Yonsei Medical Journal Vol. 44, No. 6, pp. 1101-1105, 2003 Homonymous Hemianopia after Embolization of an Aneurysm-associated AVM Supplied by the Anterior Choroidal Artery Dong Joon Kim, Dong Ik Kim, Seung-Koo Lee, and Si Yeon Kim Department of Diagnostic Radiology, Yonsei University College of Medicine, Seoul, Korea. The primary objective for the treatment of arteriovenous malformations (AVM) of the brain is to reduce the risk of hemorrhage. The risk of hemorrhage is known to increase with the presence of an aneurysm associated with AVM. The purpose of this report is to describe the development of visual complications after the embolization of a hemorrhagic anterior choroidal artery feeding AVM with an associated aneurysm and to describe the possible causes. Key Words: Intracranial arteriovenous malformations, emboli- zation, therapeutic, cerebral infarction INTRODUCTION The primary objective for treating arteriovenous malformations (AVM) of the brain is to prevent future hemorrhage, or to at least decrease its fre- quency.” Many factors such as deep venous drain- age, prior bleeding, venous stenosis and arterial aneurysms are known to cause a greater incidence of hemorrhage, and these factors must be con- sidered in conjunction with the potential risks and benefits of treatment.’* The purpose of this report is to describe the development of visual complications after the embolization of a hemorrhagic anterior choroidal artery feeding AVM with an associated aneurysm and to describe the possible causes. Received April 11, 2003 Accepted July 18, 2003 Reprint address: requests to Dr. Dong Ik Kim, Department of Diagnostic Radiology, Yonsei University College of Medicine, 134 Shinchon-dong, Seodaemun-gu, Seoul 120-752, Korea. Tel: 82-2- 361-6277, Fax: 82-2-393-3035, E-mail: dikint@yunic.yonsei.ac.kr CASE REPORT A 43 year old man presented with symptoms of acute headache, nausea and vomiting. Intraventri- cular hemorrhage was noted on initial CT and a subsequent MR revealed multiple signal void vas- cular structures in the lateral ventricle with en- larged aneurysmal structures (Fig. 1A). Right ICA angiogram showed an AVM with nidus mea- suring 2.9 x 3.2 x 1.6cm with feeders from the right anterior choroidal artery and the lenticulo- striate arteries. Drainage was into the straight sinus via the basal vein of Rosenthal. There were two flow-related aneurysms distal to the plexal point of the right anterior choroidal artery (Fig 1. B). Because the patient had intraventricular hem- orrhage, probably associated with the aneurysms, the benefits of preradiosurgical embolization of the aneurysms and the nidus was considered to outweigh the potential risks of the embolization procedure and the hemorrhagic risk of the aneu- rysm. After superselection of the plexal segment of the anterior choroidal artery, proximal to the flow related aneurysms with the Elite 1.5 micro- catheter (Boston Scientific, Fremont, CA), 50 mg of sodium amytal was injected intra-arterially (Fig. 1 C). No newly developed neurologic signs in- cluding hemiplegia, hemianesthesia and hemian- opia were noted after the injection of sodium amytal. Twenty-five percent NBCA was injected at this site and occlusion of the aneurysms and the anterior choroidal feeder beyond the plexal point was noted with residual nidus filling from the lenticulostriate feeders (Fig. 1D and E). However, on neurologic examination, immediately after the Yonsei Med J Vol. 44, No. 6, 2003 1102 Dong Joon Kim, et al. Fig. 1. A 43-year-old man presented with symptoms of acute headache, nausea and vomiting. (A) Initial CT (left) revealed intraventricular hemorrhage. MR (right) revealed multiple signal void structures in the lateral ventricle. Enlarged aneurysmal vascular structures were also noted in the right lateral ventricle. (B) Right ICA angiogram AP (left) and lateral (tight) views showed an AVM nidus with feeders from the enlarged right anterior choroidal artery and the lenticulostriate arteries. Drainage was into the straight sinus via the basal vein of Rosenthal. There were flow-related aneurysms distal to the plexal point of the right anterior choroidal artery (arrows). (C) Sodium amytal test after superselection distal to the plexal point (arrow) of the anterior choroidal artery and proximal to the flow related aneurysms. (D) 25% NBCA was injected. (E) Occlusion of the aneurysms and the anterior choroidal feeder beyond the plexal point with residual feeders from lenticulostriate arteries was noted. (F) Post-embolization CT reveals embolic materials in the anterior choroidal artery and the previous site of flow-related aneurysms. (G) A visual field test of the patient two months after the embolization still shows left homonymous hemianopia. Embolization of AVM with Anterior Choroidal Artery Feeder 1103 embolization, the patient developed left homony- mous hemianopia. No pupillary abnormality was noted. The patient did not show any signs of hemiplegia or hemianesthesia. A visual field test performed two months after the embolization showed homonymous hemianopia correlating with the neurologic exams (Fig. 1G). Gamma knife surgery was performed on the residual lesion after embolization. DISCUSSION Embolization of an AVM with arterial supply from the AchA is an effective adjunct to surgery or radiation therapy, but is potentially hazardous as the AchA supplies crucial structures including the internal capsule, basal ganglia, medial tem- poral lobe, optic pathways, cerebral peduncle and choroids plexus of the lateral ventricle” The AchA is a small vessel that originates from the internal carotid artery 2 to 4mm distal to the origin of the posterior communicating artery. It may originate from the proximal middle cerebral artery or the posterior communicating artery.” Anatomical dissections of the AchA consistently separate this artery into its phylogenetically old (inferior cerebral artery) parenchymal ramifica- tion, the cisternal segment, and its newly acquired choroidal ramification, the plexal segment. The cisternal segment supplies the optic tract, cerebral