Posterior Choroidal Artery Research Articles

Perivascular nerves of the human basal cerebral arteries: I. Topographical distribution.

In the present study the topographical distribution of the intrinsic nerve plexuses of the basal cerebral arteries in humans was quantified and the relation between vessel diameter and nerve density was investigated. Whole-mount preparations of various segments of the basal cerebral arteries from middle-aged patients were stained for protein gene product (PGP) 9.5. The deep nerve plexuses, located at the adventitial-medial border, were quantified by image analysis. Confocal scanning laser microscopy was used to study nerve plexuses throughout the adventitia. Transverse cryostat sections were stained for PGP 9.5, tyrosine hydroxylase and neurofilament, and quantified. The results showed a three-layered configuration of the adventitial nerves. Measurements on whole-mounts demonstrated that nerve densities were highest in the posterior communicating artery (PCom), and next highest in the proximal parts of the posterior cerebral artery (PCA) and anterior choroidal artery. There appeared to be no clear relation between nerve density and vessel diameter. The measurements on sections confirmed the high nerve densities in the PCom and PCA. Tyrosine hydroxylase- and neurofilament-immunoreactivities appeared to demonstrate separate subpopulations of the overall nerve plexuses, representing sympathetic and, possibly, sensory fibers, respectively. Densities of both subgroups generally followed those of PGP 9.5-immunoreactive nerves. Transmission electron microscopy suggested motor function of the deep nerve plexuses. The results indicate a stronger neuronal influence on this part of the cerebral circulation than hitherto reported. It is concluded that human basal cerebral arteries display a topographical distribution of deep perivascular nerves, and that nerve density is determined by locality rather than by vascular diameter.

The syndrome of posterior choroidal artery territory infarction.

Posterior choroidal artery (PChA) territory infarcts remain the least well-known type of thalamic infarcts. Our study of 10 personal cases, selected from 2,925 stroke patients admitted consecutively to a community-based primary care center, and 10 published cases of unilateral PChA territory infarct suggests that they can often be differentiated clinically from other thalamic infarcts. Patients with PChA territory infarct associated with superficial posterior cerebral artery territory infarct or with another infarct were excluded. Damage was characteristically limited to the lateral geniculate body, pulvinar, posterior thalamus, hippocampus, and parahippocampal gyros, without involvement of the upper midbrain and the anterior nucleus of thalamus. In lateral PChA territory infarct, the most common clinical manifestations included homonymous quadrantanopsia, with or without hemisensory loss and neuropsychological dysfunction (transcortical aphasia, memory disturbances). A homonymous horizontal sectoranopsia is exceptional but particularly suggestive of the involvement of the lateral geniculate body in this territory. Media] PChA territory infarct was less frequent. Its neurologic picture was dominated by eye movement disorders not particularly suggestive of thalamic involvement. Late disability was usually absent or slight, being related to pain and delayed abnormal movements. The most common stroke etiology was presumed small-vessel occlusive disease.

Thalamic haemorrhage.

Thalamic haemorrhage is usually considered a single entity although the thalamus is composed of anatomically as well as functionally discrete subregions receiving blood from different arteries. The clinical features vary according to the intrathalamic location of the haematomas and the bleeding artery. We investigated the impact of haematoma location and vascular territory on the clinical symptoms and signs, neuro-imaging findings and clinical courses of patients with thalamic haemorrhages by a retrospective analysis of 175 consecutive patients with thalamic haemorrhage. Based on the neuro-imaging findings we classified thalamic haematomas into four regional types and one global type according to the primary bleeding sites: (i) anterior type occurring in the territory of the tuberothalamic arteries, (ii) posteromedial type occurring in the territory of the thalamic-subthalamic paramedian arteries, (iii) posterolateral type occurring in the territory of the thalamogeniculate arteries. (iv) dorsal type occurring in the territory of the posterior choroidal arteries and (v) global type occupying the entire area of the thalamus. We studied the clinical and neuroimaging characteristics of each type. Eleven patients (7%) had the anterior type: these were the smallest haematomas and often ruptured into the anterior horn of the lateral ventricle. The major clinical signs were acute behavioural abnormalities: the clinical course was usually benign. Twenty-four patients (14%) had the posteromedial type in which haematomas often ruptured into the third ventricle, causing marked hydrocephalus, and often extended mediocaudally, involving the mesencephalon. The prognoses of this type depended on the presence of mesencephalic involvement which was associated with the worst outcome among the types even if the size of the haematoma itself was not large. The posterolateral type was most frequent (77 patients, 44%) and was characterized by large haematomas, rupture into the posterior horn of the lateral ventricle and frequent extension into the posterior limb of the internal capsule. Clinical signs included marked sensory and motor signs, hemineglect in right-side haematomas and language abnormalities with left-side haematomas. The case fatality with this type was relatively high (35%) and permanent neurologic sequelae frequently resulted. In the dorsal type (32 patients, 18%) haematomas were best visualized at the level of the body of the lateral ventricle on CT scans. The size was moderate and haematomas often extended posterolaterally into the adjacent subcortical white matter. Sensory and motor signs were common and about one third of the patients were first misdiagnosed as having lacunar infarcts. The prognoses were excellent. The global type (31 patients, 18%) of thalamic haemorrhage was clinically and radiologically very similar to the posterolateral type except that the haematomas were too large to define the bleeding focus. Severe sensory and motor signs were almost always present. In this type 25 patients died (the case fatality was 81%).

