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Bilateral Persistent Trigeminal Arteries Associated with Bilateral Carotid Aneurysms

2007; Elsevier BV; Volume: 18; Issue: 5 Linguagem: Inglês

10.1016/j.jvir.2007.01.027

1535-7732

Ali Saad, Matthew T. Walker,

Moyamoya disease diagnosis and treatment

During the embryonic development of the intracranial vasculature, several anastomoses exist between the carotid and vertebrobasilar systems. The most common of these to persist into adulthood is the trigeminal artery, which extends from the internal carotid artery to the basilar artery at the level of the cavernous sinus. The prevalence of the trigeminal artery has been reported to be 0.1%–0.6% in large angiographic series (1Silver J. Wilkins R.H. Persistent embryonic intracranial and extracranial vessels.in: Wilkins R. Rengachary S.S. Neurosurgery. 2nd ed. McGraw-Hill, New York, NY1996: 1990-1991Google Scholar). The coexistence of more than one anastomosis in an adult, however, is rare. Herein, we present a case of a patient with bilateral persistent trigeminal arteries (PTAs) with associated aneurysms at their origins. A 55-year-old woman underwent magnetic resonance imaging at an outside institution; an incidental right cavernous internal carotid artery aneurysm was found. The patient was referred to our institution for further evaluation and possible endovascular therapy. Computed tomographic (CT) angiography of the head revealed a 13-mm aneurysm of the right internal carotid artery at its petrocavernous junction. The aneurysm gave rise to a PTA that supplied the posterior circulation (Fig 1a, 1b). An 8-mm aneurysm was seen at the left petrocavernous junction, and that aneurysm gave rise to a left PTA (Fig 1a, 1c). The bilateral PTAs inserted into the mid-basilar artery. The basilar artery proximal to their insertion was hypoplastic. This vascular anatomy precluded further discussion of endovascular therapy. Quain was the first to describe the PTA while studying an autopsy specimen in 1844, and Sutton was the first to demonstrate the anomaly at angiography in 1950 (2Sutton D. Anomalous carotid-basilar anastomosis.Br J Radiol. 1950; 23: 617-619Crossref PubMed Scopus (65) Google Scholar). Since then, the finding has been reported frequently in the literature and is estimated to be present in 0.1%–0.6% of individuals (1Silver J. Wilkins R.H. Persistent embryonic intracranial and extracranial vessels.in: Wilkins R. Rengachary S.S. Neurosurgery. 2nd ed. McGraw-Hill, New York, NY1996: 1990-1991Google Scholar). The embryologic development and involution of these vestigial carotid-basilar anastomoses has been described by Padget (3Padget D. The development of the intracranial arteries in the human embryo.Contrib Embryol. 1948; 32: 205-262Google Scholar). The fetal carotid-basilar anastomoses form on approximately the 24th day of fetal embryogenesis, when the embryo is 3 mm in size. The trigeminal artery arises as the second of two branches of the first aortic arch (the first branch representing the primitive internal carotid). Progressing caudally, the otic, hypoglossal, and proatlantal intersegmental arteries arise similarly, communicating anteriorly with the internal carotid artery and posteriorly with the longitudinal neural arteries. In general, the fetal arteries exist for 7–10 days and transiently serve as the primary blood supply to the longitudinal neural arteries. These fetal arteries disappear by the time the embryo is 14–15-mm in size, at which time the paired longitudinal neural arteries have fused into the basilar artery and the posterior circulation has fully developed (1Silver J. Wilkins R.H. Persistent embryonic intracranial and extracranial vessels.in: Wilkins R. Rengachary S.S. Neurosurgery. 