Variations in carotid sinus anatomy and their relevance to carotid interventions.

BACKGROUND: The carotid sinus (CS) is a dilatation in the carotid bifurcation usually at the origin of proximal internal carotid artery (ICA). It contains baroreceptors which influence blood pressure. Variations in the location of the CS are of importance as atheromatous plaque commonly forms in this area and procedures such as carotid endarterectomy are performed to reduce the risk of stroke. Inadvertent stimulation of the CS baroreceptors during interventions can have profound effects on the patient's haemodynamic status both intra- and postoperatively, causing serious complications. The aim of this study is to determine the inter- and intra-individual variations in the location of the CS. MATERIALS AND METHODS: Eighty-two carotid arteries were dissected bilaterally from 41 cadavers. The locations of the CS were noted and divided into four potential sites. RESULTS: The commonest site is the origin of the ICA (74.3%), but the CS can also be found in the distal part of the common carotid artery (CCA) inferior to the bifurcation (17.1%); at the bifurcation involving the distal CCA and origins of both the external carotid artery (ECA) and ICA (7.32%); and at the origin of the ECA (1.22%). In individual cadavers, the CS was located at the origin of the ICA in 97.6% on at least one side. The sites of the CS were asymmetrical in 34.1%. CONCLUSIONS: Clinicians performing carotid interventions should be aware of these anatomical variations to avoid inadvertent stimulation of the CS which can cause profound bradycardia and hypotension

Carotid Intern Aneurysms

Cerebral aneurysms (CA) are acquired lesions, affecting 5–10% of the population, being about three times more common in women than in men. The absolute majority of CA is asymptomatic. However, in symptomatic cases, cerebral aneurysms present without about 80% of cases with severe intracranial hemorrhage, with mortality up to 50% and severe morbidity of up to 80%. At this point, the carotid siphon is particularly important because it is the blood gateway to the anterior cerebral circulation, being the most sinuous portion of the internal carotid artery, and because it houses about 30% of the intracranial aneurysm. The constant interactions of blood flow with carotid siphon curvatures are apparently intrinsically related to the epidemiology of these lesions in the various locations of the intracranial circulation and their presentation form. It is well established that a greater anterior knee angle has a significant independent relation with intracranial aneurysms located after carotid siphon, larger aneurysms, and greater risk of rupture. These findings may be associated with the hemodynamic interactions of blood flow and the curvature of carotid siphon. Little is known about the anatomical changes in carotid siphon and, consequently, the repercussions of the hemodynamic changes that the neurosurgical interventions mechanisms could entail. Devices such as intracranial stents, detachable coils, and even clips of aneurysms can modify the morphology of carotid siphon, and the knowledge of these consequences could be used to obtain better therapeutic results. In the last 10 years, a new device for the treatment of intracranial aneurysms has been presenting promising results, flow diverters stents (FDS), and its use to treat aneurysms in carotid siphon appears to cause morphological changes characterized by increased anterior and posterior angles. Specifically, the anterior angle increase was associated with better angiographic results. Aneurysms of the extracranial carotid artery (ECAA) are rare and little is known about its natural history. The etiology is diverse and most ECAA are asymptomatic, but they may progress to a pulsatile mass, cranial nerve compression, or cause a stroke. ECAA treatment is still controversial and a better insight into natural history and risk of complications of the different treatments is needed in order to get the consensus

Protrusion of the carotid canal into the sphenoid sinuses: evaluation before endonasal endoscopic sinus surgery