Successful removal of large pineal region meningiomas: two case reports

Pineal region meningiomas are extremely rare tumors and comprise about 8% of tumors of this region. Two cases of large pineal region meningiomas in young males are presented. Computed tomography (CT) scan and cerebral angiography were used to evaluate the patients preoperatively. Both patients were operated on through an occipital transtentorial approach either as a single- or two-stage procedure. Preoperative work-up revealed that both tumors received their main blood supply from the posterior lateral choroidal arteries and were therefore originating from the velum interpositum cerebri (superior tela choroidea). Complete tumor removal was effected in the first patient using a right occipital transtentorial approach. In the second patient, after partial removal using the same approach, complete resection was achieved at a second stage via the left occipital transtentorial approach 3 months later. Cerebral angiography, which must include vertebral angiography, is important in the preoperative surgical planning of these tumors. The occipital transtentorial approach provides good access. However, a two-stage procedure using right and left sides may be necessary for large meningiomas receiving a bilateral blood supply from both posterior lateral choroidal arteries. Diagnosis, the surgical approach, and methods of tumor excision are discussed.

Microsurgical anatomy of the posterior choroidal arteries

In this study, we analysed the microanatomy of the medial and lateral posterior choroidal arteries, which supply vital central nervous system structures to the brainstem and choroids plexus. We traced the anatomical course of the medial and lateral posterior choroid arteries, their origin, diameter, number of branches, length, and anatomical variations. Twenty-six human unfixed brains were injected through the vertebral and carotid arteries with silicon rubber. Fifty-one out of a total of 129 vessels were medial posterior, and 78 were lateral posterior choroidal arteries. We divided the medial posterior choroidal artery into three segments: around the brainstem, quadrigeminal-pineal, and choroidal. The mean length of the medial posterior choroidal artery was 77.6 +/- 15 mm on the right side, and 77.1 +/- 15 mm on the left; the mean outer diameter observed was 0.8 +/- 0.5 mm on the right side, and 0.8 +/- 0.4 mm on the left. The number of branches arising from the medial posterior choroidal arteries averaged 25 +/- 9. In the lateral posterior group, the mean length observed was 49.5 +/- 26 mm on the right, and 58.0 +/- 23 mm on the left. There were instances of duplication and triplication of the lateral posterior choroidal vessels. The outer diameter averaged 0.72 mm on the right, and 0.6 mm on the left. The posterior choroidal arteries are clearly an important vascular component. A comprehensive knowledge of their anatomy will aid the neurosurgeon during surgery of the brainstem, pineal region, and third ventricle, and will limit complications resulting from injury to these arteries.

