Ruptured Internal Carotid Artery Mycotic Pseudoaneurysm as Sequela to a Retropharyngeal Abscess in an Immunocompetent Child

Significance Statement

An ICA pseudoaneurysm may occur as a rare complication of deep neck space abscess. The role of endovascular management is not clearly defined in very young children. While bacterial etiologies prevail, fungal pathogens should be considered.

Case Report

A 2-year-old boy known for X-linked mucopolysaccharidosis II presented to the emergency department with a 3-day history of fever, nasal congestion, and cough. Initial assessment revealed a febrile and ill-appearing child, with bilateral exudative tonsillitis and restricted neck extension. Broad-spectrum intravenous antibiotics were initiated pending investigations. A lateral soft-tissue neck X-ray showed thickened prevertebral soft tissues highly suspicious for a retropharyngeal abscess and laboratory investigations revealed marked neutrophilic leukocytosis. Shortly after the presentation in the emergency room, he choked on solid food with desaturation and complete airway obstruction requiring intubation in the emergency department. An urgent bronchoscopy was performed, and small pieces of bread and frothy pink sputum were suctioned from the distal airways. Computed tomography (CT) of the neck showed a large retropharyngeal abscess extending to the right parapharyngeal space, with bifocal stenosis of the right internal carotid artery (ICA) (Figure 1A). Transoral drainage in the operating room was performed yielding copious purulent discharge within 24 hours of presentation.

Figure 1.

Initial CT-A (A, day 1) and MR-A (B, day 3) show right ICA bifocal stenosis. MR-A (C, day 6), CT-A (D, day 7), MR-A (E, day 8), and CT-A (F, day 10) show a rapidly growing ICA pseudoaneurysm. The top row represents coronal views, while the bottom row shows sagittal vies of the right ICA on the maximum intensity project of the CT-A (A and D) and MR-A (B, C, E) of the neck vessels. Of note, transoral drainage of the adjacent retropharyngeal abscess was performed on day 1, and through a transcervical for a residual collection on day 3. CT, computed tomography; MR, magnetic resonance; ICA, internal carotid artery.

The patient remained intubated postoperatively due to poor lung compliance secondary to aspiration pneumonitis. A left-sided hemiparesis was noted on post-admission day 3. Urgent magnetic resonance imaging (MRI) revealed a residual parapharyngeal space collection, ICA arteritis with 2 segments of severe arterial narrowing and large ensuing right middle and posterior cerebral artery infarcts (Figure 1B). Urgent transcervical drainage was performed, with the insertion of a Penrose drain in the parapharyngeal space. Intravenous methylprednisolone and prophylactic aspirin were initiated by the neurology service. Anticoagulation was not given due to the risk of hemorrhagic transformation of the ischemic stroke.

Cultures from the initial transoral drainage grew Candida lusitaniae in 2 separate samples but no bacterial species, and intravenous fluconazole was started. Subsequent cultures from the transcervical drainage showed no bacterial or fungal growth. Of note, an immunology work-up was ultimately negative for an underlying immunodeficiency.

MRI angiography and CT angiography demonstrated satisfactory evacuation of the parapharyngeal collection but the development of a 1.3 cm ICA pseudoaneurysm with no endoluminal thrombosis (Figure 1C). In discussion with neurointerventional radiology and vascular surgery services, both endovascular coiling or stenting and open reconstruction with vein interposition were deemed high risk in the context of active fungal arteritis. The distal ICA diameter was measured at 3 mm, further precluding the use of endovascular-covered stents. Evidently, ICA ligation carried a significant risk of massive stroke.

In discussion with the involved services and the patient’s family, a nonsurgical approach was decided upon first, with consideration for pseudoaneurysm repair upon resolution of the infectious process. However, it rapidly progressed on serial images (Figure 1C–F), and new slow bloody discharge was noted from the Penrose site and the mouth 4 days after the initial cross-sectional imaging had first diagnosed the ICA pseudoaneurysm. The patient was taken to the operating room for ICA ligation through a parapharyngeal approach. Intraoperatively, a large clot was found in the parapharyngeal space corroborating our suspicion of a contained aneurysmal rupture (Figure 2). Despite signs of ongoing vessel arteritis at the level of the pseudoaneurysm, approximately 1 cm segment of healthy ICA was noted at the level of the skull base allowing to perform a double ligation of the proximal ICA and distally at the skull base. Intravenous antibiotics and antifungals were continued for a total duration of 6 weeks.

Figure 2.

Open surgical ligation of the internal carotid artery (*) with clotted blood in the parapharyngeal space indicative of a contained aneurysmal rupture (arrow).

