Milan Milisavljević

Perforating branches of the middle cerebral artery. Microanatomy and clinical significance of their intracerebral segments.

Perforating branches of the middle cerebral arteries (MCA) were examined on the forebrain hemispheres of fourteen human brains. It was noticed that their intracerebral segments arose from the MCA main trunk, and its terminal and collateral (cortical) branches. They terminated in certain parts of the basal ganglia and internal capsule. The course, direction, shape, diameters and branches of these segments were examined in detail. Classification of all the vessels was made according to caliber. It was concluded that the size of lacunar infarcts depends on the caliber and ramification zone extent of the occluded perforating vessels. Diameters of the intracerebral segments of vessels ranged from 80 to 840 microns, of their terminal branches from 80 to 780 microns, and of the collateral branches from 50 to 400 microns. The average size of the ramification zone was: 41.6 X 15.5 mm for the entire perforating artery; 37.9 X 15.5 mm for the intracerebral segment; 23 X 13 mm for the terminal branches; 8.9 X 5.5 mm for larger collateral branches; and 2.6 X 1.4 mm for the smallest branches.

BRANCHES OF THE ANTERIOR COMMUNICATING ARTERY : MICROSURGICAL ANATOMY

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

Microvascular anatomy of the hippocampal formation

The hippocampal vessels were examined in 25 forebrain hemispheres injected with india ink or methylmethacrylate. There were two to seven hippocampal arteries, which measured 200-800 microns in diameter. The anterior hippocampal artery (AHA), which was present in 88.2% of the hemispheres, most often originated from the posterior cerebral and the anterior temporal arteries, that is, within the rostral hippocampo-parahippocampal arterial complex. It arose from the anterior choroidal artery in 29.4% of the hemispheres. The AHA extended between the uncus and the parahippocampal gyrus, and it supplied the head of the hippocampus. The middle hippocampal artery was constant. It most often arose from the posterior cerebral and the common temporal arteries. The middle hippocampal artery coursed just caudal to the uncus, in close relationship with the lateral posterior choroidal artery, and it usually supplied the middle part of the hippocampal formation. The posterior hippocampal artery, which existed in 94.1% of the hemispheres, most often arose from the posterior cerebral and the splenial arteries. It irrigated the caudal part of the hippocampal formation. The anastomoses connecting the posterior, middle, and the anterior hippocampal arteries were present in 29.4% of the hemispheres. The hippocampal arteries gave rise to the straight vessels, which divided into the large and the small intrahippocampal arteries. The highest density of the capillary network was noted in the pyramidal and molecular layers of the hippocampal formation. The clinical significance of the obtained microanatomical findings is discussed.

The anatomical basis for the cerebellar infarcts.

BACKGROUND Very little can be found in the literature concerning the variation of the irrigation area of the cerebellar arteries, as well as the characteristics of anastomoses among these vessels. The anatomical features may determine certain features of cerebellar infarcts. Consequently, we examined the irrigation area of and the anastomoses among the cerebellar arteries. METHODS The anatomical features of the posterior inferior cerebellar artery (PICA), the anterior inferior cerebellar artery (AICA), and the superior cerebellar artery (SCA) were studied in 26 cerebella injected with india ink, while their irrigation areas and anastomoses were examined in 8 of these cerebella. RESULTS The PICA, which most often (82%) arose from the vertebral artery, was found most commonly (81.3%) to supply the largest part of the occipital surface of the cerebellar hemisphere, the caudal or caudomedial part of the tentorial surface, and the inferior vermis. The AICA, which usually (92%) arose from the basilar artery, commonly (68.8%) supplied most of the petrosal surface of the hemisphere and the flocculus. The SCA, which divided into the medial and the lateral trunks, always irrigated most of the tentorial surface of the cerebellum, the superior vermis, and the dentate nucleus. The PICA, AICA, and SCA were always interconnected by anastomoses, which ranged from 40 microns to 420 microns in diameter. CONCLUSIONS Cerebellar infarcts were documented by computed tomography (CT) or magnetic resonance imaging (MRI) examinations in 10 patients. The infarcts were located in the PICA territory (60%) or the SCA region (40%). The authors compared the obtained anatomic data to the features of the cerebellar infarcts in these patients.

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.

Interpeduncular perforating branches of the posterior cerebral artery. Microsurgical anatomy of their extracerebral and intracerebral segments

Interpeduncular perforating branches were found in all 69 examined posterior cerebral arteries. They varied in number from 1 to 10, with an average of 2. They arose directly from the posterior cerebral artery (47.8%), from the collateral branches of the posterior cerebral artery (30.3%), or by their own common stems (88.4%). Their extracerebral segments varied from 100 to 750 microns in diameter (average, 321 microns). They gave off collateral branches to the cerebral peduncle, posterior perforated substance, oculomotor nerve, and mammillary bodies. Intracerebral segments had proximal and distal portions. The mean diameter of the former was 254 microns, and of the latter, 227 microns. The perforating arteries were divided into short interpeduncular and long mesencephalic and diencephalic vessels. Anastomoses among them were noticed in four-fifths of the cases. Despite this fact, the perforating arteries must be preserved during operations on aneurysms in the interpeduncular fossa.

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)

Anastomoses in the territory of the posterior cerebral arteries.

Anastomoses in the region of the posterior cerebral arteries were found in all of 40 brains examined. Anastomoses were channel-like, plexiform or combined. The former measured from 0.07 mm to 1.1 mm in diameter. They were most often found among the interpeduncular perforating vessels (71.2%), and between the branches of the posterior and anterior cerebral arteries (75.7%). The functional significance of the anastomoses is discussed.

Microvascular anatomy of the uncus and the parahippocampal gyrus.

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

Microsurgical anatomy of the perforating branches of the vertebral artery.

BACKGROUND There is limited data in the literature related to the microanatomic features of the perforating branches of the vertebral artery. METHODS The 44 vertebral arteries and their branches were injected with india ink or a radiopaque substance and examined under the stereoscopic microscope. RESULTS The perforating arteries were noted to range in number from 1 to 11 (mean, 6.5) and in diameter between 100 microm and 520 microm (average, 243 microm). They arose from the vertebral artery (VA) (54.54%), 8 from the right, the left or both VAs. The anterior spinal artery (ASA), which was singular (81.82%), duplicated (13.64%), or plexiform (4.55%), always gave rise to the perforators. The vascular roots of the ASA were the source of the perforators in 95.45% of the brains. The latter vessels arose from the anterolateral arteries in 50% of the cases. The anastomoses involving the perforators, which were present in 40.91% of the brains, varied in diameter between 100 microm and 350 microm (mean, 169 microm). The perforating vessels gave rise to the side branches in 95.45% of the brains that varied in diameter from 100 microm to 300 microm (average, 161 microm). The perforators usually entered the foramen cecum and the anterior median sulcus, and then continued close and parallel to the raphe of the medulla. The perforators can be compressed by a VA aneurysm, which was found in one among the 71 examined patients with cerebral aneurysms. CONCLUSIONS The obtained data give additional information about the vascular anatomy of the pontomedullary region.