Keywords common trunk - external jugular vein - retromandibular vein
Introduction
The venous system of the embryo is mainly formed by the cardinal veins during the
early stages of the intrauterine life. The left and right anterior cardinal veins
drain the cephalic part and the left and right posterior cardinal veins drain the
caudal part of the embryo.[1 ] The anterior cardinal veins afford the primary venous drainage of head and eventually
forms the internal jugular vein (IJV), while the plexus of veins in the face form
the external jugular vein (EJV). The jugular veins are the major components of the
head and neck venous system. The retromandibular vein (RV) is formed within the parotid
gland by the union of superficial temporal and maxillary veins.[2 ] The RV later divides into anterior and posterior divisions. Its anterior division
receives the facial vein to form common facial vein, which eventually opens into IJV.
The union of its posterior division with the posterior auricular vein forms the EJV,
which drains into the subclavian vein.[2 ]
The course and structure of the veins are more variable than those of the arteries.[3 ] The knowledge of such variations is extremely essential for the clinical practice.
The major veins of the neck are often used as the standard anatomical landmarks during
surgical procedures. However, variations in the anatomy of these veins may have significant
clinical outcomes. The IJV is used to measure the jugular venous pressure (JVP) during
the routine physical examination. The EJV is the preferred route for cannulation to
administer intravenous fluids, drugs and blood products. The EJV is also used to collect
blood samples,[4 ] and also has been used as a recipient for free flap microsurgeries and venous manometers.[5 ] The EJV can be made more dilated and clearly visible during clinical examination
by the using the Valsava maneuver.[6 ] Since the EJV has various clinical implications, its absence may cause difficulties
during routine general physical examination, diagnostic, and therapeutic procedures.
In this article, we report a case of undivided RV, which led to the absence of EJV
over the right neck.
Case Report
During the routine dissection of a male cadaver, aged ∼ 72 years, a variation in the
venous system over the right side of the face and neck was observed. The right RV
was undivided; however, its formation within the parotid gland was normal. The posterior
auricular vein drained into the RV ([Fig. 1 ]) to form a common trunk (CT1), just above the angle of the mandible. Near the angle
of the mandible, the CT1 joined the facial vein to form another common trunk (CT2;
[Fig. 1 ]). The CT2 drained directly into the IJV. The IJV joined the subclavian vein, thus
bypassing the whole venous drainage area of the EJV. The variant pattern in the right
jugular venous system observed in the present case is schematically represented in
[Fig. 2 ]. The arterial pattern of the right side of the head and neck was found normal in
this cadaver. The left side of the neck showed the usual morphological pattern of
arteries and veins.
Fig. 1 Right side face and neck of the dissecting room cadaver showing the absence of external
jugular vein. The retromandibular vein was undivided, which was receiving the posterior
auricular vein to form a common trunk (CT1). The common trunk (CT1) joined the facial
vein to form another common trunk (CT2), which drained directly into the internal
jugular vein. Abbreviations: CT 1, first common trunk; CT 2, second common trunk;
FV, facial vein; IJV, internal jugular vein; PAV, posterior auricular vein; RMV, retromandibular
vein.
Fig. 2 Schematic representation of the variant pattern in the right jugular venous system,
which was observed in the present case. Abbreviations: BCV, brachiocephalic vein;
CT 1, first common trunk; CT 2, second common trunk; FV, facial vein; IJV, internal
jugular vein; MV, maxillary vein; PAV, posterior auricular vein; RMV, retromandibular
vein; STV, superficial temporal vein; SV, splenic vein.
Discussion
There are few anatomical studies available in the scientific literature about the
EJV system. Olabu et al[7 ] reported that the EJV was absent in 14.2% of the studied cases. They observed that
variations of the EJV were common on the right side and the male population. It is
worth noticing that this present study is also of a male, and on his right side, supporting
the observations of Olabu et al.[7 ] Patil et al[8 ] reported an interesting case in which the maxillary vein was split into anterior
and posterior divisions. The posterior division joined the superficial temporal vein
to form the EJV. Shankar et al[9 ] reported the trifurcation of the RV near the angle of the mandible. Shankar et al
[9 ] described that these anomalous venous patterns are due to the regression and retention
of the venous anastomotic channels during the embryo development.
