Mastoiditis

Mastoiditis is a suppurative infection of the mastoid air cell system. It is the commonest serious complication of acute otitis media, occurring when infection spreads from the middle ear cleft into the contiguous mastoid air cells.

The clinical spectrum ranges from mastoiditis with periosteitis (a milder, earlier presentation) to coalescent mastoiditis, a more advanced, destructive process with breakdown of the bony septa between mastoid air cells. In the most severe cases there is subperiosteal abscess formation and intracranial extension.

Prompt recognition and treatment are essential, because uncontrolled infection can cause serious sight- and life-threatening complications. This is particularly relevant in the paediatric population, in whom the condition most commonly occurs.

Pathophysiology

• The mastoid air cell system communicates directly with the middle ear cleft via the aditus ad antrum. Acute otitis media is therefore universally accompanied by some degree of mastoid air cell inflammation.
• Acute mastoiditis is progression of this inflammation to a more significant, suppurative infection with the potential for bony destruction and abscess formation. It is not an entirely separate infective process.
• Progression to coalescent mastoiditis reflects breakdown of the thin, bony septa separating individual mastoid air cells, producing a single, confluent, pus-filled cavity.
• Further extension through the outer cortical bone of the mastoid produces a subperiosteal abscess, classically with postauricular swelling and protrusion of the pinna.
• Deeper, more extensive extension can produce serious intracranial complications, including meningitis, extradural or subdural abscess, and lateral sinus thrombosis.
• Streptococcus pneumoniae, Streptococcus pyogenes, and Staphylococcus aureus are the commonest causative organisms, broadly reflecting the bacterial pathogen profile of the acute otitis media from which mastoiditis characteristically evolves.

• The classic presentation of established mastoiditis is postauricular pain, swelling, erythema and tenderness, with protrusion of the pinna. It typically develops in a child with a preceding or concurrent history of acute otitis media.
• Pinna protrusion reflects the underlying subperiosteal abscess or significant mastoid swelling displacing the ear outward and downward or forward, depending on the direction of swelling.
• Fever, often high, and systemic upset accompany the postauricular findings.
• Otoscopy shows evidence of acute otitis media (a bulging, erythematous, or perforated tympanic membrane) or, in some cases, persistent otorrhoea despite apparently adequate treatment of an initial episode.
• A history of inadequately treated, recurrent or persistent acute otitis media, or otitis media that has not responded to standard antibiotics as anticipated, should raise suspicion for evolving mastoiditis. This applies particularly where new postauricular symptoms or signs develop.
• Red flag features suggesting complicated disease with intracranial extension are severe headache, altered consciousness, focal neurological deficit, and meningism. They warrant urgent further evaluation and escalation of care.

• The characteristic clinical presentation substantially supports the diagnosis. The classic combination is postauricular swelling, erythema and pinna protrusion with a preceding or concurrent acute otitis media.
• Contrast-enhanced computed tomography of the temporal bones is the standard, essential imaging investigation. Include the brain where there is any concern about intracranial extension.
• Imaging confirms the diagnosis and characterises the extent of disease, including coalescence, subperiosteal abscess, or any evidence of intracranial extension. This directly informs management planning, particularly the need for and extent of surgery.
• Blood cultures, together with culture of any available middle ear or mastoid discharge, identify the causative organism and guide targeted antibiotic therapy.
• Assess carefully for any feature suggesting intracranial extension, with a low threshold for neuroimaging and further investigation. Missing this advanced complication has serious potential consequences.
• Where meningitis is a relevant consideration, further investigation includes lumbar puncture, following the general principles and precautions for meningitis (see meningitis).

• Intravenous broad-spectrum antibiotic therapy, covering the likely causative organisms, is the essential, standard initial treatment. Guide the regimen and duration by clinical response and, where available, culture and sensitivity results.
• Myringotomy, with insertion of a ventilation tube, is generally performed alongside antibiotic therapy for the great majority of presentations. It drains the middle ear and relieves pressure within the mastoid air cell system.
• Mastoidectomy is surgical drainage and debridement of the infected mastoid air cell system. It is the definitive surgical treatment for more advanced or treatment-refractory disease.
• Indications for mastoidectomy are coalescent mastoiditis, subperiosteal abscess, or inadequate clinical response to intravenous antibiotics and myringotomy alone.
• Any intracranial complication needs urgent management, including neurosurgical involvement and treatment following the principles for the relevant condition (meningitis, brain abscess, and lateral sinus thrombosis).
• Monitor closely as an inpatient throughout the acute treatment course. Transition to oral antibiotics and outpatient follow up once significant clinical improvement is achieved.
• Arrange audiological follow up, given the potential for associated hearing impairment.
• Mastoiditis is a potentially serious complication of acute otitis media, but is generally treated successfully with prompt recognition and appropriate intervention.