Surgical anatomy of the proximal anterior cerebral artery.

The authors present this study of proximal anterior cerebral arteries in the normal human to provide a clearer basis for strategy in aneurysm surgery. They describe patterns of origin of branches, their subarachnoid course, and parenchymal distribution. Branches that originate from the anterior cerebral artery at the internal carotid bifurcation perfuse the genu and contiguous posterior limb of the internal capsule and the rostral thalamus. Proximal 4-mm branches supply the anterior limb of the internal capsule, the neighboring hypothalamus, anteroventral putamen, and pallidum. The remaining anterior cerebral artery proximal to the communicating artery sends branches to the optic chiasm, the adjacent hypothalamus, and the anterior commissure. Heubner's artery arises directly opposite the anterior communicating artery to supply much of the striatum and internal capsule rostral to the anterior commissure. The anterior communicating artery branches supply the fornix, corpus callosum, septal region, and anterior cingulum. The parenchymal distribution of these end arteries may be surmised from the site of origin named vessels. With this anatomical information one can avoid interruption of blood supply to vital structures when dealing with the anterior cerebral artery and its branches.     

Microanatomy of the anterior cerebral artery

The microanatomic features of the anterior cerebral artery were studied in 30 unfixed human brains which were injected with tinted polyester resin via cannulation of the internal carotid arteries under microscopic dissection. The outer diameter, length, and number of perforating branches were measured for each of the following vessels: anterior cerebral artery (proximal A1 segment, distal A2 segment), anterior communicating artery, and recurrent artery of Heubner. The perforating branches of the proximal segment of the anterior cerebral artery penetrated the brain at the anterior perforated substance, lateral chiasm, and optic tracts. The perforating branches of the anterior communicating artery penetrated the brain at the lamina terminalis, anterior perforated substance, and medial chiasm. The first 5 mm of the distal anterior cerebral artery (A2) had perforating branches penetrating the brain at the gyrus rectus and olfactory sulcus. The recurrent artery of Heubner originated from the A2 segment of the anterior cerebral artery in 57% of the cases, from the anterior cerebral artery-anterior communicating artery junction in 35%, and from the A1 segment in 8%. The depth of the interhemispheric fissure at the genu was 36.0 +/- 0.5 mm and at the midbody of the corpus callosum, 35.0 +/- 0.5 mm. Extension of the dissection to approach the anterior communicating artery from the genu of the corpus callosum using the anterior interhemispheric route was an additional 31.7 +/- 0.7 mm. The callosal arterial supply from the anterior cerebral artery showed short callosal branches in all brain specimens and long callosal vessels in 10% of the specimens.     

Microsurgical anatomy of the insula and the sylvian fissure

OBJECT: The purpose of this study was to define the topographic anatomy, arterial supply, and venous drainage of the insula and sylvian fissure. METHODS: The neural, arterial, and venous anatomy of the insula and sylvian fissure were examined in 43 cerebral hemispheres. CONCLUSIONS: The majority of gyri and sulci of the frontoparietal and temporal opercula had a constant relationship to the insular gyri and sulci and provided landmarks for approaching different parts of the insula. The most lateral lenticulostriate artery, an important landmark in insular surgery, arose 14.6 mm from the apex of the insula and penetrated the anterior perforated substance 15.3 mm medial to the limen insulae. The superior trunk of the middle cerebral artery (MCA) and its branches supplied the anterior, middle, and posterior short gyri; the anterior limiting sulcus; the short sulci; and the insular apex. The inferior trunk supplied the posterior long gyrus, inferior limiting sulcus, and limen area in most hemispheres. Both of these trunks frequently contributed to the supply of the central insular sulcus and the anterior long gyrus. The areas of insular supply of the superior and inferior trunks did not overlap. The most constant insular area of supply by the cortical MCA branches was from the prefrontal and precentral arteries that supplied the anterior and middle short gyri, respectively. The largest insular perforating arteries usually arose from the central and angular arteries and most commonly entered the posterior half of the central insular sulcus and posterior long gyrus. Insular veins drained predominantly to the deep middle cerebral vein, although frequent connections to the superficial venous system were found. Of all the insular veins, the precentral insular vein was the one that most commonly connected to the superficial sylvian vein.     

Micro-anatomy of collateral perforating branches of the middle cerebral artery

The lenticulostriate arteries are the subject of a microanatomical study on 50 formalin fixed human brains. A single trunk arising from the middle cerebral artery is rarely found. In fact the branches are numerous and they are found to ramify before penetrating the anterior perforated substance. The length of the sphenoidal segment is variable and this aspect is discussed in the light of the literature data. The origin of the perforating branches is spread from the internal carotid artery to the bifurcation branches of the middle cerebral artery (M2 segment). On the other hand lenticulostriate arteries arising from the cortical branches of the middle cerebral artery are often found. These anatomical patterns are of essentially surgical interest. No branches must be damaged during the opening of the Sylvian fissure or during the dissection of an aneurysm in this region.     

