Microsurgical anatomy of the anterior perforating arteries

Microvascularization of thalamus and metathalamus in common tree shrew (Tupaia glis)

The microangioarchitecture of the thalamus and metathalamus in common tree shrew (Tupaia glis) was studied using vascular corrosion cast/stereomicroscope and SEM technique. The arterial supply of the thalamus and metathalamus was found to originate from perforating branches of the posterior communicating artery, the posterior cerebral artery, the middle cerebral artery, and the anterior choroidal artery. These perforating arteries gave rise to numerous bipinnate arterioles which in turn, with decreasing vessel diameters, branched into a non-fenestrated capillary bed. Venous blood from the superficial parts of the thalamus and metathalamus was collected into the thalamocollicular vein, whereas venous blood from internal aspects of the thalamus was conveyed to the internal cerebral vein. Some venous blood from the most rostral part of the thalamus flowed into tributaries of the middle cerebral vein before draining into the cavernous sinus. Further, the thalamic and metathalamic vascular arrangement was found to be of centripetal type. In addition, thalamic arterial anastomosis was rarely observed. Thus, obstruction of thalamic blood supply could easily lead to thalamic infraction.

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.

Tertiary microvascular territories define lacunar infarcts in the basal ganglia

Lacunar infarcts are commonly found in the basal ganglia, though little is known about the organization of small-scale microvascular territories that presumably subtend lacunae. We investigated microvascular territories of the lenticulostriate arteries, the recurrent artery of Heubner, the anterior choroidal artery, and striate branches of the anterior cerebral and anterior communicating arteries in perfusion-fixed human brains by simultaneous injection of fluorescent dyes and a radio-opaque substance in 5% gelatin. Territories were defined by ultraviolet illumination of dye and high-resolution mammography of radio-opaque substance. Brains were sectioned coplanar with the Talairach proportional grid system and vascular data were plotted, allowing for application to any human brain. The data suggest first that the lenticulostriate artery, recurrent artery of Heubner, and anterior choroidal artery supply distinct territories of the basal ganglia with minimal overlap and sparse anastomoses between major penetrating vessels. Individual territories are spatially consistent across brains and match the extent of major/minor infarcts. Second, branching patterns of parental, second-, and third-order vessels leading to circumscribed terminal vascular beds could account structurally for "lacunar" infarcts.

Angiographic analysis of blood flow modification in cerebral aneurysm models with a new asymmetric stent

We have built new asymmetric stents for minimally invasive endovascular treatment of cerebral aneurysms. Each asymmetric stent consists of a commercial stent with a micro-welded circular mesh patch. The blood flow modification in aneurysm-vessel phantoms due to these stents was evaluated using x-ray angiographic analysis. However, the density difference between the radiographic contrast and the blood gives rise to a gravity effect, which was evaluated using an initial optical dye-dilution experiment. For the radiographic evaluations, curved-vessel phantoms instead of simple straight side-wall aneurysm phantoms were used in the characterization of meshes/stents. Six phantoms (one untreated, one treated with a commercial stent, and four treated with different asymmetric stents) with similar morphologies were used for comparison. We calculated time-density curves of the aneurysm region and then calculated the peak value (Pk) and washout rate (1/τ) after analytical curve fitting. Flow patterns in the angiograms showed reduction of vortex flow and slow washout in the dense mesh patch treated aneurysms. The meshes reduced Pk down to 21% and 1/τ down to 12% of the values for the untreated case. In summary, new asymmetric stents were constructed and their evaluation demonstrates that they may be useful in the endovascular treatment of aneurysms.

MRI of hyperacute stroke in the AChA territory

The purpose of our study was to derive from the anatomical literature an easy-to-use map of the brain areas supplied by the anterior choroidal artery (AChA) and to assess the correspondence between damage within the putative AChA areas and clinical symptoms. A thorough review of the literature led to the recognition of 16 anatomical areas which could be delineated on routine diffusion-weighted MR images. A database of 138 consecutive ischemic stroke patients examined with MRI less than 6 h after symptoms onset was thereafter processed in a retrospective way. Patients presenting with at least one damaged AChA area were selected so as to assess the prevalence of AChA infarction and the clinical correlates of the condition. Fifteen patients (11%) had at least one damaged AChA area. Only two of them had "pure" AChA-restricted infarction. Contralateral hemiparesis and contralateral hemianesthesia were best predicted by lesions within the tail of the caudate nucleus with a sensitivity of 87% and 83%, respectively. Homonymous hemianopsia best correlated with lesions within the posterior limb of the internal capsule and within the retrolenticular part of the internal capsule, with a sensitivity of 100% and a specificity of 70% for both areas. We concluded that the clinical-radiological correlations did not match the neurophysiological standards, thereby highlighting the limitation of this study, which involved a cohort of acute stroke patients recruited from clinical practice and investigated the clinical impact of these brain lesions, even when documented with the most sensitive imaging modality.

