Composition of encephalic arteries and origin of the basilar artery are different between vertebrates.

Intracranial arterial anatomy is lacking for most mammalian and non-mammalian model species, especially concerning the origin of the basilar artery (BA). Enhancing the knowledge of this anatomy can improve animal models and help understanding anatomical variations in humans. We have studied encephalic arteries in three different species of birds and eight different species of mammals using formalin-fixed brains injected with arterial red latex. Our results and literature analysis indicate that, for all vertebrates, the internal carotid artery (ICA) supplies the brain and divides into two branches: a cranial and a caudal branch. The difference between vertebrates lies in the caudal branch of the ICA. For non-mammalian, the caudal branch is the origin of the BA, and the vertebral artery (VA) is not involved in brain supply. For mammals, the VA supplies encephalic arteries in two different ways. In the first type of organization, mostly found in ungulates, the carotid rete mirabile supplies the encephalic arteries, the caudal branch is the origin of the BA, and the VA is indirectly involved in carotid rete mirabile blood supply. The second type of encephalic artery organization for mammals is the same as in humans. The caudal branch of the ICA serves as the posterior communicating artery, and the BA originates from both VAs. We believe that knowledge of comparative anatomy of encephalic arteries contributes to a better understanding of animal models applicable to surgical or radiological techniques. It improves the understanding of rare encephalic variations that may be present in humans.

Fascinating wonderful network: Rete mirabile of the maxillary artery in cats - minireview.

Cats are one of the most common companion animals, and they differ from dogs in several important ways. Considering the central importance of anatomy in high-quality medicine, the treatment of the feline mandible, mostly during intraoral procedures requiring general anaesthesia, has many important features. In cats, the major artery of the brain is the maxillary artery that forms unique structure - the rete mirabile. The rete mirabile is a plexus like vascular structure that lies extracranially and communicates with brain arterial circle through the orbital fissure. The development of the brain vasculature is different in cats, and it includes obliteration mechanisms of the internal carotid artery. The course of the maxillary artery that forms the rete mirabile has a strong relationship to the angular process of the mandible. Emphasis should be placed on manipulation with the feline mandible, especially during open-mouth procedures, as mistakes can lead to blindness, deafness, and central neurological disorders due to compression of the maxillary artery by the angular process of the mandible. This paper focuses on the anatomy and function of the blood supply to the brain, which is very specific in domestic cats and other felids.

Skull base dural reflection models: tool for teaching neuroanatomy at resource-scarce centers.

Skull base dural reflections are complex, and along with various ligaments joining sutures of the skull base, are related to most important vessels like internal carotid arteries (ICA), vertebral arteries, jugular veins, cavernous sinus, and cranial nerves which make surgical approaches difficult and need thorough knowledge and anatomy for a safe dissection and satisfactory patient outcomes. Cadaver dissection is much more important for the training of skull base anatomy in comparison to any other subspecialty of neurosurgery; however, such facilities are not available at most of the training institutes, more so in low- and middle-income countries (LMICs). A glue gun (100-Watt glue gun, ApTech Deals, Delhi, India) was used to spread glue over the superior surface of the bone of the skull base over desired area (anterior, middle, or lateral skull base). Once glue was spread over the desired surface uniformly, it was cooled under running tap water and the glue layer was separated from the skull base. Various neurovascular impressions were colored for ease of depiction and teaching. Visual neuroanatomy of the inferior surface of dural reflections of the skull base is important for understanding neurovascular orientations of various structures entering or exiting the skull base. It was readily available, reproducible, and simple for teaching neuroanatomy to the trainees of neurosurgery. Skull base dural reflections made up of glue are an inexpensive, reproducible item that may be used for teaching neuroanatomy. It may be useful for trainees and young neurosurgeons, especially at resource-scarce healthcare facilities.

The Pterygosphenoidal Triangle: Surgical Anatomy and Case Series in Endoscopic Endonasal Skull Base Surgery.

