Baylor University Medical Center Proceedings January 2014, Volume 27, Number 1 | Page 38

a

c

b

Figure 2. MRI and PET images. (a) Coronal short-tau inversion recovery (STIR) image shows diffuse signal abnormality throughout the cricoid ring, more pronounced
on the right (arrows). (b) Fat-saturated T1-weighted postcontrast image demonstrates peripheral enhancement, particularly involving the right posterior cricoid cartilage
(arrow). (c) Maximal intensity projection (MIP) reconstruction from a PET scan demonstrates increased metabolic activity throughout the cricoid cartilage (arrows).

DISCUSSION
Actinomycosis was originally described in 1878 by Israel, and
the causative organism was isolated in 1891 by Wolfe (1). Actinomyces odontolyticus, a gram-positive anaerobe, is a component of
normal human flora. It has been implicated in CFA (1).
CFA has been called a “great masquerader” in diseases of the
head and neck (2). Bacteria gain entry via a defect in the mucosa
of the upper aerodigestive tract, and infection typically spreads
without regard for tissue planes. CFA commonly presents as
painless swelling over the mandible, which evolves into multiple
abscesses and draining sinus tracts that emit characteristic sulfur
granules. Risk factors for the development of CFA include poor
dental hygiene, trauma, diabetes mellitus, immunosuppression,
and treatment for head and neck neoplasm. Infection is usually
treated with a prolonged course of oral penicillin; more complex
cases may require surgery (1).
On CT imaging, CFA may present as an ill-defined soft
tissue mass with adjacent infiltrative inflammatory change
(3–5). Some studies have reported central low attenuation
and nonenhancement (4, 5). On MRI, lesions demonstrate
elevated T2 and low T1 signal with effacement of adjacent
fat planes (4, 5). PET imaging reveals elevated metabolic
activity, and PET has been used to monitor response to
antibiotic therapy (6). Actinomycosis may be mistaken for a
neoplasm on CT, MRI, and PET imaging given its infiltrative and masslike appearance. In one case series, six of seven
patients with CFA were initially misdiagnosed with cancer
on imaging studies (5).
Laryngeal actinomycosis has been described in case reports,
but few have reported imaging findings in the setting of laryngeal

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involvement (7, 8). Imaging features in our case are similar to
those in other head and neck sites: on CT, a masslike soft tissue
in the cricoid cartilage with effacement of adjacent fat planes
and destruction of cricoid and arytenoid cartilages; on MRI,
T2 signal hyperintensity in the cricoid cartilage with infiltration of adjacent fat planes, peripheral enhancement, and central
necrosis; and on PET, increased metabolic activity that improves
with penicillin therapy.
While rare, actinomycosis remains an important diagnostic
consideration in the head and neck, especially when there is a
clinical history of mucosal damage. While the imaging features
are not specific, CFA is an infection that responds to antibiotics
and should be considered before contemplating more invasive
treatment approaches.
1.
2.
3.
4.

5.

6.
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a