Background: Many reports have previously indicated the vast number of anatomical variations of the sphenoid sinuses, e.g. presence of the recesses. Notwithstanding, there are a few crucial neurovascular structures directly neighbouring with the sinuses. The following research aimed to evaluate frequency prevalence of the carotid canal’s protrusion into the sphenoid sinuses in adult population.Materials and methods: Computed tomography (CT) scans of the paranasal sinuses of 296 patients (147 females, 149 males) were analysed in this retrospective study. The patients did not present any pathology in the sinuses. Spiral CT scanner Siemens Somatom Sensation 16 was used in the standard procedure in the option Siemens CARE Dose 4D.Results: Protrusion of the carotid canal was found in the majority of the patients — 55.74%, more frequently in males (65.1% of the patients) than in females (46.26% of the patients). The said variant — regardless of gender — was noted more often bilaterally (41.55% of the cases: 29.93% females, 53.02% males) than unilaterally (14.19% of the cases: 16.33% females, 12.08% males). In the unilateral type (regardless of gender), the protrusion was more common for the left sphenoid sinus — 10.81% of the patients (12.24% females, 9.4% males) than for the right — 3.38% of the patients (4.08% females, 2.68% males).Conclusions: Complicated structure of the paranasal sinuses, derived from the high prevalence of their anatomical variations, may perplex routine surgical interventions. Henceforth, referral for a CT scan is imperative in order to abate the risks associated with an invasive procedure in the said region

The foramen spinosum: a landmark in middle fossa surgery

The foramen spinosum is an easily identifiable landmark in microsurgery of the middle cranial fossa, and knowledge of the variations in its relationship to the surrounding neurovascular structures is important when operating in this area. We studied the anatomical relationship of the foramen spinosum to the foramen ovale, the mandibular branch of the trigeminal nerve, the greater superficial petrosal nerve, and the petrous part of the internal carotid artery in 12 cadaver heads. We also tried to define an external landmark for early identification of the location of the foramen spinosum in ten dry skulls. We found considerable variations in the anatomy around the foramen spinosum. This knowledge may improve the identification and preservation of the neurovascular structures when using approaches to the middle cranial foss

Effect of calcification on the mechanical stability of plaque based on a three-dimensional carotid bifurcation model

Background: This study characterizes the distribution and components of plaque structure by presenting a three-dimensional blood-vessel modelling with the aim of determining mechanical properties due to the effect of lipid core and calcification within a plaque. Numerical simulation has been used to answer how cap thickness and calcium distribution in lipids influence the biomechanical stress on the plaque.Method: Modelling atherosclerotic plaque based on structural analysis confirms the rationale for plaque mechanical examination and the feasibility of our simulation model. Meaningful validation of predictions from modelled atherosclerotic plaque model typically requires examination of bona fide atherosclerotic lesions. To analyze a more accurate plaque rupture, fluid-structure interaction is applied to three-dimensional blood-vessel carotid bifurcation modelling

Application of Numerical Simulation in Cardiovascular Medicine

Introduction: The purpose of this thesis is to study atherosclerotic risk and thrombotic risk through application of numerical simulation to cardiovascular geometry and morphology. This has been applied to two specific situations, the angle of take-off of the left main coronary artery and the morphology of the left atrial appendage. A. The distribution of atherosclerotic plaque and the plaque rupture rate in isolated left main coronary disease is different to that seen in left main disease with multi-vessel disease, suggesting local biomechanical forces play an important part in governing plaque formation and rupture. The varying vertical left main coronary artery take-off angulation may impact on the wall shear stress. B. Different left atrial appendage morphologies seem to have different risk of thromboembolism, in patients with atrial fibrillation and low CHADS2 VASC score. From this observation, it can be hypothesized that left atrial morphology subtype with a more complex structure can lead to higher volume of blood stagnation. Aim: A. To investigate the effects of vertical take-off angulation of the left main coronary artery from aorta and varying stenosis severities on wall shear stress in the left main coronary artery. B. To investigate the impact of different left atrial appendage morphologies on slow vortical flow estimated by flow dynamics. Methods: A. Artificially created and patient-specific computed tomography-derived 3-dimensional digital models of the left main coronary artery with varying vertical take-off angulation and artery stenoses were generated. These were exported for numerical simulation to calculate the wall shear stress values and mapping in each model set. B. Patient-specific computed tomography-derived 3-dimensional digital model sets of different left atrial appendage morphologies were exported for numerical simulation to calculate the volume and distribution of slow vortical flow. Left atrial appendage emptying was assessed. Results: A. The study of left main take off demonstrated that the preferred development site of atherosclerotic plaques in pathological studies corresponds to regions of low wall shear stress. Both peak wall shear stress and mean wall shear stress increased with more vertical take-off, and this relationship was accentuated by increasing stenosis severity. The more vertically angled LMCA take-off from aorta in the presence of significant stenosis severity was also associated with a larger area of low wall shear stress. These findings may explain the higher atherosclerotic plaque rupture rate and higher percentage of proximally located plaque seen in isolated left main coronary artery disease B. For complex geometry, the Cauliflower left atrial appendage subtype contained the greatest volume of slow vortical flow at low shear rate across a range of different left atrial appendage emptying velocities. This rheological mechanistic observation correlates well with the clinical observation that the highest rate of clinical thromboembolism is seen with the Cauliflower subtype in patients with low CHADS2 VASC score atrial fibrillation. However, in the presence of severely depressed left atrial appendage function differences between left atrial appendage morphology subtypes diminish. Conclusion: A. LMCA angulation may be an additional important factor to be considered in the clinical evaluation of the pathogenesis and progression of LMCA atheromatous disease. B. Stasis of blood, assessed in this study by the volume of slow vortical flow, is shown to depend on left atrial appendage morphology, and also depends on left atrial appendage function/emptying velocity. Under conditions when function is mildly to moderately reduced, then it is likely that morphology is an important variable