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.

Hemorrhagic complication of stereotactic surgery in patients with movement disorders

OBJECT

Small, asymptomatic hemorrhages are easier to detect during stereotactic surgery when magnetic resonance (MR) imaging is used for targeting rather than when traditional approaches, such as ventriculography, are performed with contrast material. In the present study the authors examined the actual incidence of intraoperative hemorrhages in patients with movement disorders who had undergone MR imaging-targeted surgery, microelectrode recording (MER)-guided implantation of deep brain stimulation (DBS) electrodes, or radiofrequency-induced coagulation surgery performed.

METHODS

Ninety-six consecutive patients underwent a total of 116 stereotactic operations for movement disorders (57 operations for radiofrequency-induced coagulation and 59 for DBS electrode implantation) between January 1998 and November 2002. The authors investigated the correlation between hemorrhages and other factors including the location of the hemorrhage and the type of surgery performed. Postoperative computerized tomography scans demonstrated the occurrence of intraoperative hemorrhages at 12 locations during 11 procedures (9.5% of all procedures). Nine hemorrhages occurred during 57 coagulation operations (15.8%). Within this group, the frequency of hemorrhages was highest during thalamotomy (five [21.7%] of 23 procedures) and lower during pallidotomy (four [11.8%] of 34 procedures). In contrast, only two intraventricular hemorrhages developed during 59 operations in which DBS electrodes were implanted (3.4%). In no case was hemorrhage detected in the main DBS target, that is, the subthalamic nucleus.

CONCLUSIONS

When small, asymptomatic hemorrhages were included in the estimation, the actual rate of hemorrhage was higher than that previously reported. Judging from the incidence of hemorrhage during coagulation and DBS surgeries, the authors suggest that the heat induced by coagulation may play a larger role than microelectrode penetration in the development of hemorrhage.

Anatomic and clinical correlations of the lenticulostriate arteries

The authors examined the lenticulostriate (perforating) arteries in the vascular casts of 48 middle cerebral arteries (MCA), as well as in the MRI or CT scans of 32 patients with cerebral infarcts in the MCA territory. The lenticulostriate arteries ranged between two and 12 in number, and from 80 microm to 1,400 microm in size. They originated from the main trunk, terminal trunks, bifurcation site, and/or leptomeningeal branches of the MCA, either separately or from common trunks (70.8%). The extreme variations of the supplying region of the perforators were noted in seven anatomic specimens. In addition to the basal ganglia, the genu, and the anterior limb of the internal capsule, the lenticulostriate arteries seemed to supply only the rostral portion of the superior part of the posterior limb of the capsule. The patients presented with occlusion of all the lenticulostriate arteries, individual arteries, or only their twigs. Complete occlusion of these arteries resulted in a huge central hemispheric infarct. Occlusion of an individual artery most often caused a large ganglionic-capsular infarct. The authors concluded that the lacunar infarcts usually follow occlusion of a terminal or a side branch of the lenticulostriate arteries.

Ischemic complications of surgery for anterior choroidal artery aneurysms

OBJECT

Anterior choroidal artery (AChA) aneurysms account for 4% of all intracranial aneurysms. The surgical approach is similar to that for other supraclinoid carotid artery lesions, but surgery may involve a higher risk of debilitating ischemic complications because of the critical territory supplied by the AChA.

METHODS

Between 1968 and 1999, 51 AChA aneurysms in 50 patients were treated using craniotomy and clipping at the Mayo Clinic. There were 22 men (44%) and 28 women (56%) whose average age was 53 years (range 27-79 years). Twenty-four AChA aneurysms (47%) had hemorrhaged; nine patients (18%) had subarachnoid hemorrhage from another aneurysm. Three AChA aneurysms (6%) were associated with symptoms other than rupture. Forty-one patients (82%) achieved a Glasgow Outcome Scale (GOS) score of 4 or 5 at long-term follow up. The surgical mortality rate was 4%, and major surgical morbidity (GOS < or = 3) was 10%. Eight patients (16%) had clinically and computerized tomography-demonstrated AChA territory infarcts. Five of these strokes manifested in a delayed fashion 6 to 36 hours after the operation, and progressed from mild to complete deficit over hours. In 41 patients the aneurysm arose from the internal carotid artery adjacent to the AChA, and in nine patients the aneurysm arose directly from the origin of the AChA itself; four of these nine patients had postoperative infarction.

CONCLUSIONS

Surgical treatment of AChA aneurysms involves a significant risk of debilitating ischemic complications. Most postoperative strokes occur in a delayed fashion, offering a potential therapeutic window. Patients with aneurysms arising from the AChA itself have an extremely high risk for postoperative stroke.

