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DOI: 10.1148/rg.265055728
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RadioGraphics 2006;26:1501-1515
© RSNA, 2006

EDUCATION EXHIBIT

It’s Not a Cervical Lymph Node, It’s a Vein: CT and MR Imaging Findings in the Veins of the Head and Neck1

Edward J. Escott, MD and Barton F. Branstetter, MD

1 From the Departments of Radiology (E.J.E., B.F.B.) and Otolaryngology (B.F.B.), University of Pittsburgh Medical Center, 200 Lothrop St, D-132, Pittsburgh, PA 15213-2582. Received October 20, 2005; revision requested January 17, 2006 and received March 7; accepted March 8. All authors have no financial relationships to disclose. Address correspondence to E.J.E. (e-mail: escottej{at}upmc.edu).


   Abstract
Top
 Abstract
Introduction
 Normal Anatomy and Common...
 Variable Appearances and...
 Conclusions
 References
 
The anatomy and imaging appearances of the veins of the head and neck can vary considerably, and normal veins may mimic disease processes at computed tomography (CT) and magnetic resonance (MR) imaging. On unenhanced CT scans, aberrant veins may be difficult to differentiate from lymph nodes or other pathologic conditions. Even at contrast material–enhanced CT, differences in venous enhancement or the mixing of opacified with nonopacified blood can lead to confusion, particularly if the vein is focally dilated. Similarly, the size and signal intensity of head and neck veins may vary at MR imaging due to slow or turbulent flow or variable enhancement, resulting in misdiagnosis. A thorough understanding of the normal venous anatomy and common variants is necessary to properly differentiate an unopacified or focally dilated vein from lymphadenopathy or some other disease entity and can help the radiologist avoid the erroneous interpretation of findings.

© RSNA, 2006


   Introduction
Top
 Abstract
 Introduction
Normal Anatomy and Common...
 Variable Appearances and...
 Conclusions
 References
 
The anatomy and imaging appearance of the veins in the head and neck can be highly variable, such that the veins can occasionally simulate disease entities, particularly pathologic lymph nodes or other neck masses. Enhancement characteristics can be variable at magnetic resonance (MR) imaging and computed tomography (CT) and can simulate disease processes such as venous occlusion or thrombus. Knowledge of the normal venous anatomy, common variants, enhancement characteristics, and variations in signal intensity and attenuation at MR imaging and CT can help avoid these diagnostic pitfalls. In this article, we demonstrate the normal venous anatomy and common variants of the head and neck to help the radiologist correctly recognize the appearance of these entities so as not to confuse them with pathologic processes. Examples of normal venous anatomy and common variants were collected from routine clinical cases in a busy academic radiology department by two neuroradiologists who spend the majority of their clinical time interpreting head and neck imaging studies.


   Normal Anatomy and Common Variants
Top
 Abstract
 Introduction
 Normal Anatomy and Common...
Variable Appearances and...
 Conclusions
 References
 
The major common drainage pathways of the head are the facial veins, dural venous sinuses, and basilar emissary veins. In the neck, the jugular veins and vertebral veins are dominant. It is through these systems and their intercommunications that the majority of the venous blood flows from the cranial structures toward the heart (Fig 1).


Figure 1
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  		Figure 1.  Drawing illustrates the major venous drainage of the head and neck. The veins are shown in various shades of blue, with veins of a similar color representing the components of a major venous system. From darkest to lightest, these systems are the internal jugular vein and major central veins, the external jugular venous system and vertebral venous system, the posterior facial vein and tributaries, and the anterior facial vein and tributaries. Additional smaller veins are shown in purple.

 

Anterior Facial Vein
The anterior facial vein is formed as a direct continuation of the angular vein at the root of the nose (Fig 2a, 2b) (1). It continues to course superficial and lateral to the submandibular gland, where it has been described as a landmark to help differentiate intra- from extraglandular lesions (Figs 2c, 2d, 3, 4) (2). The vein then joins with the anterior branch of the posterior facial vein to form the common facial vein, which in turn enters the internal jugular vein (Figs 5, 6).


Figure 2
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  		Figure 2a.  Course of the anterior facial vein. (a) Contrast material–enhanced CT scan obtained at the level of the inferior orbit shows the angular veins (arrows) along the sides of the nose. (b) Contrast-enhanced CT scan obtained at the level of the far inferior orbit shows the anterior facial veins (arrows) as a direct continuation of the angular veins. (c) Contrast-enhanced CT scan obtained at the level of the maxillary sinuses shows the anterior facial veins (arrows) coursing along the anterior aspect of the maxillae. (d) Contrast-enhanced CT scan obtained at the level of the maxillary alveolar ridge shows the anterior facial veins (arrows) coursing posteriorly.

 

Figure 2
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  		Figure 2b.  Course of the anterior facial vein. (a) Contrast material–enhanced CT scan obtained at the level of the inferior orbit shows the angular veins (arrows) along the sides of the nose. (b) Contrast-enhanced CT scan obtained at the level of the far inferior orbit shows the anterior facial veins (arrows) as a direct continuation of the angular veins. (c) Contrast-enhanced CT scan obtained at the level of the maxillary sinuses shows the anterior facial veins (arrows) coursing along the anterior aspect of the maxillae. (d) Contrast-enhanced CT scan obtained at the level of the maxillary alveolar ridge shows the anterior facial veins (arrows) coursing posteriorly.

