Snake eyes (facial nerve)

Last revised by Daniel J Bell on 5 Mar 2021

Snake eyes, also known as snail eyes, is a term used to refer to the appearance of the facial nerve on coronal CT within its canal in the petrous temporal bone as the tympanic segment doubles back next to the labyrinthine segment. Anteriorly, these two segments converge at the geniculate ganglion.

Snake eyes refers to the appearance of dice when two "ones" or "pips" are rolled (see picture). Snail eyes refers to these segments located superolaterally to the cochlea, which looks like a snail's shell.

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Cases and figures

  • Figure 1: "Snake Eyes"
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  • Figure 2: "Snake Eyes" (annotated)
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  • Figure 3: "Snake eyes" on dice
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  • Case 1: PTB fracture with loss of normal snake eyes
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