Arteriovenous malformations of the basal ganglia region: rationale for surgical management

Surgical indications for arteriovenous malformations (AVMs) arising at the region of the basal ganglia are questionable and the majority of cases are considered inoperable. Albeit not free from risks of morbidity and mortality, the treatment of choice is usually radiosurgery for small lesions, and embolization plus radiosurgery for larger lesions. Nevertheless, some lesions may be amenable for surgical resection due to their favorable location. Eighteen cases of such AVMs were selected for a direct approach in our series. Seventeen cases were classified as Spetzler and Martin [22] grade III, and one case was a grade V. Ten patients were males and eight females. The mean age was 28.3 years (ranged from 2 to 43 years). Sixteen patients had had previous hemorrhagic events prior to hospital admission. Eleven patients had pre-operative well established neurological deficits, and seven patients although symptomatic had a normal neurological exam at admission. Fifteen patients had their AVMs completely resected. Among the eleven patients with previous neurological deficits nine had no change in their pre-operative condition and two experienced postoperative neurological worsening. In the long-term follow-up six patients had a complete recovery and five recovered only partially. Among the seven patients whose neurological examination was normal pre-operatively five remained unchanged, one had a transient motor deficit, and one died due to a thalamic venous infarction and massive bleeding into the thalamus. The anatomical knowledge and the precise localization of the arteriovenous malformation through the aid of neuroimage studies has provided the means to classify these AVMs and plan operative strategies for some small selected cases with relatively low morbidity.

The insular lobe: physiopathological and surgical considerations

OBJECTIVE

Surgery of the insula represents a technical challenge, because of the proximity of the internal capsule to the lenticulostriate arteries and the lack of certainty concerning its functionality. Using intraoperative direct cerebral stimulation, combined with neuronavigation, the authors operated on 12 insular gliomas. On the basis of this experience, the physiopathological and surgical implications are discussed.

METHODS

A low-grade insular glioma, revealed by seizures, was diagnosed in 12 right-handed patients with a normal neurological status. Preoperative magnetic resonance imaging showed that, according to Yasargil's classification system, three patients harbored Type 3 lesions and nine patients had Type 5 lesions (10 tumors on the right side and 2 on the left dominant side). All patients underwent surgery using direct cerebral stimulation, under general anesthesia in nine patients (motor mapping) and under local anesthesia in three patients (sensorimotor and language mapping). Ultrasonography and/or neuronavigation was used in all cases. Preoperative angio-computed tomographic scanning showed the lenticulostriate arteries in two patients.

RESULTS

The internal capsule was systematically detected, and the language areas were identified within the left insula in the awake patients. The lenticulostriate arteries were seen in two patients. Seven patients presented an immediate postoperative deficit; six of them recovered completely within 3 months. Four resections were total, six were subtotal, and two were partial (left insula).

CONCLUSION

The use of intraoperative direct cerebral stimulation and neuronavigation allows surgery of the insula with minimization of the risk of sequelae, but its use is still limited with regard to the dominant hemisphere, owing to the essential role of this structure in language.

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.

The striatum is the most vulnerable region in the brain to mitochondrial energy compromise: a hypothesis to explain its specific vulnerability

The striatum, together with the hippocampus, is one of the most vulnerable regions in the brain. Recently, genetic abnormalities or mutations have been linked to various neurodegenerative diseases, that is, Huntington's disease, Alzheimer's disease, amyotrophic lateral sclerosis (ALS), etc., but the processes from genetic abnormality to the final phenotypic expression are not well understood. Disturbances in energy metabolism especially in mitochondrial energy compromise could facilitate genetic abnormalities and enhance neuronal cell death. Here, we report that the striatum is the most vulnerable brain region to systemic intoxication with 3-nitropropionic acid (3-NPA), an inhibitor of succinate dehydrogenase inducing energy compromise. We hypothesize that the striatum-specific lesion by 3-NPA is due to cummulative insults characteristic to the striatum including glutamatergic excitotoxicity, dopaminergic toxicity, vulnerability of the lateral striatal artery and high activity in the glutamate-transporter. The former two are extravascular in origin while the latter two are intra-/perivascular. We also discuss the possibility that a high turnover rate in metabolism of nitric oxide (NO) might underlie the vulnerability of the lateral striatal artery. We posit that systemic intoxication with 3-NPA offers a good animal model to investigate the pathophysiology of neuronal/glial cell death, neurodegenerative disease, dysfunction of the blood-brain barrier (BBB), neuroimmune disorders, and stroke.

High resolution MRI of the deep brain vascular anatomy at 8 Tesla: susceptibility-based enhancement of the venous structures

PURPOSE

The purpose of this work was to describe the deep vascular anatomy of the human brain using high resolution MR gradient echo imaging at 8 T.

METHOD

Gradient echo images were acquired from the human head using a transverse electromagnetic resonator operating in quadrature and tuned to 340 MHz. Typical acquisition parameters were as follows: matrix = 1,024 x 1,024, flip angle = 45 degrees, TR = 750 ms, TE = 17 ms, FOV = 20 cm, slice thickness = 2 mm. This resulted in an in-plane resolution of approximately 200 microm. Images were analyzed, and vascular structures were identified on the basis of location and course.