 

Figure 2
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  		Figure 2c.  Course of the anterior facial vein. (a) Contrast material–enhanced CT scan obtained at the level of the inferior orbit shows the angular veins (arrows) along the sides of the nose. (b) Contrast-enhanced CT scan obtained at the level of the far inferior orbit shows the anterior facial veins (arrows) as a direct continuation of the angular veins. (c) Contrast-enhanced CT scan obtained at the level of the maxillary sinuses shows the anterior facial veins (arrows) coursing along the anterior aspect of the maxillae. (d) Contrast-enhanced CT scan obtained at the level of the maxillary alveolar ridge shows the anterior facial veins (arrows) coursing posteriorly.

 

Figure 2
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  		Figure 2d.  Course of the anterior facial vein. (a) Contrast material–enhanced CT scan obtained at the level of the inferior orbit shows the angular veins (arrows) along the sides of the nose. (b) Contrast-enhanced CT scan obtained at the level of the far inferior orbit shows the anterior facial veins (arrows) as a direct continuation of the angular veins. (c) Contrast-enhanced CT scan obtained at the level of the maxillary sinuses shows the anterior facial veins (arrows) coursing along the anterior aspect of the maxillae. (d) Contrast-enhanced CT scan obtained at the level of the maxillary alveolar ridge shows the anterior facial veins (arrows) coursing posteriorly.

 

Figure 3
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  		Figure 3.  Course of the anterior facial vein relative to the submandibular gland. Contrast-enhanced CT scan obtained at the level of the submandibular glands shows the right anterior facial vein (solid arrow) coursing along the superolateral aspect of the right submandibular gland. Note the anterior branch of the right posterior facial vein (dotted arrow) coursing along the posterior aspect of the submandibular gland.

 

Figure 4
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  		Figure 4.  Anterior facial vein as a landmark for differentiating intra- from extraglandular lesions. Contrast-enhanced CT scan obtained at the level of the submandibular glands shows the right anterior facial vein (dotted line) separating the right submandibular gland (SM) from adjacent abnormal lymph nodes (N).

 

Figure 5
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  		Figure 5.  Junction of the anterior facial vein and the anterior branch of the posterior facial vein to form the common facial vein. Contrast-enhanced CT scan shows the anterior facial veins (AFv) and the anterior (AB) and posterior (PB) branches of the posterior facial vein. The anterior facial vein and the anterior branch of the posterior facial vein join to form the common facial vein (CFv).

 

Figure 6
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  		Figure 6.  Common facial vein entering the internal jugular vein. Contrast-enhanced CT scan obtained at the level of the piriform sinuses shows the common facial vein (CFv) draining into the internal jugular vein (IJ).

 
In a recent article, Chikui et al (3) agreed that the anterior facial vein is useful for differentiating intra- from extraglandular lesions but cited difficulties with this method in that the vein cannot always be identified and sometimes courses within a lesion.

Posterior Facial Vein (Retromandibular Vein)
The frontal and parietal branches of the superficial temporal vein join to form the main trunk of the superficial temporal vein, which then enters the parotid gland (Fig 7) (1). The posterior facial vein (retromandibular vein) is formed by the main trunk of the superficial temporal vein joining with the internal maxillary vein in the parotid gland (Fig 7b). The internal maxillary vein is a short vein that drains the pterygoid venous plexus. The posterior facial vein divides into anterior and posterior branches (Fig 8).


Figure 7
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  		Figure 7a.  Formation of the posterior facial vein. (a) Contrast-enhanced CT scan obtained at the level of the right temporal scalp shows the frontal and parietal branches of the superficial temporal vein. (b) Contrast-enhanced CT scan obtained at the superior aspect of the parotid gland shows the main trunk of the right superficial temporal vein (ST v) just before it joins with the internal maxillary vein (IM v). The pterygoid venous plexus (arrows) lies medially.

 

Figure 7
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  		Figure 7b.  Formation of the posterior facial vein. (a) Contrast-enhanced CT scan obtained at the level of the right temporal scalp shows the frontal and parietal branches of the superficial temporal vein. (b) Contrast-enhanced CT scan obtained at the superior aspect of the parotid gland shows the main trunk of the right superficial temporal vein (ST v) just before it joins with the internal maxillary vein (IM v). The pterygoid venous plexus (arrows) lies medially.

 

Figure 8
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  		Figure 8a.  Posterior facial vein. (a) Contrast-enhanced CT scan shows the right posterior facial vein (retromandibular vein) (arrow) in the right parotid gland. (b) Contrast-enhanced CT scan obtained just inferior to a shows the anterior (dashed white arrow) and posterior (solid white arrow) branches of the right posterior facial vein to be nearly equal in size. The anterior facial vein (black arrow) courses posteriorly to join with the anterior branch of the posterior facial vein.

