Thin-section bone-algorithm CT: trace the fracture through the otic capsule, the facial nerve canal, the carotid canal and the venous sinuses — those four decide what happens next.
Orient first
- The temporal bone holds the cochlea and labyrinth (otic capsule), the facial nerve canal, the ossicles and the petrous carotid canal. A fracture matters by what it crosses, not by its direction.
- Pneumocephalus, fluid in the mastoid air cells or middle ear, and an air-fluid level in the sphenoid sinus in a trauma patient are indirect signs of a skull-base fracture until proven otherwise.
- Sutures, vascular channels and the normal fissures of the temporal bone (petrotympanic, tympanosquamous, the cochlear and vestibular aqueducts) mimic fractures; knowing where they are is how you avoid over-calling.
Acquire the study
- Thin-section (≤ 1 mm, ideally sub-millimetre) bone-algorithm CT of both temporal bones, reconstructed in the axial and CORONAL planes; the head CT data set can be re-reconstructed rather than re-scanned.
- Compare with the contralateral side on every slice — the normal side is the internal control for a subtle fissure.
- CTA of the head and neck when the fracture involves the carotid canal (blunt cerebrovascular injury screening).
The manoeuvre
- Trace the fracture line from the squamous temporal bone medially on axial bone-window slices, then confirm on coronal reformats.
- Decide OTIC CAPSULE sparing versus violating: follow the line to the cochlea, vestibule and semicircular canals. A line into the capsule is violating.
- Follow the facial nerve canal through its labyrinthine segment, geniculate ganglion, tympanic and mastoid segments, and state whether the fracture crosses it.
- Check the ossicular chain: incudostapedial and incudomalleolar articulation on axial (the "ice cream cone"), and the lenticular process.
- Check the CAROTID CANAL and the jugular foramen; follow any line across the sigmoid and transverse sinuses.
- Look for pneumolabyrinth (air in the cochlea or vestibule) and for fluid levels in the middle ear and sphenoid sinus.
What confirms it
- A lucent line with sharp, non-corticated margins that crosses expected anatomy, with fluid or air in the adjacent compartment.
- Asymmetry against the contralateral temporal bone at the same level.
What licenses you to exclude it
- A normal head CT reconstructed on a soft-tissue kernel does not exclude a temporal bone fracture — the dedicated thin bone reconstruction is required before you say none.
The classic misread
- Calling a normal fissure (tympanosquamous, petrotympanic) or the cochlear aqueduct a fracture — check the other side.
- Describing the fracture only as longitudinal or transverse; the treating team needs capsule, facial canal and carotid status.
- Missing incudostapedial separation because the ossicles were not specifically inspected.