Medullary Arteries Research Articles

Exogenous long-term treatment with 17?-oestradiol alters the innervation pattern in pig ovary

The aim of the present study was to determine the effect of long-term 17β-oestradiol (E2) exposure, a simulation of pathological states that occur with oestrogen overproduction, on the innervation patterns of ovaries in adult gilts. The intraovarian distribution and density of nerve fibres immunoreactive (IR) to protein gene product (PGP) 9.5 and containing dopamine-β-hydroxylase (DBH), neuropeptide Y (NPY), somatostatin (SOM) and galanin (GAL) were determined. From Day 4 of the first oestrous cycle to Day 20 of the second cycle studied, experimental gilts were injected with E2 (1000μg every 12h) whereas control gilts were injected with corn oil. After E2 administration, there was an increase in the number of PGP9.5-, DBH-, NPY- and GAL-IR fibres. Numerous PGP9.5-IR terminals were observed within the ground plexus around secondary follicles and small or medium tertiary follicles. Long-term E2 treatment increased the density of DBH- and NPY-IR fibres in the cortical part of the ground plexus, DBH- and GAL-IR fibres in the medullary part of the ground plexus, DBH-IR fibres near small and medium tertiary follicles and NPY-IR fibres around medullary arteries. The data indicate that long-term exposure of gilts to E2 increases the total number of intraovarian fibres, including sympathetic fibres. These results suggest that elevated E2 levels that occur during pathological states may affect the innervation patterns of ovaries and their function(s).

Atypical MRI Findings in a Spinal Dural Arteriovenous Fistula - Histology as Clue to the Diagnosis (P05.258)

Objective: Atypical presentations of spinal dural arteriovenous fistulas (SDAVF) represent a rare condition. Background In differential diagnostic reflections one should keep in mind atypical SDAVF as a significant cause of myelopathy. Design/Methods: We present an elucidating case of atypical diagnostic features in SDAVF. Results: A 60-year-old man developes a fluctuating spinal syndrome over a 3.5-year period. He presents with undulating spastic paraparesis, paresthesias in both legs, disturbances of micturition and defecation, sexual dysfunction and gait difficulties. Spinal MRI demonstrates a slightly contrast enhancing intramedullary lesion with an extension from D6 through D10. Due to the fluctuating clinical course, a SDAVF is considered, but the MRI shows no dilated veins or conus involvement. Cerebrospinal fluid findings are normal. With a differential diagnosis of either myelitis or spinal astrocytoma, treatment with corticosteroids and plasmapheresis is started without any effect. A spinal biopsy reveals no evidence of a tumor, but abnormal fibrotic blood vessels are seen. Therefore a spinal angiography is performed, which shows a SDAVF starting from the segmental thoracic medullary artery at D6 level and slowly draining into a not dilated vein, ranging over 5 vertebrae with no efflux out of the spinal canal. Since embolization seems too dangerous because of the connection between the involved segmental medullary artery and a posterior spinal artery, the fistula is disconnected surgically. During the operation, an atypical course of the vessels on the rather left side of the spinal cord is seen, explaining the atypical MR-findings. Postoperative MRI shows regression of medullary hyperintensity. Conclusions: In this case, the atypical findings in MRI without dilated veins or conus involvement lead to the misdiagnosis of a tumor. Only after the results of a spinal biopsy demonstrating pathological blood vessels spinal angiography is performed. With clinical symptoms of a SDAVF, a spinal angiography is justified even in MRI-negative presentations. Disclosure: Dr. Becker has nothing to disclose. Dr. Kraemer has nothing to disclose. Dr. Stracke has received personal compensation for activities with EV 3 as a consultant. Dr. Keyvani has nothing to disclose. Dr. Berlit has nothing to disclose.

Aneurysms of the medullary segments of the posterior-inferior cerebellar artery: considerations on treatment strategy and clinical outcome