 

Figure 8
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  		Figure 8b.  Posterior facial vein. (a) Contrast-enhanced CT scan shows the right posterior facial vein (retromandibular vein) (arrow) in the right parotid gland. (b) Contrast-enhanced CT scan obtained just inferior to a shows the anterior (dashed white arrow) and posterior (solid white arrow) branches of the right posterior facial vein to be nearly equal in size. The anterior facial vein (black arrow) courses posteriorly to join with the anterior branch of the posterior facial vein.

 
The anterior branch of the posterior facial vein extends medially and inferiorly superficial to the external carotid artery and beneath the facial nerve, coursing posterior to the submandibular gland, where it joins with the anterior facial vein to form the common facial vein (Figs 5, 8b).

The posterior branch of the posterior facial vein extends inferiorly in the parotid gland and joins with the posterior auricular vein to form the external jugular vein in or immediately inferior to the parotid gland (Fig 9).


Figure 9
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  		Figure 9a.  Posterior branch of the posterior facial vein and formation of the external jugular vein. (a) Contrast-enhanced CT scan shows the posterior auricular vein (dotted arrow) and the posterior branch of the posterior facial vein (solid arrow) in the right parotid gland. (b) Contrast-enhanced CT scan obtained just below the parotid gland shows the posterior branch of the posterior facial vein (solid arrow) and the posterior auricular vein (dotted arrow) joining to form the external jugular vein. (c) Contrast-enhanced CT scan obtained inferior to b shows the right external jugular vein (arrow) slightly below its origin, superficial to the sternocleidomastoid muscle (SCM).

 

Figure 9
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  		Figure 9b.  Posterior branch of the posterior facial vein and formation of the external jugular vein. (a) Contrast-enhanced CT scan shows the posterior auricular vein (dotted arrow) and the posterior branch of the posterior facial vein (solid arrow) in the right parotid gland. (b) Contrast-enhanced CT scan obtained just below the parotid gland shows the posterior branch of the posterior facial vein (solid arrow) and the posterior auricular vein (dotted arrow) joining to form the external jugular vein. (c) Contrast-enhanced CT scan obtained inferior to b shows the right external jugular vein (arrow) slightly below its origin, superficial to the sternocleidomastoid muscle (SCM).

 

Figure 9
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  		Figure 9c.  Posterior branch of the posterior facial vein and formation of the external jugular vein. (a) Contrast-enhanced CT scan shows the posterior auricular vein (dotted arrow) and the posterior branch of the posterior facial vein (solid arrow) in the right parotid gland. (b) Contrast-enhanced CT scan obtained just below the parotid gland shows the posterior branch of the posterior facial vein (solid arrow) and the posterior auricular vein (dotted arrow) joining to form the external jugular vein. (c) Contrast-enhanced CT scan obtained inferior to b shows the right external jugular vein (arrow) slightly below its origin, superficial to the sternocleidomastoid muscle (SCM).

 
Common Facial Vein
The common facial vein is formed by the union of the anterior facial vein and the anterior branch of the posterior facial vein posterior to the submandibular gland (Fig 5). The common facial vein then extends inferiorly to drain into the internal jugular vein (see "Anterior Facial Vein") (Fig 6).

External and Anterior Jugular Veins
As mentioned earlier, the external jugular vein is formed by the confluence of the posterior branch of the posterior facial vein and the posterior auricular vein in or just below the parotid gland (Fig 9b, 9c). It then travels caudally superficial to the sternocleidomastoid muscle (Figs 9c, 10) and along the anterolateral lower neck (Fig 11a), terminating in the jugulosubclavian confluence, the subclavian vein (Fig 11b), or, least commonly, the internal jugular vein (4,5). Variations include partial duplications (Fig 11a), confluence with a branch of the anterior jugular vein, termination of the anterior jugular vein in the external jugular vein (Fig 11a), and varying caliber of the veins. The external and internal jugular veins typically have a reciprocal size relationship (Fig 11a) (4,5). The anterior jugular veins begin at the hyoid level from the confluence of several superficial veins and may receive communication from the facial veins or the internal jugular vein (Fig 10) (4). The anterior jugular veins extend along the anterior border of the sternocleidomastoid muscles medially or between the midline and the anterior border of these muscles (Fig 11a) and generally terminate in either the subclavian veins or the external jugular veins. They may communicate with the contralateral vessels or with other veins via the anterior jugular arch (jugular venous arch) at the base of the neck and upper chest (4,6). The termination of the anterior jugular veins and the jugular venous arch can create a collateral network between the anterior, external, and internal jugular veins and subclavian veins, and catheters or thrombus can at times extend into these vessels (6).


Figure 10
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  		Figure 10.  External jugular venous system in the upper neck. Contrast-enhanced CT scan obtained at the level of the submandibular glands shows the left anterior jugular vein (AJ) and a branch (CB) from the common facial vein (CF) coursing medial to the submandibular gland toward the anterior jugular vein. The common facial vein continues caudally to drain into the internal jugular vein (IJ). EJ = external jugular vein.