BACKGROUND: Safe exposure of the lacerum segment of the carotid artery remains a challenge in endoscopic endonasal surgery. OBJECTIVE: To introduce the pterygosphenoidal triangle as a novel and reliable landmark for facilitating access to the foramen lacerum. METHODS: Fifteen colored silicone-injected anatomic specimens were dissected using an endoscopic endonasal approach to the foramen lacerum region in a stepwise manner. Twelve dried skulls were studied and 30 high-resolution computed tomography scans were analyzed to measure the borders and angles of the pterygosphenoidal triangle. Surgical cases incorporating the foramen lacerum exposure between July 2018 and December 2021 were reviewed to provide surgical outcomes of the proposed surgical technique. RESULTS: The pterygosphenoidal triangle is delineated by the pterygosphenoidal fissure medially and the vidian nerve laterally. The palatovaginal artery is located at the base of the triangle anteriorly, while the apex is formed by the pterygoid tubercle posteriorly, which leads to the anterior wall of the foramen lacerum and lacerum internal carotid artery. In the reviewed surgical cases, 39 patients underwent 46 foramen lacerum approaches for resection of pituitary adenoma (12 patients), meningioma (6 patients), chondrosarcoma (5 patients), chordoma (5 patients), or other lesions (11 patients). There were no carotid injuries or ischemic events. Near-total resection was achieved in 33 (85%) of 39 patients (gross-total in 20 [51%]). CONCLUSION: This study details the pterygosphenoidal triangle as a novel and practical anatomic surgical landmark for safe and effective exposure of the foramen lacerum in endoscopic endonasal surgery.

A rare variant of accessory posterior cerebral artery.

BACKGROUND: The posterior cerebral artery (PCA) leaves from the distal end of the basilar artery (BA) and is joined to the internal carotid artery (ICA) by the posterior communicating artery (PComA). METHOD: The archived computed tomography angiogram of a 67 y.o. male patient was studied anatomically. RESULTS: Anatomically normal PCAs left the BA. Both anterior choroidal arteries were found but the right one was hyperplastic. As the latter distributed parieto-occipital and calcarine branches, it was regarded as an accessory PCA. It was laterally to the normal one, inferior to the vein of Rosenthal. CONCLUSION: The terms "accessory PCA" and "hyperplastic anterior choroidal artery" describe the same morphology. Rare anatomical variants could benefit from a homogenous terminology.

Morphometry and morphological analysis of carotico-clinoid foramen: an anatomical study with clinical implications.

BACKGROUND: The dural fold between anterior and middle clinoid processes on mineralisation leads to the formation of caroticoclinoid foramen (CCF). Different morphology of this foramen presents with different clinical features. The present study reports the frequency of CCF in the population of Bihar, while providing an account of assimilated information from previous literature regarding the association of caroticoclinoid ligament ossification with age and human genetics. MATERIALS AND METHODS: The study was conducted on 100 adult dry human skulls of unknown age and sex, and 50 lateral view radiographs of the head. RESULTS: Of the 100 dry skull bones, 9 presented with different forms of CCF. Bilateral complete foramina were noticed in 2 (2%) skull bones, while the incomplete foramina were observed bilaterally in 3 (3%) and unilaterally in 4 (4%) skulls. The lateral view radiograph data (n = 50) presented with a bilateral foramen in one subject and unilateral complete CCF in two different subjects. On measurements of the diameters of the complete CCF the mean values observed were 4.06 mm and 4.51 mm on the right side, while that on the left side were 5.15 mm and 4.14 mm. For the incomplete foramina, the mean values for the vertical diameter were 4.48 mm on the right and 4.19 mm on the left side, respectively. CONCLUSIONS: The frequency of CCF in the present study population of Bihar was much lesser than that of previously studied populations. However, the variation in frequency of different morphological types of CCF was observed to be the same across populations. The variations in CCF's metric data could help in predicting the morphological changes it causes to the clinoidal segment of the internal carotid artery, as well as in distinguishing its varieties.