Management Strategies and Surgical Techniques for Deep-seated Supratentorial Arteriovenous Malformations

The therapeutic options for arteriovenous malformations (AVMs) of the thalamus and the basal ganglia have expanded to include preoperative embolization, stereotactic radiation, and microsurgery. Adjuncts to surgery such as stereotactic guidance, electrophysiological monitoring, intraoperative ultrasound, intraoperative angiography, and induced hypotension have significantly reduced postoperative morbidity. We review the management and outcome of 65 consecutive patients who were treated for deep-seated supratentorial vascular malformations; 45 patients (69%) were treated surgically, 10 patients (15%) were treated conservatively, and 10 patients (15%) underwent radiosurgery. This retrospective study (1976-1993) includes 51 AVMs (78%), 14 cavernous angiomas (22%), and 10 associated vascular anomalies (15%). Initially, 59 (91%) of 65 patients presented with hemorrhage; 23 patients (39%) suffered recurrent hemorrhages. Malformations ranged in size from 1 to 7.5 cm (mean, 2.8 cm). AVMs were fed principally by the anterior and posterior choroidal, thalamoperforate, and lenticulostriate arteries. Venous drainage was uniform via the deep venous system. Among 39 patients who underwent surgery for AVMs, 26 (67%) improved, 7 (18%) remained unchanged, 5 (13%) worsened, and 1 (3%) died. Among six patients who underwent surgery for cavernous angiomas, four (66%) improved, one (17%) remained unchanged, and one (17%) worsened. Operative complications included transient neurological deficits in seven patients (16%), permanent neurological deficits in six patients (13%), and new bleeding from residual AVMs in four patients (9%). Among 10 patients treated conservatively, 3 (30%) had repeat hemorrhages, 2 (20%) had progressive neurological deficits, and 1 (10%) died.(ABSTRACT TRUNCATED AT 250 WORDS)

Delayed Unilateral Akathisia with Posterior Thalamic Infarct

We report a patient with a small infarct in the posterior thalamic nuclei involving the pulvinar, probably in the territory of the lateral branches of the left posterior choroidal artery, who first pr

The neurovascular relationships and the blood supply of the oculomotor nerve: The microsurgical anatomy of its cisternal segment

The 27 oculomotor nerves were examined after injection of India ink or methylmethacrylate into the vertebral and the internal carotid arteries. The ventral surface of the cisternal segment of the nerve was noted to be in close relationship with the superior cerebellar artery (96.3%) and its pontine (37.0%), mesencephalic (25.9%) and perforating branches (81.5%); the posterolateral pontine artery (70.4%) and its branches; the anterolateral pontine branches (29.6%), and the perforating branches (85.2%) of the basilar artery; the mesencephalic perforating arteries (11.1%) and their peduncular branches (62.9%); the peduncular branches of the diencephalic perforators (11.1%) and the P1 segment (18.5%); and the accessory collicular artery (3.7%). The dorsal surface of the nerve was in close relationships to the P1 and P2A segments (100%) of the posterior cerebral artery and their peduncular branches (22.2%); the posterior communicating artery (100%); the collicular (100%) and the accessory collicular artery (33.3%), and their peduncular (51.8%) or the perforating branches (22.2%); the medial posterior choroidal artery (25.9%) and its branches (11.1%); and the mesencephalic and diencephalic perforating arteries (100%). Vascular penetration was noted in 51.8% of the third nerves. The most common penetrating vessel was the collicular artery (18.5%) and its branches (22.2%). The cisternal segment of the oculomotor nerve was most often supplied by the mesencephalic perforators (88.9%). The authors discuss the possible clinical significance of the obtained anatomic data.

Pure midbrain infarction

We studied 22 patients with first stroke and infarct limited to the midbrain on MRI. We selected these patients (8%) from 281 with posterior circulation infarct admitted consecutively into a primary care center. All patients underwent a systematic protocol of investigations including MR imaging and angiography, and echocardiography. Most infarcts fitted well to arterial territories drawn in preestablished templates. Middle midbrain involvement was the most common, mainly in the paramedian territory supplied by the basilar artery. Infarct in the mesencephalic territory of the posterior cerebral artery was less common, while superior cerebellar artery territory infarct was extremely rare, and posterior choroidal artery territory infarct did not occur. The neurologic picture was dominated by eye-movement disorders. Patients with isolated upper or lower midbrain infarct had no localizing clinical findings, but patients with middle midbrain infarct had a localizing picture mainly with nuclear or fascicular third nerve palsies that commonly developed in isolation. Vertical gaze paresis, pure motor hemiparesis, four-limb ataxia from unilateral lesion, and hypesthetic ataxic hemiparesis also occurred. Contrary to a common view, cardioembolism was not a more common etiology than basilar artery stenosis or small-vessel disease.

Microsurgical anatomy of the hippocampal arteries.

