Modalities of origin of the middle cerebral artery. Incidence on the arrangement of the perforating branches

In a series of 100 anatomical dissections on the basal brain arteries a case of real duplication at the middle cerebral artery level has been found. The importance of such a finding is discussed in the light of literature data. The knowledge of similar anatomical patterns is fundamental in the study of the lenticulostriate arteries arising from the sphenoidal segment of the middle cerebral artery. In fact the neurosurgeon must be familiar with all the possible variations of these perforators, given that the opening of the Sylvian fissure is by now an obligatory manoeuvre for the transcisternal access to the circle of Willis.     

Aneurysms at the early branch of middle cerebral artery

The cortical arteries arising from the proximal (Ml) segment of the middle cerebral artery (MCA) are called "early branches". We retrospectively analyzed clinical features in 10 patients with aneurysms located at the early branches of MCA. The incidence of these aneurysms was 9.5% among 95 MCA aneurysms. Patients consisted of 4 males and 6 females. Ages were 33-77 years old (average of 54.4). Four patients presented with subarachnoid hemorrhage (2 of them had intracerebral hematoma). The aneurysms were classified into 2 groups, the group of the early frontal branch (EFB: 7 cases) and the early temporal branch (ETB: 3 cases). All aneurysms were smaller than 6mm in diameter. The surgical treatment was performed through the pterional approach. Poor outcome occurred in 3 ruptured aneurysms of EFB (MD 1, SD 1, and D 1). At surgery, it is necessary to produce the working space by dissecting sylvian fissure sufficiently and to prevent ischemic complication by avoiding injury of the lenticulostriate arteries (LSA).     

Confirmation of blood flow in perforating arteries using fluorescein cerebral angiography during aneurysm surgery

OBJECT: The authors performed fluorescein cerebral angiography in patients after aneurysm clip placement to confirm the patency of the parent artery, perforating artery, and other arteries around the aneurysm. METHODS: Twenty-three patients who underwent aneurysm surgery were studied. Aneurysms were located in the internal carotid artery in 12 patients, middle cerebral artery in six, anterior cerebral artery in three, basilar artery bifurcation in one, and junction of the vertebral artery (VA) and posterior inferior cerebellar artery in one. After aneurysm clip placement, the target arteries were illuminated using a beam from a blue light-emitting diode atop a 7-mm diameter pencil-type probe. In all patients, after intravenous administration of 5 ml of 10% fluorescein sodium, fluorescence in the vessels was clearly observed through a microscope and recorded on videotape. RESULTS: The excellent image quality and spatial resolution of the fluorescein angiography procedure facilitated intraoperative real-time assessment of the patency of the perforating arteries and branches near the aneurysm, including: 12 posterior communicating arteries; 12 anterior choroidal arteries; four lenticulostriate arteries; three recurrent arteries of Heubner; three hypothalamic arteries; one ophthalmic artery; one perforating artery arising from the VA; and one posterior thalamoperforating artery. All 23 patients experienced an uneventful postoperative course without clinical symptoms of perforating artery occlusion. CONCLUSIONS: Because the fluorescein angiography procedure described here allows intraoperative confirmation of the patency of perforating arteries located deep inside the surgical field, it can be practically used for preventing unexpected cerebral infarction during aneurysm surgery.     

Selective lenticulostriate arterial occlusion. A reproducible model of primate focal cerebral ischemia

The anatomic variations of the lateral lenticulostriate arteries of 13 baboons have been detailed from surgical exposures and postmortem silicone rubber-injected specimens. Although the lateral lenticulostriate arteries most frequently arise directly from the orbital frontal artery, they may also arise directly from the middle cerebral artery. Extraparenchymal anastomoses between the medial and lateral lenticulostriates were not found in our operations. Through a microsurgical procedure, selective occlusion of the origins of the lateral lenticulostriate arteries has been accomplished consistently, immediately creating an area of absent flow and subsequent infarction within the normal distribution of these vessels. We believe that selective lateral lenticulostriate occlusion in the baboon produces a lesion that should be useful in the study of cerebral infarction and its treatment.     

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.     

Anatomic pathways facilitating middle cerebral artery bypass

Occlusion of the middle cerebral artery by thrombi is a relatively common occurrence resulting in stroke. Prompt intervention by dissolution or bypassing the thrombi could reduce the severity of the effects. Here, the anatomic pathways facilitating a bypass are explored. Four possible arteries, the two superficial temporals, left and right, and two middle meningeals, left and right, are in positions adjacent to branches of the middle cerebral arteries, the trunks of which are located in the lateral fissures of the brain. The first possibility is anastomosing a branch of the superficial temporal artery with the middle cerebral artery segment in the lateral fissure where this segment is usually clear of thrombi. The second possibility is anastomosing a branch of the middle meningeal artery with the postthrombotic segment of the middle cerebral artery. These anastomoses are to be done with donor and recipient arteries of the same side. In the unlikely event that these two possibilities are lost, it is still possible to anastomose the affected middle cerebral artery with the superficial temporal or middle meningeal artery of the opposite side using several inches of saphenous vein.     

Fate of branch arteries after intracranial stenting

OBJECTIVE: One concern with respect to stent procedures performed to treat patients with intracranial lesions is the fate of normal major arterial branches after stents are placed across them. Because most of these lesions occur at vessel bifurcations or at branch points, a normal major branch often arises near the lesion and may be difficult to avoid during stent positioning. The aim of this article is to describe the angiographic outcome of intracranial major branch arteries crossed by a stent in the intracranial circulation. METHODS: We examined the immediate postprocedural cerebral angiograms of the 40 patients who underwent intracranial stenting at the University at Buffalo, Buffalo, NY, between June 1998 and April 2000. In each of 10 patients, the stent was placed across a normal major branch artery. Stents were used to treat aneurysms in seven patients and intracranial stenosis in three patients. The latest cerebral angiogram available was reviewed, and the patency of the major branch arteries was evaluated. RESULTS: The angiographic follow-up period ranged from 4 days to 35 months (mean follow-up, 10 mo). Each of the 10 major branch arteries was patent. No infarcts were associated with the territory of the major branch arteries crossed by the stents, and no patient experienced a related episode of clinical ischemia. Four patients died as a result of causes unrelated to the stenting procedure. The histology of a middle cerebral artery stent that was placed across a lenticulostriate perforator is presented. CONCLUSION: The flexible, low-profile stents used in this study had no angiographically or clinically apparent effect on the major intracranial branches across which they were placed.     

Arterial dissections of penetrating cerebral arteries causing hypertension-induced cerebral hemorrhage

OBJECT: For the past 130 years, it has been believed that hypertension-induced cerebral hemorrhages are the result of ruptures of microaneurysms or ruptures of arteries that have degenerative changes. The majority of previous investigations have focused on autopsied brain. In this study, the authors attempted to verify the cause of hypertension-induced cerebral hemorrhage by using surgical specimens of the penetrating arteries responsible for the hemorrhages. METHODS: Between 1997 and 1999, the authors performed pathological studies in surgical specimens of lenticulostriate arteries that had been confirmed during microsurgery to be the cause of hypertension-induced hemorrhage of the putamen. Nineteen lenticulostriate arteries were collected from 12 patients. Fifteen of these arteries were verified as the pathological causes of hemorrhage. They included six arterial dissections, six arterial ruptures with substantial degenerative changes, and three arterial ruptures with few degenerative changes. The pathological findings in the lenticulostriate artery dissections were similar to those of typical arterial dissections in major cerebral arteries. CONCLUSIONS: To the best of the authors' knowledge, arterial dissections of lenticulostriate arteries have not been identified as a cause of hypertension-induced cerebral hemorrhages. When penetrating arteries are included as causative vessels, cerebral arterial dissections may be much more common than previously thought.     

Arteries of the insula

OBJECT: The insula is located at the base of the sylvian fissure and is a potential site for pathological processes such as tumors and vascular malformations. Knowledge of insular anatomy and vascularization is essential to perform accurate microsurgical procedures in this region. METHODS: Arterial vascularization of the insula was studied in 20 human cadaver brains (40 hemispheres). The cerebral arteries were perfused with red latex to enhance their visibility, and they were dissected with the aid of an operating microscope. Arteries supplying the insula numbered an average of 96 (range 77-112). Their mean diameter measured 0.23 mm (range 0.1-0.8 mm), and the origin of each artery could be traced to the middle cerebral artery (MCA), predominantly the M2 segment. In 22 hemispheres (55%), one to six insular arteries arose from the M1 segment of the MCA and supplied the region of the limen insulae. In an additional 10 hemispheres (25%), one or two insular arteries arose from the M3 segment of the MCA and supplied the region of either the superior or inferior periinsular sulcus. The insular arteries primarily supply the insular cortex, extreme capsule, and, occasionally, the claustrum and external capsule, but not the putamen, globus pallidus, or internal capsule, which are vascularized by the lateral lenticulostriate arteries (LLAs). However, an average of 9.9 (range four-14) insular arteries in each hemisphere, mostly in the posterior insular region, were similar to perforating arteries and some of these supplied the corona radiata. Larger, more prominent insular arteries (insuloopercular arteries) were also observed (an average of 3.5 per hemisphere, range one-seven). These coursed across the surface of the insula and then looped laterally, extending branches to the medial surfaces of the opercula. CONCLUSIONS: Complete comprehension of the intricate vascularization patterns associated with the insula, as well as proficiency in insular anatomy, are prerequisites to accomplishing appropriate surgical planning and, ultimately, to completing successful exploration and removal of pathological lesions in this region.     

Perforating branches of the basilar bifurcation

The perforating branches of the upper basilar artery and of the first (P1) segment of the posterior cerebral artery were studied in 50 fixed brains obtained from human cadavers. No vertical branches arose from the basilar bifurcation. The upper basilar artery gave rise to horizontal branches, which were studied with reference to their angle of origin. Perforating arteries arising from P1 segments were found in all specimens. Rare branches were found to come from the inferior and anterior surfaces of P1 segments. The anatomical patterns of these branches are discussed in the light of previous reports. Preoperative knowledge of some anatomical aspects (the position of the basilar apex, the angle between the right P1 and left P1 segments, and relationships to the dorsum sellae and the mammillary bodies) can help in the selection of a neurosurgical approach and may improve the operative results in the surgical treatment of basilar apex aneurysms.     

The variations of lenticulostriate arteries in the middle cerebral artery aneurysms

Summary This study attempts to analyse the intra-operative anatomical findings of the lenticulostriate artery (LSA) in 60 patients with middle cerebral artery (MCA) aneurysms who were operated on at the Neurosurgical Department of Atatürk University Medical School, Erzurum, Türkiye.All patients underwent radical surgery for aneurysm by the right or left pterional approach. The findings were recorded during surgical intervention using slides and videotapes of the operations. On average there were 4 (range, 1–14, total number=240) LSAs, in one hemisphere, per case with MCA aneurysm. Twenty percent of LSAs (n=48) arise from the prebifurcation part of the M₁ segment, 65% (n=156) arise from the postbifurcation part of the M₁ segment, and 15% (n=36) arise from the proximal part of the M₂ segment. The great majority of the LSAs (85%, n=204) orginated along the proximal part of the MCA. Of a total of 240 LSAs, 125 (52%) originated from one single large vessel, a stem artery which then divided after 2–10 mm into many branches, 85 (35%) originated as two large proximal trunks, and 30 (13%) originated as multiple small arteries arising along the whole infero-medial wall of the M₁ segment of MCA.We concluded that recognition of the anatomical variations of the LSA and detailed knowledge of the microvascular relationships of the MCA aneurysms, will allow neurosurgeons to construct a better and safer microdissection plan, to save time, and to prevent postoperative neurological deficits.     

