An unusual artery causing an unusual stroke.

Bilateral thalamic infarctions are uncommon and often lead to more severe and long-lasting symptoms than unilateral thalamic infarctions. This article describes a patient with bilateral thalamic infarction caused by occlusion in the artery of Percheron, an anatomic variant thought to be present in 4% to 12% of the population.

Microsurgical anatomy of the central core of the brain.

OBJECTIVE The purpose of this study was to describe in detail the cortical and subcortical anatomy of the central core of the brain, defining its limits, with particular attention to the topography and relationships of the thalamus, basal ganglia, and related white matter pathways and vessels. METHODS The authors studied 19 cerebral hemispheres. The vascular systems of all of the specimens were injected with colored silicone, and the specimens were then frozen for at least 1 month to facilitate identification of individual fiber tracts. The dissections were performed in a stepwise manner, locating each gray matter nucleus and white matter pathway at different depths inside the central core. The course of fiber pathways was also noted in relation to the insular limiting sulci. RESULTS The insular surface is the most superficial aspect of the central core and is divided by a central sulcus into an anterior portion, usually containing 3 short gyri, and a posterior portion, with 2 long gyri. It is bounded by the anterior limiting sulcus, the superior limiting sulcus, and the inferior limiting sulcus. The extreme capsule is directly underneath the insular surface and is composed of short association fibers that extend toward all the opercula. The claustrum lies deep to the extreme capsule, and the external capsule is found medial to it. Three fiber pathways contribute to form both the extreme and external capsules, and they lie in a sequential anteroposterior disposition: the uncinate fascicle, the inferior fronto-occipital fascicle, and claustrocortical fibers. The putamen and the globus pallidus are between the external capsule, laterally, and the internal capsule, medially. The internal capsule is present medial to almost all insular limiting sulci and most of the insular surface, but not to their most anteroinferior portions. This anteroinferior portion of the central core has a more complex anatomy and is distinguished in this paper as the "anterior perforated substance region." The caudate nucleus and thalamus lie medial to the internal capsule, as the most medial structures of the central core. While the anterior half of the central core is related to the head of the caudate nucleus, the posterior half is related to the thalamus, and hence to each associated portion of the internal capsule between these structures and the insular surface. The central core stands on top of the brainstem. The brainstem and central core are connected by several white matter pathways and are not separated from each other by any natural division. The authors propose a subdivision of the central core into quadrants and describe each in detail. The functional importance of each structure is highlighted, and surgical approaches are suggested for each quadrant of the central core. CONCLUSIONS As a general rule, the internal capsule and its vascularization should be seen as a parasagittal barrier with great functional importance. This is of particular importance in choosing surgical approaches within this region.

Microsurgical anatomy of perforated arteries in the hypothalamic area.

AIM: This study aimed to investigate the microsurgical anatomy of perforating arteries in the hypothalamic area, which are associated with diabetes insipidus. MATERIAL AND METHODS: A total of 20 adult cadaver heads soaked in formalin were infused with red latex through the carotid artery and vertebral artery, and supplementary perfusion was performed after 1 day. RESULTS: The perforating arteries in the hypothalamic area could be divided into three groups according to their origins, namely, the former, below and outside groups. The former group mainly comprised the perforating arteries near the current communicating arteries. The outside group comprised the perforating arteries from the upper clinoid segment of the internal carotid and posterior communicating arteries. The below group comprised the bottom hypophyseal arteries of the cavernous segment from the internal carotid artery. CONCLUSION: Vascular injuries that occur during surgery can be minimised by understanding the distribution of the aforementioned vessels.

Decreased consciousness: bilateral thalamic infarction and its relation to the artery of Percheron.

This case series highlights two patients seen in the same stroke centre presenting with unusual symptoms. They were later diagnosed with bilateral thalamic infarcts, probably related to an unusual anatomical variant. The difficulties in establishing the diagnoses due to their relative rarity and complexity could have impacted on patient outcomes.

Redefining thalamic vascularization vicariously through gerald percheron: a historical vignette.