Microsurgical anatomy of the distal anterior cerebral artery

The microsurgical anatomy of the distal anterior cerebral artery (ACA) has been defined in 50 cerebral hemispheres. The distal ACA, the portion beginning at the anterior communicating artery (ACoA), was divided into four segments (A2 through A5) according to Fischer. The distal ACA gave origin to central and cerebral branches. The central branches passed to the optic chiasm, suprachiasmatic area, and anterior forebrain below the corpus callosum. The cerebral branches were divided into cortical, subcortical, and callosal branches. The most frequent site of origin of the cortical branches was as follows: orbitofrontal and frontopolar arteries, A2; the anterior and middle internal frontal and callosomarginal arteries, A3; the paracentral artery, A4; and the superior and inferior parietal arteries, A5. The posterior internal frontal artery arose with approximately equal frequency from A3 and A4 and callosomarginal artery. All the cortical branches arose more frequently from the pericallosal than the callosomarginal artery. Of the major cortical branches, the internal frontal and paracentral arteries arose most frequently from the callosomarginal artery. The distal ACA of one hemisphere sent branches to the contralateral hemisphere in 64% of brains. The anterior portions of the hemisphere between the 5-cm and 15-cm points on the circumferential line showed the most promise of revealing a recipient artery of sufficient size for an extracranial-intracranial artery anastomosis. The distal ACA was the principal artery supplying the corpus callosum. The recurrent artery, which arose from the A2 segment in 78% of hemispheres, sent branches into the subcortical area around the anterior limb of the internal capsule.     

Microvascular anatomy of the uncus and the parahippocampal gyrus.

The microanatomical examination of the uncal and the parahippocampal arteries was performed in 17 brain hemispheres injected with India ink and gelatin. The mentioned arteries may originate from the anterior choroidal artery, the internal carotid artery, the middle cerebral artery, and the posterior cerebral artery. The uncal or the unco-parahippocampal branches of the anterior choroidal artery were divided into rostral and caudal; the former were present in 70.6%, and the latter were present in 94.1%. The uncal or the unco-parahippocampal branches of the internal carotid artery, which originated 1.4 to 4.2 mm from its bifurcation site, existed in 58.8%. The same branches of the middle cerebral artery, which most often arose from the temporopolar artery, were present in 64.7%. Finally, these branches of the posterior cerebral artery, which usually arose from the anterior hippocampal artery, were observed in 47.1%. Large parahippocampal branches of the anterior choroidal artery were noted in 52.9%. The internal carotid artery and middle cerebral artery gave rise to these branches in 23.5 and 64.7%, respectively. The posterior cerebral artery always gave off 2 to 10 parahippocampal vessels. The largest of them originated within the rostral hippocampo-parahippocampal arterial complex. The authors discuss the microanatomical characteristics and possible clinical significance of the uncal and the parahippocampal arteries.     

Microsurgical anatomy of the early branches of the middle cerebral artery: morphometric analysis and classification with angiographic correlation

OBJECT: The cortical arteries arising from the main trunk of the middle cerebral artery, proximal to its bifurcation or trifurcation, are called "early branches." The purpose of this study was to characterize these early branches. METHODS: The early branches were characterized according to their sites and patterns of origin, diameters, and relative proximity to the internal carotid artery bifurcation, as well as the course and area of supply of their cortical branches based on an examination of 50 hemispheres. Special attention was directed to the perforating arteries that arose from the early branches and entered the anterior perforated substance. The anatomical findings were compared with data obtained from 109 angiograms. CONCLUSIONS: Early branches directed to the temporal and frontal lobes were found in 90 and 32% of the hemispheres, respectively. The early branches that arose more proximally from the M1 segment were larger than those arising distally. Lenticulostriate arteries arose from 81% of the early frontal branches (EFBs) and from 48% of the early temporal branches (ETBs). An average of two cortical arteries arose from the EFBs and 1.3 from the ETBs, the most common of which supplied the temporopolar and orbitofrontal areas. Although the microsurgical anatomy of the early branches demonstrates abundant diversity, they can be classified into clearly defined patterns based on anatomical features. These patterns can prove helpful in evaluating angiographic data and in planning an operative procedure.     