 

Figure 11
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  		Figure 11a.  External jugular venous system in the lower neck to the external jugular terminus in the subclavian veins. (a) On a contrast-enhanced CT scan obtained at the level of the thyroid gland, the external jugular veins (solid arrows) are seen laterally. Note their reciprocal size relationship to the internal jugular veins (arrowheads). Note also the different degrees of venous enhancement: The larger left external jugular vein demonstrates soft-tissue attenuation, so that it could be mistaken for a lymph node on a single section. The left anterior jugular vein (open arrow) is seen crossing the sternocleidomastoid muscle posterolaterally and terminates in the left external jugular vein. Dashed arrows indicate duplicate right anterior jugular veins. (b) On a contrast-enhanced CT scan obtained at the level of the clavicles, the external jugular veins are seen terminating bilaterally in the subclavian veins (solid arrows). The internal jugular veins (arrowheads) are seen adjacent to the common carotid arteries (open arrows).

 

Figure 11
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  		Figure 11b.  External jugular venous system in the lower neck to the external jugular terminus in the subclavian veins. (a) On a contrast-enhanced CT scan obtained at the level of the thyroid gland, the external jugular veins (solid arrows) are seen laterally. Note their reciprocal size relationship to the internal jugular veins (arrowheads). Note also the different degrees of venous enhancement: The larger left external jugular vein demonstrates soft-tissue attenuation, so that it could be mistaken for a lymph node on a single section. The left anterior jugular vein (open arrow) is seen crossing the sternocleidomastoid muscle posterolaterally and terminates in the left external jugular vein. Dashed arrows indicate duplicate right anterior jugular veins. (b) On a contrast-enhanced CT scan obtained at the level of the clavicles, the external jugular veins are seen terminating bilaterally in the subclavian veins (solid arrows). The internal jugular veins (arrowheads) are seen adjacent to the common carotid arteries (open arrows).

 
Internal Jugular Vein
The internal jugular vein begins in the posterior compartment of the jugular foramen, where it is mildly dilated (superior bulb) as the continuation of the sigmoid sinus (Fig 12) (4). It is joined by the inferior petrosal sinus in or below the jugular foramen (Fig 13) (7). Additional tributaries include the common facial, lingual, pharyngeal, superior, and middle thyroid veins and sometimes the occipital vein (Fig 6). The internal jugular vein then continues caudally in the neck lateral to the internal carotid and common carotid arteries and lies within the carotid sheath (Figs 10, 11). The thoracic duct on the left and the right lymphatic duct usually open into the angle of the union of the internal jugular and subclavian veins. The internal jugular veins join with the subclavian veins to form the brachiocephalic veins (Fig 14).


Figure 12
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  		Figure 12.  Formation of the internal jugular vein. Contrast-enhanced CT scan shows the right internal jugular vein (IJ) in the jugular foramen and the sigmoid sinus (SS) draining into the vein.

 

Figure 13
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  		Figure 13a.  Variations in the emissary veins and dural venous sinuses: inferior petrosal sinus. Three-dimensional contrast-enhanced spoiled gradient-recalled acquisition in the steady state MR images (25/5) (b obtained inferior to a) show a large right inferior petrosal sinus (arrow) extending inferiorly and laterally toward the jugular bulb.

 

Figure 13
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  		Figure 13b.  Variations in the emissary veins and dural venous sinuses: inferior petrosal sinus. Three-dimensional contrast-enhanced spoiled gradient-recalled acquisition in the steady state MR images (25/5) (b obtained inferior to a) show a large right inferior petrosal sinus (arrow) extending inferiorly and laterally toward the jugular bulb.

 

Figure 14
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  		Figure 14.  Terminus of the internal jugular vein. Contrast-enhanced CT scan obtained at the level of the clavicles shows the right internal jugular vein (IJ) joining with the subclavian vein (SC) to form the brachiocephalic vein.

 
Vertebral Veins
The other major drainage pathway of intracranial blood is the vertebral venous system (Figs 15–17) (8). A number of emissary veins at the skull base provide alternative routes for intracranial drainage. The dominant routes are the anterior condylar veins (venous plexus of the hypoglossal nerve), the lateral and posterior condylar veins (condylar emissary veins), the anterior condylar confluence, the mastoid emissary veins, and, occasionally, the occipital emissary vein (Figs 13, 18, 19) (8–10). Other anastomotic networks also exist. These vessels drain into the internal or external vertebral venous plexus. The internal vertebral venous plexus is located along either the anterior or (less commonly) the posterior epidural space, and the external vertebral venous plexus is located along the anterior or posterior aspects of the vertebrae (as well as between the dorsal muscles) (11). The vertebral vein, like the vertebral artery venous plexus, follows the course of the vertebral artery and generally exits the spine at the level of the C6 transverse foramen (4,8). It receives tributaries from the internal and external vertebral venous plexuses (in part via the intervertebral veins) and from the deep and anterior cervical veins (Figs 15, 17) (11). In addition, Palombi et al (12) recently suggested that for much of its course within the transverse canal the vertebral vein is actually more similar in structure to a dural venous sinus, except at its proximal and distal ends (C1 and usually C6), where it forms a plexus. The plexus then forms a discrete vein upon exiting the transverse foramen in the lower cervical region. The vertebral vein then terminates in the brachiocephalic vein near the junction of the internal jugular and subclavian veins (4). San Millan Ruiz et al (8) suggested that the vertebral venous systems provide the primary route of cerebral blood return in the standing position, with the jugular veins serving in this capacity (a) in the supine position or (b) with increased central venous pressure in the standing position.