An anatomical study of the vascularization of the hippocampus was performed on 30 hemispheres. There were a total of 140 arteries supplying the hippocampi, for an average of 4.7 arteries per hemisphere (range three to seven arteries). Based on the origin and caliber of the arteries supplying the hippocampus, the hemispheres were divided into five groups: A) in 57% of the hemispheres studied, the origin was mixed and included the anterior choroidal artery (AChA), the main trunk of the posterior cerebral artery (PCA), and the inferior temporal, lateral posterior choroidal, and splenial branches of the PCA; B) in 27%, all of the inferior temporal branches of the PCA predominantly supplied the hippocampus; C) in 10%, the anterior inferior temporal branch of the PCA was the predominant supplier: D) in 3%, the hippocampus was predominantly supplied by arteries originating from the main trunk of the PCA (Uchimura artery); and E) in 3%, the AChA gave origin to the hippocampal vessel. It was found as a result of this study that the PCA directly and by its branches contributes much more to the blood supply of the hippocampal formation than the AChA. The uncal sulcus was found to be an important anastomotic site between the hippocampal branches of the AChA and the hippocampal branches of the PCA. In 26.6% of hemispheres, one of the hippocampal arteries arose from the lateral posterior choroidal artery. The splenial artery made a loop close to the extraventricular part of the hippocampal tail and gave off multiple vessels to this structure in 36.6% of hemispheres. The finding that the AChA passes through the choroid fissure as a trunk and its later division into the lateral plexal and medial perforating branches within the choroid plexus may be of surgical significance.

Magnetic Resonance Angiography of Arteriovenous Malformation in the Thalamus

A comparative study of magnetic resonance angiography and conventional angiography of arteriovenous malformation in the thalamus showed that both methods clearly visualized the feeding arteries: perforating branches of the posterior cerebral artery, posterior choroidal artery and lenticulostriate artery. Draining veins such as the internal cerebral vein were also demonstrated well.

Microvascular anatomy of the hippocampal formation

The hippocampal vessels were examined in 25 forebrain hemispheres injected with india ink or methylmethacrylate. There were two to seven hippocampal arteries, which measured 200–800 μm in diameter. The anterior hippocampal artery (AHA), which was present in 88.2% of the hemispheres, most often originated from the posterior cerebral and the anterior temporal arteries, that is, within the rostral hippocampo-parahippocampal arterial complex. It arose from the anterior choroidal artery in 29.4% of the hemispheres. The AHA extended between the uncus and the parahippocampal gyrus, and it supplied the head of the hippocampus. The middle hippocampal artery was constant. It most often arose from the posterior cerebral and the common temporal arteries. The middle hippocampal artery coursed just caudal to the uncus, in close relationship with the lateral posterior choroidal artery, and it usually supplied the middle part of the hippocampal formation. The posterior hippocampal artery, which existed in 94.1% of the hemispheres, most often arose from the posterior cerebral and the splenial arteries. It irrigated the caudal part of the hippocampal formation. The anastomoses connecting the posterior, middle, and the anterior hippocampal arteries were present in 29.4% of the hemispheres. The hippocampal arteries gave rise to the straight vessels, which divided into the large and the small intrahippocampal arteries. The highest density of the capillary network was noted in the pyramidal and molecular layers of the hippocampal formation. The clinical significance of the obtained microanatomical findings is discussed.

Feeder に動脈瘤を伴った AVMの塞栓術

Two cases of ruptured cerebellar arteriovenous malformations (AVMs) and one case of ruptured thalamic AVM with a peripheral aneurysm in their main feeders of AVMs were treated by endovascular techniques. In the first case, the aneurysm was located in the midportion of the superior cerebellar artery (SCA) which fed the nidus; in the second case, the aneurysm was in the anterior inferior cerebellar artery (AICA); and in the third case, the aneurysm was in the medial posterior choroidal artery (MPCA). All aneurysms were thought to be the cause of bleeding from CT and MRI findings. A microcatheter was inserted very carefully just proximal to the aneurysm via the transfemoral route, and after negative results of a provocation test by amytal was confirmed, the aneurysm and nidus were embolized using ethylene-vinyl-alcohol copolymer (EVAL) simultaneously. In each cases disappearance of the aneurysms and reduction of nidus size were recognized after embolization without new neurological deficits. EVAL is a new liquid embolic agent which forms an ethylene-vinyl-alcohol copolymer upon contact with blood and is not adhesive and soft enough to resect after embolization. In cases of AVMs with the peripheral aneurysm in the feeding artery, it is ideal to embolize aneurysms and AVMs simultaneously to prevent a rupture of the aneurysm following the increase in the intraluminal arterial pressure after embolization of the pedicle of AVM. EVAL is an appropriate embolic agent in this type of cases, because it makes repeated injection, possible until the complete disappearance of an aneurysm.