Our patient experienced a prolonged neurological recovery, with ongoing hemiparesis and dysphagia, both of which were improving slowly with post-stroke community rehabilitation at 6-month follow-up. An ipsilateral right vocal cord paralysis was noted on postoperative nasolaryngoscopy, possibly as a result of the infection or due to a traction injury of the vagus nerve during ICA ligation. Injection laryngoplasty of the right vocal cord and cricopharyngeal myotomy were performed to help with ongoing dysphagia.

Discussion

An infectious extracranial carotid artery pseudoaneurysm is a rare, yet potentially fatal pathology, with a recent review identifying only 31 cases in the pediatric literature. ¹ Clinically, these may present with a painful growing pulsatile neck mass, fever, and potentially cranial nerve palsies or Horner’s syndrome. ² While traumatic cases and infectious seeding from septic emboli have been described, the underlying etiology in children is typically a deep neck space infection with contiguous inflammation or direct injury to one or more of the layers of the vessel wall.^1-3 Early recognition is critical, as catastrophic complications may ensue, including septic cerebral thromboemboli, aneurysmal rupture with massive hemorrhage, or death. ¹

The term “mycotic aneurysm” was first coined by Sir William Osler in 1885 to describe infectious arterial wall dilations as they resembled fleshy fungi. ⁴ This is somewhat of a misnomer, as the most common culprit microorganisms in infectious carotid artery pseudoaneurysm are bacterial rather than mycotic, namely Staphylococcus aureus and Streptococcus species in the post-antibiotic era.^4,5 While Salmonella species have a propensity to adhere to damaged vascular endothelium and potentiate aneurysm formation through the production of elastase, they are more frequently identified in adults and are associated with intravenous recreational drug use.^6,7 Candida carotid arteritis is exceedingly rare, particularly in the absence of a known underlying immunosuppressed state. ⁸ While initially felt to be a contaminant, radiologic progression of the parapharyngeal collection despite early broad-spectrum intravenous antibiotic therapy strengthens our suspicion of pathogenic fungal involvement in this child’s presentation.

The diagnosis of a pseudoaneurysm can be established based on cross-sectional imaging with contrast-enhanced CT or MRI with an angiogram phase. ⁹ Larger proximal pseudoaneurysms may also be visualized on ultrasonography. ¹⁰ While at times evident with a clear outpouching with intense enhancement similar to the parent artery, more subtle signs such as poor visualization of the ICA in the presence of an abscess may be indicative of a developing pseudoaneurysm. ¹⁰

Untreated infectious ICA pseudoaneurysms were lethal in upwards of 75% of patients in the pre-antibiotic era. ¹¹ The advent of antibiotics and an expanded armamentarium of contemporary surgical treatments have drastically improved outcomes. Optimal surgical management of infectious extracranial carotid pseudoaneurysms nonetheless remains controversial, with options including surgical ligation, open arterial reconstruction, and endovascular techniques. ⁵ While surgical ligation allows definitive treatment and source control through debridement of infected tissues, endovascular techniques have been described as an alternative in hopes of decreasing surgical morbidity. ³ Neurointerventional aneurysmal coiling and covered stents may be a viable option in some cases, yet reliable long-term data on their safety and efficacy are lacking. ¹² As was the case in our patient, concern remains that deployment of endovascular devices within an acutely inflamed and friable vessel may lead to protracted bacterial contamination of prosthetic materials ⁵ and, most importantly, a non-negligible risk of rupture without easy access for distal control. In addition, arteriopathy from intimal vascular deposits has been described in children with mucopolysaccharidosis, ¹³ thus further increasing the risk of stent thrombosis in an already stenotic vessel.

Although resection and reconstruction with autologous grafting were entertained to restore vascularity, the risk of anastomotic, conduit, or native arterial complications in the context of active infection was also deemed significant. Intraoperative anticoagulation would have been required for anastomosis, which was not advised in the context of an ischemic stroke with a high risk of hemorrhagic transformation. As such, surgical ligation was favored. An important consideration was the proximity to the skull base, specifically sufficient clearance distal to the aneurysm to allow ligation of the carotid cephalically.

Finally, while pre-occlusion, balloon test occlusion, may be considered to evaluate collateral cerebral perfusion through the Circle of Willis prior to carotid sacrifice,^1,12 it should not delay urgent intervention when faced with prodromal bleeding and imminent rupture.

Conclusion

This case highlights the complexity of infectious extracranial carotid artery pseudoaneurysms in pediatric patients and the need for an interdisciplinary management approach. Prompt recognition and diagnosis are crucial for timely intervention and prevention of potentially catastrophic complications. Bacterial etiologies prevail, but fungal involvement should be considered in cases with progression of disease despite appropriate broad-spectrum intravenous antibiotics and abscess drainage. While endovascular therapies have been favored in the most recent literature, ICA ligation may be required in the context of an imminent rupture or sentinel bleed.