Gerard Percheron, M.D., a practicing neurologist and prolific researcher at the Institute Nationale de la Sante et de la Recherche Medicale (INSERM), made significant and valuable contributions to medicine, in particular, to the vascular anatomy of the basal ganglia. His particular interest in the thalamus eventually led to the identification of an anatomic variation in its vascular supply. This newly identified artery was subsequently named the artery of Percheron (AOP). Given the estimated prevalence of the AOP in up to one third of the population and its significant proportion of all thalamic infarcts, it is necessary for physicians to be aware of this anatomic vascular variant and its clinical consequences. Although occlusion of the AOP may present similar to other arterial thalamic occlusions, it can be identified through susceptibility-weighted imaging and ruled out with conventional or magnetic resonance angiography. Occlusion of the AOP typically causes a simultaneous and symmetric infarction. Treatment efficacy is time-dependent and necessitates thrombolytics and anticoagulative medications. Here, we trace a course from the artery's initial description in 1973 to its current implications in cerebrovascular stroke, and offer a synopsis of the proposed treatment.

Bilateral thalamic infarcts due to occlusion of the Artery of Percheron and discussion of the differential diagnosis of bilateral thalamic lesions.

The Artery of Percheron is a rare vascular variant in which a single dominant thalamoperforating artery arises from one P1 segment and bifurcates to supply both paramedian thalami. Occlusion of this uncommon vessel results in a characteristic pattern of bilateral paramedian thalamic infarcts with or without mesencephalic infarctions. We report a case of a 31-year-old man with acute bilateral thalamic infarcts and a truncated Artery of Percheron demonstrated on magnetic resonance angiography (MRA). Occlusion of the vessel was presumably due to embolism from a patent foramen ovale that was subsequently closed. The case presentation is followed by a discussion of bilateral paramedian thalamic infarcts including the causes and clinical presentation. The differential diagnosis of vascular and nonvascular etiologies of bilateral thalamic lesions is also discussed.

Surgical treatment for musicogenic epilepsy.

We report a patient with medically intractable musicogenic epilepsy (ME) who was treated with surgery. Using the non-invasive methods of ictal and interictal electroencephalography (EEG), MRI, interictal single photon emission computed tomography and clinical manifestations, we first localized the musicogenic seizures (MS). The ictal onset zone was then further localized using intracranial EEG to the middle part of the left superior temporal gyrus. Surgical resection of the epileptogenic zone was then performed. The patient had two seizures within 2 weeks post-operatively, but has then had no seizures during the following year (Engel class II). The results suggest that patients who have medically intractable ME combined with unilateral ictal onset zones should be considered for the surgical treatment of epilepsy.

The middle perforated substance of the diencephalon.

The diencephalon, upper brain stem and other basal brain structures are supplied chiefly by penetrating branches of the cerebral arteries. We examined the retrochiasmatic space between the superior border of the pons and posterior edge of the optic chiasm in six randomly selected adult fresh brain specimens. Lateral or anterolateral to the mamillary bodies, two small quadrangular spaces (2.5 x 3.5 mm) were found that were limited laterally by the junction of the optic tract and crus cerebri. These spaces were pierced on each side by 1 to 5 small penetrating branches (premamillary arterial complex) of the posterior communicating artery. A single, large and obliquely oriented penetrating branch of the posterior communicating artery (the so-called premamillary, thalamotuberal or mamillothalamic artery) was found to pierce this area in all specimens. Based on our findings, the above-mentioned vessels of this perforating substance supply the floor of third ventricle, hypothalamus and ventral thalamic nuclei. Hence, special attentions should be made during surgery in this area such as third ventriculostomy for hydrocephalus.

Vascular anatomy of the optic nerve head.

