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Tau sign

The tau sign represents the appearance of a persistent primitive trigeminal artery on the sagittal plane of an angiogram or on sagittal MRI images. It resembles the Greek letter τ, pronounced 'tau', and is equivalent to the modern day 'T' in the Latin alphabet.

The persistent trigeminal artery arises from the junction between the petrous and cavernous ICA and runs posterolaterally along the trigeminal nerve through, or adjacent to, the cavernous sinus.

Inspired signs
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Article information

rID: 17589
Section: Signs
Synonyms or Alternate Spellings:
  • Tau sign (persistent primitive trigeminal artery)

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Cases and figures

  • Figure 1: schematic: tau sign
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  • Case 1
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  • Case 2: pineal cyst and trigeminal artery
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