Ultrasound findings in Actinomyces infection of the neck
[Aug/Sep 2020]

Ultrasound findings in Actinomyces infection of the neck

AUTHORS:
Anja Brosig, Christopher Bohr, Julian Künzel
Department of Otorhinolaryngology, University Hospital of Regensburg, Germany
Franz-Josef-Strauß-Allee 11
93053 Regensburg
Germany

Preoperative ultrasonographic findings showed an oval hypoechoic inhomogeneous mass, approximately 4 x 3 x 1.5 cm in levels III to IV of the left side of the neck below the sternocleidomastoid muscle. (Fig. 1) The mass was partly indistinct to the adjacent tissue and demonstrated peripheral perfusion with no central vascularity. (Fig. 2) The surrounding soft tissues appeared oedematous and thickened. (Fig. 1 – 2)

Figure 1. Hypoechoic inhomogeneous mass partly indistinct from the adjacent tissue in Levels III to IV of the left neck; ACC = Common carotid artery; MSCM = sternocleidomastoid muscle.

Figure 2. Peripheral vascularity with no central flow or distinct hilum; MSCM = sternocleidomastoid muscle.

There was further lymphadenopathy in the left neck, Levels Ib to II and IV, very close to the mass described above. (Fig. 3 – 4)
Figure 3. Lymphadenopathy Level IV on the left neck. VJI = Internal jugular vein, ACC = Common carotid artery; MSCM = sternocleidomastoid muscle.

Figure 4. Lymphadenopathy at Level Ib to II of the left neck. UK = Mandible.

MRI neck with contrast medium (T1 + CM) 11 days after beginning of treatment
Figure 5. Residual inflammation and fluid collection on the left sternocleidomastoid muscle (arrow), with a small collection in the left thyroid lobe (*). Reactive lymph nodes in the left vascular sheath.

Ultrasonographic check corresponding to MRI
Figure 6. Anechoic foci around the left thyroid lobe (sd) corresponding to the MRI scan. The drain (lasche) is within the area of the previous abscess area.

Sonographic check 2.5 weeks after start of treatment
Figure 7. Status after 2,5 weeks of i.v. antibiotic therapy and drainage. The fluid formation in the left thyroid lobe (sd li) has resolved. The infrahyoid muscle (ihm) and the sternocleidomastoid muscle (mscm) are still mildly thickened. The drain is still in place (lasche in situ). acc = Common carotid artery.

1Case Report

A 17-year old boy was admitted to the hospital with a moderately painful and increasing cervical mass which he first noticed a few days previously. He had been suffering from a strong and productive cough for two weeks but had no fever. Apart from neurodermatitis as a child, no previous illnesses were known. He had been wearing braces since October 2018. There were no abnormalities in the orthodontic check-up one week prior. Physical examination revealed a firm and reddened swelling on the left neck which was painful on palpation and looked like an abscess. The patient had also the beginnings of torticollis. Ultrasound revealed a hypoechoic inhomogeneous mass approximately 4 x 3 x 1.5 cm in size compatible with an infected lymph node collection as well as more discrete lymphadenopathy in the left neck. (Fig. 1 – 4).

An incision of the lymph node collection was carried out on the day of admission and a drain inserted. Histopathologically there was a purulent abscess and chronic-granular inflammation with evidence of actinomycete glands.

Microbiological tests showed no evidence of tuberculosis, toxoplasmosis, Bartonella or MOTT. Although there was no microbiological detection of actinomycetes, an actinomycete infection was assumed.
The patient received intravenous antibiotic therapy with amoxicillin /clavulonic acid for 3 weeks. During the course, a MRI of the neck was performed, which showed residual fluid in the former abscess cavity and another fluid collection in the left thyroid lobe, which appeared to be in contact. (Fig. 5) A sonographic check showed an echo-poor area around the left thyroid lobe corresponding to the MRI findings (Fig. 6). Owing to these findings and continued secretions from the wound area, revision surgery with wound drainage was carried out. Healing and improvement was confirmed on a subsequent sonographic check. (Fig. 7)
The antibiotic therapy was then oralized and the patient was discharged after three weeks in hospital. The total duration of antibiotic treatment was 8 weeks.