The Thalamogeniculate Perforators of the Posterior Cerebral Artery: The Microsurgical Anatomy

The thalamogeniculate (TG) arteries of 30 forebrain hemispheres were examined. These vessels varied from 2 to 12 in number (mean, 5.7), and from 70 to 580 microns in caliber (mean, 345.8 microns). The average caliber of all the TG vessels per posterior cerebral artery ranged from 700 to 3400 microns (mean, 1972 microns). The TG arteries most often originated as individual vessels; however, in 26.67% of the hemispheres examined they shared a common site of origin, and 33.33% of the hemispheres they arose from common stems. The common stems ranged from 320 to 800 microns in diameter (mean, 583 microns). The TG branches arose from the crural or ambient (P2) segment of the posterior cerebral artery in 80% of the hemispheres, from the P2 and the quadrigeminal (P3) segment in 20%, from both the distal segment of the posterior cerebral artery and the common temporal artery (13.33%), or from the distal segment and either the calcarine (3.33%) or parieto-occipital artery (3.33%). The TG arteries usually penetrated the medial geniculate body (100%), pulvinar thalami (80%), brachium of the superior colliculus (53.33%), or lateral geniculate body (13.33%). The collateral branches of the TG arteries were noted to reach the medial geniculate body (76.67%), pulvinar (70%), brachium of the superior colliculus (40%), crus cerebri (40%), and lateral geniculate body (6.67%). The anastomoses were present in 66.67%, usually between the TG vessels and the medial posterior choroidal artery (33.33%), or the mesencephalothalamic artery (26.67%). They ranged in number from 1 to 3 (mean, 1.2), and in caliber from 90 to 400 microns (mean, 197 microns).(ABSTRACT TRUNCATED AT 250 WORDS)

Scanning electron microscopic study on pineal vascularization of the common tree shrew (Tupaia glis)

The detailed blood supply including microvascularization of pineal gland in the common tree shrew (Tupaia glis) was investigated using a vascular corrosion cast technique in conjunction with scanning electron microscopy. Adult common tree shrews of both sexes, divided into 3 groups, were injected with red latex, blue vinyl resin, and Batson's No. 17 plastic mixture for the studies of arterial supply, venous drainage, and microvasculature of the pineal gland, respectively. It was found that the pineal gland is a highly vascularized organ. It receives two to four branches from the medial posterior choroidal arteries. Two types of capillary arrangements, fan-like and network, are observed. As in the human, usually one and occasionally two pineal veins, draining directly into the great cerebral vein of Galen, are observed. A pineal portal system is not demonstrated.

Posterior Choroidal-Artery Infarct with Homonymous Horizontal Sectoranopia

In a 67-year-old man with left horizontal homonymous sectoranopia and slight facio-brachial hemiparesis, CT showed recent infarction in the right posterior choroidal-artery region. This particular visual-field defect may be explained by partial involvement of the lateral geniculate body which is supplied both by the anterior and posterior choroidal artery.

