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.
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