Keywords
anatomical variation - persistent trigeminal artery - stroke
Introduction
The trigeminal artery (TA) is normally present in embryonic life and maintains blood
circulation in the basilar artery before the development of the vertebral artery and
posterior communicating artery. Generally, it appears at the age of 6 days of embryogenesis[1] and maintains its patency up to 7 to 10 days after that its TA undergoes regression,
and if it fails to regress and persists after 10 days of embryogenesis then it is
defined as persist TA.[1] In persistent TA (PTA), the main cavernous segment of the internal carotid artery
(ICA) communicates with the basilar artery (BA) between the anterior inferior cerebellar
artery and superior cerebellar artery[2]
[3]
[4] and the incidence varies from 0.1 to 0.6%[5] with different anatomical variation.[6] PTA and its relationship with the abducens nerve are the basic criteria for its
variations.[7]
Classification of Persistent Trigeminal Artery
-
Salas classification
-
Saltzman angiographic classification
Salas Classification
-
The medial type: Also known as sphenoidal type persistent primitive trigeminal artery (PPTA), it
may be a different carotid-basilar anastomosis of the PTA, and the remnant of this
vessel may form the future meningohypophyseal trunk of the ICA.[8]
-
The lateral type: Also known as petrosal type of PPTA, this is true PTA. In this variety pontine perforating
arteries along with branches to the trigeminal ganglion may arise from the PTA, embryogenesis.
Saltzman angiographic classification: This is a widely accepted classification.
Our case depicts a lateral variation of the PTA and angiographically is a Saltzman
type 1 ([Fig. 1] and [2]). Assessment of presence of collaterals are best evaluated by digital subtraction
angiography (DSA) and presence of collateral shows less extension of infarct.[9]
Fig. 1 (A) Diffusion magnetic resonance imaging (MRI) shows the pinpoint area of diffusion
restriction in the dorsal pon near the 6th nerve nuclei. (B) MRI angiography shows poor visualization of the proximal 2/3 of the basilar artery.
Fig. 2 (A) Digital subtraction angiography (DSA) showing the origin of the lateral type of
persistent trigeminal artery which originates from the left internal carotid artery
(ICA) and good flow in distal 1/3 of the basilar artery. (B) It shows type 1 TPA with no anterograde filling of the basilar artery.
Case Report
A 60-year-old male brought on casualty with complain of sudden-onset giddiness, imbalance
left facial numbness, and double vision. Urgent magnetic resonance imaging (stroke
protocol) was done which was suggestive of acute pontine infarct. Dual antiplatelet
was started and planed for DSA. Cerebral angiography identified the presence of left
PTA, hypoplastic bilateral vertebral artery, and minimal stenosis of the right supraclinoid
ICA ([Table 1]). After angiographic finding dual antiplatelet was started along with physiotherapy
and lifestyle modification was advised. With medical management the patient gradually
improved and was discharged after 4 days.
Table 1
Saltzman[18] and Wollschlaeger[1] angiographic classification of PTA
|
Type 1
|
Type 2
|
Type-3
|
|
Known as fetal PTA
|
Adult type PTA
|
Rare variant
|
|
Absent Pcom
|
Maintain blood flow in SCA and PCA
|
Never terminate in BA
|
|
Hypoplastic/absent distal BA with hypoplastic vertebral arteries
|
It predominantly received blood flow from Pcom A
|
It directly supplies SCA, AICA, and PICA
|
Abbreviations: AICA, anterior inferior cerebellar artery; BA, basilar artery; PCA,
posterior cerebral artery; Pcom, posterior communicating artery; PICA, posterior inferior
cerebellar artery; PTA, persistent trigeminal artery; SCA, superior cerebellar artery.
Discussion
During embryogenesis PTA maintains posterior brain blood circulation until vertebra-basilar
system develops[10]
[11] and after that it undergo natural regression. But in some cases it fails to regress
and manifest in the form of PTA. This is very rare with documented anatomical developmental
variation with a reported incidence of between 0.1 and 0.68%.[10]
[11]
[12]
[13] The presence of ischemic stroke associated with PTA is a rarely reported event and
its contribution to stroke is understood. Hypoplastic proximal BA and bilateral vertebral
arteries may have some role in posterior circulation stroke. PTA can act as the site
for thrombus formation with distal migration which directly contributes to posterior
circulation stroke. The majority of case reports show that PTA may increase the risk
of ischemic stroke[14]
[15]
[16] and it also leads to brainstem transient ischemia stroke.[17]
