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Bezold abscess

Bezold abscess is suspected when a patient presents with deep neck infection, swelling, or suppuration in the setting of known or suspected mastoid infection. Imaging is performed to confirm the mastoid source and demonstrate the cervical abscess collection extending into deep neck spaces.

Key Images

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Look For First
  • Opacification of middle ear and mastoid air cells with coalescent mastoiditis on CT
  • Low-attenuation, rim-enhancing fluid collection extending inferiorly from the mastoid tip deep to the sternocleidomastoid
  • Mastoid-tip cortical defect or erosion visible on thin-section temporal bone CT with bone reconstructions
  • Tract of infection tracking from the mastoid source through the digastric groove into deep cervical tissues
Key Image Findings
  • CT temporal bone with thin-section bone reconstructions demonstrates trabecular destruction within the mastoid and focal cortical erosion at the mastoid tip, the point of breakthrough.
  • Contrast-enhanced neck CT shows a low-attenuation, rim-enhancing abscess cavity with surrounding inflammatory edema, extending inferiorly from the mastoid source into tissues deep to the sternocleidomastoid muscle.
  • The collection typically courses near the digastric groove, the anatomic pathway through which infection extends from the mastoid compartment into the deep neck.
  • MRI with DWI reveals central diffusion restriction within the abscess, indicating restricted water movement from purulent material, with peripheral enhancement after gadolinium administration.
  • Associated findings include opacification of the middle ear space (otitis media), coalescent mastoiditis with air-cell coalescence, and possible involvement of adjacent mastoid trabecular bone.
  • Mastoid-tip erosion is present in approximately 53% of cases; its absence does not exclude the diagnosis, so absence of visible cortical defect should not be used to rule out Bezold abscess.
  • Vascular imaging (MR angiography or contrast-enhanced CT) is useful to assess for sigmoid sinus thrombosis or internal jugular vein involvement as potential complications.
  • Intracranial extension, though uncommon, should be assessed on both CT and MRI to exclude meningitis, subdural empyema, or brain abscess.
Differential Diagnosis
  • Subperiosteal abscess (from acute mastoiditis): lacks the deeper involvement into the infrahyoid neck and digastric region; collection remains superficial to the sternocleidomastoid.
  • Lymphadenitis or suppurative cervical lymph node: typically shows central low-attenuation without rim enhancement and does not show connection to a mastoid source.
  • Branchial cleft cyst: lacks the inflammatory rim enhancement and central diffusion restriction on MRI; no associated mastoid infection or coalescent changes.
  • Thyroid abscess: located in the midline thyroid gland; no mastoid source and not associated with otomastoiditis.
  • Epidural abscess (intracranial extension): confined to the epidural space; mastoid source may be present, but the collection does not extend into the deep neck.
  • Retropharyngeal abscess from pharyngeal source: can mimic deep neck Bezold abscess; careful attention to the mastoid source and digastric-groove tracking should help distinguish it.
Discussion

Bezold abscess represents a breakthrough perforation of the mastoid cortex with extension of coalescent mastoiditis into deep neck tissues, bypassing the superficial tissues.

The anatomic pathway through the digastric groove is the critical finding that links the mastoid source to the cervical collection and defines the diagnosis.

Coalescent mastoiditis (air-cell coalescence and trabecular destruction) indicates bone-resorbing inflammation and increases the risk of cortical perforation and deep-neck extension.

Absence of a visible mastoid-tip defect on imaging should not exclude the diagnosis; clinical correlation and careful assessment of the collection's relationship to the mastoid are essential.

Complications including sigmoid sinus thrombosis, meningitis, or intracranial empyema must be actively screened for at the time of diagnosis to guide urgent management.

MRI with DWI and vascular sequences adds sensitivity for detecting purulent collections and vascular complications, particularly when cholesteatoma or intracranial infection is a concern.

Reporting Pearls

Clearly state the side, size, and extent of the abscess collection; confirm the presence or absence of a mastoid-tip cortical defect and tract; specify which deep neck spaces are involved (digastric, SCM, infrahyoid); and document any complications (sigmoid sinus thrombosis, intracranial extension) in a concise, organized format.

Pitfalls
  • Failing to obtain dedicated thin-section temporal bone imaging with bone reconstructions, which may miss the mastoid-tip defect and the connection to the mastoid source.
  • Over-relying on the presence of a visible cortical defect; approximately 47% of Bezold abscesses lack a radiologically apparent mastoid-tip erosion, so absence of a defect does not exclude the diagnosis.
  • Misinterpreting a subperiosteal collection overlying the mastoid as a Bezold abscess; careful attention to the depth (deep to the sternocleidomastoid) and the extension into the digastric groove is required.
  • Omitting assessment of the sigmoid sinus and internal jugular vein, intracranial compartment, and skull base; these complications must be evaluated to guide urgent surgical intervention.
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