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by the American Institute of Ultrasound in Medicine J Ultrasound Med 21:747-751 • 0278-4297 Jugular Valve IncompetenceA Study Using Air Contrast Ultrasonography on a General PopulationDipartimento di Scienze Mediche e Chirurgiche, Università Degli Studi di Brescia, Brescia, Italy. Nabil Maalikjy Akkawi, MD, Clinica Neurologica II, Spedali Civili, Piazzale Spedali Civili, 25100 Brescia, Italy.
Objective. Internal jugular valves are the only venous valves between the heart and the brain. Conditions such as coughing and other precipitating activities may result in retrograde cerebral venous flow because of the absence or presence of internal jugular valve incompetence, allowing brief transmission of high venous pressure and resulting in brain disturbance. Knowledge of these valves and their noninvasive evaluation might be useful in clinical practice. Methods. We applied air contrast ultrasonographic venography to a large sample of healthy subjects (n = 125) to evaluate the ultrasonographic aspects of internal jugular valves and their competence. Results. The valves were observed in 121 (96.8%) of 125 subjects and were present bilaterally in 107 (85.6%) and unilaterally in 14 (11.2%). In 4 subjects we did not detect the valves. Retrograde venous flow was present in 48 (38.4%) of 125 subjects. The frequency of internal jugular valve incompetence was significantly higher on the right side (36 [30.2%] of 119) than on the left (7 [6.4%] of 109; P < .0001). Retrograde venous flow due to incompetence of jugular valves was significantly more frequent at older ages (<50 years, 20%; and  50 years, 38.75%; P < .03) and was more frequent in men (33 [25%] of 132) than in women (10 [10.41%] of 96; P < .02). Conclusions. Air contrast ultrasonographic venography is a noninvasive method for evaluating internal jugular valves and identifying retrograde venous flow. This information may be useful in clinical and interventional care.
Key Words: air contrast ultrasonography • internal jugular valve incompetence • venography Abbreviations: ACUV, air contrast ultrasonographic venography • IJ, internal jugular • RVF, retrograde venous flow
Internal jugular (IJ) veins are involved in the principle route of cerebral venous drainage.1 The distal portion of IJ veins is characterized by the presence of valves, which are the only venous valves between the right atrium and the brain. An autopsy study showed the presence of these structures in 93.3% of cases, most being bicuspid.2 The absence or incompetence of IJ valves has been associated with neurologic symptoms, because in conditions such as coughing, straining to defecate, the Valsalva maneuver, and chest compression during cardiopulmonary resuscitation, the transmission of intrathoracic pressure to the IJ vein is not counterbalanced. This in turn might determine cerebral venous engorgement, increased intracranial pressure, and hence transient brain disturbances.3 Knowledge of these valves and their noninvasive evaluation might be useful in clinical practice, because IJ veins are increasingly used for vascular access to avoid damage during percutaneous procedures of these delicate structures. Furthermore, there is evidence that IJ valve incompetence may represent a risk factor for transient global amnesia.4,5 In this regard, to our knowledge no studies have investigated the prevalence of IJ valve incompetence in a general population and whether it is dependent on demographic variables such as sex or age. Previously, IJ valve competence was investigated in a few cases by IJ venography during the Valsalva maneuver or coughing.6 However, IJ venography is an invasive procedure and is not free from risk of associated complications. More recently, some authors have proposed the use of color-coded duplex ultrasonography.4 However, color-coded duplex ultrasonography is unreliable and difficult to interpret, because venous flow might be disturbed as a result of pulsation of nearby arteries.5 Intravenous air contrast agent injection during the Valsalva maneuver combined with B-mode monitoring of the IJ veins has been proposed recently for assessing the competence of the IJ valves.7 In the present study, we applied air contrast ultrasonographic venography (ACUV) to a large sample of healthy subjects to evaluate the presence, location, and ultrasonographic aspects of the valves, the prevalence of IJ valve incompetence, and the relationship with demographic variables.
The study was conducted in accordance with local clinical research regulations. Written informed consent was obtained from all subjects. The study was performed on healthy subjects, including at least 10 for each age decade (range, 20–79 years). None of the subjects had a history of cerebrovascular disorders, pulmonary disease, right-sided heart failure, tricuspid insufficiency, superior vena cava obstruction, or any neurologic diseases or deficits, and none had received notable trauma to the cervical and supraclavicular region. Sonographic examination was performed with a 7.5-MHz linear transducer and a color-coded ultrasonographic system (Sonoline Elegra; Siemens AG, Munich, Germany). Internal jugular valves and their competence were investigated with ACUV. The volunteers rested in a supine position with the head slightly tilted upward and slightly turned to the contralateral side. The site of investigation of the jugular vein was 1.5 to 2.0 cm distal to the brachiocephalic vein.
