scholarly journals Dimensions and Anatomical Variants of the Foramen Transversarium of Typical Cervical Vertebrae

2015 ◽  
Vol 2015 ◽  
pp. 1-5 ◽  
Author(s):  
Santosh Kaur Sangari ◽  
Paul-Michel Dossous ◽  
Thomas Heineman ◽  
Estomih Phillip Mtui
Keyword(s):  
Vertebral Artery ◽  
Thrombus Formation ◽  
Cervical Vertebrae ◽  
Uncinate Process ◽  
Vertebrobasilar Insufficiency ◽  
Transverse Foramen ◽  
Medial Margin ◽  
Significant Difference ◽  
The Mean ◽  
The Right

The study was conducted on random sample of seventy-one dried, typical cervical vertebrae (C3–C6). The data on the age, sex, and built was not available. Using vernier calipers with 0.01 mm accuracy, the anteroposterior and transverse diameters of transverse foramina and their distance from the medial margin of the uncinate process were measured bilaterally. The mean diameter of the right/left transverse foramen varied from 2.54 mm to 7.79 mm (mean = 5.55 ± 0.87 mm) and from 2.65 mm to 7.35 mm (mean = 5.48 ± 0.77 mm), respectively. The transverse foramen was less than 3.5 mm in three vertebrae on the right and two on the left. The osteocytes observed in 21.3% of specimens and the narrow transverse foramen may place patients at risk for vertebrobasilar insufficiency or thrombus formation. The mean distance of the transverse foramen from the medial margin of uncinate process is an important landmark to avoid vertebral artery laceration and was 5.0 ± 0.87 mm (range: 3.5–7.9 mm) on the right and 5.0 ± 1.0 mm (range: 3.2–7.7 mm) on the left side. No statistically significant difference was observed between the right and left sides. The accessory transverse foramina seen in 24% of vertebrae suggest duplications or fenestrations in the vertebral artery.

scholarly journals An Anatomical Study of the Morphometric Differences between Complete Arcuate Foramina and Ipsilateral Foramina Transversaria in Human Atlas Vertebrae: Could these Be Responsible for Vaso-occlusive Symptoms?

2019 ◽  
Vol 08 (03) ◽  
pp. 106-111
Author(s):  
Monika Lalit ◽  
Anupama Mahajan ◽  
Sanjay Piplani ◽  
Jagdev S. Kullar
Keyword(s):  
Vertebral Artery ◽  
Anatomical Study ◽  
Cross Sectional Area ◽  
Posterior Arch ◽  
Sectional Area ◽  
Cross Sectional ◽  
Significant Difference ◽  
The Mean ◽  
The Difference ◽  
The Right

Abstract Background and Aims Arcuate foramina (AF), the atlas bridges formed by a delicate bony spicule over the posterior arch of atlas, have been implicated in the compression of the vertebral artery during extreme rotation of head and neck movements. Reduction in the size of arcuate foramina as compared with foramen transversarium (FT) is also an important cause for the compression of vertebral artery. Aim of the present study was to determine the morphometric differences between complete AF and ipsilateral foramina transversaria. Materials and Methods Eighty dry adult human atlas vertebrae were obtained in the Department of Anatomy, Government Medical College and Sri Guru Ram Das Institute of Medical Sciences and Research, Amritsar, Punjab, India. Measurements were taken of the maximum dimensions of AF and ipsilateral FT and cross-sectional area was also calculated. Results The following results were obtained.The AF were seen in total 11 (13.75%) vertebrae, 3 (3.75%) on the right side, 6 (7.5%) on left side, and 2 (2.5%) bilateral.• The mean ventrodorsal (AFL) and superoinferior (AFH) diameter of AF was 8.79 mm and 5.98 mm, and 8.11 mm and 5.54 mm on the right and left sides, respectively, and the difference was found to be highly significant.• The mean ventrodorsal (FTL) and mediolateral (FTW) diameter of the FT 8.19 mm and 6.56 mm, and 7.31 mm and 6.86 mm on the right and left sides, respectively, with significant difference on the right side.• The mean cross-sectional area of AF was 41.32 mm2 and 35.38 mm2, and FT was 42.53 mm2 and 39.71 mm2 on the right and left sides, respectively, and AF has smaller area than ipsilateral FT. Conclusions Knowledge about the dimensions and cross-sectional area of the AF and ipsilateral foramina transversaria of the atlas vertebra can improve the success rate of surgeries, thus preventing damage to the adjoining vital structures.

