Persistent primitive trigeminal artery- a study of two cases
Correspondence Address: Source of Support: None, Conflict of Interest: None DOI: 10.4103/0028-3886.232285
Source of Support: None, Conflict of Interest: None
Multiple foetal arterial anastomoses exist between the internal carotid artery (ICA) and the vertebro-basilar system during the early stages of embryogenesis. These anastomoses include the persistence of the trigeminal, otic, hypoglossal or proatlantal arteries between the two systems of circulation. All these primitive arterial connections regress and then disappear when definitive cerebral circulation forms. One or more of these anastomoses may persist in postnatal life and may result in one of the many insignificant variations in the cerebral circulation. These arterial anastomoses are most often found incidentally during cerebrovascular imaging done for unrelated causes. Out of these, the persistence of the trigeminal artery is the most common variation and is seen in 0.1-1% of the healthy population.[1-6]
A 34-year old male patient was referred to our clinic for the evaluation of chronic headache from the last 2 years. The patient had a normal neurological, ophthalmological and otorhinolaryngological examination.
The computed tomographic (CT) examination was performed on a 64-slice CT scanner (Siemens Healthcare, Germany). The non-contrast CT (NCCT) scan of the head did not reveal any abnormality. On computed tomographic angiogram (CTA), there was a definite vascular connection (the presence of a persistent trigeminal artery) [Figure 1]a, [Figure 1]b, [Figure 1]c between the cavernous segment of the left ICA and the basilar artery. The basilar artery proximal to this vascular connection was hypoplastic. The left PCA also had a fetal origin from the posterior communicating artery.
Based on the CTA examination and the clinical symptoms, it was concluded that the patient may have had headache due to the persistent trigeminal artery. Currently, the patient is taking non-steroidal anti-inflammatory druds (NSAIDS) intermittently for his headache.
A 23-year old male patient was referred to our clinic with ataxia, vertigo and dizziness for the last 1 month. The patient had a normal otological examination.
The MRI examination was performed on a 1.5 Tesla magnetic resonance imaging (MRI) scanner (Magneton Avanton Siemens). On MRI, no abnormality was detected. However, on post-contrast T1 weighted and time of flight images, there was a vascular connection between the cavernous part of ICA and the basilar artery [Figure 2]a and [Figure 2]b. The basilar artery proximal to this vascular connection was hypoplastic. Sagittal magnetic resonance imaging (MRA) showed the characteristic Tau sign [Figure 3].
As all other causes of tinnitus were ruled out, it is possible that the tinnitus that the patient was having was probably attributable to this persistent abnormal vascular connection.
In the majority of cases, persistent trigeminal artery is an incidental finding; however, it is often implicated as a rare cause of various neurological symptoms like headache, tinnitus, ataxia or vertigo. The etiology of vertebrobasilar insufficiency may occasionally be the embolism from the ICA to the posterior circulation via the persistent trigeminal artery.
Based upon its configuration, a persistent trigeminal artery has been classified into 2 types by Saltzman:
Type I: The persistent trigeminal artery reconstitutes the distal basilar artery while the proximal basilar artery is usually hypoplastic, and the ipsilateral posterior communicating artery is absent.
Type II: The persistent trigeminal artery is supplying the superior cerebellar artery, and ipsilateral posterior cerebral artery has an origin from the posterior communicating artery.
In conclusion, we present two cases of trigeminal artery with different symptomology. Both of them can be classified as Saltmanz's Type II persistent trigeminal artery. Thus, a persistent trigeminal artery can be associated with a myriad of neurological symptoms; the course of this persistent artery should be well delineated before undertaking any surgical intervention around this area; and, embolism from the carotid artery can involve the posterior cerebral circulation in patients with a persistent trigeminal artery.
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There are no conflicts of interest.
[Figure 1], [Figure 2], [Figure 3]