HRCT of temporal bone illustrating the intratemporal course of the chorda tympani nerve.
Axial images (image1) illustrate branching of the chorda tympani nerve (red arrow) from the proximal mastoid segment of the facial nerve (blue arrow). The chorda tympani can be seen on the posterolateral wall of the middle ear cavity at the level of the manubrium of malleus/long process of incus. The tympanic segment of the chorda tympani cannot be seen as it traverse posteroanteriorly through the middle ear. The chorda tympani reemerge from the anterior wall of middle ear cavity and enters the petrotympanic fissure.
Sagittal images (image 2) demonstrate the superoinferior course of the petrotympanic course. The coronal image (image 3) demonstrate that the petrotympanic course is also in a lateromedial direction.
Lastly the final two axial images (image 4) demonstrate the chorda tympani existing the petrotympanic fissure into the infratemporal course. Note the close proximity to the lateral pterygoid muscle. The chorda tympani will eventually join the lingual nerve.