RESULTS

High resolution ultra high field magnetic resonance imaging (UHFMRI) enabled the visualization of many small vessels deep within the brain. These vessels were typically detected as signal voids, and the majority represented veins. The prevalence of the venous vasculature was attributed largely to the magnetic susceptibility of deoxyhemoglobin. It was possible to identify venous structures expected to measure below 100 microm in size. Perforating venous drainage within the deep gray structures was identified along with their parent vessels. The course of arterial perforators was more difficult to follow and not as readily identified as their venous counterparts.

CONCLUSION

The application of high resolution gradient echo methods in UHFMRI provides a unique detailed view of particularly the deep venous vasculature of the human brain.

Microsurgical anatomy of the temporal lobe: part 1: mesial temporal lobe anatomy and its vascular relationships as applied to amygdalohippocampectomy

OBJECTIVE

We review the anatomy of the mesial temporal lobe region, establishing the relationships among the intraventricular, extraventricular, and surrounding vascular structures and their angiographic characterization. We also demonstrate the clinical application of these anatomic landmarks in an anatomic temporal lobectomy plus amygdalohippocampectomy.

METHODS

Fifty-two adult cadaveric hemispheres and 12 adult cadaveric heads were studied, using a magnification ranging from 3x to 40x, after perfusion of the arteries and veins with colored latex.

RESULTS

The intraventricular elements are the hippocampus, fimbria, amygdala, and choroidal fissure; the extraventricular elements are the uncus and parahippocampal and dentate gyri. The uncus has an anterior segment, an apex, and a posterior segment that has an inferior and a posteromedial surface; the uncus is related medially to cisternal elements and laterally to intraventricular elements. The anterior segment is related to the proximal sylvian fissure, internal carotid artery, proximal M1 segment of the middle cerebral artery, proximal cisternal anterior choroidal artery, and amygdala. The apex is related to the oculomotor nerve, uncal recess, and amygdala; the posteromedial surface is related to the P2A segment of the posterior cerebral artery inferiorly, to the distal cisternal anterior choroidal artery superiorly, and to the head of the hippocampus and amygdala intraventricularly. The choroidal fissure is located between the thalamus and fimbria; it begins at the inferior choroidal point behind the head of the hippocampus and constitutes the medial wall of the posterior two-thirds of the temporal horn.

CONCLUSION

Not only is the knowledge of these relations useful to angiographically characterize the mesial temporal region, but it has also proven to be of extreme value during microsurgeries involving this region.

The surgical anatomy of the perforating branches of the anterior choroidal artery

BACKGROUND

The available information about certain microanatomic features of the AChA perforators is incomplete. Precise knowledge of these vessels is necessary to understand the consequences of their occlusion and to safely operate in their region.

METHODS

The AChA perforators were microdissected and examined under the stereoscopic microscope in 10 vascular casts and in 20 hemispheres injected with india ink or radiopaque substance.

RESULTS

The perforating branches ranged in number from 2 to 9 (mean, 4.6) and in diameter between 90 microm and 600 microm (mean, 317 microm). The most proximal perforator arose 3.2 mm on average caudal to the AChA origin. The most distal (capsulothalamic) perforator varied in size from 200 microm to 610 microm (mean, 431 microm). One or more of the perforators always originated from the AChA (100%), but some of them also from the uncal (33.3%) or parahippocampal branch (10%) of the AChA, either as individual vessels only (70%) or from common trunks (30%). The perforators gave off the peduncular (20%), optic (23.3%), or uncal side branches (26.7%).

CONCLUSIONS

Our findings concerning the origin, position, number, size, branching, penetration site, and relationships of the AChA perforators gave the anatomic basis for safe operations in patients with AChA aneurysms or mediobasal limbic epilepsy.

Surgical treatment of anterior circulation aneurysms

The purpose of this paper is to present the results, assessed by an independent observer, of surgical treatment of 428 consecutive patients harbouring aneurysms of the anterior circulation, together with a review of relevant anatomy and operative strategy. At follow-up (mean 5.6 years) 89.3% lived at home and were independent, 5.1% lived at home but needed some kind of assistance, 2.0% lived in institution, whereas information was unavailable in 3.6% of living patients. Two hundred and fifty-three patients (64.5%) had unchanged employment status, 0.3% worked in sheltered environment, whereas 30.9% went out of work due to their subarachnoid hemorrhage (SAH). Information about employment status was unavailable in 4.3%. For aneurysms of the internal carotid, anterior communicating and middle cerebral artery, respectively, mortality was 3.2, 3.9 and 5.6%, whereas 92.0, 88.1 and 89.0% of surviving patients lived at home and were independent and 67.0, 63.6 and 63.0% had unchanged employment status. Three-months mortality of all causes was 4.2%. In the postoperative period 53 (12.4%) patients developed clinical signs of vasospasms, 6 (1.4%) had cardiac infarction, 4 (0.9%) lung oedema, 4 (0.9%) deep vein thrombosis, and 7 patients (1.6%) infection. During the follow-up period shunt-dependent hydrocephalus developed in 4.2% and 0.2% had a subsequent SAH from the same aneurysm. Forty-three patients were on anticonvulsive therapy.

