct extension, thrombophlebitis, and bony pathways resulting in sequela that include subperiosteal abscess, sigmoid sinus thrombosis, meningitis, and intracranial abscess.
The most common pathogen in mastoiditis is streptococcal pneumonia. Other common pathogens include Group A beta-hemolytic streptococci, Staphylococcus aureus, Streptococcus pyogenes, and Haemophilus influenzae. Risk factors for mastoiditis include age less than two years old, immunocompromised state, recurrent acute otitis media, or incomplete pneumatization fo the mastoid process.
Most commonly, the patient will be a child under the age of two years presenting with irritability, fussiness, lethargy, fever, ear pulling, ear pain. The adult patient will typically complain of severe ear pain, fever, and headache. Physical examination in both children and adults will reveal postauricular erythema, tenderness, warmth, and fluctuance with protrusion of the auricle.
The otoscopic examination will reveal a bulging of the posterosuperior wall of the external auditory canal and bulging of and pus behind the tympanic membrane. Often the tympanic membrane can be ruptured and draining pus. Some important considerations include the following. A normal tympanic membrane usually, but not always, excludes acute mastoiditis. Also, although a history of recent or concurrent otitis media is common, it is not required to make the diagnosis of acute mastoiditis as some cases may take place rapidly during the onset of acute otitis media.
Mastoiditis is a clinical diagnosis. Laboratory and imaging are used as an adjunct when you are unsure of the diagnosis or considering a complication of acute mastoiditis. Laboratory studies to obtain include a CBC with differential, ESR, and CRP. Most commonly, one will see an elevated white blood cell count with a left shift, and elevated inflammatory markers ESR and CRP. Radiologic evaluation of acute mastoiditis uses CT imaging. CT imaging can reveal the disruption of the bony septation in the mastoid air cells and the potential extension of the infection. In particular, CT imaging in patients with mastoiditis reveals the following:
Although antibiotics are the centerpiece of mastoiditis treatment, antibiotics alone have shown to result in an 8.5% complication rate. Additional measures, including myringotomy, tympanostomy tube placement, and mastoidectomy may be indicated depending on the severity of the infection. The majority of patients with acute mastoiditis are admitted to the hospital.
Uncomplicated patients with no significant medical history have had successful treatment as an outpatient with daily IV ceftriaxone with low complication rates—uncomplicated acute mastoiditis qualifies as patients with no significant past medical history and minimal physical examination findings. The patient case becomes complicated if the patient develops a large post auricular lesion, imaging studies showing bone erosion, high fevers, or neurological signs. Uncomplicated inpatient cases are manageable with IV antibiotics, high dose IV steroids, and myringotomy with placement of tympanostomy tube.
Serial physical examinations are necessary as the patient clinical status can deteriorate quickly. If mastoiditis does not improve in 48 hours, mastoidectomy is indicated. IV antibiotic of choice for patients without chronic otitis media is IV vancomycin alone to cover for the most common pathogens, including Streptococcus pneumoniae. Other common pathogens include Group A beta-hemolytic streptococci, Staphylococcus aureus, Streptococcus pyogenes, and Haemophilus influenza.
In patients with a chronic history of ear infections, an anti-pseudomonal agent is added to vancomycin. In a multicenter study, Streptococcus pyogenes correlated with the highest rate of complications at presentation, with n nearly 50% of cases, and Staphylococcus aureus correlated with the highest rate of complications during hospitalization.
It is essential to have a thorough history and physical examination, as common mimics can be overlooked, resulting in missed diagnosis and delay in treatment. Common mimics of acute mastoiditis include cellulitis, otitis externa, lymphadenopathy, trauma, and tumor. In particular, there have been many case reports of confusing tumors or cancer for mastoiditis, including rhabdomyosarcoma, Ewing sarcoma, myofibroblastic tumor. Tumors were more likely to be bilateral, have cranial nerve involvement, and less likely to have a fever. These differentials are an important consideration as the pediatric population is a common demographic for both mastoiditis and tumor.
The majority of patients with uncomplicated acute mastoiditis have a resolution of symptoms with conservative measures, including antibiotics, steroids, and myringotomy, without the need for mastoidectomy. However, research in conservative versus invasive treatment for acute mastoiditis is lacking. Additionally, it is critical to monitor patients who are receiving treatment for acute mastoiditis, particularly in the first 48 hours. In cases where the patient's clinical status does not change or deteriorates from admission, mastoidectomy is then indicated.
The progression of uncomplicated acute mastoiditis can result in devastating consequences. Based on the location of the mastoid process, opportunistic infections can spread inward towards the brain or outward toward the periphery. Extracranial complications of acute mastoiditis include the following:
Intracranial manifestations of acute mastoiditis occurred in 6 to 23% of cases. These patients will often present with physical exam findings concerning intracranial involvement, including seizures, nuchal rigidity, headaches, and altered mental status. They include:
Emergency medicine, family medicine, and ENT providers are often presented with patients, both pediatric and adult, complaining of ear pain. Many of these patients will have otitis media or otitis externa and will receive antibiotic therapy. The scope of practice for the EM or FM practitioner stops at this point.
If the patient has clinical signs and symptoms of acute mastoiditis, they should proceed to an emergency department with ENT coverage as this patient will likely be admitted to the hospital for IV antibiotics, myringotomy, tympanostomy tube placement, and possible mastoidectomy. Patients who are presenting for frequent episodes of acute otitis media or chronic otitis media who are otherwise stable and no concern for mastoiditis can be safely referred by either EM or FM practitioner to an ENT provider on an outpatient basis for consultation in regards to risk and prevention of mastoiditis.
The most important method of prevention for mastoiditis is vaccination. Unvaccinated patients will be more susceptible to pneumococcus, which commonly causes otitis media and thus leads to mastoiditis. Additionally, early treatment for acute otitis media can prevent progression to mastoiditis. Other risk factors for mastoiditis that are not modifiable include age less than two years old, immunocompromised state, recurrent acute otitis media, or incomplete pneumatization of the mastoid process.
Interestingly, there has been a study in the literature describing the use of ultrasound in identifying complications of mastoiditis. In a patient population of 10, ultrasound was able to identify complications in 9 of the cases.
Currently, CT scan is the standard of care; however, given the promising results from this study, consideration should be given to further research efforts aimed at using ultrasound to identify complications of mastoiditis; this is especially important in the pediatric population as it can prevent unnecessary CT scan radiation exposure. Even if ultrasound only serves as an adjunct to screening patients who will ultimately receive a CT scan, the benefit is tremendous for the pediatric population and overall healthcare costs.
An important topic of debate amongst physicians in regards to treatment for otitis media is the sequela if left untreated. As discussed above, otitis media can progress to mastoiditis, which can have fatal complications. Many cases of otitis media are viral; however, patients are still receiving antibiotic therapy. From the prescriber perspective, it is extremely difficult to tell based on physical examination if the patient's infection is bacterial or viral. Of course, the patient's history can aid in the diagnosis, but it is still challenging. Furthermore, the physician must consider the sequela of the infection if left untreated.
Ultimately, this can lead to overprescribing antibiotics and poor stewardship, which can lead to resistant infections. To enhance patient outcomes, the physician must take a thorough history, adequate physical, discuss with the patient or patient family, and specialist, if possible, because something as simple as an ear infection can ultimately lead to death. Finally, to enhance outcomes of the healthcare system as a whole, there should be further studies and additional consideration given to outpatient management non-complicated acute mastoiditis. Avoiding hospital admissions prevents iatrogenic complications, increases patient satisfaction, and reduces healthcare costs.
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