Chorda Tympani Nerve

A 27-year-old female medical student is on her emergency medicine rotation. She is learning ear anatomy. The following image of her left ear is obtained. Can you help her identify the chorda tympani nerve?  The chorda tympani nerve traverses medial to (“behind”) the malleus and lateral to (“in front of”) the incus. In this image the chorda tympani is visible behind a highly translucent tympanic membrane:

Chorda Tympani Nerve

Surprisingly, the function of this nerve has nothing to do with the ear, it simply traverses the middle ear space where on occasion it can be seen behind a transparent eardrum, as in this case. The nerve is a branch of the facial nerve and provides sensation to the anterior two-thirds of the tongue. It also provides parasympathetic fibers that provide motor innervation to the submandibular and sublingual glands. Here is a second example of the chorda tympani nerve from a 10-year-old female: