Middle cerebral artery: anatomical and radio-graphic study

A New, More Accurate Classification of Middle Cerebral Artery Aneurysms

BACKGROUND:

Classification of middle cerebral artery (MCA) aneurysms is sometimes difficult because the identification of the main MCA bifurcation, the key for accurate classification of MCA aneurysms, is inconsistent and somewhat subjective.

OBJECTIVE:

To use the meeting point of the M1 and M2 trunks as an objective, generally accepted, and angiographically evident hallmark for identification of MCA bifurcation and more accurate classification of MCA aneurysms.

METHODS:

We reviewed the computed tomographic angiography data of 1009 consecutive patients with 1309 MCA aneurysms. The M2 trunks were followed proximally until their meeting with the M1 trunk at the main MCA bifurcation. The aneurysms were classified according to their relative location: proximal, at, or distal to the MCA bifurcation. The M1 aneurysms were further subgrouped into M1 early cortical branch aneurysms and M1 lenticulostriate artery aneurysms, extending the classic 3-group classification of MCA aneurysms into a 4-group classification.

RESULTS:

The main MCA bifurcation was the most common location for MCA aneurysms, harboring 829 aneurysms (63%). The 406 M1 aneurysms comprised 242 M1 early cortical branch aneurysms (60%) and 164 M1 lenticulostriate artery aneurysms (40%). We found 106 MCA aneurysms (8%) at the origin of large early frontal branches simulating M2 trunks liable to be misclassified as MCA bifurcation aneurysms. Even though 51% of the 407 ruptured MCA aneurysms were associated with an intracerebral hematoma, this did not affect the classification.

CONCLUSION:

Studying MCA angioarchitecture and applying the 4-group classification of MCA aneurysms is practical and facilitates the accurate classification of MCA aneurysms, helping to improve surgical outcome.

Three-dimensional morphometrical analysis of the M1 segment of the middle cerebral artery: potential clinical and neurosurgical implications

With an increase in the understanding of the formation and treatment of cerebral aneurysms and an improvement in imaging technology, actual standardized measurement values for the cerebral arteries are necessary. Therefore, the aim of this study was to provide a detailed assessment of the three-dimension (3D) morphology (vessel's curvature and trajectory) and 3D-morphometry of the M1 segment of the middle cerebral artery using computer tomography angiography (CTA) images. The DICOM files from CTA of 40 male and 75 female individuals with a mean age of 50.1 years were analyzed using an interactive postprocessing 3D volume-rendering algorithm. Specifically, the M1 segment was evaluated. Calculations included the length, internal diameter, volume, deviation (DI) and tortuosity indices (TI). The M1 segment had a mean internal diameter of 2.23 mm and was greater in men. M1 asymmetry was identified in 23.4% of the individuals and was more common in women. The mean length was 15.62 mm and the left M1 segments were a little longer. The mean volume of the M1 segments was 63.92 mm(3) , and this was typically greater in men and on the left sides. The mean TI and DI for the M1 segment were 0.91 and 2.17 mm, respectively. Therefore, the M1 segments are only slightly curved or straight in their course. In addition, the longest vascular M1 segments are more deviated (curved) and more tortuous. Such standardized data as presented herein may be useful in the preprocedural evaluation of patients with intracranial vascular pathology of the M1 segment.

The striatocapsular infarction and its aftermaths

Ischaemic stroke syndromes in the vascular territory of middle cerebral artery may have atypical presentation and radiographic findings because of the variable anatomy of that artery. Therefore, misdiagnosis of these syndromes as neoplastic or infectious processes is not uncommon. This case describes a 69-year-old comatose woman who was referred to us as having 'a brain tumour with massive surrounding oedema.' Further work-up revealed that she had a large left-sided lenticular nuclear infarction with some extension into the surrounding areas-the striatocapsular infarction.

The topographic anatomy of the central artery: a neuronavigational-based study

BACKGROUND/AIM

The central area of the brain, including the pre- and post-central gyri with their vascular structures, is one of the most crucial regions to preserve in neurosurgical intervention. The central sulcus is also a landmark of utmost importance for neurosurgeons. Although the arteries supplying the central region have been briefly described, their exact course has not been studied. The aim of the study is to establish the position and course of the central sulcus artery in relation to the central sulcus and its convolutions.

METHODS

Computer-assisted three-dimensional (3-D) anatomical reconstructions of the central area and of the central sulcus artery were performed with the aid of neuronavigational software in 13 patients operated at the Montreal Neurological Institute (MNI).

RESULTS

The central sulcus artery was coincident with the central sulcus and course(s) was almost similar on both hemispheres.

CONCLUSIONS

The knowledge of the exact course of the central sulcus artery is of paramount importance in cases of lesions or epileptic foci involving the central area. 3-D reconstruction with neuronavigation has proven to be a reproducible and reliable technique to provide the surgeon with the necessary surgical topographic anatomy of the central sulcus artery and central area.

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.

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.

Microsurgical anatomy of the proximal segments of the middle cerebral artery

The microvascular anatomy of the proximal segments (M1 and M2) of the middle cerebral artery (MCA) was studied in 70 unfixed brain hemispheres from 35 cadavers. The arteries were injected with a tinted polyester resin and dissected under magnification by microsurgical techniques. The authors studied the outer diameter (OD), length, site of origin, and pattern of branching of the main trunk, secondary trunks, and the initial insular portion of the cortical branches of the MCA. The degree of mobilization of the arteries lying over the insular cortex was also assessed. The main trunk of the MCA, which had an OD of 3 +/- 0.1 mm bilaterally and a length of 15 +/- 1.1 mm in the right hemisphere and 15.7 +/- 1.3 mm in the left hemisphere, could be divided into four groups: Group I: absence of a main division (that is, a single-trunk type of MCA) (in 6% of cases); Group II: bifurcation (64%); Group III: trifurcation (29%); and Group IV: quadrifurcation (1%). The secondary trunks resulting from the division of the main trunk of the MCA had a mean OD ranging from 1.4 to 2.3 mm and a mean length that varied from 12.1 to 14.9 mm. The mean OD of the cortical branches measured near their origin in the main and secondary trunks indicated that the angular artery was the largest vessel, with a mean OD of 1.5 mm on both sides of the brain. The temporopolar artery was the smallest, with a mean OD of 0.8 mm in the right hemisphere and 0.9 mm in the left hemisphere. The authors also describe the patterns of origin of the cortical vessels from the main trunk (early branches) and from the secondary trunks, as well as their branching pattern at the site of origin (single vessels and common stems). These anatomical data indicate that it is possible to perform microvascular reconstructive procedures, such as anastomosis, grafting, and reimplantation of branches in the insular area. The advantages of using unfixed specimens, intravascular injections, and magnification to reproduce in vivo conditions as closely as possible are also discussed.

Balloon catheter as a model of cerebral emboli in humans

A striking similarity has been found between the distribution of occlusions in various cerebral arteries and the statistical regularity of the pathways of balloon drifting freely in the blood stream. Based on the assumption that the course of a balloon is determined by the same hydrodynamic laws as that of an embolus of similar size, it is concluded that the majority of occlusions of the cerebral arteries are of embolic origin. Emboli, then, might also be an explanation for most of the TIAs.

Microsurgical anatomy of the middle cerebral artery

The microsurgical anatomy of the middle cerebral artery (MCA) was defined in 50 cerebral hemispheres. The MCA was divided into four segments: the M1 (sphenoidal) segment coursed posterior and parallel to the sphenoid ridge; the M2 (insular) segment lay on the insula; the M3 (opercular) segment coursed over the frontoparietal and temporal opercula; and the M4 (cortical) segment spread over the cortical surface. The Sylvian fissure was divided into a sphenoidal and an operculoinsular compartment. The M1 segment coursed in the sphenoidal compartment, and the M2 and M3 segments coursed in the operculoinsular compartment. The main trunk of the MCA divided in one of three ways; bifurcation (78% of hemispheres), trifurcation (12%), or division into multiple trunks (10%). The MCA's that bifurcated were divided into three groups: equal bifurcation (18%), inferior trunk dominant (32%), or superior trunk dominant (28%). The MCA territory was divided into 12 areas: orbitofrontal, prefrontal, precentral, central, anterior parietal, posterior parietal, angular, temporo-occipital, posterior temporal, middle temporal, anterior temporal, and temporopolar. The smallest cortical arteries arose at the anterior end and the largest one at the posterior end of the Sylvian fissure. The largest cortical arteries supplied the temporo-occipital and angular areas. The relationship of each of the cortical arteries to a number of external landmarks was reviewed in detail.

Clinical features and long-term follow-up of patients with reversible ischemic attacks (RIA)

The clinical features of 102 cases with transient attacks due to cerebral ischemia were evaluated, and 94 out of 102 cases were followed for an average of 6 years. 1) The clinical study makes comparisons between two groups of patients grouped under the somewhat new definition of Reversible Ischemic Attacks (RIA): classical Transient Ischemic Attacks (TIA) and Stroke with Full Recovery (SFR), in which a complete recovery took place over a longer period, on the average 3 weeks. 2) SFR constitutes the 34.31% of the total cases with transient ischemic episodes. In the carotid district the onset was more frequently gradual in SFR than in TIA and aphasia more frequent in TIA than in SFR. Multiple attacks prevailed in TIA over the SFR group. The definition of transient attack due to ischemia is discussed. 3) Completed strokes occurred in 11 cases (11.7%) with RIA. Hypertension and cardiac disease were significantly frequent in cases with subsequent stroke. The conclusion was reached that TIA is a symptom, not a pathological state, and TIA should be considered an important symptom but not a specific harbinger of completed stroke.

The angiographic diagnosis of occlusions of the posterior cerebral artery

The angiographic appearance of twenty-seven unilateral or bilateral occlusions of the posterior cerebral artery (PCA) are described. They are classified into proximal, interpeduncular, ambient or distal occlusions according to their prefered location. Ambient occlusions were by far the most common and have therefore probably not developed from a stenosing arteriosclerosis since this forms preferentially in the proximal and interpeduncular segment. Leptomeningeal anastomoses were common between all respective branches of the middle cerebral artery and the PCA but the anterior cerebral artery and the interarterial anastomoses rarely contributed to the collateral blood supply. A retrograde progression of the occlusion was observed on reangiography occasionally in cases in which there was no major artery originating just proximal to the occlusion. Anterograde progression and disintegration of obstructing material was also observed. PCA occlusions had a good prognosis in terms of survival but the associated visual field defects rarely improved.

Abnormal dynamic scintigraphy in hydrocephalus: a proposed mechanism

Dynamic brain scintigraphy was performed on seven patients with documented hydrocephalus of various aetiologies. The patients had a characteristic abnormality consisting of lateral displacement of the proximal middle cerebral activity associated with a paracentral lucent zone. No focal areas of increased activity were identified on the static brain images. A proposed mechanism for these findings is discussed.