Proximal aneurysms of the medullary postero-inferior cerebellar artery (PICA) tract are peculiar due to critical anatomical location, small size and tortuosity of the parent vessel, close origin to brainstem perforators, and fragility of the sac wall. Moreover, most patients present after bleeding, increasing the challenges. Aim of this study is to evaluate the treatment modality and outcome of these patients during the last decade at the University Clinic of Torino. Databases of the Neurosurgical and Neuroradiological Department of the University of Torino were analyzed to retrieve patients treated for aneurysms of the medullary PICA tract. Charts and neuroradiological documentation were revised to complete the database. Of 621 patients treated for an intracranial aneurysm, 23 had PICA aneurysm, 18 located at the medullary tract. Only two were unruptured and 16 were ruptured aneurysms. Sixteen underwent endovascular treatment and two underwent surgery. In six cases the aneurysm was cured by parent vessel occlusion. At 6 months follow-up, the Glasgow outcome scale was high (5 and 4) in 16 patients; two patients had died in the acute phase, for reasons unrelated to the procedure. If not adequately compensated, parent vessel occlusion associates with high risks of ischemia and related brain swelling. In the present series sufficient collateral flow contributed to a good tolerance toward occlusion in all cases. Despite the small size of the present series, most treated cases presented a good outcome. Nevertheless, distal revascularization of the occluded artery would be indicated where collateral flow is insufficient.

Aneurysm of the lateral spinal artery: A case report

The lateral spinal artery (LSA) constitutes one of the longitudial pathways that connect the extradural and intradural vascular upply. The LSA arises from the intradural vertebral artery (VA) at he C1 level, courses caudally, and descends laterally, parallel to the pinal component of the 11th nerve between the dentate ligament nd the posterior spinal nerve roots [1]. The ascending rami of the SA establish small connections with the posterior inferior cerebelar artery (PICA), whereas the descending rami feed the posterior adicular branches (particularly C-2) (Fig. 1) [1,2]. Posteriorly, there s a connection to the contralateral system via rich pial anastomois. The posterior medullary superficial arteries are branches of the osterior spinal artery or the LSA in the lower medulla oblongata, hereas these vessels arise from the PICA in the upper medulla blongata [3]. The LSA anastomoses with the posterior spinal artery t the C-4 or C-5 level were at a site dorsal to the posterior root of he spinal nerves [1,2]. There have been four reported cases of LSA aneurysm; all of hich presented with subarachnoid hemorrhage (SAH) (Table 1) 4–6]. The present report describes a case of a patient with an LSA neurysm associated with bilateral VA occlusion. Among the five ases, three were required sacrifice of the parent artery [4]. We iscuss the mechanisms underlying the formation of this aneurysm nd review optimal treatments.

Abstract No. 310: Potential pitfalls of bronchial artery embolization

Review a multitude of potential complications specific to the bronchial artery embolization procedure. Bronchial artery embolization is an important therapeutic method used to control acute and chronic hemoptysis. Bronchial artery embolization has been proven to be a safe and effective nonsurgical treatment for patients with hemoptysis. This pictorial review will emphasize complications and potential complications associated with bronchial artery embolization. Technical complications related to the procedure including: bronchial artery aneurysm, spasm, dissection, pseudoaneyrusm, and rupture will be depicted. Digitial subtraction images will depict bronchial-artery to pulmonary artery shunts and subsequent pulmonary infarction via computed tomography images. Digital subtraction images will also depict a bronchial artery to pulmonary vein shunt. One of the most disastrous complication of bronchial artery embolization, non-target embolization of the anterior medullary artery, will also be addressed. The review will be highlighted by a case that occured at our institution that resulted in posterior circulation infarction and death as a consequence of the procedure likley due to nonvisable bronchial artery to vertebral artery collaterals. Anomalous bronchial arteries will also be depicted as potential pitfall in clinically unsuccessful bronchial artery embolization. Images will demonstrate the more common origin of the anomalous bronchial arteries: subclavian artery, aorta, internal mammary artery, thyrocervical trunk, and inferior phrenic artery. 1) Identify potential pitfalls of the bronchial artery embolization procedure. 2) Identify potential technical procedural complications. 3) Recognize potential visible sources of non-target embolization. 4) Describe potential nonvisible sources of non-target embolization. 5) Identify possible sources of anomalous bronchial arteries as a potential cause of clinically unsuccessful bronchial artery embolization.