Figure 15
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  		Figure 15.  Vertebral venous system: internal and external venous plexuses. Contrast-enhanced fat-saturated T1-weighted MR image (repetition time msec/echo time msec =550/10) obtained at the level of C2 shows the anterior internal vertebral venous plexus (solid arrow) with anastomoses (dashed arrow) to the external vertebral venous plexus.

 

Figure 16
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  		Figure 16.  Vertebral venous system: vertebral artery venous plexus. Contrast-enhanced CT scan obtained through the midcervical region shows the vertebral artery venous plexus and intervertebral veins (black arrow) in the right transverse foramen. White arrow indicates the vertebral artery.

 

Figure 17
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  		Figure 17a.  Vertebral venous system in the lower neck. (a) Contrast-enhanced CT scan obtained at the level of C7 shows the reflux of contrast material into the internal vertebral venous plexus (black arrows). Note the collateral vessels (intervertebral veins) (white arrow) coursing to the external vertebral venous plexus–vertebral vein and the formation of the vertebral vein as it exits the transverse foramen (arrowhead). (b) Contrastenhanced CT scan obtained caudad to a shows the vertebral veins (solid arrows) coursing anteriorly. The right vertebral artery (dotted arrow) is seen anterior to the corresponding vertebral vein.

 

Figure 17
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  		Figure 17b.  Vertebral venous system in the lower neck. (a) Contrast-enhanced CT scan obtained at the level of C7 shows the reflux of contrast material into the internal vertebral venous plexus (black arrows). Note the collateral vessels (intervertebral veins) (white arrow) coursing to the external vertebral venous plexus–vertebral vein and the formation of the vertebral vein as it exits the transverse foramen (arrowhead). (b) Contrast-enhanced CT scan obtained caudad to a shows the vertebral veins (solid arrows) coursing anteriorly. The right vertebral artery (dotted arrow) is seen anterior to the corresponding vertebral vein.

 

Figure 18
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  		Figure 18.  Variations in the emissary veins and dural venous sinuses: anterior condylar vein. Contrast-enhanced CT scan shows enlargement of the right hypo-glossal canal with an associated enlarged anterior condylar vein (varix) (arrow).

 

Figure 19
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  		Figure 19.  Variations in the emissary veins and dural venous sinuses: mastoid emissary vein. Axial three-dimensional time-of-flight MR angiographic image (30/3) shows a large mastoid emissary vein (arrow) with flow-related enhancement.

 

   Variable Appearances and Variants That May Simulate Disease
Top
 Abstract
 Introduction
 Normal Anatomy and Common...
 Variable Appearances and...
Conclusions
 References
 
The most common pathologic structure for which a vein can be mistaken is an abnormal lymph node. This misinterpretation can have a variety of causes, including variable anatomy and size, side-to-side asymmetry, and lack of contrast, as well as variable degrees of enhancement related to bolus timing, which can cause a vein to appear to have soft-tissue attenuation at CT (Figs 11a, 20–22).


Figure 20
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  		Figure 20.  Common facial vein mimicking a lymph node. On a contrast-enhanced CT scan obtained at the level of the inferior aspect of the submandibular glands, the left common facial vein (solid arrow) is larger and enhances less than its contralateral counterpart (*), and thus could be mistaken for an enlarged lymph node. The vein was confirmed as such on the basis of its draining into the internal jugular vein on inferior images and its being formed by the anterior facial vein and the anterior branch of the posterior facial vein on superior images. The right common facial vein is seen draining into the internal jugular vein (dashed arrow).

 

Figure 21
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  		Figure 21.  Vein simulating a lymph node. Unenhanced CT scan of the neck shows a large left anterior jugular vein or distal common facial vein (arrow), a finding that was initially thought to represent a lymph node. The finding was confirmed to be a vein on the basis of its continuity with adjacent vessels. Because of contrast bolus timing or lack of contrast, veins can have different degrees of enhancement or attenuation similar to that of soft tissue, and, when asymmetric, they can simulate nodes.

 

Figure 22
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  		Figure 22a.  Variant course of the external jugular vein. (a) Initial unenhanced CT scan shows rounded structures (arrows) along the anterior aspects of the anterior scalene muscles. These findings might be mistaken for a pathologic process if unilateral but probably would not be misconstrued in this case because they are symmetric. Arrowheads indicate the internal jugular veins. (b, c) Contrast-enhanced CT scans reveal that the rounded structures in a represent the external jugular veins (arrows). These veins enhance somewhat less than the other veins due to contrast bolus timing and are seen to cross medially and to terminate atypically in the internal jugular veins (arrowheads) (c). The external jugular veins normally terminate in the subclavian veins.