The flow pattern and morphologic characteristics of the IJ valves were investigated bilaterally before and after the Valsalva maneuver. The Valsalva maneuver lasted for 10 seconds and was monitored by a pressure gauge connected to a flexible tube. Air contrast ultrasonographic venography was performed by monitoring the jugular veins with B-mode real-time ultrasonography before and after intravenous injection of agitated air and saline (1 mL of air and 9 mL of normal saline manually agitated). As noticed by Ratanakorn et al,7 in the case of valve incompetence, contrast air bubbles appear on B-mode imaging as distinct, bright, mobile echoes in the IJ vein (Figs. 1 and 2
The study included 125 subjects (52 women and 73 men) with a mean age ± SD of 53.52 ± 16.76 years. All detected valves were found in the distal portion of the IJ veins just proximal to their distal bulb. The valves were observed in 121 (96.8%) of 125 subjects. There was no significant difference in the frequency of the valves between women and men. Valves were present bilaterally in 107 subjects (85.6%), involving 45 (86.5%) of 52 women and 62 (84.9%) of 73 men. Unilateral valves were observed in 14 subjects (11.2%; 6 women and 8 men): 12 (5 women and 7 men) on the right and 2 (1 woman and 1 man) on the left. In 4 subjects (1 woman and 3 men), we failed to detect the valves. Of the 228 valves, only 2 were unicuspid, made up of 1 left-sided valve in a man and 1 right-sided valve in a woman, whereas the remaining valves (99.1%) were bicuspid (Fig. 3  ).
The total number of subjects with right, left, or bilateral retrograde venous flow (RVF) was 48 (38.4%) of 125. The 4 subjects in whom valves were not detected had RVF in both the right and left IJ veins. Of the subjects with bilateral jugular valves (n = 107), 29 had right RVF, 4 had left RVF, and 3 had bilateral RVF. In those subjects with unilateral jugular valves (n = 14), 4 had right RVF due to incompetence of the jugular valves, whereas in another 4 subjects, RVF was present on the left side where the valves were not detected. In the remaining 4 subjects with unilateral right valves and the 2 subjects with unilateral left valves, we could not detect RVF on either side. Thus, the total number of RVF cases in 125 subjects was 55, as shown in Figure 3  .
The frequency of IJ valve incompetence was greater on the right side (36 [30.2%] of 119) than on the left (7 [6.4%] of 109;
The aim of this study was to evaluate the prevalence of IJ valves in the general population and to determine whether ACUV is a good method for assessment of the valves, giving adequate information on their presence, morphologic characteristics, location, and competence. Our study compares well with previous reports in the literature.2,8 In agreement with a large autopsy study, IJ valves were shown in 96.8% of subjects, and there was no association with sex.2 Although some authors have described IJ valves on the left and right sides with the same prevalence,9 we found a slight right-sided predominance, as previously reported by others.2,8 Such a discrepancy probably has to be interpreted as a result of an artifact, because the left IJ vein has a more medial distal portion than the right, hence the visualization of the valve behind the clavicle, especially with certain body habitus, which would make imaging more difficult.10 The presence and exact morphologic characteristics of the valves were often difficult to discern on previous ultrasonographic studies. In a previous study, less than half of the valves were bicuspid,2 whereas in our study, 99.1% of the valves found were bicuspid. Our data are in agreement with a large cadaveric study.2,8,9,11 The discrepancy between our data and previous ultrasonographic studies is likely due to the fact that contrast air bubbles elicit contrast on the valve's leaflets during the Valsalva maneuver, therefore facilitating detection of the precise limits of each leaflet. We know of 2 reports of high-resolution ultrasonographic visualization of IJ valves in the literature.2,12 However, our study investigated retrograde jugular venous flow with ACUV on a large sample of healthy subjects. In this report, we showed retrograde jugular venous flow in a relatively high number of subjects (38.4%). Furthermore, we found a significant association between the occurrence of retrograde jugular venous flow due to incompetence of jugular valves and both sex and age. These findings suggest that IJ valve incompetence might not be a static phenomenon and might be induced by various factors. Incompetence of jugular valves was more frequent on the right side than on the left. In this regard, we propose that the right-left discrepancy may be due to the fact that the right valves sustain higher retrograde pressure during Valsalva-like activities, being closer to the intrathoracic cavity, and therefore are more susceptible to failure. If this is true, then all conditions favoring increase of intrathoracic pressure may predispose IJ valves to incompetence. The clinical importance of such an abnormality is not clear yet. Internal jugular valves collapse rhythmically during right atrial contractions and help maintain unidirectional anterograde blood flow, and they close when reversal of the anterograde pressure gradient occurs, as during the Valsalva maneuver. Venous back pressure due to incompetence or absence of IJ valves, if sufficiently high, may give rise to transient disturbances of the brain. It has been hypothesized that incompetence of these valves may be associated with respiratory brain syndrome.12–15 Positive end-expiratory pressure for long periods may induce incompetence of the IJ valves with consequent cerebral venous back flow contributing to the venous engorgement shown in these patients. Another clinical manifestation may be cough-induced headaches, which may be caused by a sudden rise of the intrathoracic pressure with consequent sudden venous back pressure to the brain.13 In conclusion, this study shows that ACUV is a noninvasive method for evaluating IJ valves and identifying RVF.
Received February 12, 2002, from the Dipartimento di Scienze Mediche e Chirurgiche, Università Degli Studi di Brescia, Brescia, Italy.
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Abstract
Introduction
2, P < .0001). Valve incompetence was significantly more frequent in men (33 [25%] of 132) than in women (10 [10.41%] of 96; 