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.     

Ruptured aneurysm at the origin of the accessory middle cerebral artery: case report

The accessory middle cerebral artery is a rare vascular anomaly of the brain. We describe a case of a ruptured aneurysm at the junction of the accessory middle cerebral artery and the horizontal portion of the anterior cerebral artery. The lesion was demonstrated by angiography and confirmed at surgery. No perforating arteries arising from this accessory artery were found. There have been only four previous reports of aneurysms located at the origin of the accessory middle cerebral artery. The relevant literature is briefly reviewed.     

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.     

Effects of surgical revascularization on peripheral artery aneurysms in moyamoya disease: report of three cases

OBJECTIVE AND IMPORTANCE: The beneficial effects of surgical revascularization on rebleeding in moyamoya disease remain unclear. This report is intended to clarify the effects of surgical revascularization on peripheral artery aneurysms, which represent one of the causes of intracranial bleeding in moyamoya disease. CLINICAL PRESENTATION: Findings for three female patients who experienced intracranial bleeding are presented. Cerebral angiography revealed that intracranial bleeding resulted from the rupture of peripheral artery aneurysms arising from dilated collateral vessels such as the lenticulostriate artery. INTERVENTION: The patients successfully underwent superficial temporal artery-middle cerebral artery anastomosis combined with encephaloduromyoarteriosynangiosis. Angiography demonstrated obliteration of the peripheral artery aneurysms, together with the disappearance or decrease in caliber of the parent collateral arteries, after surgery. None of the patients experienced rebleeding during the follow-up period (up to 52 mo). CONCLUSION: The results strongly suggest that surgical revascularization potentially improves cerebral circulation and decreases hemodynamic stress on collateral vessels, obliterating peripheral artery aneurysms.     

“Reverse” superficial temporal artery-middle cerebral artery bypass

A new technical variant on the superficial temporal artery-middle cerebral artery anastomosis was performed in a patient with occlusions of both the left internal and external carotid arteries and persistent ischemic symptomatology. Instead of anastomosing the proximal segment of the superficial temporal artery to the middle cerebral artery as is conventionally done, the distal segment of the superficial temporal artery was anastomosed to a cortical branch of the left middle cerebral artery. Reconstituted flow of the left superficial temporal artery via right superficial temporal artey collateral branches proved adequate to relieve the patient's ischemic episodes. “Reverse” superficial temporal artery-middle cerebral artery anastomosis should be considered in those cases where occlusive disease of the external carotid circulation renders conventional bypass procedures ineffective in the treatment of ischemic symptomatology.     

Perforating branches of the middle cerebral artery. Microsurgical anatomy of their extracerebral segments

Perforating branches of the middle cerebral artery (MCA) were examined under magnification in 50 formalin-fixed brain hemispheres. Perforating vessels varied in number from three to 18, with an average of nine. The greater the number of vessels, the smaller was their diameter. In this study, the perforating arteries were divided into medial, middle, and lateral groupings. Those in the medial group usually arose directly from the MCA main trunk close to the carotid bifurcation. There were usually three vessels in the middle group, which originated not only from the MCA trunk, but also from the MCA collateral (cortical) branches. Common stems, when present, gave rise to individual perforating vessels and occasionally to thin olfactory and insular rami. Perforating arteries in the lateral group varied from one to nine in number. In addition to an origin from the MCA trunk, they also arose from cortical branches supplying the frontal and temporal lobes. The fact that lateral perforating vessels often originated from division sites and from terminal branches of the MCA is of clinical significance, because aneurysms are more commonly located at the MCA bifurcation. Anastomoses were not found among the perforating arteries. In two specimens, a fusion between a perforating artery and the MCA trunk was noted. Since the perforating vessels are obviously end arteries, injury to them must be avoided during operations for MCA aneurysms.     