Rotational vertebral artery occlusion: Case report and review of literature

2018 ◽  
pp. 1-3
Keyword(s):  
Vertebral Artery ◽  
Head Rotation ◽  
Transcranial Doppler Ultrasound ◽  
Artery Occlusion ◽  
Vascular Lesion ◽  
Vascular Compression ◽  
Vertebrobasilar Insufficiency ◽  
Transverse Foramen ◽  
Vertebral Artery Occlusion ◽  
The Right

Rotational vertebral artery occlusion (RVAO) classically involves transient, position-dependent vertebrobasilar insufficiency (VBI) that occurs when an extra-vascular lesion (e.g. osteophyte or fibromuscular band) compresses a dominant vertebral artery with turning of the head to one side. Our patient presented with VBI associated vertigo, dizziness, and lightheadedness that occurred when her head was turned to the right. RVAO was initially suggested by transcranial Doppler ultrasound (TCD) changes that were not supported by initial catheter angiography. After her symptoms worsened over a course of two years, the diagnosis was confirmed with repeat angiography with head rotation. Further imaging with computed tomography and magnetic resonance demonstrated spondylosis at the C5-C6 vertebrae and an osteophyte near the C5 transverse foramen, which caused position-dependent extra-vascular compression. She was treated with surgical decompression and anterior discectomy and fusion at C5-C6. The unique anatomical pathology of this case combined with the diagnostic discrepancy between early TCD and angiography make it an interesting contribution to the otherwise limited body of literature on RVAO.

scholarly journals POS0586 RHEUMATOID ARTHRITIS IS AN INFLAMMATORY DISEASE WITH A HIGH CARDIOVASCULAR RISK

2021 ◽  
Vol 80 (Suppl 1) ◽  
pp. 526.1-526
Author(s):  
L. Nacef ◽  
H. Riahi ◽  
Y. Mabrouk ◽  
H. Ferjani ◽  
K. Maatallah ◽  
...  
Keyword(s):  
Rheumatoid Arthritis ◽  
Risk Factors ◽  
Cardiovascular Risk ◽  
Carotid Artery ◽  
Internal Carotid ◽  
Subclinical Atherosclerosis ◽  
External Carotid ◽  
Significant Difference ◽  
The Mean ◽  
The Right

Background:Hypertension, diabetes, and dyslipidemia are traditional risk factors of cardiac events. Carotid ultrasonography is an available way to detect subclinical atherosclerosis.Objectives:This study aimed to compare the intima-media thickness in RA patients based on their personal cardiovascular (CV) history of hypertension (hypertension), diabetes, and dyslipidemia.Methods:The present study is a prospective study conducted on Tunisian RA patients in the rheumatology department of Mohamed Kassab University Hospital (March and December 2020). The characteristics of the patients and those of the disease were collected.The high-resolution B-mode carotid US measured the IMT, according to American Society of Echocardiography guidelines. The carotid bulb below its bifurcation and the internal and external carotid arteries were evaluated bilaterally with grayscale, spectral, and color Doppler ultrasonography using proprietary software for carotid artery measurements. IMT was measured using the two inner layers of the common carotid artery, and an increased IMT was defined as ≥0.9 mm. A Framingham score was calculated to predict the cardiovascular risk at 10-year.Results:Forty-seven patients were collected, 78.7% of whom were women. The mean age was 52.5 ±11.06 [32-76]. The rheumatoid factor (RF) was positive in 57.8% of cases, and anti-citrullinated peptide antibodies (ACPA) were positive in 62.2% of cases. RA was erosive in 81.6% of cases. Hypertension (hypertension) was present in 14.9% of patients, diabetes in 12.8% of patients, and dyslipidemia in 12.8% of patients. Nine patients were active smokers. The mean IMT in the left common carotid (LCC) was 0.069 ±0.015, in the left internal carotid (LIC) was 0.069 ±0.015, in the left external carotid (LEC) was 0.060 ±0.023. The mean IMT was 0.068 ±0.01 in the right common carotid (RCC), 0.062 ±0.02 in the right internal carotid (RIC), and 0.060 ±0.016 in the right external carotid (REC). The IMT was significantly higher in the left common carotid (LCC) in patients with hypertension (p=0.025). There was no significant difference in the other ultrasound sites (LIC, LEC, RCC, RIC, and REC) according to the presence or absence of hypertension. The IMT was also significantly increased in patients with diabetes at LCC (p=0.017) and RIC (p=0.025). There was no significant difference in the IMT at different ultrasound sites between patients with and without dyslipidemia.Conclusion:Hypertension was significantly associated with the increase in IMT at the LCC level in RA patients. Diabetes had an impact on IMT in LCC and RIC. However, dyslipidemia did not affect the IMT at the different ultrasound sites.References:[1]S. Gunter and al. Arterial wave reflection and subclinical atherosclerosis in rheumatoid arthritis. Clinical and Experimental Rheumatology 2018; 36: Clinical E.xperimental.[2]Aslan and al. Assessment of local carotid stiffness in seronegative and seropositive rheumatoid arthritis. SCANDINAVIAN CARDIOVASCULAR JOURNAL, 2017.[3]Martin I. Wah-Suarez and al, Carotid ultrasound findings in rheumatoid arthritis and control subjects: A case-control study. Int J Rheum Dis. 2018;1–7.[4]Gobbic C and al. Marcadores subclínicos de aterosclerosis y factores de riesgo cardiovascular en artritis temprana. Subclinical markers of atherosclerosis and cardiovascular risk factors in early arthritis marcadores subclínicos de aterosclerose e fatores de risco cardiovascular na artrite precoce.Disclosure of Interests:None declared