Hematoma intramural persistente secundario a la disección de la arteria carótida interna / Persistent intramural hematoma secondary to an internal carotid artery dissection

Introducción: la disección de la arteria carótida interna en pacientes con accidente cerebro vascular isquémico se diagnostica cada vez más. En adultos jóvenes representa un 20-25 %. Aún no se ha establecido un consenso respecto al diagnóstico y al tratamiento. Caso clínico: un hombre de 44 años presentó súbitamente cefalea junto a déficit motor y sensitivo en el miembro superior izquierdo después de realizar ejercicio físico. En la resonancia magnética se observó un infarto en el territorio de la arteria cerebral media derecha con transformación hemorrágica. En el angio TC de los troncos supraaórticos se observó un hematoma trombosado en la luz falsa de la disección de la carótida interna derecha. El paciente se recuperó espontáneamente. Al principio se mantuvo una actitud conservadora, pero al año de seguimiento hubo una progresión del hematoma que produjo una estenosis > 75 % de la arteria carótida interna derecha. Fue entonces cuando se optó por el implante de un stent no recubierto a este nivel. Discusión: el diagnóstico y el tratamiento temprano de la disección carotídea permiten evitar secuelas neurológicas incapacitantes. Para pacientes con disección carotídea se recomienda el seguimiento con ecografía Doppler semestral durante los primeros años.(AU)

Introduction: dissection of the internal carotid artery in patients who suff ered an ischemic stroke is increasingly being diagnosed. In young adults it represents 20-25 %. no consensus has been established regarding diagnosis and treatment. Case report: a 44-year-old man presented a sudden headache with motor and sensory defi cits in the left upper limb after doing physical exercise. on the MrI scan revealed an infarction in the right middle cerebral artery with a hemorrhagic transformation. CT angiography of the supra-aortic trunks showed a thrombosed hematoma in the false lumen of the right internal carotid dissection. The patient made a spontaneous recovery. at fi rst, we maintained a conservative attitude but after one year of monitoring, there was progression of the hematoma producing a steno- sis > 75 % of the right internal carotid artery. at this point it was decided to implant an uncovered stent at this level. Discussion: early diagnosis and treatment of carotid dissection makes possible preventing disabling neurological sequelae. In patients with carotid dissection it is recommended a biannual monitoring with a doppler ultrasound during the fi rst years.(AU)

Anatomical study of the internal carotid venous plexus: new findings with application to skull base surgery.

OBJECTIVE: The venous plexus (internal carotid venous plexus) surrounding the petrous part of the internal carotid artery (ICAp) is said to be one drainage pathway of the cavernous sinus. These veins have many potential clinical implications including iatrogenic hemorrhage during surgical approaches to the skull base and carotid-cavernous fistulas. Because there are few morphological data about this venous plexus at the skull base, this descriptive/quantitative study was performed to elucidate its anatomy. METHODS: Six latex-injected cadaveric heads (twelve sides) were dissected via a superior craniotomy approach in which the ICAp was exposed by drilling away the overlying bone. A venous plexus surrounding parts of the ICAp in all sides was documented along with the positions of its major tributaries and their connections. RESULTS: The veins were most concentrated near the junction of the ICAp and the cavernous part of the internal carotid artery, and usually along the medial and lateral sides of the ICAp. Tributaries included branches joining the basilar venous plexus posteriorly and branches joining the veins surrounding the foramen ovale anteriorly. CONCLUSION: Detailed knowledge of the anatomy of this venous plexus surrounding the ICAp is useful for interpreting imaging of the skull base and valuable for surgeons operating in this part of the cranium.

Hakuba's triangle: a cadaveric study detailing its anatomy and neurovascular contents with vascular and skull base implications.

Hakuba's triangle is a superior cavernous sinus triangle that allows for wide and relatively safe exposure of vascular and neoplastic lesions. This study provides cadaveric measurements of the borders of Hakuba's triangle and describes its neurovascular contents in order to enrich the available literature. The anatomical borders of the Hakuba's triangle (lateral, medial, and posterior borders) were defined based on Hakuba's description and identified. Then the triangle was dissected to reveal its morphology and relationship with adjacent neurovascular structures in Embalmed Caucasian cadaveric specimens. The oculomotor nerve occupied roughly one-third of the area of the triangle and the nerve was more or less parallel to its medial border. The mean lengths of the lateral border, posterior border, and medial border were 17 mm ± 0.5 mm, 12.2 mm ± 0.4 mm, and 10.6 mm ± 0.4 mm, respectively. The mean area of Hakuba's triangle was 63.9 mm2 ± 4.4 mm2. In this study, we provided cadaveric measurements of the borders of Hakuba's triangle along with descriptions of its neurovascular contents.