peduncle, uncus, lateral geniculate body, anterior perforating substance (globus pallidus and pos- terior limb of the interncal capsule), tip of the temporal lobe, hippocampus, dentate gyrus, fornix and pulvinar. The plexal segment in most cases originates as a single branch, then passes through the choroidal fissure to supply the choroids plexus.” There are profuse anastomotic communications along the choroid plexus with the PCA and a somewhat lesser number of communications with the pial branches of the PCA in the region of the lateral geniculate body. Perforating branches pas- sing through the anterior perforating substance to the globus pallidus and posterior limb of the internal capsule do not receive any significant collateral supply” Most authors emphasize the absence of branches to the cerebral tissue after the AchA’s ventricular penetration. This allows for the safe endovascular intervention distal to this entry.” However, there have been reports of some branches from the plexal segment supplying the distal part of the optic tract and the thalamus.” Anterior choroidal artery syndrome, caused by an infarct in the territory of AchA, was first described by Foix, et al. in 1925. When complete, the syndrome includes hemiplegia, hemihypoaes- thesiae and a homonymous hemianopia." Hemiplegia has been the most consistently ob- served deficit by the involvement of the posterior two thirds of the posterior limb of the internal capsule. Infarction of the optic tract, lateral geni- culate body, and midbrain is less common, pos- sibly because of the plethora of rich collateral vessels.” Pure homonymous hemianopia from anterior choroidal artery lesions without motor and sen- sory symptoms - as in our case - has rarely been reported.” Hemianopia is the most variable feature of AchA syndrome, possibly because of the collateral vessels. Although the AchA supplies the visual system at three separate loci - the optic tract, the lateral geniculate body, and the origin of the geni- culocalcarine tract in the retrolentiform portion of the internal capsule - involvement of the geni- culocalcrine tract is usually believed to be respon- sible for the visual abnormality.” Various types of visual field defects are related to the AchA infarctions including upper quadrant anopia, sectoranopia by lesions in the lateral geniculate body or homonymous hemianopia by lesions in the posterior optic tract or geniculo- calcarine tract. Ischemia of the geniculcalcarine tract could cause a congruent homonymous hemianopia, pos- sibly sparing the macula with a normal pupillary response. This visual field defect is the most com- mon visual abnormality found in patients with AchA territory infarction, but is often transient because of the rich collateral supply from the PCA branches.’ The reason for development of homonymous hemianopia after superselective embolization be- yond the plexal point in our case can be explained as follows: First, even though embolization be- Yonsei Med J Vol. 44, No. 6, 2003 1104 Dong Joon Kim, et al. yond the plexal point is generally accepted as safe, the vascular anatomy of the anterior choroidal artery is diverse with profuse anastomotic com- munications, and there are reports of branches feeding the distal optic tract and thalamus from the plexal segment.” Embolization of these unusual branches may explain the complication noted in our case. Second, inadvertent injection or migration of embolic material into the proximal cisternal segment may have occurred even though the glue was injected distal to the plexal point. This seems to be a less likely explanation since the postembolization angiogram shows the intact cisternal segment and the embolic material in the intended site of previous aneurysms. Still micro- embolization of the embolic material into the proximal branches cannot be definitively ruled out. Third, the cerebral parenchymal branches are known to originate from the cisternal segment, but this anatomic description is derived from nonpathologic cases. In cases of associated vas- cular malformations - as in our case - the vascular anatomy may have become distorted due to the abnormally high flow burden. Thus, despite the procedural precautions, complications may occur, as in our patient. The coexistence of an aneurysm with an AVM was shown to correlate significantly with intra- cranial hemorrhage at presentation, and when the aneurysm was believed to be responsible for the hemorrhage, early treatment of the aneurysm was shown to have protective effects against hemor- rhage or the recurrence of hemorrhage?” In our case, the flow-related aneurysm asso- ciated with the AVM was regarded as responsible for the hemorrhage; thus, early eradication of the aneurysm from the cerebral circulation and sub- sequent radiotherapy was considered the optimal treatment choice. The benefits of the embolization procedure were considered to outweigh the risks of the interventional procedures performed on the potentially hazardous anterior choroidal artery or the risk of rehemorrhage of an unembolized an- eurysm. Though the authors were aware of the limi- tations of the provocative test with sodium amytal, it was still performed with the micro- catheter tip at the site of anticipated embolization. A positive result from this test may have re- Yonsei Med J Vol. 44, No. 6, 2003 directed the treatment plan, but the negative result we obtained in our case provided little information in predicting the aftermath of the procedure. The streaming character of the flow in the high-flow AVM feeder may have been the cause of a false negative result,” In conclusion, embolization of AVMs with anterior choroidal feeder is a risky procedure with inherent dangers of complications despite precau- tionary measures. The presence of an aneurysm associated with the AVM, as we had in our pa- tient, may further complicate treatment planning. The pros and cons from embolization of an an- eurysm associated AVM should be carefully weighed before initiating therapy. REFERENCES 1. Byrne JV. 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