Although intraocular pressure remains the main modifiable risk factor for open-angle glaucoma, other factors such as vascular perfusion likely play a significant role. It is not clear how mechanical deformation, axonal damage, glial responses, and ischemia interact to lead to the tissue remodeling seen clinically as glaucomatous cupping. To understand the potential role of vascular risk factors in glaucoma, it is important to understand the vascular anatomy of the optic nerve head (ONH). The focus of this review is to provide a description of the vascular anatomy of the ONH and to describe recent work in the central nervous system that suggests that astrocytes play a key role in vascular regulation. Finally, the evidence for vascular regulation in the ONH and retina is reviewed.

The cerebrum. Anatomy.

The cerebrum is the crown jewel of creation and evolution. It is a remarkably delicate, intricate, and beautiful structure. The goal of this chapter is to provide the information needed to permit the neurosurgeon to navigate accurately, gently, and safely around and through the cerebrum and intracranial space. The location of deep structures is frequently described in relation to cranial and superficial cerebral landmarks in order to develop the concept of see-through, x-ray type knowledge of the cerebrum. In numerous illustrations, stepwise dissections are used to clarify the relationship between structures in different layers. Important clinical and surgical concepts are intermixed with the description of the cerebrum and its arteries, veins, and ventricles.

Branches of the anterior cerebral artery near the anterior communicating artery complex: an anatomic study and surgical perspective.

The anatomy of the branches of the anterior cerebral artery (ACA) near the anterior communicating artery (ACoA) complex were investigated to minimize neurovascular morbidity caused by surgical procedures performed in this region. Thirty-one cadaver brains were perfused with colored silicone, fixed, and studied under the operating microscope. The recurrent artery of Heubner (RAH), orbitofrontal artery (OFA), and frontopolar artery (FPA) were identified as the branches of the ACA arising near the ACoA complex. The OFA and FPA were identified in all hemispheres. Forty-nine (64%) of a total of 77 RAHs arose from the A2 segment. The OFA always arose from the A2 segment, was consistently the smallest branch, and coursed to the gyrus rectus, olfactory tract, and olfactory bulb. The mean distance between the ACoA and the OFA was 5.96 mm. The FPA arose from the A2 segment in 95% of the specimens, and coursed to the medial subfrontal region. The mean distance between the ACoA and the FPA was 14.6 mm. The RAH, OFA, and the FPA are three branches that arise from the ACA near the ACoA complex. These vessels have similar diameters, but can be distinguished by the final destination. Distinguishing these vessels is important since the consequences of injury or occlusion of the FPA and OFA are significantly less than of the RAH.

Blood capillary distribution correlates with hemodynamic-based functional imaging in cerebral cortex.

Our study concerns the mechanisms that underlie functional imaging of sensory areas of cortex using hemodynamic-based methods such as optical imaging of intrinsic signals, functional magnetic resonance imaging and positron emission tomography. In temporal cortex of chinchilla, we have used optical imaging of intrinsic signals evoked by acoustic stimulation to define the functionally responsive area and then made (scanning electron microscopy) observations of the corresponding capillary networks prepared by corrosion cast methods. We report that intrinsic signals associated with auditory cortex correlate directly with discrete capillary beds. These capillary beds, within the cortical surface layers, are distributed across the cortex in a non-uniform fashion. Within cortex both the arterial supply and the capillary network contain various flow control structures. Our study suggests a causal relationship between the metabolic demands of local neuronal activity and both the density of the capillary network and the placement of the control structures. Such relationships will affect the ultimate spatial resolution obtainable by hemodynamic-based functional brain imaging studies. These relationships will also affect quantitative comparisons of activity levels in different areas of cortex.

CURVES: curve evolution for vessel segmentation.

The vasculature is of utmost importance in neurosurgery. Direct visualization of images acquired with current imaging modalities, however, cannot provide a spatial representation of small vessels. These vessels, and their branches which show considerable variations, are most important in planning and performing neurosurgical procedures. In planning they provide information on where the lesion draws its blood supply and where it drains. During surgery the vessels serve as landmarks and guidelines to the lesion. The more minute the information is, the more precise the navigation and localization of computer guided procedures. Beyond neurosurgery and neurological study, vascular information is also crucial in cardiovascular surgery, diagnosis, and research. This paper addresses the problem of automatic segmentation of complicated curvilinear structures in three-dimensional imagery, with the primary application of segmenting vasculature in magnetic resonance angiography (MRA) images. The method presented is based on recent curve and surface evolution work in the computer vision community which models the object boundary as a manifold that evolves iteratively to minimize an energy criterion. This energy criterion is based both on intensity values in the image and on local smoothness properties of the object boundary, which is the vessel wall in this application. In particular, the method handles curves evolving in 3D, in contrast with previous work that has dealt with curves in 2D and surfaces in 3D. Results are presented on cerebral and aortic MRA data as well as lung computed tomography (CT) data.