A large anomalous anterior choroidal artery associated with internal carotid artery-posterior communicating artery aneurysm. Case report

A case of a large anomalous anterior choroidal artery (AchA) associated with internal carotid artery-posterior communicating artery aneurysm is reported. At surgery, the large anomalous AchA mimicked the PcomA. Therefore, we initially mistook the large anomalous AchA for the PcomA, and the ICA-PcomA aneurysm for the dorsal ICA aneurysm arising at a location of other than an arterial division. This is a rare case of an anomaly of the AchA with an associated aneurysm found at surgery. Anatomical and surgical considerations are made.

Territories of the perforating (lenticulostriate) branches of the middle cerebral artery

The territories of the central branches of the middle cerebral artery (MCA) were examined in 21 injected human brains. It was noted that these central arteries supplied: the caudate nucleus (dorsolateral half of the rostral part of its head; the entire caudal part of the head; the body and rostral portion of the tail in some cases), the putamen (dorsolateral part of its rostral portion, the remainder of the putamen, except the most caudal part occasionally), the globus pallidus (the entire lateral segment, except the ventrorostral and, sometimes, the most caudal part), the basal forebrain (lateral parts of the basal nucleus of Meynert and the nucleus of the diagonal band, as well as fiber bundles in this region), the internal capsule (dorsal and ventrocaudal part of the anterior limb, dorsal part of the genu, dorsal and ventrorostral part of the posterior limb), the corona radiata (a narrow strip close to the internal capsule) and the cerebral cortex (the caudal orbitofrontal cortex occasionally). The presented data may have certain neuroradiologic, neurologic and neurosurgical significance.

Estrogen protects against while testosterone exacerbates vulnerability of the lateral striatal artery to chemical hypoxia by 3-nitropropionic acid

Gender differences in the vulnerability of the lateral striatal artery (1STR artery) to systemic intoxication with 3-nitropropionic acid (3-NPA, succinate dehydrogenase inhibitor) were studied. Subcutaneous injection of 3-NPA (20 mg/kg once a day for 2 days) induced striatal selective lesions in half of male rats associated with motor symptoms (rolling, paddling, recumbency, etc) while female rats were resistant. Lesions were located in the lateral striata and characterized by astroglial necrotic cell death, enhanced immunoreaction to factor VIII-related antigen, edema, extravasation of IgG and sometimes bleeding. The motor and histological disturbances were highly sex-dependent and modulated by changes in hormonal levels. Males were more susceptible than females. Castration had little effect but ovariectomy enhanced the vulnerability. Replacement therapy with testosterone increased while estradiol or tamoxifen suppressed the vulnerability in ovariectomized females. Investigation of the arterial architecture of the brain often revealed rectangular and acute angled branchings in the centrolateral striatum where the ISTR artery feeds. A parallel in vitro toxicity study demonstrated that an extreme Ca++ overload and a strong cellular swelling resulted in astrocytic cell death. Data suggest that 1STR artery and astrocytes are highly vulnerable to 3-NPA intoxication in males. The greater vulnerability of the ISTR artery may contribute to the pathogenesis of neurodegenerative diseases, striatal bleeding, etc. Protective effects of estrogen and tamoxifen may mediate gender differences often observed in these disorders and suggest their potential use as therapeutic agents for these disorders.

A brief history of pallidotomy

A large number of surgical procedures involving the globus pallidus and ansa lenticularis were performed from 1939 to the late 1950s for alleviation of rigidity and tremor, two of the main symptoms of Parkinson's disease. Several groups reported beneficial effects using a wide array of techniques and targets within the pallidum and its projections. Over time, pallidal targets lying in the ventral and posterior portions of the internal pallidum were considered to be the most effective. Based on anatomic studies, surgical misadventures, and empirical observations, there was an abrupt shift regarding the favored target to treat parkinsonian tremor to the thalamus, and most neurosurgeons abandoned pallidotomy in the 1960s. With the advent of L-dopa and the realization of its striking clinical benefits in the mid 1960s, within 5 to 10 years, virtually all surgery for Parkinson's disease ceased. We are now witnessing a rediscovery of pallidotomy as patients with Parkinson's disease are experiencing the shortcomings of medical therapy. In this article, we examine the evolution of pallidotomy and discuss the reasons for the renewed interest in this procedure.

Subcortical hypoperfusion associated with asymptomatic white matter lesions on magnetic resonance imaging

BACKGROUND AND PURPOSE

We examined whether hemodynamic and metabolic abnormalities in the cerebral white matter, basal ganglia, and thalamus are associated with asymptomatic white matter lesions (WML) depicted on MR images.

