Anatomical variations of the vertebral artery and its relation to the atlas vertebra - Radiological and dry bone study

Vertebral artery (VA) variations are important for diagnostic angiographic procedures. This study aimed to describe the anatomical variations of VA using multidetector computed tomography angiography (MDCTA), and to provide a quantitative and qualitative anatomy of the VA groove in dry atlas vertebrae. The study was carried out on 100 MDCTA images from adult Egyptian individuals (69 males; 31 females) and 50 dry atlas fully ossified and of unknown age and sex. MDCTA films were evaluated for VA origin, level of entrance into foramen transversarium, caliber, and distance from the midline. VA grooves in dry bones were examined for the presence of ponticulus posticus (PP). Inner and outer distances from the midline, width and thickness were measured using sliding Vernier caliper. The results revealed that the left VA arose directly from the aortic arch in 7% of cases and was absent in 2% of cases. Atypical entry of VA into foramen transversarium was through C5 (4.5%), followed by C7 (1.5%), then C4 (1%). The left vertebral arteries with direct aortic origin were more medially located than the left arteries with subclavian origin (p=0.005). The mean diameter was significantly greater on the left (3.67±1.07 mm), as compared to the right side (3.36±0.93 mm) (p=0.038). PP was detected in 47% of cases in radiological images and 96% of dry bones. It could be concluded that the most important variations of VA were the aortic origin of the left VA and abnormal entry through transverse foramina. PP was a common variation in atlas vertebrae. These variations should be taken into consideration during radiological and orthopedic procedures

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Age-related morphologic changes of the vertebral artery in the transverse process. Analysis by multidetector computed tomography angiography.

BACKGROUND CONTEXT: The V2 segment of the vertebral artery (VA) ascends and passes through the transverse foramen (TF) of the C6-C1 vertebrae. Atherosclerosis of the VA and degenerative changes in the cervical spine are likely to occur with aging, and subsequent morphologic changes may alter the normal anatomy. PURPOSE: The aim was to determine the morphologic changes of TF and VA in relation to aging. STUDY DESIGN/SETTING: This was a retrospective cross-sectional study. PATIENT SAMPLE: One hundred ten consecutive patients who had undergone computed tomography angiography were included. METHODS: The subjects were then divided into three groups according to age: Group A, less than 45 years; Group B, from 45 to 65 years; and Group C, older than 65 years. Cases with stenosis and dissection of the VA were excluded from the quantitative analysis. The areas of the VA and TF were measured, and the VA/TF occupation ratio (OR) was calculated accordingly. The presence of VAs tortuosity within the TF was also noted. RESULTS: The TF was larger in the oldest group, but the difference was not statistically significant. There was also no significant statistical difference among the age groups in terms of the VA and VA/TF ORs (p>.05). In the Group C, the rate of overall tortuosity of the VA was 73%, and arterial tortuosity in the TF was 28.6%. In cases with tortuous VA, C6 and C4 TFs were found to be significantly larger. CONCLUSIONS: Tortuous VAs tend to be associated with enlargement of C6 and C4 TFs. Knowledge of such changes in the anatomy is crucial during instrumentation used for cervical spine surgeries, to prevent serious complications in patients aged older than 65 years.

Neonatal Acid-Base Status in Fetuses with Abnormal Vertebro- and Cerebro-Placental Ratios.

OBJECTIVE: A low cerebro-placental ratio (CPR) at term suggests the existence of failure to reach growth potential (FRGP) with a higher risk of poor neonatal acid-base status. This study aimed to evaluate whether similar findings were also seen in the vertebral artery (vertebro-placental ratio, VPR), supplying 30% of the cerebral flow. METHODS: We studied term fetuses classified into groups according to birth weight (BW), CPR and VPR. BW was expressed in centiles and ratios in multiples of the median (MoM). Subsequently, associations with neonatal pH values were evaluated by means of regression curves and Mann-Whitney tests. RESULTS: VPR MoM correlated with BW centiles (p < 0.0001, R2 = 0.042) and its distribution resembled that of CPR MoM (p < 0.001). When both arteries were compared, adequate-for-gestational-age (AGA) fetuses with either low CPR or low VPR had lower neonatal venous pH values (p < 0.05, p < 0.01, respectively). However, in case of small-for-gestational-age (SGA) fetuses, only those with low VPR had significantly lower neonatal arterial and venous pH values (p < 0.05). CONCLUSIONS: Blood flow in the vertebral artery mimics that in the middle cerebral artery supporting the FRGP model. Both CPR and VPR identify AGA fetuses with lower neonatal pH values, but only VPR identifies SGA with lower pH values. Hypoxemia might be reflected as a generalized cerebral vasodilation demonstrated as low CPR and VPR.

Development of optimized vascular fractal tree models using level set distance function.

Using the concepts of fractal scaling and constrained constructive optimization (CCO), a branching tree model, which has physiologically meaningful geometric properties, can be constructed. A vascular branching tree model created in this way, although statistically correct in representing the vascular physiology, still does not possess a physiological correct arrangement of the major arteries. A distance-function based technique for "staged growth" of vascular models has been developed in this work to address this issue. Time-dependent constraints based on a signed-distance level set function have been added, so that the tree models will first be grown near the designated surface(s) and, then, gradually allowed to penetrate into the enclosed volume. The proposed technique has been applied to construct a model of the human cerebral vasculature, which is characterized by the above-mentioned distribution of the arteries.

Evaluation of vertebral artery hypoplasia and asymmetry by color-coded duplex ultrasonography.

Distinguishing stenosis and hypoplasia of the extracranial vertebral artery (VA) is clinically important, but there is no agreement in defining VA hypoplasia. We endeavored to attain reference values for VA flow volume by color Doppler ultrasonography (CDU), analyze age and gender effects on VA flow volume and develop a definition of VA hypoplasia. CDU was performed in 447 subjects free of cerebrovascular diseases or carotid stenosis. The VA diameter, peak systolic velocity, end-diastolic velocity, time-averaged mean velocity, resistance index (RI) and flow volume were recorded bilaterally. We found significant asymmetries in diameter, flow velocities and flow volume with left-sided dominance. Diameters were different on left (0.297 +/- 0.052 cm) and right (0.323 +/- 0.057) sides (p < 0.001). Flow volume was different on right (83.0 +/- 36.9 mL/min) and left (96.6 +/- 42.4) sides (p < 0.001). Women had significantly smaller diameters, higher flow velocities and lower RIs than men. VA flow volume did not change with aging. We defined hypoplasia as a significant decrease in flow velocities and increase in RI for VA diameters < 0.22 cm. This definition is supported by findings of an increase in ipsilateral flow resistance (RI >/= 0.75), contralateral diameter (side-to-side diameter difference >/= 0.12 cm), and flow volume (side-to-side flow volume ratio >/= 5). This definition and these reference values may lead to better differentiation between congenital variation and steno-occlusion clinically.

Origen aórtico de la arteria vertebral en el hombre / Aortic origin of the vertebral artery in man

La arteria vertebral se origina normalmente de la arteria subclavia, pudiendo existir otros orígenes tales como: en el arco aórtico, en el tronco braquiocefálico u otros. Se describen tres casos de origen de la arteria vertebral en el arco aórtico, naciendo entre las arterias subclavia izquierda y carótida común izquierda, encontradas en disecciones de rutina en la disciplina de anatomía topográfica de la Facultad de Medicina de la Universidad de La Frontera. La parte proximal del segmento V1 de la arteria vertebral adquiere importancia clínica y quirúrgica ante un origen en el arco aórtico