2nd ed. McGraw-Hill, New York, NY1996: 1990-1991Google Scholar). If any of these arteries fail to regress, they become developmental persistent fetal carotid-basilar anastomoses. Except for the proatlantal intersegmental artery, the rate at which these arteries persist is inversely correlated with their order of regression. Consequently, the primitive trigeminal artery, the last to regress, is the most common to persist of the fetal carotid-basilar anastomoses. Bilateral PTAs are rare. Although there are many explanations for the failure of regression of the trigeminal artery, the precise reason is unknown. One explanation is that the cervical portions of the internal carotid artery may become occluded in the fetus, and the forebrain thereby receives blood supply in a retrograde fashion from the basilar artery via these vessels (4Okuno T. Nishiguchi T. Hayashi S. et al.A case of carotid superior cerebellar artery anastomosis associated with bilateral hypoplasia of the internal carotid artery represented as the rupture of posterior cerebral artery-posterior communicating artery aneurysm.No Shinkei Geka. 1988; 16 ([in Japanese]): 1211-1217PubMed Google Scholar). Another possibility, and this was observed in our case, is that the posterior circulation may not develop completely and, to maintain supply to the hindbrain, the PTAs cannot regress and persist after birth. PTAs are associated with a variety of vascular malformations and anomalies. These include unilateral or bilateral vertebral artery hypoplasia, absence of the posterior communicating artery, hypoplasia or absence of the proximal portion of the basilar artery, arteriovenous malformations, brain tumors, carotid-cavernous fistulas, moyamoya disease, and aortic arch anomalies (1Silver J. Wilkins R.H. Persistent embryonic intracranial and extracranial vessels.in: Wilkins R. Rengachary S.S. Neurosurgery. 2nd ed. McGraw-Hill, New York, NY1996: 1990-1991Google Scholar, 5Cloft H.J. Razack N. Kallmes D.F. Prevalence of cerebral aneurysms in patients with persistent primitive trigeminal artery.J Neurosurg. 1999; 90: 865-867Crossref PubMed Scopus (82) Google Scholar). The most important relationship—and the one that is most relevant to our case—is the one between the PTA and aneurysms. There are numerous reports in the literature of aneurysms arising from the PTA or its junction with the internal carotid artery. This occurrence is seen in an estimated 2% of PTA cases (1Silver J. Wilkins R.H. Persistent embryonic intracranial and extracranial vessels.in: Wilkins R. Rengachary S.S. Neurosurgery. 2nd ed. McGraw-Hill, New York, NY1996: 1990-1991Google Scholar). In our case, both anomalous vessels demonstrated aneurysms at their origin with the cavernous internal carotid artery. More commonly, aneurysms arise elsewhere in the cerebral vasculature, occurring in up to 14%–32% of PTA cases (5Cloft H.J. Razack N. Kallmes D.F. Prevalence of cerebral aneurysms in patients with persistent primitive trigeminal artery.J Neurosurg. 1999; 90: 865-867Crossref PubMed Scopus (82) Google Scholar). These high estimates, however, have resulted from studies based on collections of case reports (eg, incidental aneurysm or arteriovenous malformation associated with PTA), which biases the likelihood of finding an aneurysm. Cloft et al (5Cloft H.J. Razack N. Kallmes D.F. Prevalence of cerebral aneurysms in patients with persistent primitive trigeminal artery.J Neurosurg. 1999; 90: 865-867Crossref PubMed Scopus (82) Google Scholar) tried to eliminate this selection bias by retrospectively evaluating a series of 31 patients with PTA and excluding those with symptomatic aneurysms. In that study, incidental asymptomatic aneurysms were seen in 3% of patients with PTA—a value very close to the prevalence of 3.7% in the general population found with retrospective angiographic studies (6Rinkel G.J.E. Djibuti M. Algra A. et al.Prevalence and risk of rupture of intracranial aneurysms: a systematic review.Stroke. 1998; 29: 251-256Crossref PubMed Scopus (1217) Google Scholar). The presence of structural defects in the walls of the cerebral arteries has been suggested as the underlying cause of a cerebral aneurysm coexisting with a PTA (1Silver J. Wilkins R.H. Persistent embryonic intracranial and extracranial vessels.in: Wilkins R. Rengachary S.S. Neurosurgery. 2nd ed. McGraw-Hill, New York, NY1996: 1990-1991Google Scholar). Following the reasoning presented by Cloft et al (5Cloft H.J. Razack N. Kallmes D.F. Prevalence of cerebral aneurysms in patients with persistent primitive trigeminal artery.J Neurosurg. 1999; 90: 865-867Crossref PubMed Scopus (82) Google Scholar), however, the PTA may be a potential site of aneurysm formation simply because it is a bifurcation and has no greater predisposition for aneurysm formation than do other bifurcations. Conversely, a fetal artery that persists into adult life—whether it is a trigeminal artery, sciatic artery, or an aberrant right subclavian artery—often becomes aneurysmal.