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Original Studies

Acute Mastoiditis in Children

Necessity and Timing of Imaging

Marom, Tal MD*; Roth, Yehudah MD*; Boaz, Mona RD, PhD†‡; Shushan, Sagit MD*; Oron, Yahav MD*; Goldfarb, Abraham MD*; Dalal, Ilan MD§; Ovnat Tamir, Sharon MD*

Author Information
The Pediatric Infectious Disease Journal: January 2016 - Volume 35 - Issue 1 - p 30-34
doi: 10.1097/INF.0000000000000920


Acute mastoiditis (AM) is the most common suppurative complication of acute otitis media (AOM), which mainly affects the pediatric population. Its incidence ranges from 1.88 to 11.1/100,000 child-years.1–5 AM is typically diagnosed in children with a recent history of AOM, who present with a bulging tympanic membrane on otoscopy or otomicroscopy, otalgia, fever, posterior auricular swelling, erythema and mastoid tenderness; it may also be accompanied by protrusion of the pinna and otorrhea. AM should be treated without delay because of the potential lethal complications. The mainstay of treatment consists of parenteral antibiotics for 7–10 days, with or without myringotomy or other forms of drainage.6 In more advanced cases, surgical intervention, ie, subperiosteal abscess (SA) drainage, mastoidectomy and/or ventilating tube insertion, should be considered.6

Diagnosis of AM may be assisted by 2 imaging modalities. Computed tomography (CT) scans and magnetic resonance imaging (MRI) studies are the preferred imaging modalities for AM; each is used to evaluate different structures. Bony changes, ie, dehiscence of the mastoid cortex or coalescence of the air cells, intracranial and extracranial abscesses and vascular filling defects, suggesting thrombosis, are easily observed in contrast-enhanced brain CT scans. Current CT techniques are fast (within 1 minute), high quality and usually do not require sedation. In contrast, an MRI with gadolinium is the recommended study in children with suspected intracranial complications, owing to its higher sensitivity for detection of extraaxial fluid collections and associated vascular lesions.7,8

In the literature, debate exists whether to use imaging studies, and if so, at what time during the course of AM. Some authors defer early imaging studies in children with AM presenting with characteristic clinical findings, because they are not usually required for the initial treatment of uncomplicated cases.6,9–11 Others advocate early cranial imaging, to identify and treat intracranial complications early in the course of the disease.12–14 Many authors reported that the typical course of AM is mostly benign15–17 and caution against exposing young children to the potential deleterious effects of a brain CT scan, unless the child has clinical evidence of complications.18 Because clinicians are often required to assess the value of additional information delivered by these imaging studies and weight it against their potential detrimental effects, we reassessed the necessity and timing of imaging studies in children presenting with AM.


Study Design and Population

The study was approved by the Edith Wolfson Medical Center Institutional Review Board. We retrospectively identified all children younger than 8 years who presented between January 1, 2005, and December 31, 2014, with AM (International Classification of Diseases code 383.XX) to our hospital. This group of children was chosen because they represent the largest population of children who presented with AM. This hospital is a secondary medical care center located in Central Israel, which serves some 150,000 children (there were no appreciable differences in the population size during the study years). Although our hospital is not the only healthcare provider in our community, the majority of the children living nearby are referred to us. CT scans are available 24 hours, 7 days a week, and MRI studies were performed elsewhere, within several hours. In all children, AM diagnosis was based on the clinical findings (bulging tympanic membrane, postauricular tenderness/erythema/swelling, protruding auricle), in addition to systemic signs and symptoms (ie, fever accompanied by lethargy, irritability, poor feeding). SA diagnosis was based on the clinical findings: AM with retroauricular fluctuance and/or bulging of the posterosuperior wall of the external auditory canal.

Medical charts of eligible children were reviewed. The data analyzed included age, gender, history of current disease, history of recurrent AOM episodes (defined as ≥3 episodes of AOM within 6 months or ≥4 episodes within 12 months, including at least 1 episode during the preceding 6 months), medical and surgical history, laterality, prehospital antibiotic treatment, AM symptoms and signs, white blood cell count, C-reactive protein level, absolute neutrophil count, middle ear fluid (MEF), blood and cerebrospinal fluid culture results, antibiotic treatment during hospitalization, documented decisions leading to the performance of CT/MRI, timing of imaging studies during AM course, imaging findings, AM-related sequelae and AM-related surgical interventions during hospitalization (SA drainage, myringotomy, ventilating tube insertion and mastoidectomy). Each AM episode was considered a single episode, unless >4 weeks had elapsed between 2 consecutive AM episodes. Children with previous ear or mastoid surgery, immune deficiencies, cholesteatoma, head and neck malignancies and congenital malformations of the ear, nasopharynx and palate were excluded.