 

Figure 22
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  		Figure 22b.  Variant course of the external jugular vein. (a) Initial unenhanced CT scan shows rounded structures (arrows) along the anterior aspects of the anterior scalene muscles. These findings might be mistaken for a pathologic process if unilateral but probably would not be misconstrued in this case because they are symmetric. Arrowheads indicate the internal jugular veins. (b, c) Contrast-enhanced CT scans reveal that the rounded structures in a represent the external jugular veins (arrows). These veins enhance somewhat less than the other veins due to contrast bolus timing and are seen to cross medially and to terminate atypically in the internal jugular veins (arrowheads) (c). The external jugular veins normally terminate in the subclavian veins.

 

Figure 22
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  		Figure 22c.  Variant course of the external jugular vein. (a) Initial unenhanced CT scan shows rounded structures (arrows) along the anterior aspects of the anterior scalene muscles. These findings might be mistaken for a pathologic process if unilateral but probably would not be misconstrued in this case because they are symmetric. Arrowheads indicate the internal jugular veins. (b, c) Contrast-enhanced CT scans reveal that the rounded structures in a represent the external jugular veins (arrows). These veins enhance somewhat less than the other veins due to contrast bolus timing and are seen to cross medially and to terminate atypically in the internal jugular veins (arrowheads) (c). The external jugular veins normally terminate in the subclavian veins.

 

Occasionally, a pseudoaneurysm of the internal jugular vein can occur, usually as a consequence of prior catheterization; this entity can be mistaken for an enlarged node or neoplasm (Fig 23) (13). A vertebral vein varix can simulate a node as well as an aneurysm of adjacent arteries (Fig 24). Sometimes it is difficult if not impossible to differentiate a venous structure from a lymph node. Contrast material can be one of the most helpful aids, although bolus timing can be an issue, and images obtained after a short delay may be helpful for ensuring homogeneous venous opacification (Figs 22–24). If a new study is performed without contrast material, a search for a prior contrast-enhanced study may be helpful. The ability to follow a structure on adjacent images can help confirm its vascular nature; however, areas of focal venous dilatation can sometimes be misleading. Nevertheless, following a structure, in combination with the knowledge of normal venous anatomy and variants, usually allows differentiation.


Figure 23
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  		Figure 23a.  Internal jugular venous pseudoaneurysm mimicking a mass. The patient, who had undergone multiple renal transplantations and placement of central catheters, presented with a right-sided neck mass that changed in size with changes in his position. (a) Initial unenhanced CT scan obtained at the base of the neck shows a "mass" (arrow) lateral to the right internal jugular vein (arrowhead). The "mass" was initially interpreted as a level 4 node. (b) On a follow-up contrast-enhanced CT scan, the "mass" (large arrow) shows enhancement similar to that of the adjacent internal jugular vein (arrowhead) and communicates with the vein. The findings lateral to the left internal jugular vein likely represent a combination of an additional small pseudoaneurysm, small nodes, and possibly a dilated distal thoracic duct (small arrows). (c) Inhomogeneously fat-saturated T2-weighted MR image (3667/99) shows a "flow void" within the "mass" (arrow), with an appearance similar to that of the adjacent internal jugular vein (arrowhead). This finding confirmed the vascular nature of the "mass," which presumably represents a venous pseudoaneurysm related to prior catheter placement. Venous pseudoaneurysm is an uncommon complication of internal jugular vein catheterization (13).

 

Figure 23
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  		Figure 23b.  Internal jugular venous pseudoaneurysm mimicking a mass. The patient, who had undergone multiple renal transplantations and placement of central catheters, presented with a right-sided neck mass that changed in size with changes in his position. (a) Initial unenhanced CT scan obtained at the base of the neck shows a "mass" (arrow) lateral to the right internal jugular vein (arrowhead). The "mass" was initially interpreted as a level 4 node. (b) On a follow-up contrast-enhanced CT scan, the "mass" (large arrow) shows enhancement similar to that of the adjacent internal jugular vein (arrowhead) and communicates with the vein. The findings lateral to the left internal jugular vein likely represent a combination of an additional small pseudoaneurysm, small nodes, and possibly a dilated distal thoracic duct (small arrows). (c) Inhomogeneously fat-saturated T2-weighted MR image (3667/99) shows a "flow void" within the "mass" (arrow), with an appearance similar to that of the adjacent internal jugular vein (arrowhead). This finding confirmed the vascular nature of the "mass," which presumably represents a venous pseudoaneurysm related to prior catheter placement. Venous pseudoaneurysm is an uncommon complication of internal jugular vein catheterization (13).

 

Figure 23
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  		Figure 23c.  Internal jugular venous pseudoaneurysm mimicking a mass. The patient, who had undergone multiple renal transplantations and placement of central catheters, presented with a right-sided neck mass that changed in size with changes in his position. (a) Initial unenhanced CT scan obtained at the base of the neck shows a "mass" (arrow) lateral to the right internal jugular vein (arrowhead). The "mass" was initially interpreted as a level 4 node. (b) On a follow-up contrast-enhanced CT scan, the "mass" (large arrow) shows enhancement similar to that of the adjacent internal jugular vein (arrowhead) and communicates with the vein. The findings lateral to the left internal jugular vein likely represent a combination of an additional small pseudoaneurysm, small nodes, and possibly a dilated distal thoracic duct (small arrows). (c) Inhomogeneously fat-saturated T2-weighted MR image (3667/99) shows a "flow void" within the "mass" (arrow), with an appearance similar to that of the adjacent internal jugular vein (arrowhead). This finding confirmed the vascular nature of the "mass," which presumably represents a venous pseudoaneurysm related to prior catheter placement. Venous pseudoaneurysm is an uncommon complication of internal jugular vein catheterization (13).