A rare case of paraplegia complicating a lumbar epidural infiltration

ObjectiveWe report the case of a patient who developed paraplegia following a low lumbar epidural steroid injection. Alternative approaches to (or alternative means of) performing transforaminal injections should be considered, in order to avoid devastating neurological complications. Case reportA 54-year-old man (who had undergone surgery 14years earlier to cure an L5-S1 slipped disc with right S1 radiculopathy) presented with low back pain (which had begun 6weeks previously) and left S1 radiculopathy. During a second infiltration of prednisolone acetate, the patient reported feeling a heat sensation in his legs and concomitantly developed facial flushing. Immediately after the injection, the patient developed complete, flaccid T7 ASIA A motor and sensory paraplegia. Three days later, T2 magnetic resonance imaging (MRI) of the spine revealed a spontaneous hypersignal in the conus medullaris and from T6 to T9, suggesting medullary ischemia. Recovery has been slow; after 4months of treatment in a physical and rehabilitation medicine department, urinary and sensory disorders are still present (T7 ASIA D paraplegia). The patient can walk 200m unaided. Three months later, the MRI data had not changed. DiscussionThis is a rare case report of paraplegia following low lumbar epidural infiltration via an interlaminar route. The mechanism is not clear. Most of authors suggest that the pathophysiological basis of this type of complication is ischemia caused by accidental interruption of the medullary blood supply. Direct damage to a medullary artery, arterial spasm or corticosteroid-induced occlusion due to undetected intra-arterial injection could result in medullary infarction. This serious incident should prompt us to consider how to avoid further problems in the future. It also raises the issue of providing patients with information on the risks inherent in this type of procedure. ConclusionDespite the rarity of this complication, patients should be made aware of its potential occurrence. In the case reported here, the functional prognosis is uncertain.

Infiltrations épidurales et foraminales lombaires : mise au point

A fluoroscopy-guided lumbar spine injection procedure may be complicated by immediate paralysis. Twelve cases (five recent and seven published) that occurred between 2002 and 2008 were reviewed (history of lumbar surgery, route of injection, image-guidance, injection of contrast, type of steroid, level of paraplegia, MR imaging features). MRI showed cord ischemia from arterial origin. The high number of patients with prior lumbar spine surgery suggests that the presence of scar tissue could increase the risk of paraplegia. A transforaminal approach was used in all patients without history of lumbar surgery while transforaminal, interlaminar and juxta-zygapophyseal approaches were used in patients with prior lumbar surgery. The high number of cases in France could be explained by the exclusive use of prednisolone acetate which has a higher rate of macro-aggregate formation that could lead to embolization in medullary arteries.

Clinical and Radiologic Correlations of Small and Large Centrum Ovale Infarcts

Acute centrum ovale (CO) infarction confined to the territory of perforating long medullary arteries is rarely reported. This study was designed to investigate the full spectrum of clinical findings, topography, and pathogenesis of patients with acute CO infarct. A total of 64 patients with CO infarct were recorded. Risk factors such as age, hypertension, diabetes mellitus, hypercholesterolemia, smoking, and cardiopathy were recorded. The average age of the patients was 64.2 years. There were 46 patients (71.8%) in large-infarct group and 18 patients (28.1%) in small-infarct group. The most frequent risk factor was hypertension (89.1%). Other risk factors included smoking (39%), diabetes mellitus (29.7%), hyperlipidemia (28.1%), transient ischemic attack (15%), carotid stenosis (9%), atrial fibrillation (21%), other potential cardiac source of embolism (39%), and myocardial infarct (4%). The main clinical feature was faciobrachiocrural paralysis associated dysarthria (51.6%). Other clinical characteristics were facial, upper and lower extremity paralysis with sensorial deficits and/or dysarthria (26.6%), hemiparesis including face (12.5%), and either facial and upper or upper and lower extremity paralysis with hemisensorial deficit (9.4%). The baseline Barthel index was found to be less than 50 in 22 patients (34.4%) and greater than 50 in 42 patients (65.6%) for the entire group whereas 72% of patients were independent at discharge. In this article, risk factors, clinical spectrum, and features of CO infarcts were correlated in a large patient group. The majority of CO infarcts were large and had a poorer outcome compared to previous reports.

Retrograde Filling of a Thoracic Spinal Artery During Transforaminal Injection

Transforaminal injection of steroids has been associated with infrequent but devastating neurological complications and death. Direct injection of particulate steroids into the vertebral artery or medullary arteries is the leading theory in the majority of these complications. Practice guidelines have been published to minimize the likelihood of directly encountering vulnerable arterial structures. However, retrograde flow into a vertebral or medullary artery has not been considered in the literature. This case demonstrates retrograde flow into a common arterial trunk with subsequent antegrade flow of intravenous contrast into a thoracic spinal artery during thoracic transforaminal injection. Antegrade flow of particulate steroids through direct cannulation of a vertebral or medullary artery has been advocated as one explanation for complications involving brain or spinal cord infarction. The possibility of retrograde flow into a common arterial trunk with subsequent antegrade flow into vulnerable arteries should also be considered as a possible mechanism by which embolic spinal cord or brain injury may occur. Retrograde flow into medullary or vertebral arteries without direct cannulation can occur, and provides an alternative mechanism of potential injury to the spinal cord or brain during transforaminal injections.

