The key to avoiding damage to the horizontal facial nerve in middle-ear surgery is to formally identify the nerve in the early stages of the procedure.
In the non-infected ear this can be achieved relatively easily by identifying the oval window niche. However, in the infected ear with cholesteatoma, the safest landmark to use is the processus cochleariformis, which can be identified by three different methods.
In an infected ear that is full of granulation tissue and/or cholesteatoma, the horizontal facial nerve can be reliably identified by locating the processus cochleariformis using the three methods described. This avoids damage to the nerve and important structures around it.