Preservation of the Long Insular Artery to Prevent Postoperative Motor Deficits after Resection of Insulo-opercular Glioma: Technical Case Reports

Resection of insulo-opercular gliomas carries the risk of postoperative hemiparesis caused by ischemia of the corona radiata resulting from injury to the long insular arteries. However, intraoperative identification of these perforating arteries is challenging. We attempted intra-operative motor evoked potential (MEP) monitoring under temporary occlusion of the suspected long insular artery arising from the opercular portion of middle cerebral artery in two patients with insulo-opercular gliomas. Temporary occlusion of the artery caused decrease in MEP amplitude, which recovered after release in one patient, who had no postoperative motor deficits or ischemic lesion in the corona radiata. Temporary occlusion of the artery caused no changes in MEP amplitude, so that the artery was sacrificed for tumor removal in the other patient, who had no motor deficits but ischemic lesion was present in the corona radiata in the territory of the long insular artery sparing the descending motor pathway. These cases show that great care should be taken during surgical manipulations near the posterior part of the superior limiting sulcus to preserve the perforating branches to the corona radiata, and temporary occlusion of the branches under MEP monitoring is useful to identify the arteries supplying the pyramidal tract.     

Spontaneous middle cerebral artery occlusion leading to moyamoya phenomenon and aneurysm formation on collateral arteries

BACKGROUND: Spontaneous middle cerebral artery occlusion associated with moyamoya phenomenon is distinct from moyamoya disease. The hemodynamic stress on the collateral channel occasionally leads to aneurysm formation, which may manifest as hemorrhage. The etiology of this disease has not been fully understood. CASE DESCRIPTION: A 63-year-old woman presented with left putaminal hemorrhage. The cerebral angiogram revealed a significant stenosis in the proximal segment of the left middle cerebral artery. Collateral arteries originating from the horizontal segment of the ipsilateral anterior cerebral artery and the ambient segment of the ipsilateral posterior cerebral artery supplied the middle cerebral artery distal to the stenosis. Both of the collateral channels had associated aneurysms that were surgically obliterated. The aneurysm on the collateral artery from the posterior cerebral artery was responsible for the putaminal hemorrhage. CONCLUSIONS: Spontaneous middle cerebral artery occlusion may lead to focal moyamoya phenomenon and aneurysmal intracerebral, intraventricular, or subarachnoid hemorrhage. The presence of a co-existing anomalous collateral artery in the present case suggests a congenital etiology of the focal middle cerebral artery occlusion.     

A case of spontaneous fusiform aneurysm in a middle cerebral artery branch which causes rapidly thrombosed formation in a short period

A 61-year-old man presented with the complaint of headache. Investigations revealed a fusiform middle cerebral artery aneurysm at the M2 part. The formation of the aneurysm rapidly developed to a partially thrombosed aneurysm in the course of four months. As regards the treatment of the aneurysm, at first we tried surgery with a superficial temporal artery middle cerebral artery bypass (STA-MCA bypass) and trapping of the aneurysm. However, during the procedure, it was difficult to control bleeding from the temporal muscle, bone flap, and subdural space. Because of this, we finished the STA-MCA bypass without trapping of the aneurysm and then, four days later, we confirmed bypass patency and treated the aneurysm using endovascular coil embolization. Based on both surgical and interventional investigations in this case and a review of the reported literature, the authors propose that there are two mechanisms causing the middle cerebral artery fusiform aneurysm to develop thrombosed formation rapidly: (i) Peripheral middle cerebral artery branches demand less blood flow than other major trunk arteries. (ii) Bypass flow maintains perfusion to the distal branches. On the other hand, this flow alteration caused by surgical vascular bypass may promote the development of the aneurysm to thrombosed formation. The treatment of a fusiform middle cerebral artery aneurysm at the M2 part is also discussed.