Clinical Significance of an Unusual Variation : Anomalous additional belly of the sternothyroid muscle

The infrahyoid muscles are involved in vocalisation and swallowing; among these, the sternothyroid muscle is derived from the common primitive sheet. The improper differentiation of this muscle may therefore result in morphological variations. We report an unusual variation found during the dissection of a 65-year-old male cadaver at the Sri Manakula Vinayagar Medical College, Madagadipet, Pondicherry, India, in 2015. An anomalous belly of the right sternothyroid muscle was observed between the internal jugular (IJ) vein and the internal carotid artery with an additional insertion into the tympanic plate and petrous part of the temporal bone and the presence of a levator glandulae thyroideae muscle. The anomalous muscle may compress the IJ vein if it is related to the neurovascular structures of neck; hence, knowledge of variations of the infrahyoid muscles can aid in the evaluation of IJ vein compression among patients with idiopathic symptoms resulting from venous congestion

Neuroanatomy of <i>Gryposuchus neogaeus</i> (Crocodylia, Gavialoidea): a first integral description of the braincase and endocranial morphological variation in extinct and extant gavialoids

Morphological studies of the braincase and cranial endocast of fossil crocodylians, especially gavialids, are scarce. Here, we present a detailed description of the neuroanatomy of Gryposuchus neogaeus from the Miocene of Argentina, based on CT scans. The cranial endocast is sub-horizontal and the angle formed between the mid-brain and the hind-brain is poorly marked. When compared with Gavialis gangeticus, the mid-brain of G. neogaeus is relatively shorter, although the distribution of cranial nerves is similar. In the floor of the endocranial cavity, posterior to the dorsum sellae, there is a median foramen that leads into a canal that runs anteroventrally through the basisphenoid to penetrate the posterior wall of the pituitary fossa (open foramen for the basilar artery?). The same structure is present in G. gangeticus, but is absent in other living crocodylians, suggesting a potential synapomorphy of Gavialoidea. The pneumaticity of the skull roof and the lateral branches of the pharyngotympanic system in G. neogaeus are markedly reduced when compared with the extant species. Comparisons with the living Gavialis indicate that the pattern of braincase morphology of Gavialidae was present in the Miocene; however, the internal morphology, including brain shape, pneumaticity of the skull roof and basicranium, is different in the two species. This work is the first step to understand the variation of the neuroanatomy in this group of archosaurs and its palaeobiological implication.Facultad de Ciencias Naturales y Muse

Neuroanatomy of Gryposuchus neogaeus (Crocodylia, Gavialoidea): a first integral description of the braincase and endocranial morphological variation in extinct and extant gavialoids

