Ventral Spinal Artery Research Articles

Spinal Cord Infarct in a Calf after Aortic Catheter Implantation

Spinal Cord Infarct in a Calf after Aortic Catheter Implantation

INFLUENCE OF FIELD STRENGTH ON INTRACRANIAL VESSEL CONSPICUITY IN CANINE MAGNETIC RESONANCE ANGIOGRAPHY

Eight neurologically normal beagles were imaged using three-dimensional (3D) time-of-flight magnetic resonance angiography (MRA) in a 3T magnetic resonance scanner. Four of the eight dogs were also imaged using a 1T unit for comparison. Ten intracranial arteries were consistently identified at 3T: external and internal carotid, basilar, vertebral, rostral cerebral, middle cerebral, caudal cerebral, rostral communicating, caudal communicating, and ventral spinal arteries. Only four were reliably identified at 1T with diagnostic spatial and contrast resolution. At 3 T, vessels as small as 1 mm were reliably detected. Vessel conspicuity was superior using the 3T system. An anatomic atlas of the canine circulus arteriosus cerebri using a 3T scan was constructed. The effect of MRA parameters on vascular spatial resolution a nd conspicuity are reviewed.

Safety and Pharmacokinetics of Sirolimus-eluting Stents in the Canine Cerebral Vasculature: 180 Day Assessment

We evaluated local and systemic pharmacokinetics and pharmacodynamics of sirolimus-eluting stents (SES) in canine cerebral vessels. SES (1.5 x 8 mm, 79 microg/479 microg sirolimus) and control stents (1.5 x 8 mm stainless steel with or without polymer) were implanted in canine basilar and ventral spinal arteries. Animals were sacrificed for local pharmacokinetic (36 animals at 1, 3, 8, 30, 90, 180 days) and pharmacodynamic (60 animals at 3, 30, 90, 180 days) assessment. Postrecovery adverse clinical events were not serious, requiring no unscheduled treatment. Histologically, brain and spinal cord sections revealed scattered microinfarcts and minimal gliosis consistent with postprocedure changes in all four stent-treatment groups. All stented vessels at all time points demonstrated good luminal patency with low injury and inflammation scores and no thrombosis of either stented or branch arteries. Endothelialization was complete in all stent groups by 30 days. Intimal smooth muscle cell scores were reduced in both SES groups at 30, 90, and 180 days. Systemic sirolimus levels peaked between 1 and 7 hours postimplant (maximum concentration, 1.2 +/- 1.47, 79 microg; 4.5 +/- 1.23 ng/ml, 479 microg), then declined rapidly to 1 ng/ml or less by 96 hours. Peak local tissue sirolimus levels were 41.5 ng/mg (79 microg) and 65 ng/mg (479 microg). SES in canine cerebral vessels were associated with good luminal patency to 180 days, with complete endothelialization and no evidence of acute thrombosis. This model has shown that SES deployed within the brain do not cause neurotoxicity during a 180-day time course, even when exaggerated doses are used. The findings support the contention that SES are safe to use and maintain patency in cerebral vessels.

Aging Changes of the Angioarchitecture and Arterial Morphology of the Spinal Cord in Rats

Background: It is well known that vascular myelopathy increases with age, however, there are no systematic reports on the quantitative capillary density in the spinal cord and no reports concerning the age-related changes of vascularity and capillary density of the spinal cord. Objective: Age-related changes of vascularity and capillary density of the spinal cord and the morphology of the ventral spinal artery were observed and measured so as to provide reference to study the microcirculation of the spinal cord. Methods: Three different age groups of Wistar rats (1–2, 6–7 and >22 months old) were studied by ink-gelatin injection, corrosion casts, biological stereological technique, image analysis and transmission electron microscope. Results: The number of central arteries per centimeter of the spinal cord decreased significantly with age; the ventral spinal artery and central arteries often became tortuous in the >22 month group. Capillary density in the anterior horn was significantly higher than that in the posterior horn. Capillary density in the gray matter decreased significantly with age. These aging changes of the ventral spinal artery in the rat included that the folds of internal elastic membrane were reduced, the internal elastic membrane thinned and disrupted, the endothelial cells degenerated and broke away from the wall, and smooth muscle cells in the tunica media degenerated and protruded to the lumen. The relative content of the elastic fibers decreased significantly with age, while the relative content of the collagenic fibers and the ratio of the C/E increased significantly with age. Conclusions: The difference between capillary density in gray and white matter in the spinal cord has shown that the need of metabolization is adapted to the function of the neurons, and the anterior horn is more sensitive than the posterior horn to anoxia and is easily damaged during ischemia in the spinal cord. Aging changes of capillary density and arterial morphology of the spinal cord may be important contributory factors in vascular myelopathy.

