Approach Considerations
Despite the use of antibiotics, acute mastoiditis still remains a threat for patients with acute otitis media (AOM), especially for children younger than age 5 years. Great care is required on the part of clinicians to make an early diagnosis in order to promote adequate treatment and to prevent complications. [3]
Material for culture and sensitivity should be obtained from the ear (via tympanocentesis or myringotomy), blood, any abscess, and mastoid tissue (if it becomes available). Obtain and evaluate spinal fluid if any suggestion exists of intracranial extension of the process.
Complete blood count
A complete blood count (CBC) and sedimentation rate are obtained for baseline studies used to evaluate the efficacy of therapy. A high white blood cell count on admission may serve as a predictive factor for complicated cases.
Audiometry
In the light of the prevailing medicolegal climate, an audiometric evaluation must be obtained. Audiometry is seldom appropriate or useful for children with ASM, but it must be performed after convalescence from the acute phase and with children who have chronic mastoiditis. In the at-risk population (children < 2 y), thresholds for air and bone conduction under headphones are only rarely obtained.
Tympanocentesis/myringotomy
Tympanocentesis is a puncture of the tympanic membrane for aspiration of middle ear fluid. The tympanic membrane typically heals within several days. Send fluid for cultures, Gram stain, and acid-fast stain. It is often possible in an acute infection to convert a tympanocentesis into a myringotomy without undue discomfort by widening the needle hole with alligator forceps.
Myringotomy is a small incision of the tympanum to express fluid from the middle ear in chronic or recurrent otitis media; it often relieves discomfort associated with pressure from acute otitis media (AOM). Tympanostomy tube insertion is also performed in most cases to allow for continued drainage and so that administered therapeutic otic drops reach the middle ear.
Imaging Studies
CT scanning
CT scanning of the temporal bone is the standard for evaluation of mastoiditis, with published sensitivities ranging from 87-100%. Some argue that all suspected cases of mastoiditis warrant CT scan evaluation. [19]
The following findings are used to differentiate acute otitis media (AOM)/acute mastoiditis without osteitis, acute surgical mastoiditis (ASM), and chronic mastoiditis:
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Opacification of the mastoid air cells and middle ear by inflammatory swelling of mucosa and by collection of fluid
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Loss of sharpness or visibility of mastoid cell walls due to demineralization, atrophy, or necrosis of bony septa
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Haziness or distortion of the mastoid outline, possibly with visible defects of the tegmen or mastoid cortex
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Enhancement of areas of abscess formation
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Elevation of the periosteum of the mastoid process or posterior cranial fossa
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Osteoblastic activity in chronic mastoiditis
It is this author’s belief that in the presence of clear clinical indications of acute surgical mastoiditis, CT scanning may be omitted prior to surgical intervention, avoiding unnecessary radiation exposure as recommended by the US National Institutes of Health. [20]
MRI
Magnetic resonance imaging (MRI) is not typically the radiographic study of choice; however, it is helpful in showing inflammatory processes and differentiating certain tumors. Do not use MRI as a method of evaluating the mastoid, although it is the standard for evaluation of contiguous soft tissue, particularly the intracranial structures. However, MRI is the preferred imaging modality for the potential complications of ASM (ie, abscess formation, sinus thrombosis).
A retrospective study by Saat et al found differences in the MRI characteristics of acute mastoiditis in children, compared with adults. The study, which included 10 children and 21 adults with acute mastoiditis, reported that in the pediatric patients, the prevalences of total opacification of the tympanic cavity and mastoid air cells, intense intramastoid enhancement, destruction of outer cortical bone, subperiosteal abscess, and enhancement of perimastoid meninges were significantly higher than in adults. [21]
A study by Singh et al, however, found that incidental opacification of the mastoid is frequently seen in children, indicating that the diagnosis of pediatric mastoiditis should not hinge on radiologic reports of fluid or mucosal thickening in the mastoid air cells. The study included 515 children who underwent brain MRI for indications not involving mastoiditis or otitis media, with mastoid opacification found in 110 (21.4%) of these patients. Opacification rates in children younger than 1 year and those between ages 1 and 2 years reached 41.7% and 47.5%, respectively. [22]
Plain radiography
In areas of the world where CT scanning is not immediately available, plain radiographs of the mastoids demonstrate clouding of the air cells with bone destruction in ASM. In the vast majority of cases, radiographs suffice to establish the diagnosis but lack the sensitivity to differentiate the stages of the disease and fail to show the petrous apex in any great detail.
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Mastoiditis with subperiosteal abscess. Note the loss of the skin crease and the pointed abscess.
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Cortical mastoidectomy in a densely sclerosed mastoid.
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Preoperative preparation of the patient.
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Draping the surgical area.
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Injection of the area with 2% Xylocaine and 1:100,000 adrenaline to reduce bleeding.
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Marking the incision site.
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Placement of the incision, a few mm behind the postauricular sulcus.
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Deepening the incision down to the bone.
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Elevation of the periosteum to expose the mastoid cortex to the mastoid tip.
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Mastoid drilling in progress with simultaneous saline irrigation.
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Creation of the initial groove and the vertical line.
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Exposure of the antrum and exenteration of the mastoid air cells.
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Curetting the aditus to enlarge it.
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Further exposure.
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Healed postaural scar.
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Extent of cortical mastoidectomy in a well-pneumatized mastoid.
