Acute Mastoiditis with Retroauricular Abscess: An Expert Guide to Diagnosis, Imaging, and Treatment

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 Acute Mastoiditis with Retroauricular Abscess: An Expert Guide to Diagnosis, Imaging, and Treatment

Keywords: acute mastoiditis, retroauricular abscess, otitis media, temporal bone, mastoid CT, pediatric infection, mastoidectomy

Introduction

Acute mastoiditis with retroauricular abscess is a rare but serious complication of acute otitis media (AOM). Although antibiotics have significantly reduced the incidence of mastoiditis, it remains a critical diagnosis due to its potential for intracranial spread and long-term morbidity. In this expert column, we examine the etiology, pathophysiology, imaging features, diagnosis, and management of acute mastoiditis with retroauricular abscess, integrating clinical case insights and evidence-based literature.

Epidemiology

Acute mastoiditis primarily affects children under the age of 5. It is considered the most common complication of untreated or inadequately treated acute otitis media, with a prevalence rate of approximately 0.24 cases per 100,000 children annually in developed countries due to widespread antibiotic usage.

Etiology and Pathophysiology

The condition typically arises from bacterial extension of middle ear infections into the mastoid air cells, part of the temporal bone. The most common pathogens include:

  • Streptococcus pneumoniae (most frequent, ~65%)

  • Haemophilus influenzae (less common but more aggressive)

  • Aspergillus species (in immunocompromised or elderly patients)

  • Mycobacterium tuberculosis (increasingly recognized in immunosuppressed populations)

The infection begins as a suppurative inflammation in the mucosa lining the mastoid air cells. This can progress to osteitis, abscess formation, and bone erosion, resulting in retroauricular abscesses or even intracranial complications like meningitis or brain abscess.

Clinical Presentation

Patients with acute mastoiditis often present with:

  • Postauricular pain, erythema, and swelling

  • Protrusion of the auricle

  • Fever

  • Otorrhea

  • Hearing loss

The presence of a fluctuant retroauricular mass suggests a subperiosteal abscess, which may require urgent drainage.

Imaging Features

CT (Computed Tomography)

CT is the first-line imaging modality due to its excellent bone resolution. Findings include:

  • Partial or complete opacification of mastoid air cells (early sign)

  • Cortical bone erosion of the mastoid walls

  • Soft tissue collection in the retroauricular space

  • Fluid with peripheral enhancement, suggesting abscess formation

Figure 1. Axial CT image demonstrates mastoid opacification with associated soft tissue swelling and rim-enhancing fluid collection posterior to the auricle, indicative of retroauricular abscess.

MRI (Magnetic Resonance Imaging)

MRI is useful for intracranial extension or vascular complications. Key sequences:

  • T1-weighted: Low signal intensity in the inflamed mastoid

  • T2-weighted: High signal from fluid and edema

  • Post-contrast: Mucosal and abscess rim enhancement

  • DWI/ADC: May show restricted diffusion in abscess

Differential Diagnosis

  • Cellulitis

  • Cholesteatoma

  • Langerhans cell histiocytosis

  • Temporal bone tumor

  • Petrositis

Treatment

Antibiotic Therapy

Empirical broad-spectrum intravenous antibiotics are the first step. Typical regimens include:

  • Ceftriaxone or cefotaxime

  • Addition of vancomycin in resistant cases

  • Consider antifungal or anti-tuberculous therapy for rare pathogens

Surgical Intervention

Indicated in:

  • Abscess formation

  • Failure of medical therapy

  • Intracranial extension

Procedures include:

  • Myringotomy with or without tube placement

  • Mastoidectomy for drainage and debridement

Complications

Untreated or late-treated cases may result in:

  • Subperiosteal abscess (retroauricular abscess)

  • Bezold's abscess

  • Citelli's abscess

  • Labyrinthitis

  • Petrositis

  • Epidural/subdural abscess

  • Meningitis

  • Facial nerve palsy

  • Sigmoid sinus thrombosis (Griesinger’s sign)

Prognosis

With early diagnosis and treatment, the prognosis is excellent. Delayed intervention, however, may result in life-threatening complications or long-term hearing loss. Surgical outcomes are favorable when appropriate drainage and antibiotics are used in combination.

Clinical Case Insight

The CT findings in the uploaded image and document clearly show:

  • Right mastoid air cell opacification

  • Cortical destruction of the posterior mastoid wall

  • Rim-enhancing collection in the retroauricular region

  • No subdural empyema or dural sinus thrombosis

This presentation is typical of acute mastoiditis with retroauricular abscess, aligning well with the textbook radiographic features.

Quiz

1. What is the most common causative organism in acute mastoiditis?

A. Haemophilus influenzae
B. Aspergillus fumigatus
C. Streptococcus pneumoniae
D. Mycobacterium tuberculosis

2. Which imaging finding most reliably confirms the diagnosis of acute mastoiditis?

A. Mucosal thickening
B. Partial mastoid cell opacification
C. Cortical bone erosion
D. Sinusitis

3. Which of the following is an intracranial complication of acute mastoiditis?

A. Otitis externa
B. Petrositis
C. Sigmoid sinus thrombosis
D. Bell’s palsy

Answer & Explanation

1:  Answer: C. Streptococcus pneumoniae.  Explanation: This organism accounts for over 60% of acute mastoiditis cases, particularly in children.

2:  Answer: C. Cortical bone erosion. Explanation: While opacification can be nonspecific, bone erosion confirms mastoiditis severity.

3:  Answer: C. Sigmoid sinus thrombosis. Explanation: It's a serious complication due to infection spreading via emissary veins.

Conclusion

Acute mastoiditis with retroauricular abscess remains a clinically significant diagnosis, particularly in pediatric otolaryngology. Prompt recognition through clinical signs, imaging, and targeted management is crucial to preventing complications. With ongoing surveillance and advanced imaging techniques, the outcomes for these patients continue to improve.

References

[1] J. D. Swartz, H. R. Harnsberger, Imaging of the Temporal Bone, Thieme Publishing Group, ISBN: 3136884035.

[2] M. F. Mafee, E. L. Singleton, G. E. Valvassori, “Acute otomastoiditis and its complications: role of CT,” Radiology, vol. 155, no. 2, pp. 391–397, 1985. [PubMed]

[3] E. Vazquez et al., “Imaging of complications of acute mastoiditis in children,” Radiographics, vol. 23, no. 2, pp. 359–372, 2003. doi:10.1148/rg.232025076

[4] R. Saat et al., “MR imaging features of acute mastoiditis and their clinical relevance,” AJNR Am J Neuroradiol, vol. 36, no. 2, pp. 361–367, 2014. doi:10.3174/ajnr.A4120

[5] I. Platzek et al., “Magnetic resonance imaging in acute mastoiditis,” Acta Radiol Short Rep, vol. 3, no. 2, 2014. doi:10.1177/2047981614523415

[6] M. H. McDonald, M. R. Hoffman, L. R. Gentry, “When is fluid in the mastoid cells a worrisome finding?,” J Am Board Fam Med, vol. 26, no. 2, pp. 218–220, 2013. doi:10.3122/jabfm.2013.02.120190

[7] K. Patel, A. Almutairi, M. Mafee, “Acute Otomastoiditis and Its Complications: Role of Imaging,” Operative Techniques in Otolaryngology, vol. 25, no. 1, pp. 21–28, 2014. doi:10.1016/j.otot.2013.11.004

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