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Home , Piriform cortex

Huge Uncal Branch of the Anterior Choroidal Artery

Slobodan MARINKOVIC, Hirohiko GIBO*, and Atila ERDEM**

Institute of Anatomy, School of Medicine, University of Belgrade, Yugoslavia; *Department of Neurosurgery , Shinshu University School of Medicine, Matsumoto, Nagano; **Department of Neurosurgery, University of Ankara Ibn-i Sina Hospital, Ankara, Turkey

Abstract

A huge uncal branch of the anterior choroidal artery was found in one of 22 cerebral hemispheres. The uncal artery measured 0.7 mm in diameter. It gave off small branches to the , as well as a large parahippocampal artery, the accessory anterior temporal artery, and the anterior hippocampal artery. This uncal artery supplied, in addition to the uncus, most of the ventromedial surface of the parahip pocampal gyrus, part of its dorsal surface, the rostromedial portion of the lateral occipitotemporal gyrus, and the rostral part of the . Such a huge uncal artery has implications for surgery in the uncohippocampal region.

Key words: uncal artery, anterior choroidal artery, microanatomy, uncus, , hippocampal formation

Introduction Hussein et al.6' found a large AChA which supplied most of the ventral surface of the , and The anterior choroidal artery (AChA) and its the caudal part of the ventral surface of the temporal branches have frequently been examined.'-5.7.8,'0-'6.'s) lobe. The caliber of the AChA usually ranges from 0.4 to Our study investigated 22 hemispheres, one of 1.25 mm in diameter ,7` but a caliber up to 2.3 mm which contained a huge uncal branch of the AChA. is observed occasionally.") However, the incidence This branch supplied part of the region normally ir of such a large AChA, supplying a larger region of rigated by the PCA. This involvement of the uncal the , does not exceed 0.6%,13' and a large branch of the AChA in the supply of the PCA cor AChA may not occur in as many as 140 cerebral tical territory has not been reported. Such a huge hemispheres.'' The large AChA takes over a part of vessel could have neurosurgical and neuroradiolog the irrigation area of the adjacent cerebral arteries, ical significance, so is described in detail. especially the posterior communicating artery (PCoA) and/or the posterior cerebral artery Materials and Methods (PCA).2,3,6,'3-'5) This large AChA, associated with hypoplasia of the PCA, occurs in only a few cases. This study used 22 cerebral hemispheres removed as Blackburn 2)observed an inverse relationship between soon as possible after death. Catheters were placed the AChA and PCA in two of 220 examined. in the internal carotid artery and PCA in each In both brains, the plexal segment of the AChA gave hemisphere. After perfusion of the arterial system rise to a large arterial stem which left the choroid with physiological saline solution, a 10% mixture of plexus and entered the . This India ink and gelatin was injected into 20 stem continued over the ventral surface of the hemispheres. The specimens were then fixed in a 10% hemisphere giving off the temporal, parieto-oc formaldehyde solution for 3 weeks. The 17 best cipital, and calcarine arteries. The hypoplastic PCA prepared hemispheres were selected, and the AChA, supplied only portions of the midbrain. Similarly, internal carotid artery, middle cerebral artery, and PCA were dissected under the stereoscopic Received October 12, 1993; Accepted March 14, microscope using microsurgical instruments. 1994 Vascular casts were made of two hemispheres by in jection of methylmethacrylate to demonstrate the three-dimensional appearance of the uncal branches. Measurements were made by ocular micrometer. Statistical analysis of frequencies (%), mean values (X), and SD (±), was carried out for the 17 hemispheres injected with India ink.

