The Neuroradiology Journal 20: 186-189, 2007
www. centauro. it
Persistent Primitive Trigeminal Artery in Monochorial Twins. A Case Report
F. SCAZZERI, S. PICCHIETTI, S. LONZI, G. FERRITO, D. PROSETTI, C. PAOLI* Neuroradiology Unit, Spedali Riuniti; Livorno, Italy * Neurology Unit, Spedali Riuniti; Livorno, Italy
Key words: Persistent primitive trigeminal artery - MRI - MRA
SUMMARY – The trigeminal artery is one of the arterial structures that constitute anastomosis between the carotid and the posterior circulation during fetal life and usually regress. However these arterial structures may persist in adult life and the trigeminal artery is the one that most frequently show such behaviour. We describe the case of two monochorial female twins with a persistent primitive trigeminal artery revealed by magnetic resonance angiography.
Case Report A 46-year-old woman was referred to us for a single lipothymic episode with vertigo, for which a Doppler ultrasound (US) examination of the extracranial cerebral circulation and a transcranial Doppler US examination were carried out. The Doppler US examination revealed abnormal velocities and spectral configuration of both vertebral arteries and basilar artery. We performed neuroradiological investigations including magnetic resonance (MR), magnetic resonance angiography (MRA) and computed tomography (CT) (figure 1), showing the presence of a persistent primitive trigeminal artery originating from the left internal carotid artery (ICA) siphon. The artery had a transsellar course and joined the distal portion of the basilar artery which showed a reduced calibre of the proximal portion, thus in accord with the ultrasound findings. High resolution CT (HRCT) of the sellar region showed a discontinuity of the dorsum sellae in correspondence of the left posterior clinoid process, due to the passage of the trigeminal artery. We think that the patient’s symptoms should be considered aspecific and therefore the arterial anomaly should be considered an occasional finding. 186
A monochorionic twin of our patient showed similar patterns of velocity and spectral configuration to the transcranial Doppler US. Therefore we obtained permission for an evaluation with CT and MRA (figure 2) also in this patient, finding an abnormal artery identified as a persistent primitive trigeminal artery branching from the medial wall of the right carotid siphon, running an intrasellar course and finally joining the basilar artery through a discontinuity of the right lateral edge of the dorsum sellae. Several arterial variants were present in this patient: hypoplasia of the right A1 segment of the anterior cerebral artery and direct branching of the posterior cerebral artery from the carotid siphon. The twins have three more brothers, none of whom has ultrasound alterations dependent on the posterior circle. However, one of them has a fusiform aneurysm of the distal portion of the right common carotid artery. Discussion During fetal life some arterial structures anastomose the carotid and posterior circulations and usually regress. The trigeminal artery develops in the embryo at the stage of 4 mm and, normally, regresses after about seven
F. Scazzeri
Persistent Primitive Trigeminal Artery in Monochorial Twins
A
D
Figure 1 A, B) MRA TOF 3D. C) Axial T2-weighted MRI, D) HRCT. Transsellar course (C,D: arrow) of a persistent trigeminal artery originating from the medial wall of the right carotid siphon and anastomosing with the distal portion of the basilar artery (A,B: arrow). HRCT (D) shows an interruption of the dorsum sellae for the passage of the artery.
B
C
days, at the stage of 7-12 mm 1. However these fetal anastomoses can persist in adult life and among them the persistent primitive trigeminal artery is the most common. It has an angiographic and post-mortem incidence varying between 0.1 and 1%. It is basically a carotidbasilar anastomosis feeding the basilar trunk in hemodynamic balance with other contributors (posterior communicating artery and vertebral arteries). The trigeminal artery originates from the posterior lateral side wall of the carotid siphon, at the C4 (cavernous portion) or C4 and C5 (petrosal portion) junction. Describing a lateral course, after surrounding the superior tract of the dorsum sellae, it reaches the posterior fossa where it runs behind the clivus along the trigeminal nerve and 187
Persistent Primitive Trigeminal Artery in Monochorial Twins
F. Scazzeri
A
Figure 2 A,B) MRA TOF 3D. C) Axial T2-weighted image. Transsellar course (A-C: arrow) of a persistent trigeminal artery originating from the medial wall of the right carotid siphon. Associated hypoplasia of the right A1 segment of the anterior cerebral artery is seen while the posterior cerebral artery originates from the carotid siphon (A: small arrow).
finally joins the basilar artery, usually between the anterior inferior and superior cerebellar arteries 2-4. In other less frequent cases, as in the two subjects of our study, this primitive artery may originate from the medial wall of the carotid siphon and show a transsellar course with direct perforation of the central portion of the dorsum sellae, thus reaching the basilar artery. Usually the proximal portion of the basilar artery is hypoplasic 2. Further variants of the persistent trigeminal artery are described, formed by cerebellar arteries, most frequently the anterior inferior cerebellar artery, which originates from the precavernous portion of the internal carotid. Persistent primitive arteries are usually found incidentally but are believed to be asso188
B
C
ciated with a higher risk of vascular malformation and cerebral aneurysm. However a recent study has shown that the prevalence of aneurysms in these patients is not higher than that in the general population 3,5. Of course the identification of a persistent trigeminal artery with sellar course is of extreme importance when planning surgery for sellar pathology 3. Transcranial Doppler examination usually raises the first suspicion of such a vascular anomaly 6. MR is of some help in the diagnostic process, while MRA gives confirmation without any need for conventional angiography 7-9. From a literature review of the last 20 years, we found only one study describing the presence of a persistent primitive trigeminal artery variant in monochoriotic twins 10.