Microsurgical anatomy of the internal carotid artery at the skull base.

BACKGROUND: The aetiology and significance of internal carotid artery variations at the skull base remain controversial after decades, with limited available literature. Approximately 10-40 per cent of the general population has parapharyngeal internal carotid artery variations. METHOD: A prospective observational study was conducted on internal carotid artery variations in 36 cadavers, in a tertiary care hospital, between March 2019 to March 2020. RESULTS: The most common internal carotid artery variation observed in the specimens was tortuosity, in 30 per cent, followed by kinking in 18 per cent and coiling in 10 per cent. Thirty per cent of specimens had variations present bilaterally. A loop pattern of the internal carotid artery was identified. Coiling of the internal carotid artery may present as a node; hence, meticulous dissection is advocated near the skull base to avoid complications. These variations hold utmost importance for otorhinolaryngologists performing pharyngeal and nasopharyngeal surgical procedures. CONCLUSION: A detailed knowledge of anatomy, along with its variations, and surgical expertise, will help reduce the incidence of surgical complications.

Acesso cirúrgico ao segmento cervical distal da artéria carótida interna e à bifurcação carotídea alta - revisão integrativa da literatura e proposta de protocolo / Surgical access to the distal cervical segment of the internal carotid artery and to a high carotid bifurcation - integrative literature review and protocol proposal

Resumo Diversas manobras já foram descritas para o acesso ao segmento distal cervical da artéria carótida interna ou à bifurcação carotídea alta; entretanto, há divergências na sistematização dessas técnicas. O objetivo deste estudo é revisar as técnicas descritas e propor um protocolo prático que auxilie na seleção da técnica mais adequada para cada caso. Para isso, foi realizada uma busca nas bases de dados PubMed Central, Biblioteca Virtual em Saúde e SciELO por artigos sobre o tema, em língua inglesa ou portuguesa, publicados entre os anos de 1980 e 2021. Entre as manobras descritas, parece razoável que as duas etapas iniciais sejam a abordagem ao músculo esternocleidomastóideo, seguida pela secção/retração do ventre posterior do músculo digástrico. Caso necessário, a subluxação mandibular temporária unilateral é um recurso adicional e preferível à divisão do aparato estiloide, devido ao menor potencial de morbidade. Exposições ainda mais amplas podem ser obtidas com as osteotomias mandibulares.

Abstract Several different maneuvers have been described for obtaining access to the distal cervical segment of the internal carotid artery or to a high carotid bifurcation. However there are different approaches to systematization of these techniques. The objective of this study is to review the techniques described and propose a practical protocol to support selection of the most appropriate technique for each case. The review is based on the results of database searches on PubMed Central, the Virtual Health Library (BVSalud), and SciELO for articles on the subject published in English or Portuguese from 1980 to 2021. Among the different maneuvers described, it appears reasonable that the first two steps should be to obtain access at the sternocleidomastoid muscle, followed by section or retraction of the digastric muscle posterior belly. If needed, temporary unilateral mandibular subluxation is an additional resource that is preferable to division of the styloid apparatus process, because of its lesser potential for morbidity. Even wider exposure can be obtained using mandibular osteotomies.