Vertebral Artery Disease

2015 ◽  
Author(s):  
Gregory J. Pearl ◽  
William P. Shutze
Keyword(s):  
Vertebral Artery ◽  
Posterior Circulation ◽  
Circulation System ◽  
Common Disease ◽  
Vertebrobasilar Insufficiency ◽  
Disease Patterns ◽  
Collateral Pathways ◽  
Artery Disease ◽  
The Right ◽  
Evaluation Patterns

Vertebral artery disease (VAD) is a significant cause of severe symptoms or stroke. Approximately 25 to 30% of strokes involve the posterior circulation system; VAD will be present in 20% of these and will be the source in about 10%. The ability to properly diagnose, manage, and treat VAD is an important skill for practitioners caring for patients with extracranial cerebral occlusive disease. This review covers anatomy, presentations of VAD, evaluation, patterns of disease, treatment, and other vertebral artery (VA) syndromes. Tables outline symptoms and differential diagnoses of vertebrobasilar insufficiency, etiologies of VA compression syndromes, posterior circulation cerebrovascular accident symptoms and associated syndromes, and ultrasonography velocity and VA stenosis. Figures show the anatomy of the VA, circle of Willis, aberrant arteries, VA compression, ischemic posterior circulation, collateral pathways to the VA, common disease patterns in VAD, VA to carotid artery anastomosis, incision for the V3 bypass, VA aneurysm, VA dissection, angiography of the right VA, giant cell arteritis, and fibromuscular dysplasia. Radiologic videos are provided. This review contains 15 figures, 6 tables, 7 videos, and 71 references.

scholarly journals Sexual Dimorphism in Laryngeal Volumetric Measurements Using Magnetic Resonance Imaging

2019 ◽  
Vol 99 (2) ◽  
pp. 132-136 ◽  
Author(s):  
Abdul-Latif Hamdan ◽  
Elie Khalifee ◽  
Georges Ziade ◽  
Sahar Semaan
Keyword(s):  
Magnetic Resonance Imaging ◽  
Magnetic Resonance ◽  
Statistical Significance ◽  
Resonance Imaging ◽  
Men And Women ◽  
Mean Width ◽  
Significant Difference ◽  
The Mean ◽  
The Right ◽  
Volumetric Measurements