Vascular anatomy of the foramen of Vicq d'Azyr: a microsurgical perspective.

The foramen of Vicq d'Azyr, is a triangular-shaped area located rostral to the ventral median fissure of the medulla oblongata. Its importance relies on the fact that it is penetrated by small vessels from the vertebrobasilar axis that nourish vital pontine nuclei and tracts. We described the microvascular anatomy of the perforating vessels of the foramen of Vicq d'Azyr (FVA). The vertebrobasilar junction arteries and the perforating arteries of the foramen of Vicq d'Azyr were examined using a surgical microscope in 21 formalin-fixed brain stems. The total number of perforating branches found was 286 in the 21 brains, an average of 13.6 perforators per brain, range 7 to 22. They arose as distal branches of 73 main trunks, average of 3.5 per brain, range 2 to 5, originating mainly from the basilar artery in 41 (56.1 %); the left ventral spinal artery in 12 (16.4 %), and the left vertebral artery in 8 (11 %). The average outer diameters of the left and right vertebral arteries were 3.2 mm and 2.9 mm, 4.1 mm for the basilar artery, and 0.6 mm for the right and left ventral spinal arteries. The branching pattern and interesting anatomic variations of the main vessels of the vertebro-basilar junction are also described. The vascular anatomy of the infratentorial compartment is highly variable. These variations should be kept in mind to avoid pitfalls during vascular or tumor surgery. In contrast, the entering locations of perforating vessels remain constant, referring to these zones as key areas when planning or doing surgical procedures in this region.

Myelinated fibers of spinal cord blood vessels--sensory innervation?

Innervation of the ventral spinal artery from the lumbosacral region of dogs was studied using light, scanning, and transmission microscopy. Microscopy revealed myelinated fibers, a new observation, in addition to unmyelinated fibers expected on the basis of previous studies of autonomic innervation of this blood vessel. The myelinated axons may be sensory fibers.

A Canine Model of Acute Hindbrain Ischemia and Reperfusion

Animal models of brain stem ischemia are needed for pathophysiological study and evaluation of treatment; few such models are available currently. A new canine model of hindbrain ischemia and reperfusion is introduced in this article. Through an anterior cervical approach, the basilar artery was surgically exposed in 18 dogs. The posterior communicating and superior cerebellar arteries were embolized with cyanoacrylate glue to isolate the posterior circulation from the anterior circulation. Reversible hindbrain ischemia was induced in 14 dogs by the temporary clipping of the vertebral and ventral spinal arteries for various periods (10-30 min), then the clips were removed and reperfusion was achieved for 5 hours. In all 14 dogs, the hindbrain ischemia was confirmed by the decreased perfusion pressure in the basilar artery (< 10 mm Hg), the diminished regional cerebral blood flow as measured with a laser Doppler flowmeter at the medulla oblongata (< 10 ml/100 g/min), the flattened brain stem auditory evoked potentials, and the increased leakage of Evans blue dye from tissue. These parameters did not change in the four control dogs. The changes in brain stem auditory evoked potentials were closely related to the length of ischemic interval; after 10 minutes of ischemia, reperfusion fully reversed the changes in brain stem auditory evoked potentials, but 20-minute and 30-minute ischemic intervals partially or totally depleted the brain stem auditory evoked potentials. Delayed postischemic hypoperfusion occurred in all five dogs that underwent the 30-minute ischemic interval. The early physiological changes in this model allowed us to estimate the severity of brain stem ischemia and the resulting damage.(ABSTRACT TRUNCATED AT 250 WORDS)

COMPUTED TOMOGRAPHIC ANATOMY OF THE CANINE LUMBOSACRAL SPINE

The lumbosacral spine (L5–S3) was examined by high resolution computed tomography (CT) in five canine cadaver specimens and one anesthetized dog using 5mm thick transverse slices at 5mm intervals. In each dog, anatomic features observed on CT images were confirmed by comparison with corresponding 5 mm thick anatomic transverse sections and section radiographs. CT anatomic features visualized in all dogs included the vertebral bodies, pedicles, laminae, articular processes, spinous processes, transverse processes, mammillary processes, basivertebral venous canals, vertebral foramina, intervertebral foramina, sacral wings, median sacral crest, intermediate sacral crests, lateral sacral crests, articular process joints, sacroiliac joints, internal vertebral venous plexus, epidural fat, thecal sac, L5–S3 nerve roots, and spinal nerves. Spinal ganglia, yellow ligaments, and portions of the intervertebral discs were visible in some dogs. The spinal cord, intrathecal nerve roots, dorsal and ventral longitudinal ligaments, spinal arteries, and radicular vessels were not distinguishable. Accessory processes were identified on the caudal L5 pedicles in most dogs, an observation that differed from descriptions in standard anatomy texts. Previously undescribed osseous grooves, termed “lateral recesses,” were identified in the caudal L7 vertebral foramen of all dogs.

