B OTH the rare persistent trigeminal. Persistent trigeminal artery" its relationship to the normal branches of the cavernous carotid

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1 Persistent trigeminal artery" its relationship to the normal branches of the cavernous carotid DWIGHT PARKINSON, M.D., AND CHRISTOPHER B. SHIELDS, M.D. Department of Neurosurgery, Faculty of Medicine, University o] Manitoba, Canada The authors report a detailed study of an autopsy specimen indicating that the meningohypophyseal trunk and a persistent trigeminal artery apparently exist independently and have separate origins. KEY WORDS persistent trigeminal artery 9 meningohypophyseal trunk cavernous sinus abdueens nerve B OTH the rare persistent trigeminal artery and the normally present meningohypophyseal trunk are branches of the intracavernous portion of the internal carotid artery. The proximity of their points of origin to each other has intrigued us. Is the meningohypophyseal trunk the incompletely obliterated trigeminal artery? If not, what is their relationship to each other and to the other structures in the cavernous sinus? A fortuitous postmortem examination provided us with the answer in one particular patient. Case Report In 1966, this 78-year-old Icelandic woman suddenly developed fight hemiplegia and aphasia. Left carotid angiography (Fig. 1 ) demonstrated a persistent trigeminal artery which supplied the basilar, superior cerebellar, and contralateral posterior cerebral arteries. The left (ipsilateral) posterior cerebral artery was supplied by a large posterior communicating artery which conformed to Saltzman's Type 2 persistent trigeminal artery. 14 A hypoplastic left vertebral artery terminated in the left posterior inferior cerebellar artery. In 1971 the patient died from causes unrelated to the nervous system. Fortuitously we came across the anomaly during routine postmortem examination of cavernous sinuses as part of an ongoing study of the parasellar anatomy. On incising the lateral wall of the cavernous sinus, a large persistent trigeminal artery was seen arising from the internal carotid artery (Fig. 2). The persistent trigeminal artery coursed laterally and posteriorly, passing immediately beneath the abducens nerve (Fig. 3). Half an inch distal to the origin of the persistent trigeminal artery, the much smaller meningohypophyseal trunk rose normally from the posterior aspect of the internal carotid artery at the apogee of its first forward bend, and then ran in a posteromedial direction above the abducens nerve (Figs. 3 and 4). Viewed from behind, the persistent trigeminal artery lay medial to the trigeminal 244 I. Neurosurg. / Volume 39 / February, 1974

2 Persistent trigeminal artery basilar artery at the junction of its middle and upper thirds, between the left superior cerebeuar and anterior inferior cerebellar artery (Fig. 5). Fro. 1. Left carotid angiogram showing a persistent trigeminal artery (arrow). root and pierced the posterior dural wall of the cavernous sinus through a separate foramen located 1 cm medial to the trigeminal root and 1 cm superolateral to Dorello's canal (Fig. 4). It then joined the Discussion Quain TM in 1844 first described and illustrated the persistent trigeminal artery at autopsy. Angiographic demonstration was published by Sutton in 1950, TM and since then, this anomaly has been noted in 0.1% to 0.2% of angiograms. 7,15 Sunderland 17 found three persistent trigeminal arteries in 210 brains examined at autopsy and collected 12 cases previously recorded. He emphasized the trigeminal artery's proximity to the medial aspect of the trigeminal nerve and the fact that it represents "one of the early anastomotic channels which are usually absorbed as development proceeds." Neither his description nor photographs note the meningohypophyseal trunk. Padget '~ in a scholarly study of cerebral vascular embryology discussed the role of the trigeminal artery. She found it to be relatively constant and often of considerable importance in the early development of the basilar arteries in the human embryo beginning at the 3 mm stage. In early stages the precursors of the basilar artery are supplied largely by the trigeminal artery, which has arisen from the internal carotid FIG. 2. Autopsy photograph (left) and artist's outline (right) of lateral exposure of the left cavernous sinus region. The sixth cranial nerve (VI) runs lateral to the carotid artery and above the point of departure of the persistent trigeminal artery (asterisk). The carotid artery can be seen above the level of the sixth nerve (left arrow), while the right arrow points to the meningohypophyseal trunk. J. Neurosurg. / Volume 39 / February,

