Tau sign

Last revised by Mostafa Elfeky on 28 Jul 2023

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.

The vertical and anterior horizontal limbs of "Tau" are formed by the internal carotid artery (ICA) and the posterior horizontal limb is formed by the proximal portion of the persistent trigeminal artery.

ADVERTISEMENT: Supporters see fewer/no ads

Updating… Please wait.

 Unable to process the form. Check for errors and try again.

 Thank you for updating your details.