Radial glia give rise to perinodal processes

Nodes of Ranvier in the central nervous system in mammals are characterized by the presence of perinodal astrocytic processes. This study examines the association between processes of radial glia and the axolemma at nodes of Ranvier in the spinal cord of the mature axolotl, an animal in which radial glia represent a large portion of the total glial population. The radial glial cells have their cell bodies located close to the central canal. Those situated dorsal to the canal send long processes to the dorsal surface of the spinal cord. Along this trajectory these processes coalesce into large fascicles in the midline and form the dorsal median septum. Slender branches rise from the processes in these fascicles and extend into the adjacent white matter to terminate in close apposition to the axolemma at nodes of Ranvier. This arrangement provides an intracellular pathway extending from the perinodal region to the surface of the spinal cord. Radial glia ventral to the central canal give rise to processes that project to the glia limitans adjacent to the ventral spinal artery. These ventrally projecting processes appear to be more irregular in their branching pattern than their dorsal counterparts. Multiple slender processes are seen in close apposition to the nodal axolemma of myelinated axons in the ventral white commissure, again providing an intracellular pathway that runs from the perinodal region to the cord surface. In one instance a radial glial process was observed to occupy a pocket formed by the invagination of the nodal axolemma. The axonal cytoplasm adjacent to the invagination contained a variety of organelles, e.g. multivesicular bodies, vesicles and endoplasmic reticulum, suggesting that this relationship between the radial glial process and the axon is more than a passive interaction. These observations are consistent with the view that processes of radial glial cells may regulate the extracellular environment adjacent to the nodal axolemma, and/or play an active role in the maintenance of the nodal membrane. The existence of perinodally-directed processes of radial glial cells in the salamander indicates that this axo-glial specialization reflects an important functional interaction preserved across a large segment of the phylogenetic scale.

Intrinsic 5HT-immunoreactive neurons in the spinal cord of the fetal non-human primate

Serotonin (5HT) immunoreactive neurons were identified in the late-term fetal spinal cord of normal non-human primates. These neurons were distributed throughout the spinal cord, being concentrated in lamina X and the subjacent ventral median fissure, while their immunoreactive fibers and terminals innervated the zone surrounding the central canal and the ventral spinal artery. Even at this late fetal stage, the dorsal and ventral spinal gray matter was virtually devoid of any positive 5HT immunoreactivity, in contrast to that seen in the adult primate. These findings suggest that the intrinsic 5HT neurons of the primate during development may modulate CSF composition or provide cues for spinal cord differentiation rather than regulate sensorimotor functions as they do in the adult.

Temporary bilateral carotid artery occlusion as an aid to nasal surgery in the horse.

One of the major obstacles to successful intranasal surgery in the horse is haemorrhage, even minor interferences causing profuse bleeding. Conventional techniques for haemostasis are ineffective or inhibit the progress of the surgery. Temporary bilateral occlusion of the common carotid artery resulted in a substantial reduction in haemorrhage during intranasal surgery in five horses, with much improved visibility and facility of operation. The large contribution to the circle of Willis by the ventral spinal artery is believed to prevent cerebral ischaemia during this procedure. This paper describes the technique of temporary bilateral ligation of the common carotid artery and emphasises the importance of ancillary techniques such as packing of the nasal cavity and general postoperative management.

Immunocytochemical localization of ß-endorphin (lipotropin c-fragment) in the developing rat spinal cord and hypothalamus

Immunocytochemical studies have been performed on rat spinal cord and hypothalamus during development, using an antibody to ß-endorphin. Specific immunoreactivity was demonstrated in histological sections of spinal cord, in ventral and dorsal horn cells and nerve fibres, in the meningeal layer, the ependymal lining of the central canal, and in the endothelium of the ventral spinal artery and other blood vessels. ß-Endorphin immunoreactivity was also distributed widely in neurones, central and peripheral nerve fibres, and in non-neuronal cells in cultures of spinal cord tissue explanted from rat embryos 7–10 days before birth. Immunofluorescence disappeared abruptly after the 28th postnatal day in vivo, and in the fourth week of incubation of embryonic spinal cultures. In contrast, cultures of the ventral diencephalic (hypothalamic) region of embryonic brain at the same gestational age showed a characteristically different pattern ß-endorphin immunoreactivity which persisted for more than 7 weeks. The results provide evidence for the biosynthesis of a ß-endorphin-like peptide in rat spinal cord during development. The biosynthesis terminates at an early stage both in vivo and in vitro, suggesting that control of the biosynthesis is intrinsic to spinal cord tissue and possibly to the peptide-producing cells themselves.