Results

I. The uncal branches The uncal branches of the AChA were noted in all the hemispheres examined. Two types of these branches were distinguished: the rostral and the caudal. The rostral uncal artery (Fig. 1) was observed in 70.6% (12/17) of the hemispheres, and arose be tween 0.1 and 10.0 mm (X 4.3 ± 3.01 mm) from the origin of the AChA. The rostral uncal artery usually supplied the rostral part of the uncus, i.e. the semilunar and the ambient gyri, and/or the piriform cortex. The caudal uncal artery (Fig. 2) was noted in 94.1% (16/17) of the hemispheres, and arose from 10.1 to 16.8 mm (X 13.7 ± 2.35 mm) from the origin of the AChA. The caudal uncal artery usually sup Fig. 1 The medial view of the vascular cast show plied the caudal part of the uncus, i.e. the uncinate ing the rostra] uncal artery (arrows) arising gyrus, the band of Giacomini, and the intralimbic from the left AChA (1). 2: the perforating gyrus, and occasionally also supplied the rostral part branches of the AChA, 3: the internal carotid of the uncus, and/or the parahippocampal gyrus artery, 4: the PCoA.

Fig. 2 The medial view of the caudal uncal artery (arrows) arising from the left AChA (1). Note a large perforating branch (2), and numerous choroidal branches (3) of the AChA. 4: the distal segment of the left PCA. Fig. 3 A summarized drawing of the ventral (basal) Fig. 4 The medial and ventral view of the left view of the left hemisphere to show the supply hemisphere after removing most of the ing area (a-h) of the rostral and caudal uncal brainstem and diencephalon, showing the branches of the AChA. The uncus is displaced huge caudal uncal branch (arrows) of the left slightly medially. The magnified region cor AChA (1). Compare to Figs. 3 and 5. 2: the responds to the rectangle in the smaller draw caudal part of the uncus; 3: the semilunar ing. a and b: the caudal part of the uncus, c: gyrus; 4: the ambient gyrus; 5: the internal the parahippocampal area, d: the semilunar carotid artery; 6: the ; 7: the col gyrus, e: the caudal part of the ambient gyrus, ; 8: the parahippocampal gyrus; f: the rostral part of the ambient gyrus, g: the 9: a large parahippocampal branch, and 10: piriform cortex, h: the rostral part of the the accessory anterior temporal branch of the parahippocampal gyrus. 1: the uncus, 2: the un uncal artery; note the latter artery gives off cal sulcus, 3: the parahippocampal gyrus, 4: three terminal branches (arrowheads); 11: the the rhinal sulcus, 5: the collateral sulcus, 6: the uncal sulcus; 12, 13, and 14: the anterior, the temporal pole, 7: the . middle, and the posterior temporal arteries arising from the common temporal branch (15) of the distal segment (16) of the PCA. close to the uncal sulcus. The terminal part of the artery, after entering the uncal sulcus, may supply a portion of the rostral and the head of ambient gyrus, in 29.4% (5/17); 4) only the d region, the . in 5.9% (1/17); 5) the dorsorostral part of the uncus We found both the rostral and caudal uncal (a, b, f), and the piriform cortex (g), in 5.9% (1/17); arteries supplied the following regions (Fig. 3): 1) the 6) the entire uncus (a, b, d, e, f), and the g region, in caudal part of the uncus (a, b), with or without the 11.8% (2/17); and 7) the entire uncus (a, b, d, e, f), neighboring parahippocampal area (c), in 17.6% (3/ and the rostral part (c, g, h) of the parahippocam 17) of hemispheres; 2) the a, b, and c regions, as well pal gyrus, in 5.9% (1/17). as most of the semilunar gyrus (d), in 17.6% (3/17); 3) the a, b, and c regions, as well as the caudal part II. The huge uncal artery (e) or both the caudal and the rostral part (f) of the The huge uncal branch of the AChA (Fig. 4), which we found in a left hemisphere, was double the caliber of a "normal" uncal branch, measuring 0.7 mm in contrast to the mean caliber value of 0.33 ± 0.19 mm of the other uncal arteries, which ranged in diameter from 0.10 to 0.51 mm. This huge vessel was a