3 Dwight Parkinson and Christopher Shields FI6. 3. Autopsy photograph (left) and artist's outline (.right) after complete removal of lateral wall. The persistent trigeminal artery is seen throughout its entire course from its departure from the carotid artery (horizontal arrow) just beneath the sixth nerve (VI) through the point where it pierced the dura (seen as a marked decrease in caliber), and continuing to the right where it approximates the undersurface of the midbrain to join the basilar artery components. The fifth nerve (V) is shown running across the posterior fossa. Vertical arrow indicates the meningohypophyseal trunk. artery. However, its regression is usually subsequent development of the posterior complete at the 45 mm stage. Padget cerebral artery which takes over blood believes this vessel regresses because of the supply to the basilar artery, the increased FIG. 4. Viewed from above through the tentorial notch, after removal of the supratentorial brain, are the left fifth cranial nerve (V), and the trigeminal artery (asterisk) coming through the dura of the clivus running back to join the basilar, superior cerebellar complex partially elevated with a hook which goes straight down to the bottom of the photograph. The sixth nerve is visible just to the right of the persistent trigeminal artery, running parallel to it. The strand running off at an angle to the left of the persistent trigeminal artery is the arachnoid. The cut third nerves are both visible hanging over the tentorial margins on the right and left. 246 J. Neurosurg. / Volume 39 / February, 1974

4 Persistent trigeminal artery FIG. 5. Autopsy photograph (left) and artist's outline (right) of the base of the skull, viewed from above with the right tentorial margin intact and the left nearly completely removed along with the lateral wall and roof of the cavernous sinus region. The fifth cranial nerve (V) on the left is visible departing from the pons and entering the parasellar region. The persistent trigeminal artery (asterisk) can be seen and a solid horizontal arrow points to its departure from the carotid beneath the sixth nerve (VI), which is visible throughout its course on the left. The right sixth nerve (VI) is shown in the posterior fossa only, disappearing into the dura at Dorello's canal. The meningohypophyseal trunk is seen (broken horizontal arrow) and its three branches with the hook holding up the hypophyseal branch as it runs medially. The divergent black arrows indicate the cut ends of the supraclinoid carotid arteries; the cut ends of the right and left second cranial nerves may also be seen (II). Wrapping around the cut end of the brain stem just beneath the tentorial notch are the right and left superior cerebellar arteries shown in direct continuity with the trigeminal artery. The abrupt decrease in caliber of this artery as it left the dural confines is not explained. distance between the carotid and basilar artery, and the increased angulation between the internal carotid and trigeminal arteries. She claims the configuration of the persistent trigeminal artery in the adult is comparable to that of the 11 to 14 mm embryo. The embryological development of the meningohypophyseal trunk is entirely unknown. TM Lie 7,8 suggested that these arteries arose from an identical location on the internal carotid artery, and that the "marginal tentorial artery has occasionally been confused with the trigeminal artery." However, we found separate origins for these vessels. The persistent trigeminal artery arose from the internal carotid artery immediately after entry of the latter into the cavernous sinus, inferior to the abducens nerve. The tentorial artery arose as a branch of the meningohypophyseal trunk above the abducens nerve. Krayenbtihl and Yaw 5 state that the trigeminal artery arises from the internal carotid artery before it enters the cavernous sinus. Inasmuch as the cavernous sinus consists of a plexus of veins 12 with no delineated inferior boundary, we would be reluctant to state categorically that it originates below the cavernous sinus but rather that it originates in the area which is commonly called the cavernous sinus. Most assuredly it originates from the carotid after the carotid arises from the bony base. J. Neurosurg. / Volume 39 / February, ,47