Intracranial aneurysms: Characteristics of aneurysms by site,with special reference to anterior communicating artery aneurysms

Data are presented from an unselected series of 212 aneurysm patients for aneurysms at three major sites: the internal carotid-posterior communicating artery junction, the anterior communicating artery, and the middle cerebral artery. More than 70% of the anterior communicating artery aneurysms occurred as single aneurysms; less than 30% of the middle cerebral artery aneurysms were single. Anterior communicating artery aneurysms showed a right-side predominance in males but not in females. Both males and females had significantly higher mean systolic and diastolic blood pressures for left-side anterior communicating artery aneurysms than for right-side aneurysms. A brief review of factors relevant to anterior communicating artery aneurysms is presented.     

Branches of the anterior communicating artery

Summary The anterior communicating artery (ACoA) and its branches were examined in 22 human brains after injecting Indian ink or methylmethacrylate. The ACoA branches were divided into the small and the large. Small branches were from 1 to 5 in number (mean 2), and from 70 to 270 m in diameter (mean 151 m). Seventy-six percent of the branches originated directly from the ACoA. They tended to arise closer to the left than to the right anterior cerebral artery. Fourteen percent of them arose from the junctional site of the ACoA with the anterior cerebral arteries, and 10% from the site of origin of the subcallosal artery. Large branches were identified as the median artery of the corpus callosum, and the subcallosal artery, respectively. The former vessel was present in 9% of the patients, and the latter in 91%. The subcallosal artery was from 320 to 640 urn in size (mean 486 m). It tended to arise from the middle of the ACoA.In spite of the very frequent anastomoses involving the ACoA branches, care must be taken to avoid injury to these important vessels during operations of the ACoA aneurysms.     

A case of multiple anomalies of cerebral vessels--fenestration of the middle cerebral artery aneurysm of the anterior communicating artery and arteriovenous malformation on the frontopolar region (author's transl)

A case associated with multiple cerebral vascular anomalies, which consisted of fenestration of the middle cerebral artery, arteriovenous malformation and aneurysm of the anterior communicating artery, was reported. A 48 year-old male has been suffering from the left paralysis and mental disorder after the initial attack of subarachnoid hemorrhage, and the second attack resulted in the deterioration of the symptoms. He was admitted to our clinic on October 28, 1974. On neurological examination, mental disorders, such as disorientation, emotional incontinence, amnesia and acalculia, hemiplegia on the left and meningeal irritation signs were observed in admission period. Physical examination was negative. Cerebral angiographic findings were as follows: 1) Moderate vasospasm of the right internal carotid artery at the terminal segment, mild bowing of the anterior cerebral artery and stretching of the frontparietal opercular branches of the middle cerebral artery were observed. 2) Right frontpolar arteriovenous malformation fed by the frontobasal artery and the frontopolar artery, and drained via the aberrant cortical vein into the superior sagittal sinus. 3) Aneurysm of the anterior communicating artery was opacified by left carotid angiography. 4) An abnormal vessel derived from the terminal segment of the right internal carotid artery and terminated at the portion of the sphenoidal segment of the middle cerebral artery. Complete loop was formed between genuine middle cerebral artery and this abnormal artery. He was operated with dissecting microscope on November 11, 1974. The arteriovenous malformation at right frontopolar region was totally removed and aneurysm of the anterior communicating artery was clipped. According to the operative findings, the arachnoid membrane over the right frontopolar region was turbid and adhered to the adjacent tissues. On the contrary, no abnormal findings suggestive of previous subarachnoid hemorrhage were observed around the region of the anterior communicating artery aneurysm. These findings showed that subarachnoidal bleeding was caused by rupture of the arteriovenous malformation of right frontopolar region, but not by the aneurysm on the anterior communicating artery. The postoperative course was uneventful and during the hospitalization the patient starts on rehabilitation therapy. The authors discussed the genesis of fenestration of the middle cerebral artery and relation among these combined vascular anomalies. We inferred that fenestration of the middle cerebral artery arose from the in complete fusion of procursor vascular network in embryonic stage. Additionally, we emphasized that it was necessary to make a distinction between these two terms "fenestration" and "duplication".     