Cholesterol masses in association with spinal cord infarction due to intervertebral disc emboli

The clinical and autopsy findings are presented from three dogs with spinal cord infarction. At autopsy firm gritty masses and cystic areas were present within the spinal cord. The masses contained numerous cholesterol clefts, collagen and reticulin fibres and were accompanied by a macrophage, giant cell and lymphocytic response. The cholesterol masses were present mainly in white matter. The ventral spinal artery or its branches as well as pial arteries contained fibrillary masses often covered by endothelial cells. The staining characteristics of these emboli suggested that they were fibro-cartilagenous and probably derived from the intervertebral discs. It is assumed that the cholesterol masses were formed from myelin breakdown products within infarcted areas.

Anatomical observations on the arterial supply to the lumbosacral spinal cord of the cat.

AbstractThe pattern of arterial supply to the cat's lumbosacral spinal cord was examined in a dozen latex‐injected specimens with a view to determining what precautions might be taken in the procedure of rhizotomy to minimize embarrassment of the cord's circulation. The single ventral spinal artery was found to receive on an average 4.1 significant radicular contributions, of which one or two arteries at the fourth or third lumbar levels on the left were invariably of especially large size. Equal numbers, about six to eight, of contributions to the two dorsolateral arterial trunks were present. Anastomotic channels greater than 50 m̈ in diameter were rather poorly developed between dorsolateral and ventral arterial channels, especially across the middorsum. The dorsal radicular artery in 82 of 97 roots examined was seen to pierce the ventral root in order to reach a position along the ventral aspect of the dorsal root. In most cases this penetration occurred central to the ganglion. The bearing of this feature on reported differences in behavioral effects from rhizotomy by intradural section and by ganglionectomy is discussed, as well as other aspects of the effect of rhizotomy on cord criculation.

The vertebral-basilar system of dog in relation to man and other mammals.

AbstractThe basilar artery of the dog was studied and its branches traced to their terminations. The nomenclature used is based on the origin, course and termination of the arteries. The basilar artery arose from a spinal arterial circle formed in the vertebral canal at the level of the atlanto‐occipital articulation by union of vertebral arteries and the ventral spinal artery. The arterial supply to the membranous labyrinth arose from the anterior inferior cerebellar artery. After entering the porus acusticus, one or more tiny labyrinthine arteries arose and the parent trunk then looped dorsally out of the meatus to supply the lower portions of the cerebellum. A branch of the basilar artery, unnamed in the dog, was associated closely with the trigeminal nerve; a separate arterial supply to the caudal colliculus arose from the medial branch of the superior cerebellar artery. It was concluded that branches of the basilar artery of the dog and man are similar since, with exception of the middle inferior cerebellar artery, all branches of the basilar artery in man may be found in dog.

Comparative angiographic and corrosion cast studies of the cervicocerebral arteries in the dog.

Roentgen anatomy of the cervicocerebral circulation in the dog has been studied through arteriograms and methyl methacrylate corrosion specimens. Discrepancies from the classic description of the canine cervicocerebral circulation were observed in the present study. These involved the mode of branching of the vertebral arteries and the formation of the ventral spinal artery. The role of these vessels in the formation of the basilar artery is also noted. A more descriptive terminology is suggested for the arteries of this region. Such anatomic variations may play a vital role in the arterial supply to the dog's spinal cord, brain stem and cerebral cortex. These experiments rule out the presence of a carotid rete between the external carotid and internal carotid circulation before the formation of the arterial circle of the brain. Emphasis is on the importance of the internal carotid artery in the formation of the arterial circle of the brain in the dog.