caudal uncal branch of the AChA. It coursed across the medial surface of the uncus (Fig. 4), giving off collateral branches to the caudal part of the uncus and, partially, to the ambient gyrus. The rostral branch of the AChA was absent. The remaining rostral part of the uncus and the piriform cortex were supplied by two uncal branches of the adjacent cerebral arteries. One arose from the internal carotid artery, and the other originated from the anterior temporal branch of the middle cerebral artery. The huge uncal artery then entered the uncal sulcus and fissure, and gave rise to three large branches: the parahippocampal, the accessory an terior temporal, and the anterior hippocampal ar tery (Fig. 4). The first two arteries in all the other hemispheres arose from the PCA. The anterior hip pocampal artery also originated from the PCA in most instances. The parahippocampal artery and the accessory anterior temporal artery left the uncal fissure, and distributed branches over the ventromedial surface Fig. 5 The ventral (basal) view of the left hemisphere, of the parahippocampal gyrus and the adjacent showing the supplying area (dotted) of the huge uncal branch of the AChA. The uncus is regions. They supplied most of the ventromedial sur displaced slightly medially. The magnified face of the parahippocampal gyrus, except the most region corresponds to the rectangle in the caudal portion, as well as the rostromedial part of smaller drawing. 1: the uncus, 2: the uncal the lateral occipitotemporal gyrus (Fig. 5). sulcus, 3: the parahippocampal gyrus, 4: the The anterior hippocampal artery (Fig. 6) coursed rhinal sulcus, 5: the collateral sulcus, 6: the tem through the uncal fissure, i. e. between the ventral sur poral pole, 7: the olfactory bulb. face of the uncal gyrus and the dorsal surface of the parahippocampal gyrus. It continued along the rostral part of the dentate gyrus, close to the head of Discussion the hippocampus, which it completely supplied. There were 16 collateral branches to the hippocam The AChA with the huge uncal branch in our study pal formation, measuring from 80 to 200,um in measured 1.1 mm in diameter, but narrowed to only diameter (Fig. 6). Several branches also supplied a 0.72 mm in diameter after giving off the uncal part of the dorsal surface of the parahippocampal branch. Thus, the huge uncal artery was the reason gyrus (Fig. 6). The terminal part of the anterior hip for the larger caliber of the AChA. This huge uncal pocampal artery formed two anastomoses with the artery perfused the caudal part of the uncus, most of middle hippocampal artery arising from the PCA the ventromedial surface and rostral part of the dor (Fig. 6). The anastomotic channels were both 50,um sal surface of the parahippocampal gyrus, the in diameter. rostromedial part of the lateral occipitotemporal The other AChA branches (the perforating and gyrus, and the rostral portion of the hippocampal the choroidal) were normal. The PCoA and the PCA formation. were not hypoplastic. No variations were found Ours and previous studies show that the AChA among the other cerebral arteries. may take over only the rostral (temporal) part of the cortical region normally supplied by the PCA (our study), or the caudal (temporo-occipital) part," or the rostral, caudal, and medial (temporo-occipito Fig. 6 The dorsal and slightly medial view of the hippocampal and parahippocampal region after remov ing the uncus. The huge uncal artery (cut) (1) gives off a large parahippocampal artery (2), the ac cessory anterior temporal artery (3), and the anterior hippocampal artery (4). 5: the rostral part of the uncal fissure, 6: the dorsal surface of the parahippocampal gyrus, 7: the anterior temporal branch of the PCA (8), 9: the middle hippocampal artery, 10: the dentate gyrus, 11: the fimbria of the hippocampus, 12 and 13: the body and the head of the hippocampus (cut), 14: the uncal recess of the temporal horn of the lateral ventricle.