Children were categorized as the “younger children,” if they were younger than 2 years, because the peak for AOM and AM incidence is between 1 and 2 years of age, or as the “older children,” if they were 2–8 years of age. Leukocytosis was defined as white blood cell > 15,000/μL, and high C-reactive protein level was defined as >50 mg/L. Oral temperature ≥38.1°C and/or rectal temperature ≥37.8°C were defined as fever. MEF culture specimens were obtained during myringotomy or by direct collection of pus, with a sterile transport flocked swab (Copan Italia S.p.A., Brescia, Italy) and were processed for conventional cultures at the microbiology laboratory. Only MEF cultures that yielded Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis were considered positive, because they are commonly regarded as true otopathogens. More data on AOM and AM bacteriology from this cohort of children can be found elsewhere.19,20

Statistical Analysis

Data were stored on Microsoft Excel spreadsheet (Microsoft, Redmond, WA). The unit of analysis was AM episode (2 children presented with 2 unique AM episodes each, which were different in their course and outcomes). Statistical analysis was performed using SPSS 17.0 software (IBM Inc., Armonk, NY). Events were compared using the χ2 test, exact as appropriate. All tests were 2 sided and considered significant at P < 0.05.



Of the 88 AM episodes documented in 86 children (2 children presented with 2 unique episodes, each separated by >4 weeks interval), 55 (63%) were in boys and 46 (52%) were in children younger than 2 years. Demographic and clinical data are presented in Table 1. The overall annual incidence of AM during the 10-year study period for children aged 0–8 years was found to be 5.8 of 100,000 children. There were no considerable time trends for AM events during the study years. In 19 (22%) episodes, history of recurrent AOM was documented. A prehospital consultation with a physician (general practitioner, pediatrician or otolaryngologist) was performed in 48 (55%) children, and preadmission antibiotic treatment was prescribed in 32 (36%) episodes. The most common antibiotic prescribed was amoxicillin (78%).

Acute Mastoiditis Episodes, Younger Children (<2 Years) Versus Older Children (2–8 Years)

AM Presentation and Management

On admission, classic symptoms of AM were observed in all episodes, and classic signs of AM were observed as follows: bulging and redness of the tympanic membrane (97%), tenderness and erythema of the postauricular region (83%) and protrusion of the auricle (89%). In 19 (22%) episodes, there was bilateral AOM, which accompanied unilateral AM. Discharge from the external ear canal before or at hospital admittance was observed in 13 (15%) episodes.

Intravenous treatment was initiated in all AM cases: cefuroxime was the first-line antibiotic treatment prescribed in most children (84%), followed by ceftriaxone (14% alone and 2% in combination with another antibiotic agent). In 23 (26 %) episodes, the antibiotic treatment was changed during hospitalization (on the second median day; range, 1–7): because of bacterial antibiotic susceptibility studies (9%), deterioration in the general condition (30%) or after surgery to attain a broader antibiotic coverage (61%).

Overall, 105 bacterial specimens were collected (some children had multiple specimens obtained): from MEF during myringotomy (74%), from spontaneous otorrhea (2%), from drainage of SA (8%) and from the mastoid cavity during surgery (16%). Of the 31 (30%) positive cultures, S. pneumoniae grew in 27 (87%) episodes, H. influenzae in 2 (6%), M. catarrhalis in 1 (3%) and there was 1 (3%) mixed growth of S. pneumoniae/H. influenzae. The S. pneumoniae that grew was sensitive to penicillin in 19 (70%) of cultures, intermediate in 5 (19%) cultures and resistant to penicillin in 3 (11%) of cultures. In 3 of 27 (11%) episodes with S. pneumoniae-positive MEF cultures, there were concomitant growth of S. pneumoniae in the blood2 and in the cerebrospinal fluid.1

Myringotomy was performed in 82 (95%) episodes on admission and repeated, if deemed to be necessary, when fever persisted despite adequate antibiotic therapy, or when myringotomy incision closed within 24 hours. Hospitalization mean length was 6.8 days (range, 2–28). Hospital stay was determined by the intravenous antibiotic therapy, which was given for 6–10 days, per protocol. There were no appreciable differences between younger and older children. Children who underwent mastoidectomy had longer hospital duration (mean, 10.1 days; range, 6–28 days), when compared with children who were not operated (mean, 6.2; range, 2–9).