Anatomy of the arteries of the head in the domestic fowl

The anatomy of the cephalic arterial system in the fowl was studied in 24 specimens by means of latex‐injected preparations and by dissection. Branches of the external carotid artery supply the extracranial regions. The vertebral arteries unite with the occipitals and have no major communications with the encephalic system. Blood can reach the brain directly from the internal carotid artery and indirectly by way of the extensive cerebral‐extracranial anastomoses; especially prominent are those to the palatine and sphenomaxillary arteries from the maxillary and facial branches of the external carotid artery. A large external ophthalmic artery supplies the temporal rete and eye musculature, and an internal ophthalmic artery links the rete and the cerebral vessels. The circle of Willis is incomplete both anteriorly and posteriorly; the anterior cerebral arteries do not unite and the basilar artery is generally asymmetrical in origin. The basilar artery tapers caudally and is continued as the ventral spinal artery.

The relationship between size and vascularity in the spinal cord of developing Xenopus laevis

ABSTRACT The ability of the blood vessels of the spinal cord to increase in number during growth without differentiation of the nerve cells was tested on six sexually immature female Xenopus and eight thyroidectomized tadpoles with suitable control animals. The mean number of blood vessels in the region of spinal cord between the origins of the second and third spinal nerves is greater in metamorphosed Xenopus which are 50 mm. long than in those which are 25 mm. long, and greater in thyroidectomized tadpoles which are 100 mm. long than in normal tadpoles at the same stage of development which are 30 mm. long. The mean number of vessels, which enter the cord from the ventral spinal artery, per unit length of spinal cord between the second and third spinal nerves is inversely proportional to the length of the cord in the metamorphosed animals, but is constant in the two groups of tadpoles. It is concluded that the ability to form new branches of the ventral spinal artery is lost during metamorphosis; the development of blood vessels in the central nervous system is not associated solely with differentiation of the nerve cells; and the histogenetic cell deaths in the developing spinal cord are not precipitated by an inadequate vascular system. The hypothesis is proposed that the growth of new blood vessels is stimulated by a humoral agent produced by the nerve tissue.

THE ANATOMY OF THE ARTERIAL SUPPLY TO THE CRANIAL REGIONS OF THE SHEEP AND OX.

AbstractBy means of neoprene latex injected preparations, the anatomy of the arterial supply to the brain has been determined in the sheep and ox. In these two ruminant species, blood destined for the Circle of Willis and thence the brain must first pass through a well‐developed intra‐cranial carotid rete. The main source of blood supply to the carotid rete in the sheep is from the external carotid artery, via branches of the internal maxillary artery.In both the sheep and the ox, the internal carotid artery is poorly developed in the young animal and the portion proximal to the carotid rete is absent in the adult. The internal carotid artery, in animals of all ages, can be traced through the rete to emerge as the efferent vessel, which divides to form the Circle of Willis.In the ox, the main source of blood supply to the intra‐cranial carotid rete is the external carotid artery, via branches of the internal maxillary, but, in addition, the rete communicates directly with the vertebral arteries by way of the basi‐occipital arterial plexus.Unlike most other species, the basilar artery in both sheep and ox has only tenuous connections with the vertebrals. In both species, the basilar artery tapers caudally and is continued as the ventral spinal artery. The basilar can therefore be regarded as a caudally directed branch of the Circle of Willis in both these animals. A well‐developed occipito‐vertebral anastomosis is a marked feature of the cephalic circulation in both sheep and ox.

The effect of temporary reduction in cephalic blood flow on the EEG of sheep and calf

1. 1. The effect of reducing the cephalic blood supply upon the spontaneous electrical activity of the cerebral cortex has been studied in the sheep and calf. 2. 2. Partial cerebral ischaemia induced by occlusion of one carotid or both vertebrals had no effect upon the EEG in either sheep or calf. 3. 3. Bilateral occlusion of the carotid arteries in the sheep caused the EEG to display slow rhythmic activity. This manoeuvre had no effect in the calf because blood from the vertebral arteries passes directly to the rete mirabile through the basi-occipital plexus. 4. 4. In the sheep complete cerebral ischaemia results from occlusion of the external carotids, or simultaneous occlusion of the common carotid and vertebrals, or bilateral occlusion of the common carotid and occipital arteries. About 8 see after the onset of complete cerebral ischaemia systemic hypertension, respiratory distress and abolition of the EEG occur. Similar manoeuvres in the calf are ineffectual because blood can pass to the circle of Willis via the basioccipital plexus and prevent the onset of ischaemia. 5. 5. When all other arteries which contribute to the cephalic blood supply in the calf are occluded the ventral spinal artery can provide sufficient blood to maintain a modified form of electric activity in the cerebral cortex. 6. 6. Evidence has been obtained which suggests that the cerebral cortex of the very young calf has a much greater resistance to cerebral ischaemia and generalised asphyxia than the adult sheep.