 

Figure 24
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  		Figure 24a.  Vertebral vein varix. (a) Unenhanced CT scan of the spine shows an apparent varix (white arrow) of the left vertebral vein, a finding that was initially thought to represent either an enlarged lymph node or an aneurysm of the left subclavian artery (black arrow) or vertebral artery. The patient later returned for CT angiographic evaluation. (b) CT angiogram shows pooling of contrast material in the varix (white arrow), which demonstrates enhancement different from that of the adjacent arteries (black arrow). (c) CT angiogram obtained just above the varix shows the left vertebral vein (white arrow) posterior to the left vertebral artery (black arrow).

 

Figure 24
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  		Figure 24b.  Vertebral vein varix. (a) Unenhanced CT scan of the spine shows an apparent varix (white arrow) of the left vertebral vein, a finding that was initially thought to represent either an enlarged lymph node or an aneurysm of the left subclavian artery (black arrow) or vertebral artery. The patient later returned for CT angiographic evaluation. (b) CT angiogram shows pooling of contrast material in the varix (white arrow), which demonstrates enhancement different from that of the adjacent arteries (black arrow). (c) CT angiogram obtained just above the varix shows the left vertebral vein (white arrow) posterior to the left vertebral artery (black arrow).

 

Figure 24
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  		Figure 24c.  Vertebral vein varix. (a) Unenhanced CT scan of the spine shows an apparent varix (white arrow) of the left vertebral vein, a finding that was initially thought to represent either an enlarged lymph node or an aneurysm of the left subclavian artery (black arrow) or vertebral artery. The patient later returned for CT angiographic evaluation. (b) CT angiogram shows pooling of contrast material in the varix (white arrow), which demonstrates enhancement different from that of the adjacent arteries (black arrow). (c) CT angiogram obtained just above the varix shows the left vertebral vein (white arrow) posterior to the left vertebral artery (black arrow).

 

Enlargement and Focal Dilatation of the Internal Jugular Veins
The size of the internal jugular veins can be variable and asymmetric due to (a) their reciprocal size relationship to the external jugular veins and (b) positional and anatomic factors. The left internal jugular vein is usually larger than the right (4). There are valves present in the jugular veins cranial to their terminations. Venous size can vary due to hydration status, position, intrathoracic pressure, cardiac status, and compression from adjacent structures. Focal dilatation of the inferior aspect of the internal jugular veins can appear clinically as a mass and has been referred to as jugular phlebectasia (Fig 25). Paleri and Gopalakrishnan (14) postulate potential causes for this condition, which is discussed more in the pediatric literature than in the adult literature. They mention a number of possible explanations as to why jugular phlebectasia is more common on the right side than on the left:


Figure 25
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  		Figure 25.  Jugular phlebectasia. Contrast-enhanced CT scan through the lower neck shows a focally dilated right internal jugular vein IJ (r) (jugular phlebectasia) and a much smaller left internal jugular vein IJ (l).

 
  1. Dilatation of the inferior internal jugular vein is referred to as the inferior jugular bulb, which is located inferior to valves. These valves are located more superiorly (mean, 1.5 cm; maximum, 3.5 cm) in the right internal jugular vein than in the left, causing the right inferior jugular bulb to be larger than the left.
  2. The right brachiocephalic vein is shorter than the left and is contiguous with the superior vena cava.
  3. Valves are relatively uncommon in the brachiocephalic veins; when present, however, they are more common on the left side than on the right.

For these reasons, increased intrathoracic pressure may be more directly transmitted to the right inferior jugular bulb than to the left. Jugular phlebectasia appears to have a benign course, and, to our knowledge, no serious complications have been reported. Phlebectasia should be differentiated from true venous aneurysms, which are saccular (15).

Venous Air
Venous air is a relatively common finding at CT and is generally related to intravenous catheter placement or injection. Woodring and Fried (16) found venous air emboli on chest CT scans in 23 of 100 patients who had been intravenously injected with contrast material. Rubinstein et al (17) described the locations of incidental small venous air emboli on head and neck CT scans obtained in 27 patients. The majority of these emboli were thought to be related to intravenous catheters (placement, injection, manipulation), and all of them were asymptomatic. All but three patients with air emboli on head CT scans had gas in the cavernous sinus (Fig 26), suggesting that gas could more easily enter or persist in this region. In the neck, the most common locations were the subclavian veins and the inferior internal jugular veins, representing the least dependent portion of the venous system in a supine patient (17).


Figure 26
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  		Figure 26.  Cavernous sinus air. CT scan obtained at the level of the cavernous sinus shows air bubbles (arrows) bilaterally within the cavernous sinuses.

