Type I Saltzman persistent left trigeminal artery (PTA) with hypoplastic caudal basilar artery and distal vertebral arteries. (The case is courtesy of Dr. Ahmad Yousry, MD.)
Types of persistent carotid-verebrobasilar anastmosis:
Persistent trigeminal artery (PTA) : the most common persistent carotid-verebrobasilar anastmosis with cavernous ICA to basilar artery (BA) anastmosis, Neptune's trident sign on angiography. Types of PTA:
- Saltzman type I: PTA supplies the distal vertebrobasilar arteries. Absent PCOM. The caudal BA is absent or hypoplastic with hypolplastic distal vertebral arteries.
- Saltzman type II: PTA supplies the superior cerebellar arteries with the PCAs are supplied via the PCOM.
Persistent hypoglossal artery: It connects the cervical ICA at the level of C1-C2 to basilar artery via hypoglossal canal. This anastomosis parallels the hypoglossal nerve. It is the 2nd most common persistent carotid-vertebrobasilar anastomosis.
Persistent otic artery (POA): Courses from petrous ICA within the carotid canal and exits through internal acoustic meatus to caudal BA. Vertebral arteries may be absent or hypoplastic, POA may be dominant or only supply to the BA.
- Persistent proatlantal intersegmental artery (PIA): cervical ICA to vertebrobasilar system. Most caudal of PCBAs. Originates usually from cervical ICA at C2-C3 level (type I) or less commonly from the ECA (type II) or rarely from the CCA. PIA communicates with vertebral artery coursing between arch of C1 and occiput. Vertebral arteries may be absent or hypoplastic, PIA may be dominant or only supply to BA.
Fetal origin of the PCA: hypertrophied PCOM supplies the PCA with atretic P1 segment of the PCA.