Effect of internal carotid artery aberrations on the distance between styloid process and carotid artery / Efecto de las variaciones de la arteria carótida interna en la distancia entre el proceso estiloides y la arteria carótida

SUMMARY: The objective of this study was to evaluate the role of the variations of carotid artery course on the relationship between styloid process (SP) and internal carotid artery (ICA). Carotid CT angiography scans of 170 patients were retrospectively evaluated. The variability of the course of ICA were classified. The length and medial angulation of the SP were measured on coronal 3D images. On axial images, the shortest distance between the bone edge of the SP and ICA were measured. The distance between SP and ICA among the course patterns of carotid artery were compared statistically. In the comparison of distances between SP and ICA with respect to the course of ICA, the difference between straight and curving (p <0.001) was statistically significant. Curving caused the separation of ICA and SP. The highest and the shortest distance was at the curving and coiling group, respectively. We found that SP-ICA distance has a positive and negative correlation with SP angle (p<0.001) and SP length (p<0.001), respectively. The course of ICA is one of the major determinants affecting the relationship of ICA and SP. The curving pattern of ICA has a tendency to increase the distance between SP and ICA.

RESUMEN: El objetivo de este estudio fue evaluar el rol de las variaciones que tiene el curso de la arteria carótida en la relación entre el proceso estiloides (PE) y la arteria carótida interna (ACI). Se evaluaron retrospectivamente angiografías por tomografía computarizada carotídea de 170 pacientes. Se clasificó la variabilidad del curso de ACI. Se midieron en imágenes coronales y en 3D la longitud y la angulación medial del PE. En las imágenes axiales, se midió la distancia más corta entre el margen del PE y la ACI. Se comparó estadísticamente la distancia entre PE y la ACI entre los patrones de trayecto de la arteria carótida. La comparación de las distancias entre PE y la ACI respecto al curso de ACI, fue estadísticamente significativa, siendo la diferencia entre arterias recta y curva (p <0,001). La arteria curva provocó la separación de la ACI y del PE. Las mayores y menores distancias estaban en el grupo de arterias curvas y enrolladas, respectivamente. La distancia PE-ACI tiene una correlación positiva y negativa con el ángulo PE (p <0,001) y la longitud del PE (p <0,001), respectivamente. El curso de la arteria carótida interna es uno de los principales determinantes que afectan la relación con el proceso estiloides. El patrón de curva de la ACI tiende a aumentar la distancia entre PE y la propia arteria arteria.

Magnetic Resonance Imaging Evaluation of Distance Between Adenoid Tissue and Internal Carotid Artery in Children With Adenoid Hypertrophy.

OBJECTIVES: In the present study, we investigated the distance between adenoid tissue and internal carotid artery (ICA) in children with adenoid hypertrophy by magnetic resonance imaging. METHODS: Cranial magnetic resonance images of 200 children with adenoid hypertrophy between the ages of 5 and 15 were included. In group 1 (5-9 years of age), there were 100 children, and in group 2 (10-15 years of age), there were 100 children. In both groups, adenoid thickness, adenoid/nasopharynx) ratio, and superior, middle, and inferior adenoid-ICA distances were measured. RESULTS: Adenoid thickness is significantly higher in the 10-to-15 years age group than in the 5-to-9 years age group (P < 0.05). Adenoid-ICA distance got lower from the superior to the inferior part in both age groups and in both sexes: inferior < middle < superior adenoid-ICA distance. In the 5-to-9 years age group, the minimum adenoid-ICA distances were 2.40 mmsuperior, 0.90 mmmiddle, and 1.20 mminferior. In 10-to-15 years age group, the minimum adenoid-ICA distances were 2.50 mmsuperior, 1.00 mmmiddle, and 0.90 mminferior. As adenoid thickness increased, the inferior adenoid-ICA distance decreased bilaterally (P < 0.05). As the age got older, adenoid thickness increased, and the left superior and middle adenoid ICA distances and bilateral inferior adenoid-ICA distances decreased (P < 0.05). CONCLUSION: The distance between adenoid and ICA decreased from superior to inferior. In 10- to 15-year-old children, the distance between adenoid and ICA was determined as lower than in the 5- to 9-year-old children. The minimum distances between adenoid and ICA were found to be between 0.9 and 2.5 mm in the 10-to-15 age group and between 0.9 and 2.4 mm in the 5-to-9 age group. It should be remembered that ICA can be very close to the adenoid tissue. In addition, because thermal injury can cause deeper damage to the tissue, bipolar cautery should be used with caution in this area and unipolar cautery should not be used.

