Experimental myospherulosis of the paranasal sinuses: A histologic rabbit study

Myospherulosis or lipogranuloma formation is frequently iatrogenic and is c aused by a petrolatum, lanolin, or paraffin based ointment becoming trapped within tissue. Four different ointments, including the newly available Bac troban nasal, were studied in a rabbit paranasal sinus model to evaluate th eir proclivity to induce myospherulosis. The maxillary sinuses of 16 New Ze aland white rabbits were bilaterally inoculated with Bactroban, Bactroban n asal, tetracycline, or bacitracin ointments and compared to saline controls in two rabbits. Sinus specimens were harvested at 2 and 4-week intervals a nd processed for histologic study. Myospherulosis formation was uniformly i nduced with the Bactroban nasal, bacitracin, and tetracycline ointments in 8/8, 7/8, and 8/8 sinuses, respectively. In contrast myospherulosis was not induced in the 5/8 of the sinuses using Bactroban. The data from this inve stigation indicate that Bactroban nasal (paraffin vehide) is similar to bac itracin and tetracycline ointments (petrolatum and petrolatum-lanolin vehic les) in that they all can cause myospherulosis, In contrast, Bactroban (a w ater-soluble, polyethylene glycol base) causes myospherulosis to a much sma ller extent Our results emphasize the differences between the two types of Bactroban preparations and provide objective data that can be evaluated by otolaryngologists who apply these ointments following nasal cavity surgery.