Temporal bone CT – Pathology based approach

In this second video about the temporal bone, Dr. Katie Bailey from the University of South Florida goes over some common pathology of the temporal bone. If you haven’t seen the first video and want to learn more about a general approach to reviewing temporal bone CT, go back and check out the first video.

The overview puts this video in the context of the outside-in approach reviewed in the first video. You can think about which diseases are most prevalent in each compartment based on location. A general differential of infection, inflammation, and tumor is a good place to start.

Otitis externa – a common pathology characterized by thickening of the mucosa of the external auditory canal. It may be accompanied by fluid in the mastoids and middle ear.

Malignant otitis externa – a variant of otitis externa in which you have destruction of the adjacent bone. You can also have soft tissue or intracranial abscesses as a complication.

External auditory canal neoplasm – soft tissue in the external auditory canal with adjacent bone destruction. The imaging appearance overlaps with malignant otitis.

Otitis media – characterized by fluid within the middle ear and around the ossicles. Most commonly in the mesotympanum and hypotympanum. There is often associated fluid in the mastoid air cells (otomastoiditis).

Cholesteatoma – a soft tissue mass often originating in Prussak’s space which results in blunting of the scutum and bone erosion.

Ossicular disruption – the ossicular chain can be disrupted, most often in trauma. The most common disruption is the malleoincudal joint, or loss of the “ice cream cone”.

Aberrant ICA – as a variant, the internal carotid artery can be located too medially, where it will lack a complete bony covering in the foramen lacerum. This can lead to complications of mastoid surgery and is important not to miss.

Dehiscent jugular bulb – the jugular vein should also have a bony covering between it and the middle ear.

Tympanicum paraganglioma (glomus tympanicum) – a vascular tumor of the middle ear starting at the cochlear promontory.

Labyrinthitis ossificans – sclerosis of the cochlea or semicircular canals. The cochlea or semicircular canals may be narrowed or sclerotic, usually from prior infection.

Semicircular canal dehiscence – loss of bone adjacent to the semicircular canal. This most commonly occurs along the superior aspect of the superior semicircular canal.

Otosclerosis – abnormal bone most commonly in the fissula ante fenestrum, manifested by lucent bone where it should be dense cortical bone.

Facial nerve – the facial nerve should have a smooth bony covering around it. If you see loss of bone, you should think about a hemangioma or a facial nerve schwannoma, two tumors that frequently occur in this area.

Thanks for tuning in and be sure to come back to check out part 1, temporal bone CT search pattern. Or you can see all of the temporal bone videos or all the search pattern videos.


See this and other videos on our Youtube channel

Temporal bone CT search pattern

Today we have a special guest, Dr. Katie Bailey from the University of South Florida who is presenting her approach to the temporal bone. Special thanks to her for this great video, and hopefully we will be having a lot of great new content from her in the future. This video will be part 1 of 2 in overviewing a starting approach to reviewing the temporal bone.

In this video, she goes through her structure approach to CT of the temporal bone. This approach is based upon an outside-in strategy, where you first look at the external ear, the middle ear, and then the inner ear. The coronal view is a nice place to start.

The key feature of the external ear is the external auditory canal, which should be patent but have a thin lining of mucosa. The external auditory canal ends at the scutum a thin sliver of bone along the top of the EAC.

The middle ear begins at the tympanic membrane, which should be so thin you can barely see it. The tympanic membrane articulates with the long arm of the malleus. A key space above the scutum is called Prussak’s space, which is a common location for cholesteatomas. The middle ear should only contain soft tissue and air. The middle ear is divided into upper (epitympanum), middle (mesotympanum), and lower (hypotempanum) segments. You should also be able to see the footplate of the stapes articulating with the oval window.

The mastoids connect with the middle ear and should be filled with air (no fluid or soft tissue). The roof of the mastoids is the tegmen mastoideum.

The inner ear contains the cochlea and semicircular canals. The cochlea should have 2 ½ turns and be surrounded by bright cortical bone. You have 3 semicircular canals (superior, lateral, and inferior) and should be about the same width. The internal auditory canal is hard to evaluate by CT but should be roughly a similar diameter with no expansion or loss of bone.

The facial nerve canal can be confusing. It is easiest to find at the stylomastoid foramen. You can follow it superiorly before turning and going under the lateral semicircular canal. The bone should be intact until it reaches the geniculate ganglion.

You can then turn to the axial views and review the ossicles. The malleus and incus should look like an ice cream cone. Another key feature is the fissula ante fenestrum, or the cortical bone next to the cochlea. This is a common place where otosclerosis can begin.

Finally, you want to review the axial images for everything out of the temporal bone. This includes the brain, sinuses, orbits, nasal cavity, salivary glands, and visible portions of the pharynx.

Summary. A coronal, outside-in approach to the temporal bone is a nice way to systematically review the temporal bone.

Thanks for tuning in and be sure to come back to check out part 2, temporal bone pathology. Or you can see all of the temporal bone videos or all the search pattern videos.


See this and other videos on our Youtube channel

Temporal bone

This is a collection of videos about the temporal bone. The temporal bone can be intimidating, especially to those just beginning their review of temporal bone imaging, particularly computed tomography (CT). These videos show you a systematic approach to the temporal bone which can help you master the basics and give you a foundation as you move on to learning more specifics about the pathology.