 What I'd like to do right now is to go over some basic CT anatomy with you by PowerPoint and then we will look at a specific case and review the anatomy. So we're going to start from below and we're going to start at the level of the cochlear aqueduct. What we see here is the cochlear aqueduct. In some cases, it kind of looks like a small internal auditory canal, but this anatomic structure is below the internal auditory canal and, as you can see, is associated with the jugular vein here and the internal carotid artery canal in its petrous portion. So this is at the very lowest, most portion of the interior structures, the cochlear aqueduct. This next section up is a section through the hypotempanum, but it shows very nicely the beginning of the round window. The hypotempanum is marked by the sinus timpani as well as the pyramidal eminence and the facial nerve and the facial nerve recess. This area right here, leading to the basal turn of the cochlea, basal turn of the cochlea, is the round window. So we call this the round window niche. So we're about to enter the cochlea. The importance of the round window is that it is through the round window that the cochlear implants are inserted. That's their way of getting into the cochlea and the various turns of the cochlea. This next slice allows us to see the basal and middle turns of the cochlea. Here we have the basal turn of the cochlea and this is the middle turn. You may be getting a tiny bit of the apical turn. So the cochlea, we say, is the basal, middle and apical turns. We have the entry into the basal turn through the round window. This image also is showing us the endolymphatic sac, which is the soft tissue portion of the vestibular aqueduct. The vestibular aqueduct we usually refer to as the bony part, and what is residing within the bony part is the endolymphatic sac, also part of the inner ear structures. You're also starting to see some of the semicircular canals, including the posterior semicircular canal, and we're just getting a piece of the vestibule as well. The anatomy, another section showing the similar anatomy, and in this section, at least, we can see the entrance of the internal auditory canal, leading to the cochlea basal turn and middle turn, as well as the vestibule, the endolymphatic sac, and portions of these semicircular canals. Our next slice up is through the mid portion of the internal auditory canal. Here is our IAC, the internal auditory canal, and we lead to the cochlea through an area of anatomy called the cochlear aperture. This is a normal cochlear aperture, which, as you can see, is going to be around two millimeters in width. The density in the center of the cochlea is referred to as the medialis. Some people will call it the modiolus, but medialis is what we are using in the east coast, at least, and you also see a very small canal coming off of the posterior portion of the internal auditory canal, and this small canal is the singular canal, which transmits the singular nerve, which is a nerve that goes to the semicircular canals. We have the vestibule here, and if we look carefully at the vestibule, which is the entrance into the labyrinth, you can see the turns of the cora of the stapes. This is the anterior cora of the stapes. This is the posterior cruce of the stapes, cora being the plural. You have the capitellum of the stapes right here. This is going to be our oval window. We talked about the round window leading into the basal turn of the cochlea. This is the oval window in which the stapes sits and inserts on the vestibule. Again, we have the anilinfatic sac or vestibular aqueduct. Let's continue more superiorly. At this juncture, we're at the high portion of the internal auditory canal. What we see here is the internal auditory canal, and we're cutting through portions of it. We're missing the more medial aspect. What we're seeing is this nerve, which is going here. This is our seventh cranio nerve, the facial nerve. We talk about the labyrinthine portion of the facial nerve, the point where it makes its first genu. Right here is where the ganglion is, and the ganglion of the seventh cranio nerve is called the geniculate ganglion, and then it makes that bend back to the tympanic portion of the seventh cranio nerve, or horizontal portion, if you will. This is the anatomy here. You can also see the nerve going here, which is going to the vestibule. This is the vestibule of the labyrinthine, and there's a nerve going to it. We're at the upper posterior portion of the internal auditory canal, so this little canal here is likely to be the canal for the superior vestibular nerve, so facial nerve, anterior and superior, superior vestibular nerve, posterior and superior. We're just catching into the lateral semi-circular canal here. This is the remnant of the endolymphatic sac, or vestibular aqueduct. I think we have one more slice to go through. Here we are seeing portions of the semi-circular canals. We have the two crores of the superior semi-circular canal, and we have a portion of the posterior semi-circular canal. We're just at the very top of the internal auditory canal, just seeing a small portion of the geniculate ganglion, the ganglion of the seventh cranial nerve. The final slice, so there was one more slice, is also through the superior semi-circular canals, so portions of the superior semi-circular canals cut in cross-section. Here's a little bit of the posterior semi-circular canal. This little small structure here is one of the semi-arculate arteries that lead between the crore of the superior semi-circular canal. This would be a diagram of the superior semi-circular canal, and there's a little vessel that courses between the arch of the superior semi-circular canal. That's the CT anatomy we wanted to go through in PowerPoint, and now we will look at it on an actual case with all of the slices available.