METHODS

A positron emission tomographic study with H2(15)O, C15O, and 15O2 was performed in eight normal control subjects without any WML (mean +/- 1 SD age, 68.5 +/- 10.2 years) and in 15 asymptomatic subjects with WML (71.3 +/- 8.5 years) to measure regional cerebral blood flow (CBF), cerebral blood volume, oxygen extraction fraction (OEF), and oxygen metabolic rate.

RESULTS

In the cerebral white matter in the asymptomatic subjects with WML, significantly lower CBF (20.3 +/- 3.9 mL/100 mL per minute; P < .05) and significantly higher OEF (0.43 +/- 0.08; P < .05) were found compared with those for control subjects (23.5 +/- 2.6 mL/100 mL per minute and 0.37 +/- 0.06, respectively). The severity of WML was not related to the magnitude of hypoperfusion. In the basal ganglia, significantly lower CBF (44.9 +/- 6.9 mL/100 mL per minute; P < .01) and significantly higher OEF (0.54 +/- 0.08; P < .01) were found in the WML group than in control subjects (70.1 +/- 12.0 mL/100 mL/min and 0.39 +/- 0.03, respectively). In the thalamus, there was no significant difference in CBF and OEF between the control and WML groups.

CONCLUSIONS

Hypoperfusion of the cerebral white matter and basal ganglia in asymptomatic WML subjects may be induced by the arteriosclerosis of long penetrating medullary arteries and lenticulostriate arteries but may not be directly related to the production of WML. The role of hypoperfusion in the production of WML and acceleration of its development remains to be elucidated.

Middle cerebral artery revascularization. Anatomical studies and considerations on the anastomosis site

In the surgical management of skull base lesions and vascular diseases such as giant aneurysms, involvement of the internal carotid artery may require the resection or the occlusion of the vessel. The anastomosis of the external carotid artery and the middle cerebral artery with venous graft may be indicated to re-establish the blood flow. To determine the best suture site in the middle cerebral artery, an anatomical study was carried out. Fourteen cerebral hemispheres were analysed after the injection of red latex into the internal carotid artery. The superior and inferior trunk of the main division of the middle cerebral artery have more than 2 mm of diameter. They are superficial allowing an anastomosis using a venous graft. The superior trunk has a disadvantage, it gives rise to branches for the precentral and post-central giri. The anastomosis with the inferior trunk presents lower risk of neurological deficit even though the angular artery originates from it.

The surgical anatomy of the relationships between the perforating and the leptomeningeal arteries

OBJECTIVE

Despite detailed studies of the perforating arteries, their relationships with the leptomeningeal arteries are almost unknown. These relationships can be of great significance during neurosurgical operations.

METHODS

The arteries of the hemispheres, which ranged in number from 17 to 36, were injected with india ink or methylmethacrylate.

RESULTS

The perforating vessels were noted to arise from the following leptomeningeal arteries: the subcallosal branch of the anterior communicating artery (26.6%); the median artery of the corpus callosum (6.6%); the medial orbitofrontal (6.6%) and the olfactory branch (3.3%) of the anterior cerebral artery; the accessory middle cerebral artery (3.3%); the frontal and temporal branches of the middle cerebral artery (66.6%); the temporal branches of the internal carotid and the anterior choroidal arteries (25% each); the peduncular branch of the posterior communicating artery (4.8%); the peduncular, collicular and medial posterior choroidal branches of the posterior cerebral artery (40%); the cerebellar branches (100%); the long pontine branches (20-26.6%); the anterolateral branches (33.3%) of the basilar artery; and the anterolateral or the lateral medullary branches (35.3%) of the vertebral artery. From 19.4 to 100% of some leptomeningeal vessels originated in the large perforating arteries.

CONCLUSION

From 4.8 to 100% of certain groups of the perforating vessels originated in the leptomeningeal arteries. Occlusion of a leptomeningeal artery that gives rise to the perforating vessel(s) may lead to superficial and deep infarcts in the same patient.

The variations of lenticulostriate arteries in the middle cerebral artery aneurysms

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) originated 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.

Aneurysm of superior branch of anterior choroidal artery mimicking carotid bifurcation aneurysm--case report

Aneurysm of the superior branch of anterior choroidal artery is very rare. We report this rare case with unique angiographic findings mimicking an internal carotid bifurcation aneurysm. A 35-year-old woman was admitted to our hospital because of severe headache. Lumbar puncture disclosed numerous red blood cells. Computed tomography revealed an enhanced circular area in the left basal cistern with moderate hydrocephalus. Cerebral angiography showed a saccular aneurysm near the left internal carotid bifurcation. During operation, the aneurysm was not found at the internal carotid bifurcation, but located deeper budding from the superior branch of the anterior choroidal artery. The aneurysm was successfully clipped. The postoperative course was favourable without any neurological deficit. The postoperative angiogram showed that the aneurysm was clipped well with preservation of the main trunk of the anterior choroidal artery. Computed tomography of the brain did not show any infarction area, 3 months after the surgery. The uniqueness of this case is the favourable outcome after sacrificing the superior branch of the anterior choroidal artery. The role of collaterals of the anterior perforating substance is emphasized.