www. centauro. it
The Neuroradiology Journal 20: 186-189, 2007
References 1 Robertson R, Caruso PA, Truwit CL et Al: Disorders of brain development. In Scott W. Atlas. Magnetic Resonance Imaging of the Brain and Spine. Third Edition. Lippincott Williams and Wilkins, Philadelphia 2002. 2 Boukobza M, Houdart E, Chapot R et Al: Persistent trigeminal artery and its variant. Contribution of MRI and MR-angiography. J Radiol 78: 1147-1151, 1997. 3 Berenstein A, Lasjaunias P, Ter Brugge KG: Surgical Neuroangiography. 2nd edition. Spinger 2004. 4 Uchino A, Mizushima A, Aibe H et Al: MR imaging and MR angiography of persistent trigeminal artery and its variant. Clin Imaging 20: 247-252, 1996. 5 Clofth HJ, Razack N, Kallmes DF: Prevalence of cerebral aneurysms in patients with persistent trigeminal artery. J Neurosurg 90: 865-867, 1999. 6 Strasser S, Forteza A.M, Romano JG: Transcranial sonography in a patient with a persistent trigeminal artery. J Neuroimaging 9: 236-238, 1999. 7 Piotin M, Miralbes S, Cattin F et Al: MRI and MR angiography of persistent trigeminal artery. Neuroradiology 38: 730-733, 1996. 8 Boyko OB, Curnes JT, Blatter DD et Al: MRI of basilar hypoplasia associated with persistent primitive trigeminal artery. Neuroradiology 38: 11-14, 1996.
9 Uchino A, Kato A, Takase Y et Al: Persistent trigeminal artery variants detected by MR angiography. Eur Radiol 10: 1801-1804, 2000. 10 Suzuki S, Morioka T, Matsushima T et Al: Moyamoya disease associated with persistent primitive trigeminal artery variant in identical twins. Surg Neurol 45: 263240, 1996.
Silvia Picchietti, MD U.O. Neuroradiologia Ospedale Civile Viale Alfieri, 36 57124 Livorno, Italy Tel.: +0039 0586 223308 Fax: +0039 0586 223021 E-mail: [email protected]
189
www. centauro. it
Persistent Primitive Trigeminal Artery in Monochorial Twins. A Case Report
F. SCAZZERI, S. PICCHIETTI, S. LONZI, G. FERRITO, D. PROSETTI, C. PAOLI* Neuroradiology Unit, Spedali Riuniti; Livorno, Italy * Neurology Unit, Spedali Riuniti; Livorno, Italy
Key words: Persistent primitive trigeminal artery - MRI - MRA
SUMMARY – The trigeminal artery is one of the arterial structures that constitute anastomosis between the carotid and the posterior circulation during fetal life and usually regress. However these arterial structures may persist in adult life and the trigeminal artery is the one that most frequently show such behaviour. We describe the case of two monochorial female twins with a persistent primitive trigeminal artery revealed by magnetic resonance angiography.
Case Report A 46-year-old woman was referred to us for a single lipothymic episode with vertigo, for which a Doppler ultrasound (US) examination of the extracranial cerebral circulation and a transcranial Doppler US examination were carried out. The Doppler US examination revealed abnormal velocities and spectral configuration of both vertebral arteries and basilar artery. We performed neuroradiological investigations including magnetic resonance (MR), magnetic resonance angiography (MRA) and computed tomography (CT) (figure 1), showing the presence of a persistent primitive trigeminal artery originating from the left internal carotid artery (ICA) siphon. The artery had a transsellar course and joined the distal portion of the basilar artery which showed a reduced calibre of the proximal portion, thus in accord with the ultrasound findings. High resolution CT (HRCT) of the sellar region showed a discontinuity of the dorsum sellae in correspondence of the left posterior clinoid process, due to the passage of the trigeminal artery. We think that the patient’s symptoms should be considered aspecific and therefore the arterial anomaly should be considered an occasional finding. 186
A monochorionic twin of our patient showed similar patterns of velocity and spectral configuration to the transcranial Doppler US. Therefore we obtained permission for an evaluation with CT and MRA (figure 2) also in this patient, finding an abnormal artery identified as a persistent primitive trigeminal artery branching from the medial wall of the right carotid siphon, running an intrasellar course and finally joining the basilar artery through a discontinuity of the right lateral edge of the dorsum sellae. Several arterial variants were present in this patient: hypoplasia of the right A1 segment of the anterior cerebral artery and direct branching of the posterior cerebral artery from the carotid siphon. The twins have three more brothers, none of whom has ultrasound alterations dependent on the posterior circle. However, one of them has a fusiform aneurysm of the distal portion of the right common carotid artery. Discussion During fetal life some arterial structures anastomose the carotid and posterior circulations and usually regress. The trigeminal artery develops in the embryo at the stage of 4 mm and, normally, regresses after about seven
F. Scazzeri
Persistent Primitive Trigeminal Artery in Monochorial Twins
A
D
Figure 1 A, B) MRA TOF 3D. C) Axial T2-weighted MRI, D) HRCT. Transsellar course (C,D: arrow) of a persistent trigeminal artery originating from the medial wall of the right carotid siphon and anastomosing with the distal portion of the basilar artery (A,B: arrow). HRCT (D) shows an interruption of the dorsum sellae for the passage of the artery.