2Background
Cervical lymphadenopathy can be caused by many infectious and neoplastic diseases. Infectious mononucleosis, cat scratch disease, toxoplasmosis, syphilis, tuberculosis and HIV infection are examples of infectious diseases that can be associated with a specific reactive lymph node involvement. (1) Actinomycosis is a rare infectious disease caused by actinomycetes, gram-positive, non-acid-fast, mostly anaerobic bacteria. (3, 7) Disease manifestation is found in over 50% of cases in the cervicofacial region. The infection can also affect the thoracic, abdominopelvic and Central Nervous System (CNS) areas. Most cervicofacial infections are odontogenic in nature and develop primarily in male, immunocompetent individuals. (2, 4, 5, 7) The patient described in our case study is an immunocompetent young man with no tooth focus. In this case, the etiology remained unclear. However, a micro lesion of the oral mucosa caused by the dental braces could have been the reason for the infection.

A distinction is made between acute, subacute and chronic forms of actinomycosis. While acute actinomycetes infection usually result in soft tissue swelling or abscess formation, patients with a long history of illness usually develop painless, coarse masses that can also form fistulas with drainage channels to the skin. (4)

3Imaging
Actinomycetes tend to infiltrate the surrounding tissue (4, 6) and this was confirmed sonographically in our case. In the preoperative ultrasound, it was not possible to delineate the cervical abscess from the surrounding tissue. A possible explanation for the infiltrative growth is the production of proteolytic enzymes by the actinomycetes. Since actinomycetes do not spread via the lymphatic system, there is usually no regional lymphadenopathy. (1, 4) Nevertheless, cases have been described, as in our example, where lymphadenopathy also occurred in the areas of infection (1, 5). This can make it difficult to differentiate it from malignant disease.

4Therapy and Outcome
The generally accepted treatment for an actinomycete infection is antibiotic therapy with penicillin or amoxicillin /clavulonic acid. In severe cases, however, a combination of surgical intervention and i.v. antibiotic therapy followed by oral antibiotic therapy for a further 4-6 weeks is necessary. (3, 4). The need for comparatively long antibiotic treatment with this infection is due to the poor penetration of antibiotics within the fibrous tissue. Early termination of therapy should therefore be avoided. With early diagnosis and optimal treatment, actinomycosis has an excellent prognosis. However, since relapses are common, follow-up is indicated. (4, 7)

5Conclusion
The imaging diagnosis of this infectious disease is largely non-specific. An actinomycete infection may present on ultrasound as a mass with a central necrosis zone that cannot be clearly delineated from the surrounding tissue. There may also be associated lymphadenopathy. These features can be difficult to differentiate from malignancy and ultimately require sampling.

6References
1. Amrikachi M, Krishnan B, Finch CJ, Shahab I. Actinomyces and actinobacillus actinomycetemcomitans-Actinomyces-associated lymphadenopathy mimicking lymphoma. Arch Pathol Lab Med. 2000;124:1502–5.
2. Schaal K.P., Lee H.J. Actinomycete infections in humans--a review. Gene. 1992;115:201–211.
3. Moghimi M., Salentijn E., Debets-Ossenkop Y., Karagozoglu K.H., Forouzanfar T. Treatment of cervicofacial actinomycosis: A report of 19 cases and review of literature. Med. Oral Patol. Oral Cir. Bucal. 2013;18:e627–e632.
4. Heo SH, Shin SS, Kim JW, et al. Imaging of actinomycosis in various organs: a comprehensive review. Radiographics 2014;34:19-33.
5. Lancella A., Abbate G., Foscolo A.M., Dosdegani R. Two unusual presentations of cervicofacial actinomycosis and review of the literature. Acta Otorhinolaryngol. Ital. 2008;28:89–93.
6. Park JK, Lee HK, Ha HK, Choi HY, Choi CG. Cervicofacial actinomycosis: CT and MR imaging findings in seven patients. AJNR Am J Neuroradiol 2003;24:331-5.
7. Stájer A, Ibrahim B, Gajdács M, Urbán E, Baráth Z. Diagnosis and Management of Cervicofacial Actinomycosis: Lessons from Two Distinct Clinical Cases. Antibiotics (Basel). 2020 Mar 25;9(4).

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