Anatomical and technical aspects of the contralateral approach for multiple aneurysms

Microsurgery of multiple aneurysms is still a controversial subject. In order to avoid the risk of rebleeding and the consequent increase in morbidity in such cases all aneurysms or at least as many aneurysms as possible should be treated in the first operative procedure. To reach that goal aneurysms located on the contralateral side should also be considered for clipping during the first operation. Between 1984 and 1994 a series of 51 patients harboring multiple aneurysms of which 55 aneurysms were located on the contralateral side of the craniotomy were operated at our institution. No mortality or morbidity could be directly ascribed to the aneurysm that was clipped contralaterally. Based on that series we have described the anatomical features, technical aspects and surgical difficulties of approaching bilateral aneurysms through the same craniotomy.

Saccular aneurysms of the proximal (M1) segment of the middle cerebral artery

We report A series of 20 consecutive patients with 21 saccular aneurysms of the proximal (M1) segment of the middle cerebral artery. The incidence of M1 aneurysms was 3.0% among 660 patients with intracranial aneurysms and 12.9% among 155 patients with middle cerebral artery aneurysms in our center. Of the 20 patients, 2 were men and 18 were women. The aneurysms were classified into two types: the superior wall type (9 cases), arising at the origin of the lenticulostriate or fronto-orbital artery, and the inferior wall type (12 cases), arising at the origin of the early temporal branches. Twelve (60%) patients had ruptured M1 aneurysms. The incidence of multiple aneurysms was high (nine patients, 45%), and M1 aneurysms were responsible for subarachnoid hemorrhage in four patients. Of 14 M1 aneurysms greater than 5 mm in diameter, 11 (78.6%) ruptured. In contrast, only one (14.3%) of seven small (< or = 5 mm) aneurysms ruptured. In 12 patients with ruptured M1 aneurysms, intracerebral hematomas were recognized in 6 (50%). Intracerebral hematomas by the superior wall M1 aneurysms were located in the frontal lobe, and those by the inferior wall M1 aneurysms were in the temporal lobe. Fifteen patients (75%) made a useful recovery 6 months after surgery. Four patients (20%), who were in poor grade condition preoperatively, remained severely disabled. One patient died of sepsis 2 months after she recovered well from the operation. Special attention to the lenticulostriate arteries to avoid injury is critical for successful surgical treatment.

Decreased cerebrovascular dilatory capacity in subjects with asymptomatic periventricular hyperintensities

BACKGROUND AND PURPOSE

The clinical significance of the periventricular hyperintensity incidentally found on magnetic resonance images of the brain is questionable. We evaluated resting cerebral blood flow and cerebrovascular dilatory capacity of subjects with asymptomatic periventricular hyperintensities to study their cerebral hemodynamics.

METHODS

Magnetic resonance imaging of the brain was performed in 28 asymptomatic subjects with cerebrovascular risk factors to determine the severity of periventricular hyperintensity. Mean gray matter flow was computed by a 133Xe-clearance technique in subjects at rest and after the administration of 1 g acetazolamide. Flow values were correlated with the scores for periventricular hyperintensity.

RESULTS

Resting gray matter flow was not significantly correlated with the severity of periventricular hyperintensity for the whole brain (rs = -.364), whereas flow after acetazolamide loading (rs = -.783, P < .001) and the absolute value of increased flow (rs = -.567, P < .01) were significantly and negatively correlated with the severity of periventricular hyperintensity.

CONCLUSIONS

A decrease in vasodilatory capacity and compensatory vasodilation occur in the cerebral cortex of subjects with asymptomatic periventricular lesions and maintain cerebral blood flow.

The surgical anatomy of the perforating branches of the basilar artery

The perforating branches of the basilar artery were examined in 14 brain stems injected with india ink or methylmethacrylate. Three groups of the perforators were distinguished: the caudal, the middle, and the rostral. The caudal perforators varied in number from two to five and in diameter from 80 to 600 microns. In addition to their terminal branches, which entered the foramen cecum, the perforators occasionally branched off the pontomedullary artery, the pyramidal vessels, and the hypoglossal branches. The middle perforators arose either separately from the basilar artery or along with the basilar artery collateral branches. They ranged in number from five to nine and in diameter from 210 to 940 microns. The perforators gave rise to the pontomedullary artery (8.3%), the long pontine arteries (25.0%), and the anterolateral vessels (100%). The rostral perforators originated from the terminal part of the basilar artery (91.6%), as well as from the superior cerebellar artery (91.6%) and the posterolateral artery (16.6%). They varied in number from one to five and in diameter from 190 to 800 microns. The anastomoses among various perforating vessels were noted in 41.6 to 66.6% of the cases. The authors discussed the possible clinical significance of the anatomical data observed in this study.