Imaging Studies and Complications

In 20 (23%) episodes, CT scans were performed, and in 3 (3%) episodes, additional MRI studies were performed. Figure 1 shows the rationales and findings of imaging studies in our study population. We found a positive relationship between the suspected AM complications and the findings in both imaging studies (more clinical and laboratorial details can be found in Table, Supplemental Digital Content 1, The decision for performing imaging studies was the evolvement of a clinically diagnosed SA, despite intravenous antibiotic therapy (9, 45%), lack of clinical improvement or worsening despite adequate antibiotic therapy (7, 35%) or new onset of focal neurological signs (4, 20%). Intratemporal complications observed in the CT scans and magnetic resonance (MR) studies in these episodes included SA in 14 (70%) episodes and Luc abscess (purulent collection deep to the temporalis muscle) in 1 (5%) episode, whereas intracranial complications included perisinus empyema in 2 (10%) episodes, epidural abscess in 2 (10%) episodes, proven sigmoid sinus thrombosis in 1 (5%) episode and general dural enhancement in 1 (5%) episode (some children presented with multiple complications). These findings indicated an intracranial complication rate of 7% (6/88). Figure 2 displays the timing of imaging studies during AM course in relation with the development of complication(s) (which were the rationales for those studies) and surgical interventions that addressed these findings. Younger children had imaging studies as often as older children; however, they were more likely to undergo surgery. Examples of positive imaging are shown in Figure 3. All children who were included in the study did not present with neurological or other sequelae, with a median follow-up of 3 months, and there were no deaths.

Rationales and findings in imaging studies, according to age pie segments present percent of children in each age group who underwent imaging studies. (A) Rationales for imaging studies, <2 years (n = 12) versus 2–8 years (n = 8). (B) Findings in imaging studies, <2 years (n = 12) versus 2–8 years (n = 8). FNS, focal neurological signs; LOI, lack of improvement despite adequate antibiotic therapy; SA, subperiosteal abscess.
Timing of imaging studies, complications and surgery† during acute mastoiditis course. Not all the children who had AM complication required surgical interventions. (A) Children younger than 2 years (n = 12, all patients underwent CT scans, and 1 also had MRI study). In 2 children, aspirations of subperiosteal abscess were also considered as surgical interventions. (B) Children aged 2–8 years (n = 8, all patients underwent CT scans, and 2 patients also had MRI studies).
Intracranial complications in acute mastoiditis. (A) Axial brain CT, with contrast material. Subperiosteal abscess is seen overlying the destructed squamous part of the right temporal bone (white arrow), with an underlying adjacent epidural abscess (black arrowhead). (B) Axial brain CT, with contrast material. Filling defect in the right sigmoid sinus, suggesting a thrombosis (white arrow).The mastoid cavity is completely opacified, when compared with the partially aerated left mastoid cavity. (C) Coronal brain CT, with contrast material. An epidural abscess, “lens”-shaped, deep to the left temporal bone (white arrow). (D) Coronal contrast-enhanced T1-weighted MRI, demonstrating thickening of the cranial dura mater, extending from the right sigmoid sinus level toward the spinal canal (black arrow). A hypointense lesion is demonstrated within the right suboccipital soft tissue, compatible with a deep subperiosteal abscess (white arrow).

Surgical Interventions

Drainage of a SA was performed in 14 (16%) episodes and was performed more commonly in younger children when compared with older children [9/46 (20%) vs. 5/42 (12%), statistically insignificant]. Mastoidectomy was performed in a total of 14 (16%) episodes, also more commonly in younger children: in 10 of 48 episodes in younger children versus 4 of 42 episodes in older children (P = 0.05).


Our study showed that the majority of children presenting with clinically diagnosed AM, who were adequately treated with intravenous antibiotic therapy, with or without myringotomy, presented with a benign course of disease on a median follow-up period of 3 months. Even though the majority of children in our study did not undergo imaging studies, there were no eventful sequelae.

We favored a conservative approach in the utilization of imaging studies in AM treatment. As previously reported, treatment with a second-generation cephalosporin antibiotic seems to be sufficient in most children.3–5 The addition of myringotomy without ventilating tube insertion in our study was found to be adequate in most children, unlike other authors who recommended that most children should be treated with ventilating tube insertion.5 Temporary drainage of the middle ear through myringotomy alone may reduce the risks after ventilating tube insertion, such as tympanic membrane perforation and cholesteatoma formation.