視床AVMの手術

In this report, three operations for thalamic arteriovenous malformation (AVM) are discussed, mainly from the viewpoint of surgical approach and technique.Case 1 was a 20-year-old male with a history of three episodes of intracranial hemorrhage. Angiogram demonstrated a nidus 2cm in diameter at the anterior inferior site of the left thalamus. The malformation was fed by anterior and posterior choroidal arteries and the anterior thalamoperforating artery. First surgery was performed using a subtemporal approach. The left posterior communicating artery which mainly fed the nidus was trapped. Second surgery was performed via a bifrontal craniotomy. An anterior transcallosal approach was used to expose the AVM. Nidus was totally excised via the left lateral ventricle. Postoperatively, no new neurological deficit appeared.Case 2 was a 36-year-old female who experienced a sudden intraventricular hemorrhage. Angiogram demonstrated a nidus 2cm in diameter at the posterior superior site of the left thalamus. The malformation was fed by the anterior and posterior choroidal arteries. Surgery was performed via a left parietal craniotomy. A transparietal approach was used to expose the AVM and the nidus was totally excised. Although the patient exhibited Gerstmann syndrome and right homonymous hemianopsia, they were transient, and the patient was discharged with no deficit.Case 3 was a 51-year-old female with a history of three episodes of intracranial hemorrhage. Angiogram demonstrated a nidus 4cm in diameter at the right thalamus. The malformation was fed by the anterior and posterior choroidal arteries, the anterior thalamoperforating artery and the thalamogeniculate artery. Surgery was performed via a right fronto-temporo-parietal craniotomy. At first, the feeder was clipped using a subtemporal approach. And then the nidus was totally excised using a transparietal and transventricle approach. Postoperatively, impairment of consciousness appeared.It appeared to be important in surgery for AVM's in a critical area like the thalamus that management of the feeder be performed first, bleeding should be avoided as much as possible, and the normal brain tissue should not be damaged. Although the border between the nidus and the normal brain tissue should be ascertained, MRI was considered to be useful in determining these relationships. While it is reasonable to excise the thalamic AVM via the lateral ventricle, it is difficult to manage the feeder at first. Previous feeder clipping was useful in two cases. The trans parietal approach was used in two cases. Even at the dominant hemisphere, neurological deficit associated with this approach did not remain. Monitoring of SEP and using doppler sonography were also useful.

Anatomic basis for surgical approach to the distal segment of the posterior cerebral artery.

The distal segment of the posterior cerebral artery (PCA), which extends from the junction with the posterior communicating artery to its terminal division into the parieto-occipital and calcarine arteries, was examined in 37 brains. Three types of distal segment were distinguished. In the first type (42.9%), the terminal division was located either in the calcarine sulcus or in the quadrigeminal cistern. In the second type (41.4%), the terminal division had the same position, but the distal segment, in addition to its terminal stems, also gave off the common temporal artery. In the third type (15.7%), the terminal division was seen in the ambient cistern. The distal segment of the PCA gave rise to several collateral branches: the collicular artery (2.8%), the anterior (28.6%), middle (30.0%), and posterior (28.6%) hippocampal arteries, the proximal (82.9%) and distal (20.0%) lateral posterior choroidal arteries, the proximal (40.0%) and distal (41.4%) medial posterior choroidal arteries, the peduncular, thalamogeniculate and splenial branches, the lingual gyri artery and the temporal arteries. Several anatomic variants of the distal segment were observed in this study: fenestration of the distal segment (1.4%), location of the distal segment dorsal to the uncus (2.8%), origin of the collicular (2.8%) and anterior choroidal arteries (1.4%) from the distal segment, and protrusion of the parieto-occipital arterial loop into the lateral ventricle (2.8%). The authors discuss the clinical significance of these anatomic data.

モヤモヤ病に合併した脳動脈瘤

We have had six cases of moyamoya disease associated with aneurysms during the past 17 years. The incidence was 16%. In three cases, the aneurysms were located on moyamoya vassels or on the peripheral small arteries such as Heubner's artery, the posterior choroidal artery and the tentorial artery and were classified as a “pseudoaneurysm”. Two pseudo-aneurysms disappeared spontaneously within three months after onset. Therefore, pseudo-aneurysms required no direct surgery, though STA-MCA anastomosis had a preventative effect on rebleeding. Conversely, the remaining three cases were classified as saccular aneurysms, located on the circle of Willis such as the carotid fork, anterior communicating artery or basilar bifurcation. Of these three cases, only one, the basilar bifurcation aneurysm, rebled two years later, causing death due to vasospasm, while the other two aneurysms, on the carotid artery system, did not rebleed and showed gradual reduction in size. Based on our experience, it was suggested that aneurysms on the vertebrobasilar system should have direct surgery because of a high probability of rupture, whereas aneurysms on the carotid artery system, showing better prognosis, can be treated conservatively with careful follow-up angiography.

Midline Arteriovenous Malformation on the Floor of the Third Ventricle

We treated a patient with an arteriovenous malformation within the third ventricle. The vascular malformation was fed by the right medial posterior choroidal, posterior thalamoperforating, and thalamogeniculate arteries and drained into the vein of Galen. The lesion was approached via the interhemispheric transcallosal route and totally extirpated. The literature concerning arteriovenous malformations involving the ventricular system is reviewed in the context of primary intraventricular hemorrhage, and surgical approaches to the third ventricle are discussed.