In the head and neck region, the EJV system drains the scalp and the face. Though
the tributaries of the EJV drain a much smaller area in comparison to the IJV, the
EJV is an important peripheral vein in the neck to get intravenous access during emergency
procedures. The EJV is clinically used as an alternative to the cephalic vein for
performing cannulation.[10 ]
[11 ] It has been described that the risk of air embolism after the central venous cannulation
is very minimal with the EJV. Due to the clinical implications of the EJV, its absence
prevents the clinician from using this important route to the intravenous access.[12 ] It was stated that the variant anatomy of the EJV may not favor the blind surgical
procedures of the neck. It is recommended that, if the EJV is not observed during
the emergency procedure, the surgeon should not waste time searching for it[7 ] and should use another vein because the EJV may be absent on few occasions.
The free flaps form an important modality for plastic and reconstructive surgeries
after the excision of the malignancy. Veins like the EJV are usually preferred as
recipient veins during the oral cavity reconstruction. Preoperative knowledge of the
absence of the vein, through imaging, will help the surgeon to plan the procedures
with minimal time.[5 ]
[13 ]
The RV acts as a guide while exposing the branches of facial nerve during parotid
surgeries and open reduction of temporo-mandibular joint fractures. The RV and its
tributaries should be ligated during the surgery to prevent excessive bleeding.[3 ] The RV can also be used as a reliable landmark during investigative procedures,
like computed tomogram, ultrasonography, and magnetic resonance imaging.[14 ] In the present case, the RV was undivided and the knowledge about this type of venous
variation is enlightening to the clinician to avoid unnecessary complications. The
knowledge is also helpful to cranio-maxillo-facial and head neck surgeons.
Also, to know the course of the EJV is essential during surgical procedures, like
portosystemic shunts and transjugular liver biopsy.[15 ] It is advised that the surgeons take precautionary measures while ligating the variant
veins during the dissection of en-bloc metastatic lymph nodes in the neck. In order
to find the perfect choice for the patient, the surgeon should know as many veins
as possible. This is because the percutaneous insertion of venous catheters is performed
using the anatomic landmarks. The successful placement of these catheters depends
on the correct position of the vein.[16 ]
Near the common carotid artery bifurcation, the common facial vein opens into the
IJV. This is an important landmark which helps the surgeons while they explore the
carotid sheath. In the present case, the RV was undivided and joined by the posterior
auricular vein forming a common trunk. The facial vein opened to the common trunk
to form another common trunk, which drained into the IJV. Also, the termination of
the vein into the IJV was at a higher level than the bifurcation of the common carotid
artery. This variation should be considered during surgical procedures to avoid complications
like catastrophic bleeding and air embolism.
The EJV, when not collapsed or thrombosed, becomes a choice if the patient requires
an emergency venous access when other veins are collapsed.[17 ] Sectioning the EJV is used in parenteral nutrition and chemotherapy administration,
and the absence of the EJV should be considered while performing these procedures.[18 ]
[19 ]
Nagase et al [20 ] advise that a preoperative evaluation of the venous network patterns of the head
and neck region is required before surgery. This can be done by the precise clinical
appraisal, followed by color Doppler studies to prevent intraoperative complications.
Conclusion
A rare case of variation in the jugular venous system is reported. The significance
of the present case is a variation in the course of the RV along with the absence
of EJV. The undivided RV joined the posterior auricular vein forming a common trunk,
which eventually opened into the IJV after joining with the facial vein. These variant
trunks have drained the EJV area, since it was not formed. We believe that this report
is enlightening to head and neck surgeons, anesthesiologists and cardiovascular surgeons.
This has implications in emergency medicine and plastic surgery as well.