Variability of the territories of the major cerebral arteries.

Recent morphological and functional studies on the circle of Willis suggest that the areas of supply of the six major cerebral arteries show a considerable variation in distribution, in contrast to the relatively consistent pattern generally accepted; therefore, the cortical and intracerebral distribution of the territories of these arteries was investigated in 25 unfixed human brains obtained at routine autopsy. The six major cerebral arteries were simultaneously injected under the same pressure with different-colored Araldite F mixtures under standardized conditions to obtain the most realistic territorial distribution. The cortical boundaries were examined and recorded in relation to the cerebral gyri and sulci, and the territories of the anterior, middle, and posterior cerebral arteries were analyzed and compared. The intracerebral distribution of these territories was investigated after the injected brains were cut in parallel slices. The variability of the territories of these arteries was much larger than generally described in the literature. Twenty-six variations in the territory of the anterior cerebral artery, 17 variations in the area of the middle cerebral artery, and 22 variations in the area of the posterior cerebral artery were found in the cortex of 50 hemispheres. Intracerebrally, the anterior, middle, and posterior cerebral arteries contributed in varying degrees to the blood supply of the lobar white matter, the internal capsule, the caudate nucleus, and the lentiform nucleus. The large variation in the area in which the cortical and intracerebral boundaries between these territories was located was demonstrated by illustrating the minimum and maximum extent of each. The results are compared with prior findings, and their implications for both experimental model studies and clinical practice are discussed.

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)

Normal perivascular spaces mimicking lacunar infarction: MR imaging.

Perivascular (Virchow-Robin) spaces normally surround perforating arteries that enter the medial temporal lobes, corpus striatum, and thalamus. The high soft-tissue sensitivity of magnetic resonance (MR) imaging allows for the frequent detection of such cerebrospinal fluid (CSF)-filled spaces. Especially on axial images, these CSF-filled perivascular spaces may be confused with pathologic lesions, such a lacunar infarcts. Postmortem brain specimens demonstrate the anatomy of perivascular spaces around perforating arteries. Orthogonal images in the living patient help confirm this anatomic relationship. The characteristic CSF signal patterns from these foci are further evidence of their anatomic identification and true benign nature.

Microsurgical anatomy of the choroidal fissure.

The microsurgical anatomy of the choroidal fissure was examined in 25 cadaveric heads. The choroidal fissure, the site of attachment of the choroid plexus in the lateral ventricle, is located between the fornix and thalamus in the medial part of the lateral ventricle. The choroidal fissure is divided into three parts: (a) a body portion situated in the body of the lateral ventricle between the body of the fornix and the thalamus, (b) an atrial part located in the atrium of the lateral ventricle between the crus of the fornix and the pulvinar, and (c) a temporal part situated in the temporal horn between the fimbria of the fornix and the lower surface of the thalamus. The three parts of the fissure are the thinnest sites in the wall of the lateral ventricle bordering the basal cisterns and the roof of the third ventricle. Opening through the body portion of the choroidal fissure from the lateral ventricle exposes the velum interpositum and third ventricle. Opening through the temporal portion of the choroidal fissure from the temporal horn exposes the structures in the ambient and crural cisterns. Opening through the atrial portion of the fissure from the atrium exposes the quadrigeminal cistern, the pineal region, and the posterior portion of the ambient cistern. The neural, arterial, and venous relationships of each part of the fissure are reviewed. The operative approaches directed through each part of the fissure are also reviewed.