Fil: Bona, Paula. División Paleontología Vertebrados. Facultad de Ciencias Naturales y Museo. Universidad Nacional de La Plata; ArgentinaFil: Carabajal, Ariana Paulina. Instituto de Investigaciones en Biodiversidad y Medioambiente (INIBIOMA). Universidad Nacional del Comahue. San Carlos de Bariloche; ArgentinaFil: Brandoni de Gasparini, Zulma Nélida. División Paleontología Vertebrados. Facultad de Ciencias Naturales y Museo. Universidad Nacional de La Plata; Argentin

Foramen caróticoclinoideo en cráneos humanos: incidencia, morfometría y sus implicaciones clínicas

The caroticoclinoid foramen is an inconstant structure, formed by the union of the anterior and middle clinoid processes. The aim of this study was to perform an incidence and morphometry of the caroticoclinoid foramen in Brazilian human skulls and discuss its clinical implications. Eighty dry human skulls with sex distinction were used, and 3 groups of incidence were determined: General, sex, and sides. The morphometry was performed using a manual caliper and the major diameter of the foramina was measured; the values were also divided in general, according to sex and sides. The incidence of skulls with at least one foramen was 8.5%. According to the sides, 8.5% of the skulls showed foramen on the right side and 2.5% on the left. We found 2.5% of the skulls with bilateral foramen and 6.25% with unilateral foramen. In relation to sex, the foramens were found in 5% of male skulls and 12.5% of female skulls. The major diameter of this structure presented on mean, values of 5.23 mm on general, 5.18 mm on the right side and 5.35 mm on the left, 5.30 mm in male skulls and 5.18 mm in female skulls. The anatomical characteristics of this foramen should be considered in view of its clinical implications associated with neurosurgery as clinoid process removal, and symptoms as headache due to internal carotid artery alterations in this region. In conclusion knowledge of this structure supports the diagnosis and treatment of clinical complications related to this variation.The caroticoclinoid foramen is an inconstant structure, formed by the union of the anterior and middle clinoid processes. The aim of this study was to perform an incidence and morphometry of the caroticoclinoid foramen in Brazilian human skulls and discuss its clinical implications. Eighty dry human skulls with sex distinction were used, and 3 groups of incidence were determined: General, sex, and sides. The morphometry was performed using a manual caliper and the major diameter of the foramina was measured; the values were also divided in general, according to sex and sides. The incidence of skulls with at least one foramen was 8.5%. According to the sides, 8.5% of the skulls showed foramen on the right side and 2.5% on the left. We found 2.5% of the skulls with bilateral foramen and 6.25% with unilateral foramen. In relation to sex, the foramens were found in 5% of male skulls and 12.5% of female skulls. The major diameter of this structure presented on mean, values of 5.23 mm on general, 5.18 mm on the right side and 5.35 mm on the left, 5.30 mm in male skulls and 5.18 mm in female skulls. The anatomical characteristics of this foramen should be considered in view of its clinical implications associated with neurosurgery as clinoid process removal, and symptoms as headache due to internal carotid artery alterations in this region. In conclusion knowledge of this structure supports the diagnosis and treatment of clinical complications related to this variation292427431Das, S., Suri, R., Kapur, V., Ossification of caroticoclinoid ligament and its clinical importance in skull-based surgery (2007) São Paulo Med. J, 125, pp. 351-353Dodo, Y., Ishida, H., Incidence of nonmetric cranial variant in several population samples from East Asia and North America (1987) J. Anthrop. Soc. Nippon, 95, pp. 161-167Dolenc, V.V., A combined epi and subdural direct approach to carotidophthalmic artery aneurysms (1985) J. Neurosurg, 5, pp. 667-672Donald, P.J., (1998) Surgery of the Skull Base, , Philadelphia, Lippincott- RavenErturk, M., Kayalioglu, G., Govsa, F., Anatomy of the clinoidal region with special emphasis on the caroticoclinoid foramen and interclinoid osseous brid- ge in a recent Turkish population (2004) Neurosurg. Rev, pp. 22-26Gupta, N., Ray, B., Ghosh, S., A study on anterior clinoid process and optic strut with emphasis on variations of caroticoclinoid foramen (2005) Nep. Med. Coll. J, 7, pp. 140-144Hochstetter, F., Über die Taenia interclinoidea,die Commissura alicochlearis und die Cartilago supracochlearis des menschlichen Primordialkraniums.Gegenbaurs Morph (1940) Jahrb, 84, pp. 220-243Inoue, T., Rhoton Jr., A.L., Theele, D., Barry, M.E., Surgical approaches to the cavernous sinus:A microsurgical study (1990) Neurosurg, 6, pp. 903-932Kier, E.L., Embryology of the normal optic canal and its anomalies.An anatomic and roentgenographic stud (1966) Invest. Radiol, 1, pp. 346-362Kobayashi, S., Kyoshima, K., Gibo, H., Hedge, S.A., Takemae, T., Sugita, K., Carotid cave aneurysms of the internal carotid artery (1989) J. Neurosurg, 70, p. 216Lee, H.Y., Chung, I.H., Choi B., Y., Anterior, C., (1997) Yonsei Med. J, 38, pp. 151-154Narolewski, R., Significance of anatomic variants of bony surroundings of the internal carotid artery and their significance for lateral surgical approaches to the cavernous sinus (2003) Ann. Acad. Med. Stetin, 49, pp. 205-229Saka, E., Ozdoǧmus, O., Tulay, C., Gürdal, E., Uzün, I., The anatomy of the carotico-clinoid foramen and its relation with the internal carotid artery (2003) Surg. Radiol. Anat, 25, pp. 241-246Reisch, R., Vutskits, L., Filippi, R., Patonay, L., Fries, G., Perneczky, A., Topographic microsurgical anatomy of the paraclinoid carotid artery (2002) Neurosurg Rev, 25, pp. 177-183Sekhar, L.N., Akin, O., Anatomical study of the cavernous sinus emphasizing operative approaches and related vascular and neural reconstruction (1987) Neurosurg, 21, pp. 806-816Seoane, E., Rhoton, A.L., Oliveira, E., Microsurgical anatomy of the dural collar (carotid collar) and rings around the clinoid segment of the internal carotid artery (1998) Neurosurg, 42, pp. 869-886Sicher, H., du Brul, E.L., (1977) Oral Anatomy, , 6ed. Rio de Janeiro, Guanabara KooganStandring, S., Overview of the Development of the Head and Neck Head: Skull and Mandible Gray's anatomy: The anatomical basis of clinical practice, p. 2005. , New York, ElsevierEl foramen caróticoclinoideo es una estructura inconstante formada por la unión de la procesos clinoides anterior y medio. El objetivo de este estudio fue revisar la incidencia y la morfometría del foramen caróticoclinoideo en cráneos humanos brasileños y discutir sus implicaciones clínicas. Se utilizaron 80 cráneos humanos secos, de ambos sexos, determinando tres variables: sexo y lados derecho e izquierdo. La morfometría se realizó con un cáliper manual midiéndose el diámetro máximo del foramen. La incidencia de cráneos con al menos un foramen fue de 8,5%. El 8,5% de los cráneos presentó un foramen en el lado derecho y el 2,5% en el izquierdo. El 2,5% de los cráneos presentó un foramen bilateral y el 6,25% un foramen unilateral. En relación al sexo, los forámenes se encontraron en el 5% de los cráneos de hombres y el 12,5% de los cráneos de mujeres. El diámetro máximo de esta estructura presentó en promedio, valores de 5,23 mm; 5,18 mm en el lado derecho y 5,35 mm en el izquierdo; 5,30 mm en cráneos de hombres y 5.18 mm en cráneos de mujeres. Las características anatómicas de este foramen deben ser consideradas debido a las implicaciones clínicas asociadas a la neurocirugía, como la eliminación del proceso clinoides y a síntomas como cefaleas producto de alteraciones en la arteria carótida interna en esta región. En conclusión, el conocimiento de esta estructura mejora el diagnóstico y tratamiento de las complicaciones clínicas relacionadas con esta variació