Clinical Imaging Findings of Oropharyngeal Tularemia: The Diagnostic Value of Imaging Findings

Infection caused by Francisella tularensis may manifest as oropharyngeal tularemia (OT). The aim of this study was to characterize the imaging findings of this infection in the head and neck. The medical records and imaging examinations of 13 patients with serologically diagnosed OT were reviewed (8 US, 5 CT, 10 MRI, and 1 PET/CT).The typical presentation of OT (n=13) was an enlarged, non-tender neck mass that was unresponsive to conventional antibiotics. Clinical imaging tools revealed bilateral asymmetric lymphadenopathy with three different shapes: ellipsoid (n=2), round (n=9) and indistinct (n=2). Cutaneous extension and inflammatory stranding of the subcutaneous fat were observed in one patient. The lymph nodes involved level I (n=3), level II (n=11), level III (n=6), level IV (n=3), the parotid space (n=1), and the retropharyngeal space (n=2). US revealed lymph nodes with ellipsoid (n=2) or oval-round (n=6) shape. Three patients exhibited large, necrotic lymph nodes; one of the lymph nodes had invaded the surrounding tissue and could not be differentiated from the sternocleidomastoid muscle on sonography. In one patient, sonography revealed strong echoes within the lymph nodes due to calcifications. Loss of the normal nodal shape with spread into the subcutaneous tissue was observed in two patients. The lymph nodes showed central necrosis and ring enhancement (n=9) mostly in CT and MRI scans, exhibited diffusion restriction and displayed low ADC (apparent diffusion coefficient) values ranging from 0.691x10-3 mm2/s to 0.796x10-3 mm2/s. The one patient who underwent PET/CT, exhibited high FDG uptake (SUV=6.1) in the involved lymph nodes. In OT of the head and neck, most of the imaging features are not characteristic. However, some suggestive imaging features including low-density ring-enhancing LAP showing rare cutaneous extension, conglomeration and calcification including in the upper neck levels and the retropharyngeal space may be observed. Our data suggest that imaging could serve as an easy non-invasive method for the detection and classification of this disease for treatment planning