Medullary serotonin neurons and central CO2 chemoreception.

Serotonergic (5-HT) neurons are putative central respiratory chemoreceptors, aiding in the brain's ability to detect arterial changes in PCO2 and implement appropriate ventilatory responses to maintain blood homeostasis. These neurons are in close proximity to large medullary arteries and are intrinsically chemosensitive in vitro, characteristics expected for chemoreceptors. 5-HT neurons of the medullary raphé are stimulated by hypercapnia in vivo, and their disruption results in a blunted hypercapnic ventilatory response. More recently, data collected from transgenic and knockout mice have provided further insight into the role of 5-HT in chemosensitivity. This review summarizes current evidence in support of the hypothesis that 5-HT neurons are central chemoreceptors, and addresses arguments made against this role. We also briefly explore the relationship between the medullary raphé and another chemoreceptive site, the retrotrapezoid nucleus, and discuss how they may interact during hypercapnia to produce a robust ventilatory response.

Traumatic vertebral artery dissection and Wallenberg syndrome after a motorcycle collision

Wallenberg syndrome is also called lateral medullary syndrome or posterior inferior cerebellar artery syndrome. The clinical presentations include ipsilateral Horner syndrome, ipsilateral cerebellar signs, and the hypalgesia of ipsilateral face and contralateral body. A considerable number of cases of Wallenberg syndrome were reported to be associated with vertebral artery dissection (VAD). Nowadays, the preferred imaging tool comes down to magnetic resonance imaging because it provides high spatial resolution, which is especially important for assessment of lesions in posterior fossa. The optimal treatment of VAD remains controversial. Most patients receive conservative treatments with anticoagulants or antiplatelet drugs. Overall, most cases have good prognosis. However, the rarity and various presentations of VAD may challenge emergency physicians in making correct diagnosis in the emergency department. Hence, maintaining a high index of suspicion is needed for an early diagnosis, especially in young people without risk factors attributing to cerebrovascular accident.

Spinal intradural arteriovenous fistula with unusual presentation: case report and literature review

The authors present their experience with a Cervical Spinal intradural arteriovenous fistula (AVF) with unusual clinical presentation in a pediatric patient and review of the international literature on this condition. A 5-year-old girl was found by her parents in bed screaming and talking inappropriately. Later on, she calmed down and complained of occipital, back and neck pain. She was admitted to the CHEO-ICU for work up and observation. The admission head CT scan showed evidence of SAH. Brain MRI showed blood in the third and fourth ventricles. MRA showed a C2 vascular lesion consistent with spinal cord AVF. Conventional angiogram was done which confirmed the AVF fed by a posterior medullary artery originating from the left vertebral artery. An attempt to embolize the AVF with glue was made but proved to be unsuccessful. On December 4, 2002, direct surgery on the AVF was performed, through a midline posterior approach (C2-C3 laminectomies) and microsurgical technique a complete excision of the intradural extramedullary AVF was achieved. The postoperative course was uneventful and the patient remained neurologically intact. Post-operative angiography confirmed complete excision of the AVF. The rarity of a pediatric spinal AVF presenting with spontaneous Intracranial SAH, makes this case very peculiar. This is the first reported pediatric case of cervical cord AVF with this clinical presentation found in the literature.

Conus perimedullary arteriovenous fistula in a child: unusual angio-architectural features and pathophysiology

The perimedullary arteriovenous fistulas are located on the pial surface and are usually supplied by spinal medullary arteries, that is, either by the anterior or posterior spinal arteries, with no intervening nidus between the feeder arteries and the venous drainage. The clinical findings are, more commonly, caused by progressive radiculomedullary ischemic processes secondary to steal vascular mechanism. As the vascular supply to the spinal cord and to the arteriovenous fistulas (AVF) is not shared with one another, the vascular steal phenomenon cannot be implicated in this case's physiopathology. Most probably, the mass effect caused by the giant venous dilatation was the pathophysiological mechanism involved in this lesion. The authors describe the case of a 6-year-old girl with an intradural ventral arteriovenous fistula, with a giant venous dilatation, fed directly by L2 and L3 radiculomedullary arteries at the conus medullaris. There was no arterial supply to the fistula from the anterior or posterior spinal arteries. Selective spinal angiography showed an arteriovenous fistula supplied directly by two radiculomedullary arteries, with a large draining vein caudally. Interposing the arterial and venous vessels was a giant venous aneurysmal dilatation located ventral to the conus medullaris and extending from L3 to T6. The patient was successfully treated by a surgical approach through a laminotomy from L3 to T11. The type IV-C spinal arteriovenous malformations or perimedullary AVFs are rare lesions predominately described at the conus medullaris with various types of angio-architecture and controversial treatment.

