Figure 1
Axial diffusion weighted image
Small area of acute infarct present in right frontal lobe in same patient.
Variants of posterior cerebral circulation: A case of PTA with bilateral FPCA
SectionNeuroradiology
Case TypeAnatomy and Functional Imaging
AuthorsDr.Muhammad Salman Rafique, Dr.Maryam Asghar, Dr.Maham Jehangir
Connected authors
58 years, male
Clinical History
A 58-year-old male patient presented to the emergency department with right-sided body weakness for 4 days. He had no known comorbidities apart from essential hypertension. His initial assessment and baseline workup were carried out. His non-enhanced MRI brain was performed to rule out acute stroke.
Imaging Findings
The non-enhanced MRI brain showed multiple watershed infarcts in deep border zone of left middle cerebral artery (MCA) and anterior cerebral artery (ACA) territory. Another smaller acute infarct was present in the right frontal lobe.
MR angiogram showed that the bilateral posterior cerebral arteries (PCAs) had a fetal origin from posterior communicating arteries (PComs) and P1 segments were absent.
A variant artery was arising from the right internal carotid artery running posterolaterally and then medially to join basilar artery just inferior to the origin of superior cerebellar arteries (SCAs) representing persistent trigeminal artery (PTA) making tau sign on sagittal MRI images.
Caudal part of basilar artery and left vertebral artery were hypoplastic.
The presence of fetal posterior cerebral artery (FPCA) and PTA was classified as type II according to Saltzman classification. However, the FPCA was present bilaterally in this patient in contrast to unilateral FPCA as described in Saltzman type II.
MR angiogram showed that the bilateral posterior cerebral arteries (PCAs) had a fetal origin from posterior communicating arteries (PComs) and P1 segments were absent.
A variant artery was arising from the right internal carotid artery running posterolaterally and then medially to join basilar artery just inferior to the origin of superior cerebellar arteries (SCAs) representing persistent trigeminal artery (PTA) making tau sign on sagittal MRI images.
Caudal part of basilar artery and left vertebral artery were hypoplastic.
The presence of fetal posterior cerebral artery (FPCA) and PTA was classified as type II according to Saltzman classification. However, the FPCA was present bilaterally in this patient in contrast to unilateral FPCA as described in Saltzman type II.
Discussion
The embryologic development of cerebral circulation is a nature’s miracle. At approximately 30-days of gestation, the internal carotid arteries (ICAs) arise from dorsal aortic arches and anastomose with longitudinal neural arteries to form a primitive vertebrobasilar system at four major sites [1] named according to their neighbouring structures as trigeminal, otic, hypoglossal and proatlantal intersegmental arteries. Failure of regression of these vessels lead to persistent primitive carotid-vertebrobasilar anastamoses of which most cephalic and most common is PTA [1]. Its reported prevalence is 0.1%–0.6% [2] of cerebral angiograms. Internal carotid artery gives origin to PTA which then anastomoses with the midbasilar artery. Basilar artery is usually hypoplastic caudal to this anastomosis [2].
There are two types of PTA, lateral and medial. In the lateral type, the artery runs posterolaterally with the trigeminal nerve [2]. Medial type shows intrasellar or transhypophyseal course; the artery runs posteromedially from its origin, compresses the pituitary gland and penetrates the dorsum sellae [2].
PTA is often associated with ipsilateral FPCA where the posterior communicating artery may have the same or greater calibre than ipsilateral P1 segment which may be absent [2]. FPCA is a common variant seen in 30% of individuals; right-sided, left-sided or bilateral in 10 %, 10% and 8 % of the general population, respectively [2].
In Saltzman type 1, PTA supplies the entire vertebrobasilar system distal to the site of anastomosis and the PCom is absent. The caudal basilar artery is absent or hypoplastic with hypoplastic distal vertebral arteries. In Saltzman type 2, PTA supplies the SCAs. There is unilateral FPCA supplied by the PCom [2]. Saltzman type 3 is further subdivided into type 3a, 3b, and 3c if the PTA supplies directly the SCA, AICA, or PICA, respectively. Type 3b is common [3].
PTA may be associated with aneurysms, ischaemia, trigeminal neuralgia and trigeminal cavernous fistula [1, 4]. In 25% of cases, an association of PTA is found with other vascular anomalies of which 14% are aneurysms [5].
In the presence of FPCA, anterior circulation thromboembolism may result in paradoxical PCA territory infarction and vice versa [6].
Manipulation of PTA in parasellar surgical approach or in percutaneous Gasserian ganglion procedure for treatment of trigeminal neuralgia may cause haemorrhage or ischaemia, because PTA passes close to the Meckel's cave [7]. During transsphenoidal surgery for pituitary adenoma accidental transection of persistent trigeminal artery may result in a life-threatening haemorrhage (7).
The knowledge of anatomic variations is important for the surgical/endovascular treatment planning to avoid any unexpected cerebrovascular event.
There are two types of PTA, lateral and medial. In the lateral type, the artery runs posterolaterally with the trigeminal nerve [2]. Medial type shows intrasellar or transhypophyseal course; the artery runs posteromedially from its origin, compresses the pituitary gland and penetrates the dorsum sellae [2].
PTA is often associated with ipsilateral FPCA where the posterior communicating artery may have the same or greater calibre than ipsilateral P1 segment which may be absent [2]. FPCA is a common variant seen in 30% of individuals; right-sided, left-sided or bilateral in 10 %, 10% and 8 % of the general population, respectively [2].