The younger children group underwent more surgical interventions (SA drainage and mastoidectomy), which resulted in a longer hospital stay. This can be explained by the relatively unaerated mastoid air cells in younger children, which consequently favors the rapid evolvement of SA. Most of the younger children required longer intravenous antibiotic therapy because of the higher pathogenicity of bacteria isolated (data not shown).

Indications for imaging studies in AM include (1) exclusion of extracranial and intracranial complications in children who fail to improve or worsen despite adequate therapy, (2) evaluation of children with neurological signs, (3) assessment of children admitted with salient general state deterioration and (4) assessing possible underlying cholesteatoma.10,12

Recent Triological Society Best Practice 2014 paper on AM, which recommends imaging, states that “if the patient fails to improve after 48 hours, or if there is deterioration in clinical status, a CT scan of the temporal bones should be obtained.”12

CT scans are indispensable in modern medicine; however, the spectacular increases in global use, coupled with relatively high doses of ionizing radiation per examination have raised radiation protection concerns. Children are of particular concern because they are more sensitive to radiation-induced cancer (particularly leukemia and brain cancer) compared with adults and have a long lifespan to express harmful effects that may offset the clinical benefits of performing a scan.21 Radiation doses from contemporary CT scans are likely to be lower than those in 1985–2005, but some increase in cancer risk is still likely from the current scans.22 Furthermore, CT scans are performed more often today because of their high availability, compared with previous years. If considered routine early in the course of each AM in children, CT cost is also a factor. In addition, CT scan for AM includes 2 different protocols: temporal bones scan (thin slices of up to 0.5 mm) without contrast and brain CT with contrast (which doubles the dose of irradiation). In contrast, although MRI is not associated with radiation exposure, it is not available in all medical facilities and is more expensive (anesthesia equipment that is MR compatible). It takes longer to perform an MRI scan, so child sedation is often necessary. In addition, certain new gadolinium-based contrast agents, such as gadobutrol, are currently approved by Food and Drug Administration for use in adults and children aged 2 years and older but cannot be administered to young infants.9

Our findings differ from reported imaging studies ratios from pediatric AM in the literature. A systematic review from 2008 reported that in 39 studies, CT scans were performed in 68% of the patients, on average (range, 3%–100%), and in 9 studies, MRI studies were performed in 30% of the patients (range, 5%–100%). In those reports, an MRI was usually performed to exclude sigmoid sinus thrombosis.8 Our numbers are relatively lower: CT, 23% and MRI, 3%.

In our study, population the rate of intracranial complications was 7%, in line with the previous reports.23 The rate of true positive imaging studies was 40% (8 of 20), and the rate of true negative imaging studies was 60% (12 of 20). These figures should be considered in light of the uneventful progression of all of our patients, who were followed up for at least 3 months after the AM episode. Hence, we believe that we did not miss any intracranial complications. These findings support our conservative approach to the use of imaging studies.

An MRI is an excellent tool for the assessment of AM and concurrent SAs, and it is the gold-standard method for the detection of AM-associated intracranial complications. In this study, we performed a supplementary MRI scan in 3 (3%) patients, when CT scans were either inconclusive or intracranial complications were suspected. Yet, some findings in MR studies can be incidental and should be clinically correlated. For example, a fluid signal intensity in the mastoid observed in T2-weighted images should not be interpreted as a sign of mastoiditis, unless signs and symptoms of inflammation coexist.20 The low specificity of MRI for mastoid findings has also been shown in T1-weighted images, with or without contrast material.7

The main strengths of our study were the clinically based diagnosis of AM episodes, which were detailed and stringently applied by senior physicians who gathered the data. The treatment protocol for most AM patients was similar, combining an intravenous second-generation cephalosporin and myringotomy that have been proven to be adequate in most cases.

We acknowledge limitations of our study. About one third of the children were previously treated with oral antibiotics, which may have changed both AM presentation and progression; however, this is true also in other reports.10,11 We conclude that imaging studies for AM in children are not always mandatory and can be postponed without an increase in complications rate or AM sequelae.


The authors thank Dr. David P. McCormick, from the University of Texas Medical Branch, Galveston, TX, for reviewing this manuscript. They also thank Ms. Nitzhit Zlikovsky, archivist, for her invaluable assistance. They further thank their residents for their hard work in the treatment of children with acute mastoiditis.


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acute mastoiditis; imaging; intracranial complications; management

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