Cervical Spine: Case Presentation, Complications, and Their Prevention

Objective. A number of case presentations of catastrophic outcomes after cervical epidural injections have occurred after both interlaminar and transforaminal injection techniques. Practitioners in pain medicine need guidance to avoid these complications Design. A systematic search of the MEDLINE database, electronically available pain journals, and recent pain and spine meeting abstracts was searched for articles relevant to cervical spine interventional procedure complications. Results. A representative case of cervical radicular pain is presented to illustrate key differences of radicular pain presenting in the cervical area from those in the lumbar area Although cervical interlaminar epidural complications more likely involve direct neurological trauma to the spinal cord or spinal nerve, the mechanism for injury after transforaminal epidural corticosteroid injections is less clear. Many investigators hypothesize that particulate steroids may be the primary cause, in that these particles may occlude segmental medullary feeding arteries that reinforce the longitudinal anterior spinal artery supply to the spinal cord. Anatomical nomenclature of spinal cord blood supply and variants of normal are presented. Conclusions. Specific examples of potential injury avoidance strategies are discussed, including: 1) the use of nonparticulate steroid preparations; 2) needle bevel/size and other technical considerations; 3) preprocedural planning and sedation considerations; 4) test dosing with local anesthetics; and 5) imaging considerations, including the use of digital subtraction to better define angiographic patterns. Recommendations for the conduct of cervical epidural injection procedures are discussed.

ProRenin/Renin Receptor is Expressed in the Collecting Duct of Normal Rat Kidney

Tubular renin is present in principal cells of collecting ducts (CD) of human, mouse and rat kidneys. The recent cloned(pro)renin renin receptor (PRR), is localized in brain, lung, heart and kidney, and binds renin or (pro)renin, thus leading to increased renin catalytic activity, or allowing (pro)renin to become fully active. Within the kidney, PRR is expressed by glomerular mesangial cells, podocytes, and renal arteries. The presence of PRR in CD might be important for potential generation of tissue angiotensin peptides in the terminal nephron segment. We investigated the immunolocalization of PRR in normal rat kidneys. Immunoperoxidase technique was performed by using a goat anti‐PRR antibody on 4% paraformaldehyde fixed normal rat perfused kidney sections. As described, positive immunostaining of PRR was visualized in mesangial cells, podocytes, and smooth muscle cells of cortical and medullary renal arteries. Interestingly, positive PRR immunoreactivity was also observed in the apical aspects of the cortical and medullary CD cells. Our results demonstrate the presence of PRR immunoexpression in cortical and medullary CD cells. Co‐expression of renin and PRR in the distal nephron suggests that renin or (pro)renin secreted by principal cells of CD into the tubular lumen anchors to the PRR allowing increased efficiency of Ang I formation contributing to angiotensin peptide generation in the CD.

Virchow-Robin Spaces at MR Imaging

Virchow-Robin (VR) spaces surround the walls of vessels as they course from the subarachnoid space through the brain parenchyma. Small VR spaces appear in all age groups. With advancing age, VR spaces are found with increasing frequency and larger apparent sizes. At visual analysis, the signal intensity of VR spaces is identical to that of cerebrospinal fluid with all magnetic resonance imaging sequences. Dilated VR spaces typically occur in three characteristic locations: Type I VR spaces appear along the lenticulostriate arteries entering the basal ganglia through the anterior perforated substance. Type II VR spaces are found along the paths of the perforating medullary arteries as they enter the cortical gray matter over the high convexities and extend into the white matter. Type III VR spaces appear in the midbrain. Occasionally, VR spaces have an atypical appearance. They may become very large, predominantly involve one hemisphere, assume bizarre configurations, and even cause mass effect. Knowledge of the signal intensity characteristics and locations of VR spaces helps differentiate them from various pathologic conditions, including lacunar infarctions, cystic periventricular leukomalacia, multiple sclerosis, cryptococcosis, mucopolysaccharidoses, cystic neoplasms, neurocysticercosis, arachnoid cysts, and neuroepithelial cysts.

