Coiling of internal carotid through ‘eye of the needle’ internal jugular vein: a dual great vessel anomaly

Abstract

A variation in the usual course of great vessels during neck dissection can predispose them to inadvertent iatrogenic injury, which can lead to massive bleeding. We present a case of a male patient with oral squamous cell carcinoma who underwent inferior maxillectomy and supra-omohyoid neck dissection. Lateral coiling of the extracranial internal carotid artery was seen through fenestration of the internal jugular vein. Anomalies of great vessels in the neck are rare. Variation in the course of any of these vessels can prove to be catastrophic if control is not achieved. Careful study of radiographic imaging with special consideration given to the course of great vessels in the neck should be undertaken prior to neck surgeries.

Introduction

Neck dissection is performed for regional control of head and neck cancer by removing lymph nodes and fibrofatty tissue from the neck. Great vessels such as the carotid and internal jugular vein (IJV) encased in the carotid sheath are also encountered during the procedure.

Extracranial internal carotid artery (eICA) has been reported to have coiling and kinking, either medially or laterally, predisposing it to injury.^1,2 Similarly, IJV duplication and fenestration (‘eye of the needle’ appearance) has been reported in the literature and can carry the same risk of injury during neck dissection or central line catheterisation.^3,4

We report the first case of lateral looping of eICA through eye of the needle fenestration of the IJV encountered during selective supra-omohyoid neck dissection.

Case history

A 53-year-old male patient with no comorbidities presented to our outpatient clinic complaining of a painless right upper alveolus lesion that had been increasing in size progressively for the past four months. Incisional biopsy revealed squamous cell carcinoma of the tongue. After pre-operative work-up, the patient underwent inferior maxillectomy and extended supraomohyoid (selective level I–IV) neck dissection.

Intraoperatively, while delineating the IJV posteriorly, a pulse was felt at level IIA. Careful blunt dissection of the IJV revealed it to be split into two tributaries, eventually reuniting again craniocaudally. To add to our surprise, the internal carotid artery took a sharp bend laterally through this bifurcation of IJV (Figure 1, Video 1). Bend of eICA and IJV fenestration can also be visualised on computed tomography (CT) scan with contrast of our patient performed preoperatively for staging of disease (Figures 2–4). The internal carotid artery loops around laterally on both sides of the neck. The IJV can be seen to be split anteriorly and posteriorly, hosting the loop of carotid in between on the right side of the neck (Figure 2).

Figure 1 .

Intra-operative view of looping of internal carotid through IJV fenestration after selective neck dissection. IJV = internal jugular vein.

Figure 2 .

CT scan axial view: showing lateral looping of internal carotid through anterior and posterior splitting of IJV. CT = computed tomography; IJV = internal jugular vein.

Figure 3 .

CT scan coronal view: showing lateral looping of internal carotid (right side). CT = computed tomography.

Figure 4 .

CT scan coronal view: showing lateral looping of internal carotid (left side) – nonoperated side. CT = computed tomography.

Postoperatively, the patient remained well and was subsequently discharged after drain removal on day 3.

Discussion

The extracranial cervical part of the internal carotid artery is thought to have a straight course in the carotid sheath lying medial and deep to the IJV.^5,6 However, variations in eICA have been described in the literature. The reported incidence of variation ranges from 4% to 66%, with up to 16% patients developing vascular insufficiency.^2,7,8 Variations include coiling, kinking and looping. Weibel et al first described these variations schematically.^1,9 Curving of the internal carotid is a slight deflection from a straight course; kinking is a sharp bend, which could be lateral or medial in relation to the pharynx; coiling is a complete loop, after which it courses towards the skull base.^1,9 In our case, the eICA was kinking laterally to the pharynx. Paulsen et al classified variation of the internal carotid based on degrees of deviation from a straight course. Up to 15° from the vertical axis is straight, 16–70° is curved, 90–145° is coiled and a 360° turn is looped.¹

Recently, an association of body mass index (BMI) with tortuosity of eICA has been reported.² It has been hypothesised that, with an increase in BMI (increased fat around the abdomen) the diaphragm is pushed upwards, which in turn exerts indirect pressure on the thoracic aorta. Upward push of the aorta causes buckling of the cervical internal carotid as it has a fixed position at the base of the skull.² A threshold of 25.04kg/m² has been computed for development of tortuosity.²

IJV duplication and fenestration have been reported in the literature. Incidence ranges from 0.4% to 3.3%.^3,10,11 Duplication of IJV occurs when it divides craniocaudally and enters the subclavian vein separately. Fenestration is when the IJV has an ‘eye of the needle’ appearance on its route to the subclavian vein.⁴ Anomalies of IVJ have been described with venous ectasia.¹¹ Patients have been reported to present with neck swelling, dyspnea and dysphagia.¹² Our patient had no such complaints. The spinal accessory nerve is seen to pass from within the fenestration, giving rise to a neural theory of IJV fenestration. However, there is also a report of the spinal accessory nerve not bisecting the IJV.¹³ We observed a spinal accessory nerve to be coursing between the fenestration in our case. Muscular theory suggests the posterior belly of the digastric bisecting the IJV.¹⁴ Vascular theory suggests weakness of the IJV leading to endothelial rearrangement during development, and bony theory suggests bifurcation at the jugular foramen at the skull base.³

Anomalies of both these great vessels in the neck can predispose to massive bleeding during neck dissection, which could prove catastrophic in inexperienced hands. We encountered a group of lymph nodes at level IIa overlying the coiled carotid at the lateral junction of one branch of the IJV (superficial). Blunt dissection of these nodes prevented inadvertent injury both to the internal carotid artery and deeper branch of the IJV. To the best of our knowledge and literature search, this is first case reporting coiling of the internal carotid artery through ‘eye of the needle’ fenestration of the IJV—a dual great vessels anomaly.

Conclusions

Anomalies of great vessels (internal carotid and IJV) in the neck are rare. They can present symptomatically or can be found incidentally on radiographic imaging or neck exploration/dissection. Variation in the course of any of these vessels can lead to massive bleeding or a potentially catastrophic outcome. Careful study of radiographic imaging, with special consideration given to the course of great vessels in the neck, should be undertaken prior to neck surgeries.