The objective of this study is to investigate the dimensional and volumetric measurements in the thyroarytenoid (TA) muscle in men and women using magnetic resonance imaging (MRI). The hypothesis is that there is a gender-related difference in these measurements. A retrospective chart review of 76 patients who underwent MRI of the neck at the American University of Beirut Medical Center was conducted. The dimension and volume of the right and left TA muscle were measured on axial and coronal planes short tau inversion recovery images. Male and female groups were compared with respect to demographic data and MRI findings using parametric and nonparametric tests. The mean length of the thyro-arytenoid muscle in males was larger than that in females on the right (males 2.44 [0.29] cm vs females 1.70 [0.22] cm) and on the left (males 2.50 [0.28] cm vs females 1.72 [0.24] cm) reaching statistical significance ( P < .001). The mean width of the thyro-arytenoid muscle in males was larger than that in females on the right (males 0.68 [0.13] cm vs females 0.59 [0.11] cm) and on the left (males 0.68 [0.12] cm vs females 0.57 [0.12] cm) reaching statistical significance ( P < .001). The mean height of the thyro-arytenoid muscle in males was larger than that in females on the right (males 1.05 [0.21] cm vs females 0.95 [0.12] cm) and on the left (males 1.05 [0.21] cm vs females 0.95 [0.12] cm) reaching statistical significance ( P < .01 on the right and P < .05 on the left). The volume of the thyroarytenoid muscle in males was larger than that in females on the right (males 0.86 [0.25] mL vs females 0.48 [0.15] mL) and on the left (males 0.89 [0.27] mL vs females 0.48 [0.17] mL) reaching statistical significance ( P < .001). The results of this investigation clearly indicate a significant difference in these measurements between men and women.

SUCCESSFUL STENTING BY COMBINATION TECHNIQUE OF REVERSE FLOW AND DOWNSTREAM FILTERING FOR LONG CHRONIC TOTAL OCCLUSION OF THE CERVICAL VERTEBRAL ARTERY

Neurosurgery ◽  
2009 ◽  
Vol 65 (2) ◽  
pp. E378-E379 ◽  
Author(s):  
Tomonori Iwata ◽  
Takahisa Mori ◽  
Hiroyuki Tajiri ◽  
Masahito Nakazaki
Keyword(s):  
Vertebral Artery ◽  
Chronic Total Occlusion ◽  
Reverse Flow ◽  
Posterior Inferior Cerebellar Artery ◽  
Vertebrobasilar Insufficiency ◽  
Total Occlusion ◽  
Combination Technique ◽  
Left Posterior ◽  
The Right ◽  
Distal Filter

Abstract OBJECTIVE To report a case of successful recanalization using the combination technique of reverse flow and downstream filtering in chronic total occlusion of the bilateral vertebral artery (VA). Clinical Presentation A 59-year-old man had experienced attacks consisting of vertigo and/or dysarthria more than 1 year before presentation. He experienced symptoms despite the administration of antiplatelet drugs and presented to our institution. Diagnostic cerebral angiography demonstrated that the right VA was not occluded at the ostium but, rather, along its midcervical portion and that the left VA ended in the left posterior inferior cerebellar artery. Intervention Long chronic total occlusion of the right cervical VA was recanalized successfully and safely by reverse flow and downstream filtering with proximal flow blockade and a distal filter device positioned in the right brachial artery. Follow-up angiography at 1 year demonstrated no re-occlusion. The patient's symptoms disappeared after recanalization and did not recur. To our knowledge, there are no reports describing successful angioplasty and/or stenting for long chronic total occlusion of the cervical VA. CONCLUSION Stenting using the combination technique of reverse flow and downstream filtering can safely open even long chronic cervical VA occlusion and may be effective in the treatment of patients experiencing vertebrobasilar insufficiency due to bilateral chronic VA occlusion.

A radiographic computed tomography–based study to determine the ideal entry point, trajectory, and length for safe fixation using C-2 pars interarticularis screws

2010 ◽  
Vol 12 (6) ◽  
pp. 602-612 ◽  
Author(s):  
Daniel J. Hoh ◽  
Charles Y. Liu ◽  
Michael Y. Wang
Keyword(s):  
Entry Point ◽  
Ct Scans ◽  
Lateral Mass ◽  
Transverse Foramen ◽  
Inferior Aspect ◽  
Significant Difference ◽  
Pars Interarticularis ◽  
Entry Points ◽  
The Mean ◽  
Inferior Edge

