Fenestration of the internal jugular vein (IJV) is an extremely rare phenomenon. An 85-year-old woman was referred to our department with T2N0M0 squamous cell carcinoma of the right floor of the mouth. The patient underwent local resection, an ipsilateral modified type 3 radical neck dissection, and microsurgical reconstruction. During neck dissection, a fenestration was observed in the middle of the IJV. No structure passed through the fenestration. Such anatomical variations are rare, but clinicians and surgeons should be aware of them in order to avoid damage to the important vascular structures, especially if a neck dissection is performed.
The internal jugular vein (IJV) is the largest vein in the neck. It drains blood from the skull, brain, face, and neck. It descends in the neck within the carotid sheath and unites with the subclavian vein behind the sternal end of the clavicle to form the brachiocephalic vein. The IJV is frequently used for central venous access and is an important anatomical reference for radiologists and head and neck surgeons. In fact, identification of the IJV and the omohyoid muscle is essential to every neck dissection.
Fenestration of the jugular vein is an extremely rare phenomenon. This finding has been reported previously in a very few cases with the spinal accessory nerve passing through the fenestration. However, in this case no structures were observed to be associated with the fenestration.
An 85-year-old woman was referred to our department with T2N0M0 squamous cell carcinoma of the right floor of the mouth and mandibular gingiva. The patient underwent local resection, an ipsilateral modified type 3 radical neck dissection, and finally reconstruction using a radial forearm free flap. During the neck dissection, a fenestration was observed in the middle of the IJV.
No structure was found to be passing through the fenestration ( Fig. 1 ). The accessory nerve passed over the IJV ( Fig. 2 ). The external jugular vein was located as usual in the subcutaneous region. On reassessment, the preoperative contrast-enhanced computed tomography (CT) image of the neck did not clearly show this fenestration of the IJV. All the veins in the right neck were large in diameter, but none showed evidence of phlebectasia or aneurysm.
A cervical dissection is usually performed during the treatment of malignant disease of the oral cavity, and it is important for the staging and treatment of cervical lymph node metastases in patients with head and neck carcinoma. The IJV is used as an important surgical reference when dissection deep to the sternocleidomastoid muscle is performed.
Malformations of the IJV are uncommon. Very few cases of duplication or fenestration of the IJV have been described. Although these terms refer to two distinct patterns of IJV anomaly, they are often used similarly in the literature. Downie et al. classified IJV malformations into two patterns. In both, the IJV begins as a single vessel in its emergence from the jugular foramen. If the duplication pattern exists, the IJV bifurcates into two veins that drain separately into the subclavian vein; meanwhile if the fenestration pattern exists, the bifurcation occurs only over a certain distance, and the two veins reunite again before joining the subclavian vein. Fenestration refers to a ‘window-like opening’ in the IJV that has a typical ‘eye-of-the-needle’ appearance.
The aetiology of IJV fenestration is not clear and several theories have been proposed, assuming its origins to be in the vascular, neural, or bony development of the neck. The vascular theory is more widely accepted. During foetal life, the accessory nerve passes between the lateral and medial veins of the head. The lateral vein usually disappears leaving the nerve superficial to the vein, according to its normal position. More rarely, the medial vein disappears, leaving the nerve located deep to the vein. Duplication is thought to result from the appearance of a secondary venous ring at a lower level surrounding the spinal accessory nerve. The neural hypothesis is linked to migration of the lateral branch of the spinal accessory nerve itself. Usually the nerve emerges in the neck at the level of the transverse process, but it may lie up to 2 cm below the process. This position can disrupt the developing IJV and lead to its duplication. The bony hypothesis suggests that a variation in the ossification of the bony bridges of the jugular foramen causes the venous duplication.
The fenestrated IJV has been reported to be related to phlebectasia, a local fusiform, soft, and non-pulsatile dilatation. In the case presented here, the IJV was not dilated and there were no other anomalies associated with the jugular fenestration.
Several authors have described duplications or fenestrations of the IJV shown by means of CT angiography or magnetic resonance imaging. In our case, the fenestration was not detected in the preoperative CT because of the limited diameter of the anomaly.
Most duplications and fenestrations occur in the upper third of the IJV and are associated with the spinal accessory nerve, which either passes between the two divisions of the vein or through the fenestration. In the case presented, the fenestration was observed to be in the middle of the IJV and no structures were observed to be associated with the fenestration.
Fenestrations of the IJV can have important clinical implications. As the IJV is so consistently positioned, percutaneous access for insertion of a central venous line is considered safe. However, variations in the IJV, such as a fenestration, could result in difficulties inserting the catheter and could cause a vascular injury. In neck dissections, fenestration of the IJV could increase the risk of bleeding, or make the complete removal of the lymph nodes more difficult. Furthermore, the IJV is often used as a recipient vein for free flaps, thus fenestrations in the IJV could be involved in flap failure.