B
C
days, at the stage of 7-12 mm 1. However these fetal anastomoses can persist in adult life and among them the persistent primitive trigeminal artery is the most common. It has an angiographic and post-mortem incidence varying between 0.1 and 1%. It is basically a carotidbasilar anastomosis feeding the basilar trunk in hemodynamic balance with other contributors (posterior communicating artery and vertebral arteries). The trigeminal artery originates from the posterior lateral side wall of the carotid siphon, at the C4 (cavernous portion) or C4 and C5 (petrosal portion) junction. Describing a lateral course, after surrounding the superior tract of the dorsum sellae, it reaches the posterior fossa where it runs behind the clivus along the trigeminal nerve and 187
Persistent Primitive Trigeminal Artery in Monochorial Twins
F. Scazzeri
A
Figure 2 A,B) MRA TOF 3D. C) Axial T2-weighted image. Transsellar course (A-C: arrow) of a persistent trigeminal artery originating from the medial wall of the right carotid siphon. Associated hypoplasia of the right A1 segment of the anterior cerebral artery is seen while the posterior cerebral artery originates from the carotid siphon (A: small arrow).
finally joins the basilar artery, usually between the anterior inferior and superior cerebellar arteries 2-4. In other less frequent cases, as in the two subjects of our study, this primitive artery may originate from the medial wall of the carotid siphon and show a transsellar course with direct perforation of the central portion of the dorsum sellae, thus reaching the basilar artery. Usually the proximal portion of the basilar artery is hypoplasic 2. Further variants of the persistent trigeminal artery are described, formed by cerebellar arteries, most frequently the anterior inferior cerebellar artery, which originates from the precavernous portion of the internal carotid. Persistent primitive arteries are usually found incidentally but are believed to be asso188
B
C
ciated with a higher risk of vascular malformation and cerebral aneurysm. However a recent study has shown that the prevalence of aneurysms in these patients is not higher than that in the general population 3,5. Of course the identification of a persistent trigeminal artery with sellar course is of extreme importance when planning surgery for sellar pathology 3. Transcranial Doppler examination usually raises the first suspicion of such a vascular anomaly 6. MR is of some help in the diagnostic process, while MRA gives confirmation without any need for conventional angiography 7-9. From a literature review of the last 20 years, we found only one study describing the presence of a persistent primitive trigeminal artery variant in monochoriotic twins 10.
www. centauro. it
The Neuroradiology Journal 20: 186-189, 2007
References 1 Robertson R, Caruso PA, Truwit CL et Al: Disorders of brain development. In Scott W. Atlas. Magnetic Resonance Imaging of the Brain and Spine. Third Edition. Lippincott Williams and Wilkins, Philadelphia 2002. 2 Boukobza M, Houdart E, Chapot R et Al: Persistent trigeminal artery and its variant. Contribution of MRI and MR-angiography. J Radiol 78: 1147-1151, 1997. 3 Berenstein A, Lasjaunias P, Ter Brugge KG: Surgical Neuroangiography. 2nd edition. Spinger 2004. 4 Uchino A, Mizushima A, Aibe H et Al: MR imaging and MR angiography of persistent trigeminal artery and its variant. Clin Imaging 20: 247-252, 1996. 5 Clofth HJ, Razack N, Kallmes DF: Prevalence of cerebral aneurysms in patients with persistent trigeminal artery. J Neurosurg 90: 865-867, 1999. 6 Strasser S, Forteza A.M, Romano JG: Transcranial sonography in a patient with a persistent trigeminal artery. J Neuroimaging 9: 236-238, 1999. 7 Piotin M, Miralbes S, Cattin F et Al: MRI and MR angiography of persistent trigeminal artery. Neuroradiology 38: 730-733, 1996. 8 Boyko OB, Curnes JT, Blatter DD et Al: MRI of basilar hypoplasia associated with persistent primitive trigeminal artery. Neuroradiology 38: 11-14, 1996.
9 Uchino A, Kato A, Takase Y et Al: Persistent trigeminal artery variants detected by MR angiography. Eur Radiol 10: 1801-1804, 2000. 10 Suzuki S, Morioka T, Matsushima T et Al: Moyamoya disease associated with persistent primitive trigeminal artery variant in identical twins. Surg Neurol 45: 263240, 1996.
Silvia Picchietti, MD U.O. Neuroradiologia Ospedale Civile Viale Alfieri, 36 57124 Livorno, Italy Tel.: +0039 0586 223308 Fax: +0039 0586 223021 E-mail: [email protected]
189