Normal imaging anatomy of the suprasellar cistern and floor of the third ventricle

This article discusses the gross, functional, and imaging anatomy of the suprasellar cistern and its contents as well as the structures that form its borders, among the most important being the floor of the third ventricle and associated structures. Specific structures discussed include the optic chiasm and optic tracts, the anterior third ventricle, the tuber cinereum, the pituitary stalk (infundibulum), the choroidal fissure, the lamina terminalis, the gyrus rectus, the uncus, and the cerebral peduncles.

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.

Verbal memory deterioration after unilateral infarct of the internal capsule in an adolescent

After an infarction in the territory of the anterior perforating arteries, a 15-year-old, previously healthy, left-handed patient developed considerable verbal long term memory disturbances which could be followed up and tested for more than nine months. An extensive memory test battery was used to determine spared and impaired functions. The patient had remote memory disturbances with respect to personal events for the last 5 years and problems in all verbal task tested which required remembering items over time periods exceeding an hour. The patient was indistinguishable from control subjects on short-term memory tests and on a number of nonverbal learning and recognition tests. The crucial lesion for the observed deficits in the genu of the left internal capsule was assumed to have disrupted the anterior and inferior thalamic peduncles, fornix (column), stria terminalis, anterior commissure and the medial part of the globus pallidus. This infarct, therefore, most likely damaged traversing fibres which intercommunicate within the Papez circuit and the basolateral limbic circuit and which in part provide access to cortical memory representing areas.

Aneurysms of the ophthalmic segment. A clinical and anatomical analysis

The clinical, radiographic, and anatomical features in 80 patients with ophthalmic segment aneurysms were reviewed, and were categorized according to a presumed origin related to the ophthalmic (41 cases) or superior hypophyseal (39 cases) arteries. There was a marked female predominance (7:1) and high incidence of multiple aneurysms (45%) within this population. Clinical presentations included subarachnoid hemorrhage in 23 cases (29%) and visual deficits in 24 (30%); five patients exhibited both hemorrhage and visual loss. Twenty-eight aneurysms were incidentally identified. Ophthalmic artery aneurysms arose from the internal carotid artery (ICA) just distal to the ophthalmic artery, pointed superiorly or superomedially, and (when large) deflected the carotid artery posteriorly and inferiorly, closing the siphon. Abnormalities relating to vision were not identified until the aneurysm realized giant proportions. The optic nerve was typically displaced superomedially, which restricted contralateral extension until late in the clinical course; unilateral nasal field loss was seen in 12 patients. Nine patients had bilateral ophthalmic artery aneurysms which were often clipped via a unilateral craniotomy. Superior hypophyseal artery aneurysms arose just above the dural ring from the medial bend of the ICA, at the site of perforator origin to the superior aspect of the hypophysis, and had no direct association with the ophthalmic artery. The carotid artery was usually located lateral or superolateral relative to the aneurysm. These lesions could extend medially beneath the chiasm (suprasellar variant), producing a clinical and computerized tomography picture similar to a pituitary adenoma, or they could extend ventrally to burrow beneath the anterior clinoid process (paraclinoid variant). Preoperative categorization of these lesions according to their likely branch of origin provides excellent correlation with visual deficits and operative findings, and has allowed the author to clip 52 of 54 lesions, with very low operative or visual morbidity.

Microanatomy and possible clinical significance of anastomoses among hypothalamic arteries

We examined anastomoses among the hypothalamic arteries in 14 human brains using an injection technique, microdissection, and a stereoscopic microscope. Five to 22 anastomoses (mean 10.1) were found in all 14 brains on each side, varying from 20 to 280 (mean 71) microns in diameter and from 0.1 to 5.3 (mean 1.52) mm long. A single hypothalamic artery may be connected to other vessels by one to 10 anastomoses. The anastomoses were channel-like or plexiform; both types may be ipsilateral or right-left. They connected the hypothalamic arteries "end-to-end," "end-to-side," and "side-to-side." The interconnected arteries ranged from 30 to 1,900 (mean 148) microns in diameter. Anastomoses were most frequent among the commissural arteries and in the distribution of the superior hypophyseal arteries and the tuberoinfundibular branches of the posterior communicating artery. The largest anastomoses were found among the tuberoinfundibular branches of the posterior communicating and internal carotid arteries, as well as among the premamillary arteries and the mamillary branches. We discuss the neurologic, neuroendocrinologic, and neurosurgical significance of the described anastomoses.

[Aneurysms of the anterior choroidal artery: clinical, anatomical and surgical aspects]

Relatamos 5 casos de doentes portadores de aneurismas da região da artéria coroidéia anterior. Aspectos clínicos, anatômicos e cirúrgicos são discutidos.