parietal) portion of the hemispheric regions.' It is in References teresting to note that the huge AChA was more often present in the left than in the right hemisphere. 1) Abbie AA: The clinical significance of the anterior The huge uncal artery found in our study may choroidal artery. Brain 56: 233-246, 1933 have considerable neuroradiological and neuro 2) Blackburn JW: Anomalies of the encephalic arteries surgical significance. The AChA and its huge uncal among the insane. J Comp Neurol Psycho! 17: 493 517, 1907 - branch might be misinterpreted on angiograms as the 3) Goldberg HI: The anterior choroidal artery, in temporal branch of the PCA which arises from the in Newton TH, Potts DG (eds): Radiology of the Skull ternal carotid artery instead of from the PCA.9' and Brain, vol2, Angiography. St Louis, CV Mosby, The huge uncal artery could give rise to the feeding 1974, pp 1628-1639 artery of an arteriovenous malformation located in 4) Helgason C, Caplan LR, Goodwin J, Hedges T: the unco-parahippocampal region. The neuroradio Anterior choroidal artery-territory infarction. Report logical occlusion of the feeding vessel is recommend of cases and review. Arch Neurol 43: 681-686, 1986 ed.") In these cases, as well as in patients with 5) Herman LH, Fernando OU, Gurdjian ES: The aneurysms, tumors, and other pathological processes anterior choroidal artery: An anatomical study of its in the same region, the huge uncal branch must be area of distribution. Anat Rec 154: 95-102, 1966 6) Hussein S, Fullekrug B, Renella RR: Seltene spared during surgery, since it supplies large portions Verorgungsvariante der A. choroidea anterior. Verh of the parahippocampal gyrus, uncus, and the hip Anat Ges 81: 322-323, 1987 pocampal formation. For the same reasons the op 7) Hussein S, Renella RR, Dietz H: Microsurgical posite is true in the neurosurgical treatment of intrac anatomy of the anterior choroidal artery. Acta table "psychomotor" epilepsy with a focus in the hip Neurochir (Wien) 92: 19-28, 1988 pocampal formation ...... ' Cauterization of the huge 8) Lang J, Schaffrath H, Fisher G: Weiter Befunde zu uncal artery will exclude from the circulation most of den Rami diencephalici. Neurochirurgia (Stuttg) 30: the mentioned structures, and thus enable successful 103-107, 1987 surgical removal. 9) Margolis MT, Newton TH, Hoyt WF: The posterior cerebral artery. Gross and roentgenographic anatomy, in Newton TH, Potts DG (eds): Radiology of Skull and Brain, volt, Angiography. St Louis, CV Mosby, 1974, pp 1557-1579 16) Schlesinger B: The Upper Brainstem in the . 10) Marinkovic S: The microanatomical variations of the Berlin, Springer-Verlag, 1976, pp 93-94 uncal, parahippocampal, and hippocampal arteries. 17) Wieser HG, Yasargil MG: Selective amygdalohip Neurosurgeons 12: 86-91, 1993 pocampectomy as a surgical treatment of mesiobasal 11) Marinkovic S, Milisavljevic M, PuškašL: limbic epilepsy. Surg Neurol 17: 445-457, 1982 Microvascular anatomy of the hippocampal forma 18) Yasargil MG: Microneurosurgery, vol 1. Stuttgart, tion. Surg Neurol 37: 339-349, 1992 Georg Thieme Verlag, 1984, pp 66-70 12) Marinkovic S, Milisavljevic M, Vuckovic V: 19) Yasargil MG: Microneurosurgery, vol IIIA. Stut Microvascular anatomy of the uncus and the parahip tgart, Georg Thieme Verlag, 1987, pp 269-280 pocampal gyrus. Neurosurgery 29: 805-814, 1991 13) Otomo E: The anterior choroidal artery. Arch Neurol 13: 656-658, 1985 14) Renella RR: Microsurgery of the Temporo-medial Address reprint requests to: H. Gibo, M.D., Department Region. New York, Springer-Verlag, 1989, pp 25-30 of Neurosurgery, Shinshu University School of 15) Rhoton AL Jr, Fujii K, Fradd B: Microsurgical Medicine, 3-1-1 Asahi, Matsumoto, Nagano 390, anatomy of the anterior choroidal artery. Surg Japan. Neurol 12: 171-187, 1979