The Use of Tc-99m-Mononuclear Leukocyte Scintigraphy for Necrotizing External Otitis Diagnosis

Background: Necrotizing external otitis (NEO) is a severe infectious disease in the external acoustic meatus (EAM) and mastoid that may extend to the cranial base. Due to the lack of a gold standard examination technique, the diagnosis is often difficult and delayed. This study aimed to evaluate the sensitivity and specificity of Tc-99m-mononuclear leukocyte scintigraphy associated with Tc-99m-phytate in suspected NEO compared to Tc-99m-MDP and Ga-67-citrate. Methods: A prospective study (32 patients) was conducted between 2011 and 2016. Results: At the end, twenty-four patients remained for the study conduction; nineteen had confirmed NEO diagnosis, one had sarcoma, one had EAM cholesteatoma, one had diffuse simple external otitis, and two had an inconclusive diagnosis. Tc-99m-mononuclear leukocyte scintigraphy plus Tc-99m-phytate was as sensitive as Tc-99m-MDP bone scintigraphy (19/19X9/19), and more sensitive than Ga-67 scintigraphy (19/19 x 17/19). Regarding specificity, it was superior to bone scintigraphy, 100% x 40% (5/5 x 2/5), and Ga-67 scintigraphy, 100% x 20% (5/5 x 1/5). After the infection resolution, all NEO patients had their leukocyte scintigraphy negativized. To the best of our knowledge, this is the first study that evaluates this technique in patients with suspected NEO. Conclusions: Tc-99m-mononuclear leukocyte was revealed to be the best option for NEO because of its specificity.