Influence of the Collateral Function of the Circle of Willis on Hemispherical Perfusion During Carotid Occlusion as Assessed by Transcranial Colour-coded Duplex Ultrasonography

OBJECTIVES: to investigate the collateral potential of the circle of Willis with transcranial colour-coded duplex ultrasonography and common carotid artery (CCA) compression. MATERIALS AND METHODS: in 46 atherosclerotic patients without cerebrovascular disease, the functional patency of the collaterals of the circle of Willis, the anterior and posterior communicating arteries, was assessed. The Peak Systolic Velocity (PSV) decrease in the middle cerebral artery (MCA) during CCA compression between complete and incomplete circles was compared. RESULTS: in 10 (22%) patients a complete and in 36 (78%) patients an incomplete circle of Willis was found, mainly due to non-functioning posterior communicating arteries. In hemispheres with collateral supply through both the anterior and the posterior communicating artery, the median PSV decrease in the MCA during CCA compression was 43%. When the posterior, anterior or both communicating arteries (1 hemisphere) were missing the PSV decrease was 58% (p =0.003), 70% (p =0.001) and 75%, respectively. CONCLUSIONS: collateral flow from the basilar to the carotid territory is often hampered by non-functioning posterior communicating arteries. A non-functioning anterior communicating artery is rare. A complete collateral circulation provides better perfusion of the MCA during carotid occlusion as compared with collateral supply through only the anterior or the posterior communicating artery in the case of an incomplete circle of Willis.     

Extracerebral course of the perforating branches of the anterior communicating artery: microsurgical anatomical study

Damage to the perforating branches arising from the anterior communicating artery, because of their blood supply to the septal nuclei and anterior hypothalamus, explains the memory impairment and the electrolyte disturbances that often follow the surgery of aneurysms located in this part of the circle of Willis. The microsurgical anatomy of these branches was studied on 60 fixed human brains, with special attention to their number, caliber, and vascular territory. The direction of the branches was evaluated, measuring the angle formed by them with the postcommunicating segment of the anterior cerebral artery. The variability of this anatomical region is discussed in light of the literature.     

A case of subacute subarachnoid hemorrhage without xanthochromic cerebrospinal fluid--usefulness of emergent MRI

We reported a case of subacute subarachnoid hemorrhage with watery clear cerebrospinal fluid. Emergent magnetic resonance image was useful not only for diagnosis by fluid attenuated inversion recovery image but also for evaluation of cerebral ischemia and vasospasm by magnetic resonance angiography, diffusion weighted image and perfusion weighted image. A 50-year-old man presented disturbance of consciousness and dysarthria. Neither computed tomographic scan nor cerebrospinal fluid study could diagnose subarachnoid hemorrhage clearly. However, emergent fluid attenuated inversion recovery image showed the show subarachnoid hemorrhage as high signal intensity. Diffusion weighted image showed multiple, round hypersignals both in the white and gray matter. In the area with diffusion hypersignal, the apparent diffusion coefficient value was 0.57 x 10(3) mm2/sec. Perfusion weighted image showed normal cerebral blood volume but prolonged mean transit time in the territory of the right middle cerebral artery. Magnetic resonance angiography revealed an aneurysm at the anterior communicating artery and severe vasospasm on the bilateral anterior cerebral artery, the right middle cerebral artery. Thus we are able to diagnose subarachnoid hemorrhage due to a ruptured anterior communicating artery aneurysm. The hyperintensity of the diffusion weighted image and the fluid attenuated inversion recovery image was caused by cerebral ischemia from vasospasm. After conservative therapy during the period of vasospasm, successful surgical clipping was performed with full clinical recovery.     

Revascularization of the Posterior Circulation

The primary objective of revascularization procedures in the posterior circulation is the prevention of vertebrobasilar ischemic stroke. Specific anatomical and neurophysiologic characteristics such as posterior communicating artery size affect the susceptibility to ischemia. Current indications for revascularization include symptomatic vertebrobasilar ischemia refractory to medical therapy and ischemia caused by parent vessel occlusion as treatment for complex aneurysms. Treatment options include endovascular angioplasty and stenting, surgical endarterectomy, arterial reimplantation, extracranial-to-intracranial anastomosis, and indirect bypasses. Pretreatment studies including cerebral blood flow measurements with assessment of hemodynamic reserve can affect treatment decisions. Careful blood pressure regulation, neurophysiologic monitoring, and neuroprotective measures such as mild brain hypothermia can help minimize the risks of intervention. Microscope, microinstruments and intraoperative Doppler are routinely used. The superficial temporal artery, occipital artery, and external carotid artery can be used to augment blood flow to the superior cerebellar artery, posterior cerebral artery, posterior inferior cerebellar artery, or anterior inferior cerebellar artery. Interposition venous or arterial grafts can be used to increase length. Several published series report improvement or relief of symptoms in 60 to 100% of patients with a reduction of risk of future stroke and low complication rates.     

