Pulsating Tonsil Due to Medial Displacement of the Internal Carotid Artery

Background

The internal carotid artery (ICA) is a branch of the common carotid artery. It has a straight course in the neck to the base of the skull, and does not have branches in this cervical portion. The human anatomy has variations between individuals, and ICA is one of the structures with anatomic variations, such as kinking, elbowing, and notches. In older individuals, such variations may be caused by arteriosclerosis and thrombosis, which can affect blood flow and cause encephalic ischemic processes [1]. The variations of the ICA include variability of pattern and degree (Figure 1). Some otolaryngology procedures carry a risk of ICA injury; these procedures include tonsillectomy, peritonsillar abscess drainage, soft palate impalement injuries, adenoidectomy, and velopharyngeoplasty [2]. The origin of these different variations has been controversial. Some are believed to represent congenital vascular anomalies, and others are related to arteriosclerotic pathology or fibromuscular dysplasia. Undetected ICA anomalies can result in fatal complications from biopsy, as well as surgical and anesthetic procedures [3]. Iatrogenic injury to the ICA is a rare complication of pharyngeal surgery. In addition, most anatomic variations of ICA are asymptomatic, and can be found incidentally during radiographic studies; these are done for unrelated reasons, or can remain undiscovered preoperatively [4]. In pediatrics, diagnosis of these variations must be considered, especially in patients indicated for tonsillectomy, in which iatrogenic injury during the surgical process may have catastrophic consequences [4,5]. Our rationale to report this case is to emphasize the fact that the surgeon must protect against vascular anomalies that may be confronted during head-neck surgery, and that preoperative examinations might be considered within this context.

Case Report

A 23-year-old Saudi female patient, with controlled sickle cell anemia, was seen in the otolaryngology clinic complaining of recurrent tonsillitis and nasal obstruction. No signs or symptoms suggested any jeopardy of cerebral blood flow. No history of stroke or other sickle cell anemia crisis, except vaso-occlusive crisis twice. On examination, the nose looked clear of polyps but the turbinate was hypertrophied, while the intra-nasal fiber optic examination was unremarkable apart from thick nasal secretion. On oropharyngeal examination, there was bilateral tonsillar hypertrophy, more prominent on the right side (grade 3), and the left side (grade 2). Our plan was to admit the patient for bilateral tonsillectomy. CT of the head and neck was requested to evaluate her paranasal sinuses; contrast was added to evaluate unilateral tonsillar enlargement and rule out other neck pathology. CT showed bilateral large tonsils, more enlarged on the right side, and overlaying a large vessel (ICA). In re-evaluating the course of treatment, we found a severe S-shape kink on the right side, bringing it close to the right tonsil by approximately 2 mm, and putting it at severe risk of injury during a simple tonsillectomy, possibly exposing the patient to serious bleeding (Figures 2, 3). The plan was thus changed to tonsillotomy as a tissue biopsy; following a right tonsillectomy, pulsation of that tonsil was noted and recorded (Video 1). The sample was sent to the histopathology laboratory, and results indicated a chronic inflammatory process. The patient made an uneventful postoperative recovery. No neurologic deficit or hemorrhage was detected during or after the operation. The patient and family were educated about this anatomic variation and told to be careful with future head and neck surgery.

Discussion

Previous studies have reported the prevalence of ICA anomalies, ranging from 16% to 60% among different age groups (Table 1) [6–12]. Macchi C et al., is the only author who did the image study on one hundred of normal healthy individuals and found 26.5% has ICA anomaly [8]. These studies also report the ICA anomaly as seen more often in elderly women [6–12]. Types of ICA angle severity were first described by Metz et al. in 1961 (Table 2) [7]. Weibel and Fields first introduced the classification of tortuosity, kinking, and coiling in 1965. Tortuosity has been described as an S- or C-shaped elongation or undulation in the course of ICA. Coiling has been defined as elongation or redundancy of the ICA, resulting in a severe S-shaped curve or a circular configuration. Kinking has been the most frequently reported carotid abnormality (CA), and described as an angulation of the ICA, graded according to the severity of the angle between the two segments forming the kink [6].

Aydogan et al. thought there were types of forces that might cause vessels elongation, buckling, and then tortuosity. The two forces identified were traction and pressure inside the lumen. Branches and perivascular tissues could thus stretch the main straight artery and cause traction, while the intraluminal pressure could push the vessels walls from inside and cause extension. The hyperdynamic circulation in sickle cell anemia patients could cause lengthening and tortuosity by high intraluminal pressure via the mechanism described above [13], as in our case.

Ekici et al. reported 607 cases of imaging evaluation of ICA. The carotid-pharyngeal distance (CPD) to the right and left ICA yielded an average of 11.13 mm. The shortest CPD was measured as 0.92 mm, while the longest CPD was 24.12 mm [11]. In our case report, the right ICA was kinking with a CPD of 2 mm. Cong et al. reported seven cases of ICA anomaly in China, of which four patients had pharyngeal bulge with pulsation, and normal pharynges in three other patients [14]. Bhandarkar et al. reported a case of a 45-year-old woman with right pulsating and swelling over the oropharynx, with normal mucosal lining. The distance between the ICA and oropharyngeal mucosa was 3 mm [15]. Another case reported by De Virgilio et al. involved a woman in her 70s with a right retropharyngeal pulsating mass, with 1 mm between the ICA and mucosal surface [16].

Some patients with ICA anomalies have episodes of cerebrovascular insufficiency related to the position of their heads [17,18], but this was not a concern in our patient.

ICAs have their embryonic origins in the third aortic arch and dorsal aorta. During normal embryonic development, the dorsal aortic root descends into the chest in the fifth to eighth week of fetal life, lengthening and straightening the course of the carotid artery. It is suggested that incomplete straightening and persistence of embryonic angulation can result in aberrant carotid arteries [19]. Postoperative bleeding is an adenotonsillectomy complication in normal anatomical circumstances. The risk of life-threatening bleeding increases with ICA anomalies. Therefore, the physicians must be careful in performing pharyngeal surgeries [11].

Conclusions

Undetected ICA anomaly variation can lead to fatal bleeding during a simple procedure, like tonsillectomy. We recommend vigilance during tonsillectomy if one is using a hot dissection method versus a cold dissection method, which may allow for detection of a perioperative ICA anomaly. Tonsillectomy performed by a junior resident should be under direct supervision, particularly if the hot dissection method is used.