Object Effective methods for fixation of the axis include C1–2 transarticular and C-2 pedicle screw placement. Both techniques pose a risk of vertebral artery (VA) injury in patients with narrow pedicles or an enlarged, high-riding VA. Pars screws at C-2 avoid the pedicle, but can cause VA injury with excessively long screws. Therefore, the authors evaluated various entry points and trajectories to determine ideal pars screw lengths that avoid breaching the transverse foramen. Methods Both pars were studied on 50 CT scans (100 total). Various pars lengths were assessed using 2 entry points and 3 trajectories (6 measurements). Entry point A was the superior one-fourth of the lateral mass. Entry point B was 3-mm rostral to the inferior aspect of the lateral mass. Using entry points A and B, Trajectory 1 was the minimum distance to the transverse foramen; Trajectory 2 was the maximum distance to the transverse foramen; and Trajectory 3 was the steepest angle to the pars/C-2 superior facet junction without transverse foramen breach. Results The mean patient age was 46 ± 17 years, and 84% of the CT scans reviewed were obtained in men. There was no significant difference in right or left measurements. Entry point B demonstrated greater pars lengths for each trajectory compared with entry point A (p < 0.0001). For both entry points, Trajectory 3 provided the greatest pars length. Using Trajectory 3 with entry point B, 84, 95, and 99% had a pars length that measured ≥ 18, 16, and 14 mm, respectively. Using Trajectory 3 with Entry point A, only 41, 64, and 87% had a pars length that measured ≥ 18, 16, and 14 mm, respectively. Conclusions Using an entry point 3-mm rostral to the inferior edge of the lateral mass and a trajectory directed toward the superior facet/pars junction, 99% of partes interarticularis in this study would tolerate a 14-mm screw without breach of the transverse foramen.

Study of Renal Iron Overload by T2* MRI in a Large Cohort of Thalassemia Major Patients

Blood ◽  
2012 ◽  
Vol 120 (21) ◽  
pp. 5177-5177
Author(s):  
Antonella Meloni ◽  
Daniele De Marchi ◽  
Vincenzo Positano ◽  
Gaetano Giuffrida ◽  
Sabrina Armari ◽  
...  
Keyword(s):  
Iron Overload ◽  
Conflicts Of Interest ◽  
Left Kidney ◽  
Significant Negative Correlation ◽  
Thalassemia Major ◽  
Iron Deposition ◽  
Significant Difference ◽  
The Mean ◽  
The Right ◽  
T2 Mri

Abstract Abstract 5177 Background. Renal dysfunction has been reported in adult subjects with thalassemia major (TM) since 1975. One of the main cause is the iron overload consequent to regular transfusions. Multiecho T2* MRI is a well-established technique for cardiac and hepatic iron overload assessment, but there very few report concerning the kidneys. The aims of this study were to describe the T2* values of the kidneys in patients with TM, to investigate the correlation between renal and myocardial or hepatic siderosis and biventricular cardiac function. Methods. 119 TM patients (58 men, 30. 7 ± 8. 2 years) enrolled in the Myocardial Iron Overload (MIOT) networks underwent MRI. For the measurement of iron overload, multiecho T2* sequences were used. The left ventricle was segmented into a 16-segments standardized model and the T2* value on each segment was calculated as well as the global value. In the liver, the T2* value was assessed in a single region of interest (ROI) in a homogeneous area of the parenchyma. For each kidney, T2* values were calculated in three different ROIs and were averaged to obtain a representative value for the kidney. The mean T2* value over the kidneys was also calculated. Cine images were obtained to quantify biventricular morphological and functional parameters in a standard way. Results. T2* values in the right kidney were significant lower than in the left kidney (40. 3±11. 9 ms vs 44. 1±12. 7 ms, P<0. 0001). The mean T2* value over the kidneys was 42. 2±11. 9 ms and 40 patients (33. 6%) had a pathological value (T2*<36 ms, lower limit of normal evaluated on 20 healthy subjects). The mean T2* value did not show a significant difference amongst men ad women (43. 2±11. 7 ms versus 41. 3±12. 1 ms, P=0. 378). The mean T2* values increased with age in a significant manner (r=0. 321, P<0. 0001). There was a significant negative correlation between serum ferritin levels and mean renal T2* values (r=-0. 446, P<0. 0001). Significant positive correlations of the mean T2* values were demonstrated for liver (r=0. 511, P<0. 0001) and global heart (r=0. 262, P=0. 004) T2* values (Figure 1). No correlation was found between renal iron overload and bi-ventricular function parameters. Conclusions. Systemic T2* differences between left and right kidneys were found, with significant lower values in the right one. Mean T2* value increased with age. We confirmed that kidney iron deposition was not very common in TM, but it was correlated with iron deposition in liver and heart. Disclosures: No relevant conflicts of interest to declare.