Thoracic radicular vessels by simultaneous intra‐arterial and intravenous injection of araldite

Spinal dural arteriovenous fistulas (SDAVF) consist of a shunt between a radicular artery and a radicular vein, resulting in a progressive paraparesis. They are most prevalent in middle-aged men (male to female ratio 5 to 1). It is unknown why the shunt develops. It is possible that there are anatomical differences between men and women, which may account for the sex difference in prevalence. We performed a study with simultaneous arterial and venous araldite injection in 5 male and 5 female human cadavers using different colors. The mean age of the human cadavers was 78 years (range 70-91). The human cadavers were not known to have suffered from spinal disease. We did not find significant differences in thoracic vasculature between men and women. Two different types of radicular arteries could be identified: The first was the arterial feeder of the root ganglion or the dura mater, which is also called the distal radicular artery. The second was the tributary of the anterior spinal artery, which is also called the medullary artery. We found three arteriovenous anastomoses between the radicular artery and the corresponding vein, and three between the radicular artery and venous plexus. We found a total of six thoracic arteriovenous shunts in four cadavers but their role in the pathogenesis of SDAVF remains uncertain. No vascular anatomic differences between men and women were found.

Ischemic complications associated with resection of opercular glioma

Opercular glioma inferolateral to the hand/digit sensorimotor area can be resected safely using a neuronavigation system and functional brain mapping techniques. However, the surgery can still sometimes cause postoperative ischemic complications, the character of which remains unclear. The authors of this study investigated the occurrence of infarction associated with resection of opercular glioma and the arterial supply to this region. The study involved 11 consecutive patients with gliomas located in the opercular region around the orofacial primary motor and somatosensory cortices but not involving either the hand/digit area or the insula, who had been treated in their department after 1997. Both pre- and postoperative diffusion-weighted magnetic resonance (MR) imaging was performed in the nine consecutive patients after 1998 to detect ischemic complications. All patients underwent open surgery for maximum tumor resection. Postoperative MR imaging identified infarction beneath the resection cavity in all patients. Permanent motor deficits associated with infarction involving the descending motor pathway developed in two patients. Cadaveric angiography showed that the distributing arteries to the corona radiata were the long insular arteries and/or medullary arteries from the opercular and cortical segments of the middle cerebral artery. Subcortical resection around the upper limiting sulcus of the posterior region of the insula and wide resection in the anteroposterior and cephalocaudal directions of the opercular region were considered to be risk factors of the critical infarction. Surgeons should be aware that resection of opercular glioma can disrupt the blood supply of the corona radiata, and carries the risk of permanent motor deficits.

Pathogenesis of deep white matter medullary infarcts: a diffusion weighted magnetic resonance imaging study

Background and Purpose: The pathogenesis of deep white matter medullary (WMM) artery infarcts remains controversial. To address this question, we analysed the stroke patterns of WMM infarcts using diffusion weighted...

Anatomy of the cervical intervertebral foramina: vulnerable arteries and ischemic neurologic injuries after transforaminal epidural injections

Cervical transforaminal epidural steroid injections are performed for the treatment of radicular pain. Multiple recent case reports have raised safety concerns regarding neurologic deficits such as anterior spinal artery syndrome and cerebellar injury after these injections. To investigate the potential causes of these injuries, an anatomic study was conducted. In this study of 10 embalmed cadavers, the cervical intervertebral foramina were examined to determine if the ascending or deep cervical arteries supplied radicular or segmental medullary arteries potentially susceptible to cannulation or needle trauma during transforaminal injection. In two specimens, dissection was carried down to the spinal cord, demonstrating the anterior spinal, radicular, and segmental medullary arteries. Of 95 intervertebral foramina dissected, 21 had an arterial vessel proximal to the posterior aspect of the foraminal opening. Seven of these 21 were spinal branches that entered the foramen posteriorly, potentially forming radicular or segmental medullary vessels to the spinal cord. One additional ascending cervical artery formed a segmental medullary artery that joined the anterior spinal artery. This would only be injured by anterior needle misplacement. Of the seven foraminal branches, three were included in the deep dissections. Two contributed to segmental medullary arteries and one to a radicular artery. Variable anastomoses between the vertebral and cervical arteries were found. Therefore, it is possible to introduce steroid particles into the vertebral circulation via the cervical arteries. Critical arteries are located in the posterior aspect of the intervertebral foramen and may be vulnerable to injection or injury during transforaminal epidural steroid injection.