 
Variable Appearance at MR Imaging
Veins can have variable MR imaging signal intensity due to entry slice phenomenon, in-plane flow, and flow turbulence effects and can have variable enhancement (Fig 27).


Figure 27
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  		Figure 27a.  Variable appearance of veins at MR imaging. (a) T2-weighted MR image (3417/101) obtained at the level of the thoracic inlet shows variable signal intensity of the internal jugular (straight solid arrows), anterior jugular (dotted arrows), and vertebral (bent solid arrows) veins. Note that the right internal jugular vein contains a low-signal-intensity "flow void," the left internal jugular vein has intermediate signal intensity, and the vertebral veins have varying degrees of increased signal intensity. The common carotid arteries (anterior to the vertebral veins) had "flow voids" with all sequences. (b) Unenhanced T1-weighted MR image (600/10) also shows variable signal intensity of the internal jugular (straight arrows) and vertebral (bent arrows) veins. (c) Contrast-enhanced fat-saturated T1-weighted MR image (567/12) shows variable enhancement of the internal jugular (straight solid arrows), anterior jugular (dotted arrows), and vertebral (bent solid arrows) veins.

 

Figure 27
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  		Figure 27b.  Variable appearance of veins at MR imaging. (a) T2-weighted MR image (3417/101) obtained at the level of the thoracic inlet shows variable signal intensity of the internal jugular (straight solid arrows), anterior jugular (dotted arrows), and vertebral (bent solid arrows) veins. Note that the right internal jugular vein contains a low-signal-intensity "flow void," the left internal jugular vein has intermediate signal intensity, and the vertebral veins have varying degrees of increased signal intensity. The common carotid arteries (anterior to the vertebral veins) had "flow voids" with all sequences. (b) Unenhanced T1-weighted MR image (600/10) also shows variable signal intensity of the internal jugular (straight arrows) and vertebral (bent arrows) veins. (c) Contrast-enhanced fat-saturated T1-weighted MR image (567/12) shows variable enhancement of the internal jugular (straight solid arrows), anterior jugular (dotted arrows), and vertebral (bent solid arrows) veins.

 

Figure 27
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  		Figure 27c.  Variable appearance of veins at MR imaging. (a) T2-weighted MR image (3417/101) obtained at the level of the thoracic inlet shows variable signal intensity of the internal jugular (straight solid arrows), anterior jugular (dotted arrows), and vertebral (bent solid arrows) veins. Note that the right internal jugular vein contains a low-signal-intensity "flow void," the left internal jugular vein has intermediate signal intensity, and the vertebral veins have varying degrees of increased signal intensity. The common carotid arteries (anterior to the vertebral veins) had "flow voids" with all sequences. (b) Unenhanced T1-weighted MR image (600/10) also shows variable signal intensity of the internal jugular (straight arrows) and vertebral (bent arrows) veins. (c) Contrast-enhanced fat-saturated T1-weighted MR image (567/12) shows variable enhancement of the internal jugular (straight solid arrows), anterior jugular (dotted arrows), and vertebral (bent solid arrows) veins.

 
 Gebarski and Gebarski (18) described the inferior petrosal sinus (inferior petrosal vein) and basilar plexus as normally enhancing structures. The inferior petrosal sinus (Fig 13) measured up to 9 x 16 mm in axial cross section, and 39% of the patients studied had markedly asymmetric inferior petrosal sinuses. Ouanounou et al (19) described flow-related enhancement in the cavernous sinus (usually in the posterior aspect) and inferior petrosal sinus at three-dimensional time-of-flight MR angiography in 10 (20%) of 50 patients. They stated that this can be a normal finding and is not necessarily a sign of carotid cavernous fistula, as had been previously suggested. They also found differences in the prevalence of flow-related enhancement in the cavernous sinus that depended on the MR imager used. They noted the absence of findings in healthy patients that would also be expected in a carotid cavernous fistula, such as flow-related enhancement in the anterior cavernous sinus or superior ophthalmic vein and the absence of linear high signal intensity that might represent the dural arteries themselves. Sakamoto et al (20) suggested that the signal intensity of the cavernous sinus and inferior petrosal sinus is due in part to antegrade upward blood flow through the sphenoparietal sinus, and that real shunts are differentiated from these "pseudoshunts" on the basis of their being associated with dilated cortical veins, enlargement of the cavernous sinus, and greater signal intensity of the sinuses.


   Conclusions
Top
 Abstract
 Introduction
 Normal Anatomy and Common...
 Variable Appearances and...
 Conclusions
References
 
The anatomy and imaging appearances of the veins of the head and neck can vary, and normal veins may mimic disease processes at CT and MR imaging. A thorough understanding of the normal venous anatomy and common variants can help the radiologist avoid misinterpreting normal veins as lymphadenopathy or some other pathologic condition.


   Acknowledgments
 
The authors wish to thank Eric Jablonowski for his assistance with image preparation and for his artistic talent in creating the drawing in Figure 1.


   References
Top
 Abstract
 Introduction
 Normal Anatomy and Common...
 Variable Appearances and...
 Conclusions
 References
 

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