5 In 200 autopsy studies of the cavernous sinus, 11 the meningohypophyseal trunk invariably arose from the posterior aspect of the first apogee of the cavernous portion of the internal carotid artery above the abducens nerve. The artery to the inferior cavernous sinus was also always above the sixth cranial nerve. However, in our patient, the persistent trigeminal artery was inferior to the abducens nerve. This relationship to the abducens nerve is maintained throughout the intradural course of these two vessels, so that the persistent trigeminal is below and the meningohypophyseal trunk and its branches are above. The external diameter of the persistent trigeminal artery was nearly as great as that of the internal carotid and much larger than that of the hypoplastic proximal basilar artery. The normal meningohypophyseal trunk has rarely been identified angiographically because of its small size. 19 In our patient, its external diameter was only one fifth that of the persistent trigeminal artery. The persistent trigeminal artery has no branches, while the meningohypophyseal trunk has three main branches, la If the meningohypophyseal trunk were a rudimentary persistent trigeminal artery it would be surprising if the latter developed branches as it regressed. We have been unable to identify a fibrous ligament in the expected site of the persistent trigeminal artery in normal patients and have no explanation as to its normal fate. The clinical importance of the trigeminal artery has previously been discussed; it has been implicated as a possible cause of trigeminal neuralgia, ~,4,s aneurysm, ~,~ carotid cavernous fistula, 2,3,16,z~ or hemorrhage during surgery near the Gasserian ganglion. 3 The meningohypophyseal trunk may be the site of a Type 2 carotid cavernous fistula ~1 or the origin of some intracavernous aneurysms. 11 References Dwight Parkinson and Christopher Shields 3. Harrison CR, Luttrell C: Persistent carotidbasilar anastomosis. Three arteriographically demonstrated cases with one anatomical specimen. J Neurosurg 10: , Jackson IJ, Garza-Mercado R: Persistent carotid-basilar artery anastomosis: occasionally a possible cause of tic douloureaux. Angiology 11: , Krayenbiihl HA, Yalargil MG: Cerebral Angiography. Philade-lphia, J B Lippincott, 1968, pp Kunc A: Aneurysms of carotid and posterior communicating arteries. Third European Congress of Neurosurgery, Madrid. Amsterdam, Excerpta Medica, Lie TA: Carotid and vertebral anomalies, in Vinken PJ, Bruyn GW (eds): Handbook of Clinical Neurology, Vol 12, Part II. Amsterdam, North Holland Publishing Co, 1971, pp Lie TA: Congenital Anomalies of the Carotid Arteries. Amsterdam, Excerpta Medica, 1968, pp Padget DH: The development of the cranial arteries in the human embryo. Contr Embryol 32: , Padget DH: Personal communication, 1961 I1. Parkinson D: A surgical approach to the cavernous portion of the carotid artery: anatomical studies and case report. J Neurosurg 23: , Parkinson D, Hunt BM: Unpublished data 13. Quain R: The Anatomy of the Arteries of the Human Body and Its Applications to Pathology and Operative Surgery, With a Series of Lithographic Drawings. London, Taylor & Walton, Saltzman GF: Patent primitive trigeminal artery studied by cerebral angiography. Acta Radiol (Stockh) 51: , Stehbens WE: Pathology of the Cerebral Blood Vessels. St Louis, C V Mosby, 1972, pp Sugar O: Pathological anatomy and angiography of intracranial vascular anomalies. J Neurosurg 8:3-22, Sunderland S: Neurovascular relations and anomalies at the base of the brain. J Neurol Neurosurg Psychiat U: , Sutton D: Anomalous carotid basilar anastomosis. Brit J Radiol 23: , Wallace S, Goldberg HI, Leeds NE, et al: The cavernous branches of the internal carotid artery. Am J Roentgen 101:34-46, Wolpert SM: The trigeminal artery and associated aneurysms. Neuroradiol (Minneap) 16: , Dandy WE: Intracranial Arterial Aneurysms. Ithaca, N Y, Comstock Publishing Co, Dandy WE, Follis RH Jr: On the pathology of the carotid-cavernous aneurysms (pulsating exophthalmos). Am J Ophthal 24: , 1941 Present address for Dr. Shields: Department of Neurosurgery, University of Vermont, Burlington, Vermont. Address reprint requests to: Dwight Parkinson, M.D., Neurosurgery, 418 Medical Arts Building, Winnipeg R3C 0L6, Canada. 248 I. Neurosurg. / Volume 39 / February, 1974