Traumatic Dissection of Arterial Cervical Vessels: Report of Two Cases and Literature Review

Even though traumatic dissection of cervical arterial vessels is themajor cause of stroke among adults, it is still an underdiagnosed disease in neurosurgical emergencies, since most patients do not have or present subtle clinical signs in the acute phase. The authors report two interesting cases of cervical artery dissection with different traumatic mechanisms and present a broad literature review about this subject.

The carotid axis revisited.

The aim was to determine the variations in the level of origin of carotid bifurcation and diameters of the common, internal, and external carotid arteries which is clinically important for several interventional procedures. Therefore, 165 human embalmed corpses were dissected. The data collected were analyzed using the Chi square-test and the Pearson correlation test. The results of previous studies have been reviewed. In relation to the level of the carotid bifurcation, taking as a reference point the hyoid bone, the values ranged from 4 cm below the hyoid body to 2.5 cm above the body of the hyoid, being the average height-0.33 cm, with a standard deviation of 1.19 cm. The right carotid bifurcation was established at a higher level (x = - 0.19 cm.) than the left one (x = - 0.48 cm.) (p = 0.046). On the contrary, no significant gender differences could be observed. The arterial calibres of the common and internal carotid arteries were higher in male than female. In the internal carotid artery (X = 0.76 cm.), the left was greater than the right (X = 0.72 cm.) (P = 0.047). However, no differences in the distribution of the calibre of the external carotid artery were found neither by side nor gender. Variations in the level of bifurcation and calibres of carotid arteries are relevant for interventional radiology procedures and head and neck surgeries. Knowledge of these anatomical references might help clinicians in the interpretation of the carotid system.

Intracavernous Branches of the Internal Carotid Artery Through an Endoscopic Endonasal Approach: Anatomical Study and Review of the Literature.

OBJECTIVE: The endoscopic endonasal transcavernous (EET) approach is an increasingly popular approach for the cavernous sinus and surrounding structure lesions as well as a surgical corridor to pre-mesencephalic cisterns. This endoscopic study describes the main intracavernous branches of the internal carotid artery, providing nuances to improve the safety of this approach. MATERIAL AND METHODS: Forty-six fresh cavernous sinus (23 heads) were injected with colored silicon and studied via an EET approach; 6 were excluded due to insufficient injection. The internal carotid artery, the meningohyphophyseal trunk (MHT) and its branches, and the inferolateral trunk were dissected, and branching patterns identified and classified. RESULTS: The MHT was identified in 82.5% of cases. Two main MHT types were identified: complete, with 3 main branches, and incomplete, with fewer than 3. The main branches encountered were the inferior hypophyseal artery, present in 92.5% of cases, the dorsal meningeal artery (DMA), present in 87.5%, and the tentorial artery, present in 87.5%. The DMA was classified as prominent medial (48.6%), prominent lateral (20%), or bifurcation type (25.7%). Complete and incomplete MHT were further classified as complete MHT (A, B, and C) and incomplete MHT (A, B, C, and D) according to the combination of the different DMA types with other branches. The inferolateral trunk was a branch of the MHT in 7% of cases. CONCLUSIONS: The MHT is a highly prevalent intracavernous branch, with 7 identifiable patterns based on DMA morphology and branch combination. This knowledge could guide surgeons in performing a safer EET approach.

Can Styloid Process and Internal Carotid Artery Anatomy be Used to Predict Carotid Artery Dissection?

