2. fetal-type or fetal PCA (FPCA)
• FPCA is called a full FPCA if the P1 segment is not visualized on computed
tomography angiography (CTA), magnetic resonance angiography (MRA), or
after injection of contrast into the vertebral artery; a partial FPCA if the P1
segment is smaller than the posterior communicating artery (PcomA); or an
intermediate FPCA if the P1 segment is as large as the PcomA.
• the FPCA is a branch of the internal carotid artery (ICA) and is therefore a
part of the carotid system or anterior circulation.
• In cases of non-fetal PCA, the PCom lies superomedial to the oculomotor
nerve, whereas, in cases of fetal PCA, it lies superior or superolateral to it.
• SIGNIFICANCE:-
Fetal PCA – independent risk factor for recurrent Pcom aneurysms.
3.
4. The persistent carotid-vertebrobasilar anastomoses
• variant anatomical arterial communications between the anterior and posterior circulations due to
abnormal embryological development of the vertebrobasilar system.
• persistent trigeminal artery- arises from proximal cavernous ICA
most common TYPE
• Saltzman classification
type I: absent ipsilateral posterior communicating artery
type II: fetal origin of ipsilateral posterior communicating artery
• persistent otic (acoustic) artery
arises from petrous ICA
rare, as it is the first anastomosis to regress
• persistent hypoglossal artery
arises from cervical ICA at C1 to C3 levels
• persistent proatlantal artery
type I arises from internal carotid artery
type II arises from external carotid artery
5. Hypoglossal artery: It arises from the distal
cervical ICA segment, usually between the C1
and C3 vertebral level. After passing through an
enlarged hypoglossal canal, it joins the basilar
artery inferiorly.
PPTA arises from the junction between petrous and
cavernous internal carotid artery, and runs
posterolaterally along the trigeminal nerve
6. left internal carotid arteriogram, anteroposterior
view, shows persistent otic artery (double solid
arrows) arising from internal carotid artery (single
solid arrow) in carotid canal that leaves internal
auditory canal and joins proximal basilar artery
(open arrow)
similar to the hypoglossal artery) but instead of
heading for the hypoglossal canal, it joins the
vertebral artery through the foramen magnum.
