giovedì 19 novembre 2009

Persistent trigeminal artery (PTA)











Findings

There is an aberrant artery arising from the cavernous segment of the right internal carotid artery, coursing posterior and medial to terminate in the basilar artery. The basilar artery is diminutive below the level of this vessel and is normal in caliber above it.


Differential diagnosis

Variant caroticobasilar anastomosis
- Persistent trigeminal artery (PTA)
- Persistent hypoglossal artery (PHA)
- Persistent otic artery (POA)
- Fetal origin of the posterior cerebral artery (FOPCA)


Diagnosis: Persistent trigeminal artery


Key points

Persistent right trigeminal artery (PTA) is the most common (0.1 - 0.2% of angiograms) of a group of persistent embryonal carotid-basilar artery anastomoses.
Multiple transient connections occur consecutively in fetal life between the carotid and vertebrobasilar circulations (named according to the cranial nerve they parallel):

- Proatlantal intersegmental artery – connects cervical ICA (C2-C3) to the vertebral artery between C1 and the occipital bone
- Persistent hypoglossal artery – cervical ICA (C1-C2) and proximal (caudal) basilar artery; 2nd most common
- Persistent otic artery – petrosal ICA to proximal basilar artery via the internal acoustic meatus; very rare; vertebral arteries may be absent or hypoplastic
- Persistent trigeminal artery – cavernous ICA to distal basilar; may see enlargement of the basilar above the level of this artery; supplies basilar before the vertebral and posterior communicating arteries develop.

Clinical significance: 25% prevalence of other vascular abnormalities (e.g. aneurysms)
Usually asymptomatic but may present with mass effect on adjacent structures like the pituitary and cranial nerves.
No treatment needed if asymptomatic.

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