Specifics of the blood supply of the sinoatrial node

The present study aims to identify the heart nodal system blood supply sources and especially those of the sinoatrial node. It included 50 unpreserved and preserved human hearts from subjects of both sexes (40 males and 10 females) aged 12 to 68, of Romanian (42) and non-Romanian origin (8). The used denominations are those recommended by DiDio & Wakefield, based on splitting of the atrial walls into four quadrants (right and left, both anterior and posterior) which are further divided into three parts (medial, middle and lateral). We used special dissection techniques and plastic mass injections followed by corrosion. Our results confirm the opinion shared by most authors, in favour of the predominance of the origin of sinoatrial node artery from the right coronary artery. The sinoatrial node was supplied by a unique source represented by the right coronary artery in 37 cases (74%) and by the circumflex artery in 8 cases (16%), and by a double source represented by two branches of the right coronary artery in 2 cases (4%) and of both coronary arteries in 3 cases (6%). The direct arterial branches to the sinoatrial node were represented mainly by the right anteromedial atrial artery with origin from the right coronary artery level with the medial third of the right anterior quadrant of the atrial wall. From the left coronary system, the left anteromedial artery is the one responsible with the sinoatrial node supply; the source is the circumflex artery and its origin is the medial third of the left anterior quadrant. Contrary to DiDio et al., we found in addition to the mainly unilateral blood supply, the bilateral one. We didn't find any case with a sinoatrial node artery originating from the trunk of the left coronary artery, or with an extracardiac origin. We may state there are no significant differences of the origin and distribution of the sinoatrial node artery related to sex or country of origin. Thus, we cannot fully confirm the theories about the influence of the general variation factors on the arterial origin. The atherosclerotic or thrombotic obstruction of the sinoatrial node artery may induce severe heart rhythm disturbances or even sudden death.     

Aneurysms located at the proximal anterior cerebral artery and anterior communicating artery associated with middle cerebral artery aplasia: case report

BACKGROUND: Aneurysms arising from the proximal anterior cerebral artery (ACA) are quite rare. Here, we report upon such a case of aneurysms located at the proximal ACA and anterior communicating artery associated with middle cerebral artery (MCA) aplasia. CASE DESCRIPTION: A 64-year-old woman complained of severe headache. Brain computed tomography scans demonstrated acute subarachnoid hemorrhage. Angiograms showed 2 aneurysms located at the anterior communicating artery and proximal ACA, but did not show an MCA shadow on the lesion side. Instead, multiple collateral vessels ran toward the sylvian fissure and supplied the MCA territory, together with hypertrophied perforating branches. The operative findings confirmed that the cordlike rudimentary MCA had no internal blood flow. The 2 aneurysms were secured by neck clipping. CONCLUSION: The combined effects of these anomalies on the hemodynamic equilibrium of the arteries and the genesis of the aneurysms are noteworthy.     

A case of anterior communicating artery aneurysm with occlusion of the bilateral middle cerebral arteries

A patient with ruptured anterior communicating artery aneurysm associated with occlusion of the bilateral middle cerebral arteries is presented. A 70-year-old woman was hospitalized for sudden onset of severe headache and vomiting. She was alert, and no neurological deficit was found. CT scan showed a subarachnoid hemorrhage. Cerebral angiogram demonstrated occlusion of the bilateral middle cerebral arteries and ruptured anterior communicating artery aneurysm. After operation, she fully recovered and was able to walk at the time of discharge. In aneurysmal formation, we know from the literatures that hemodynamic stress plays an important role. In this case, occlusion of the bilateral middle cerebral arteries caused hemodynamic stress on the anterior cerebral arteries and anterior communicating artery. It is suggested that this is a causative factor of aneurysmal formation under systemic hypertension.     

Relationship between regional cerebrovascular oxygen saturation and jugular bulb oxygen saturation during carotid endarterectomy

BACKGROUND: Carotid artery cross-clamping ischemia during carotid endarterectomy (CEA) sometimes causes perioperative neurological deficits. Therefore it is important to asses the cerebral oxygen supply/demand relationship during CEA. The aim of this study is to examine the relationship between two monitoring results in CEA. METHODS: Six patients undergoing elective carotid CEA were studied. Regional cerebrovascular oxygen saturation (rSO2) and jugular bulb oxygen saturation (SjvO2) were measured simultaneously during carotid artery cross-clamping. RESULTS: In 5 patients, rSO2 and SjvO2 changed similarly during carotid artery cross-clamping. In one patient, whose arterial cross flow through the anterior communicating artery was poor, rSO2 markedly decreased after cross-clamping, but SjvO2 was unchanged during the same procedure. CONCLUSIONS: Patients with internal carotid artery stenosis have individually different characteristics in cerebral metabolism and cerebral blood perfusion. Our results suggest that multiple monitoring of cerebral blood flow and oxygen saturation provides helpful information in CEA patients.