BACKGROUND: Carotid artery dissection is a common cause of stroke in the young. It has been related to the association of the carotid artery with fixed neighboring anatomical structures. This study assesses the association between styloid process length, internal carotid artery position and cervical carotid artery dissection (CCAD). This information would provide potential predicative radiological measurements, which could prevent delays in CCAD diagnosis. METHODS: Retrospective data was collected from 2 central London hospitals over 5 years. CCAD cases were identified from individuals who underwent computer topography angiography of the neck for suspected CCAD. The following data was collected: evidence of CCAD; bilateral styloid process length and presence of styloid-hyoid ligament calcification; bilateral styloid process-internal carotid distance; calcification of carotid arteries and whether their position was aberrant. Cases were dissection-side, age and gender matched with two non-dissection controls. RESULTS: Three hundred and fifty-five individuals were identified. Fifty individuals had CCAD, of which 4 had bilateral dissection. In individuals with CCAD, average styloid process length was 27.5 mm and styloid process-internal carotid distance was 5.14 mm. There was no significant association between styloid process length or styloid process-internal carotid distance, and CCAD when compared with matched controls. Internal carotid artery aberrancy was significant for nondissection. CONCLUSIONS: In this study, there was no association between styloid process length and styloid process-internal carotid distance with CCAD. These measurements can not be used to predict the possibility of a CCAD following trauma.

Systematization, description, and territory of arteries that promote vascularization of the midbrain and rhombencephalon in the ostrich (Struthio camelus).

Brain specimens from 30 ostriches were injected with red-dyed latex via the internal carotid arteries (Aa.). The ventral tectal mesencephalic artery (a.), invariably a medium-sized single vessel, was, on the right side, a collateral branch of the caudal branch of the carotid artery (53.4%), a direct branch of the carotid artery (43.3%) and a direct branch of the basilar artery (3.3%) and on the left side, a collateral branch of the caudal branch of the carotid artery (66.7%), a direct branch of the carotid artery (30%), and a direct branch of the basilar artery (3.3%). It vascularized only the ventral half of the optic lobe, with no involvement in cerebellar vascularization on the right (93.3%) and left (80%) sides, extending to the ventrorostral-most cerebellar lobules, which were vascularized on the right (6.7%) and left (20%) sides. The caudal ventral cerebellar arteries were a single vessel on the right (96.7%) and left (93.3%) sides. Its first branch was a common trunk: dorsal spinal-caudal cerebellar on the right (60%) and left (56.6%) sides. Its second branch was the caudal cerebellar artery on the right (76.7%) and left (86.7%) sides. Its third branch was the second component of the caudal cerebellar artery on the right (6.7%) and left (3.3%) sides. The midbrain was vascularized by dorsal and ventral tectal mesencephalic arteries. The cerebellum was vascularized by branches of the caudal ventral cerebellar artery and by the dorsal cerebellar artery.

Site of Origin of the Ophthalmic Artery Influences the Risk for Retinal Versus Cerebral Embolic Events.

BACKGROUND: Embolic events leading to retinal ischemia or cerebral ischemia share common risk factors; however, it has been well documented that the rate of concurrent cerebral infarction is higher in patients with a history of transient ischemic attack (TIA) than in those with monocular vision loss (MVL) due to retinal ischemia. Despite the fact that emboli to the ophthalmic artery (OA) and middle cerebral artery share the internal carotid artery (ICA) as a common origin or transit for emboli, the asymmetry in their final destination has not been fully explained. We hypothesize that the anatomic location of the OA takeoff from the ICA may contribute to the differential flow of small emboli to the retinal circulation vs the cerebral circulation. METHODS: We report a retrospective, comparative, case-control study on 28 patients with retinal ischemia and 26 patients with TIA or cerebral infarction caused by embolic events. All subjects underwent either computed tomography angiography or MRA. The location of the ipsilateral OA origin off the ICA was then graded in a blinded fashion and compared between cohorts. Vascular risk factors were collected for all patients, including age, sex, hypertension, hyperlipidemia, arrhythmia, diabetes, coronary artery disease, and smoking. RESULTS: We find that in patients with retinal ischemia of embolic etiology, the ipsilateral OA takeoff from the ICA is more proximal than in patients with cerebral infarcts or TIA (P = 0.0002). We found no statistically significant differences in demographic, vascular, or systemic risk factors. CONCLUSIONS: We find that the mean anatomical location of the OA takeoff from the ICA is significantly more proximal in patients with MVL due to retinal ischemia compared with patients with TIA or cerebral ischemia. This finding contributes significantly to our understanding of a long observed but poorly understood phenomenon that patients with MVL are less likely to have concurrent cerebral ischemia than are patients with TIA.