[Value of TC99m-Nanocolloid spect in diagnosis and follow-up of necrotizing external otitis]. / La spect TC99m-nanocolloide nella diagnosi e follow up delle otiti esterne necrotizzanti.

ABSTRACT

Necrotizing external otitis (NEO), or malignant external otitis, a severe penetrating infection of the ear canal and the temporal bone, which occurs almost exclusively in diabetic or immunodepressed elderly patients, is caused in most cases by Pseudomonas aeruginosa while Staphylococcus epidermidis and Aspergillus fumigatus have been described as other possible agents. Recently bone scintigraphy, carried out above all employing SPECT, has been considered an important tool in diagnosis and follow-up of NEO. Many Authors confirm the role taken by Technetium99m-methylene-diphosphonate (MDP) and Gallium67-citrate bone scanning. Benecke suggested that response to therapy could be monitored with Ga67 or In111 scans. Two cases of NEO in which diagnosis and follow-up were made using Tc99m-nanocolloid (NC) SPECT are presented in this paper. The Authors discuss the advantages of this latter radiotracer, compared to those obtained with Ga67-citrate, in the follow-up evaluation of therapy efficacy. Tc99m-NC, in fact, is a better inflammation index in that its fixation on bone tissue is determined by the permeability of the basal membrane of vessels. Furthermore, with Tc99m-NC antibiotic therapy may be continued as long as necessary. Bone scintigraphy with other radiotracers may infact result positive for a long period after disease remission in that their fixation is linked to the one remodelling process.