The vertebral artery and the cervical pedicle: morphometric analysis of a critical neighborhood

2010 ◽  
Vol 13 (1) ◽  
pp. 52-60 ◽  
Author(s):  
Andre Tomasino ◽  
Karishma Parikh ◽  
Heiko Koller ◽  
Walter Zink ◽  
A. John Tsiouris ◽  
...  
Keyword(s):  
Vertebral Artery ◽  
Ct Angiography ◽  
Posterior Instrumentation ◽  
Pedicle Screws ◽  
Safe Zone ◽  
Transverse Foramen ◽  
Sagittal Diameter ◽  
Entry Points ◽  
Cervical Pedicle ◽  
The Mean

Object The purpose of this retrospective study was to quantify the anatomical relationship between the vertebral artery (VA), the cervical pedicle, and its surrounding structures, including the incidence of irregularities. Additionally, data delineating a “safe zone,” and these data's application during instrumentation with transpedicular cervical screw fixation were considered. The anatomical proximity of the VA to the cervical pedicle prevents spine surgeons from preferring cervical pedicle screws (CPSs) over lateral mass screws at levels C3–6. Accurate placement of CPSs is often difficult to determine, because this definition can vary between 1 and 4 mm of lateral “noncritical” and “critical” pedicle breaches. No previous study in a western population has investigated the VA's proximity to the cervical pedicle, its percentage of occupancy in the transverse foramen (TF), and the incidence of irregular VA pathways. Methods One hundred twenty-seven consecutive patients who underwent CT angiography of the neck were enrolled in this study. The measurements included the following: medial pedicle border to VA; lateral pedicle border to VA; pedicle diameter (PD); sagittal diameter of the VA; coronal diameter of the VA; sagittal diameter of the TF; and coronal diameter of the TF. The cross-sections of the VA and the TF were measured to determine the occupation ratio of the VA. In addition, a safe zone was defined based on all lateral pedicle border to VA measurements in which the VA was within the TF. The level of entry of the VA into the TF as well as irregularities of the VA and the cervical pedicles were recorded. Results Vertebral artery dominance on the left side was seen in 69.3% of cases. The mean PD increased from 4.9 to 6.5 mm (from C-3 to C-7, respectively). Statistically significantly bigger PDs were seen in males. The mean PD at C-2 was 5.6 mm. Entry of the VA at C-6 was seen in approximately 80% of cases. The TF occupation ratio of the VA was found to be the greatest in C-4 and C-7 (37.1 and 74.2%, respectively). The safe zone increased from C-2 to C-6 (1.1 to 1.7 mm, respectively), but was only 0.65 mm at C-7. In 23.6% of cases, an irregular pathway of the VA or irregular anatomy of a cervical pedicle was seen, with the highest incidence of irregularities found at C-2. Conclusions Computed tomography angiography is a valuable tool that can help determine the relationships between cervical pedicles and the VA as well as irregular VA pathways. Pedicle diameter, safe zone, and occupational ratio of the VA in the foramen determine the risk associated with instrumentation and should be assessed individually. Based on the authors' measurements, C-4 and C-7 can be considered critical levels for CPS placement. Because of this and the high incidence of irregular VA pathways and different entry points, it may be helpful to review neck CT angiography studies before considering posterior instrumentation procedures in the cervical spine.

Vertebrobasilar insufficiency secondary to vertebral artery occlusion from a fibrous band

1982 ◽  
Vol 56 (4) ◽  
pp. 581-583 ◽  
Author(s):  
Timothy Mapstone ◽  
Robert F. Spetzler
Keyword(s):  
Vertebral Artery ◽  
Artery Occlusion ◽  
Vertebrobasilar Insufficiency ◽  
Fibrous Band ◽  
Content Type ◽  
Vertebral Artery Occlusion ◽  
The Right ◽  
Band Crossing ◽  
Fine Print

✓ A case is described in which vertebral artery occlusion, caused by a fibrous band, occurred whenever the patient turned his head to the right side, resulting in vertigo and syncope whenever the head was turned to the right. Release of a fibrous band crossing the vertebral artery 2 cm from its origin relieved the patient's vertebral artery constriction and symptoms.

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