In Saltzman type 1, PTA supplies the entire vertebrobasilar system distal to the site of anastomosis and the PCom is absent. The caudal basilar artery is absent or hypoplastic with hypoplastic distal vertebral arteries. In Saltzman type 2, PTA supplies the SCAs. There is unilateral FPCA supplied by the PCom [2]. Saltzman type 3 is further subdivided into type 3a, 3b, and 3c if the PTA supplies directly the SCA, AICA, or PICA, respectively. Type 3b is common [3].
PTA may be associated with aneurysms, ischaemia, trigeminal neuralgia and trigeminal cavernous fistula [1, 4]. In 25% of cases, an association of PTA is found with other vascular anomalies of which 14% are aneurysms [5].
In the presence of FPCA, anterior circulation thromboembolism may result in paradoxical PCA territory infarction and vice versa [6].
Manipulation of PTA in parasellar surgical approach or in percutaneous Gasserian ganglion procedure for treatment of trigeminal neuralgia may cause haemorrhage or ischaemia, because PTA passes close to the Meckel's cave [7]. During transsphenoidal surgery for pituitary adenoma accidental transection of persistent trigeminal artery may result in a life-threatening haemorrhage (7).
The knowledge of anatomic variations is important for the surgical/endovascular treatment planning to avoid any unexpected cerebrovascular event.
Differential Diagnosis List
Saltzman type II persistent trigeminal artery with bilateral FPCAs instead of unilateral.
Variants of persistent trigeminal artery.
Persistant primitive otic artery.
Final Diagnosis
Saltzman type II persistent trigeminal artery with bilateral FPCAs instead of unilateral.
References
[1] Zampakis P, Panagiotopoulos V, Petsas T, Kalogeropoulou C. (2015) Common and uncommon intracranial arterial anatomic variations in multi-detector computed tomography angiography (MDCTA). What radiologists should be aware of. Insights Imaging 6(1):33-42. (PMID: 25680324)
[2] Dimmick SJ, Faulder KC. (2009) Normal Variants of the Cerebral Circulation at Multidetector CT Angiography 1. Radiographics 29(4):1027-43. (PMID: 19605654)
[3] Ali S, Radaideh MM, Shaibani A, Russell EJ, Walker MT. (2008) Persistent trigeminal artery terminating in the posterior inferior cerebellar artery: case report. Neurosurgery 62(3):E746-8. (PMID: 18425001)
[4] Foerch C, Berkefeld J, Halbsguth A, Ziemann U, Neumann-Haefelin T. (2006) Brain stem infarction caused by proximal internal carotid artery stenosis in a patient with a persisting primitive trigeminal artery. Cerebrovascular Diseases 22(2-3):200-2. (PMID: 16766871)
[5] Lochner P, Zuccoli G, Brigo F, Tezzon F, Trinka E, Nardone R. (2013) Persistent trigeminal artery: an unusual rescue vessel collateralization. Can J Neurol Sci 40:429-30. (PMID: 23603183)
[6] Lambert SL, Williams FJ, Oganisyan ZZ, Branch LA, Mader Jr EC. (2016) Fetal-Type Variants of the Posterior Cerebral Artery and Concurrent Infarction in the Major Arterial Territories of the Cerebral Hemisphere. J Investig Med High Impact Case Rep 4(3) (PMID: 27660767)
[7] Meaney JF, Sallomi DF, Miles JB. (1994) Transhypophyseal primitive trigeminal artery: demonstration with MRA. J Comput Assist Tomogr 18(6):991-3. (PMID: 7962817)
Case information
| URL: | https://www.eurorad.org/case/14926 |
| DOI: | 10.1594/EURORAD/CASE.14926 |
| ISSN: | 1563-4086 |
License
This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.
Figure 2
Axial diffusion-weighted image
Multiple watershed infarcts in deep borderzone of left MCA and ACA territory.
Figure 3
TOF MRA axial MIP image
Bilateral PCAs showing a fetal origin from PComs and P1 segments are absent.
Figure 4
TOF MRA sagittal image, greek letter tau.
PTA arising from junction between petrous and cavernous ICA running posterolaterally along the trigeminal nerve adjacent to the cavernous sinus making tau sign.
Figure 5
TOF MRA coronal MIP image
PTA is arising from the right ICA running posterolaterally and then medially to join basilar artery just inferior to the origin of superior cerebellar arteries representing PTA.
Axial diffusion weighted image
Small area of acute infarct present in right frontal lobe in same patient.
Shifa Int. Hospital, Isb, Pakistan.
Shifa Int. Hospital, Isb, Pakistan.
Axial diffusion-weighted image
Multiple watershed infarcts in deep borderzone of left MCA and ACA territory.
Shifa Int. Hospital, Isb, Pakistan.
Shifa Int. Hospital, Isb, Pakistan.
TOF MRA axial MIP image
Bilateral PCAs showing a fetal origin from PComs and P1 segments are absent.
Shifa Int. Hospital, Isb, Pakistan.
Shifa Int. Hospital, Isb, Pakistan.
TOF MRA sagittal image, greek letter tau.
PTA arising from junction between petrous and cavernous ICA running posterolaterally along the trigeminal nerve adjacent to the cavernous sinus making tau sign.
Shifa Int. Hospital, Isb, Pakistan.
Shifa Int. Hospital, Isb, Pakistan.
TOF MRA coronal MIP image
PTA is arising from the right ICA running posterolaterally and then medially to join basilar artery just inferior to the origin of superior cerebellar arteries representing PTA.
Shifa Int. Hospital, Isb, Pakistan.
Shifa Int. Hospital, Isb, Pakistan.