Mycotic Aneurysm of the Extracranial Internal Carotid Artery Following Otitis Media

Abstract

Mycotic aneurysm of the internal carotid artery following otomastoiditis can manifest as a nasopharyngeal mass. This is a very rarely described condition. The case of a patient diagnosed with a retropharyngeal mycotic aneurysm of the left internal carotid artery following otitis media, treated with exclusion of the mycotic aneurysm from the circulation and transnasal drainage. Infection of the mastoid can spread to the parapharyngeal space of the nasopharynx and damage the carotid artery wall, resulting in an infected aneurysm. There are no guidelines on how to surgically approach those aneurysms. An endoscopic transnasal approach can be beneficial.

Introduction

During otomastoiditis, the infection can spread from the temporal bone to the parapharyngeal space and damage the internal carotid artery wall, causing a mycotic aneurysm.

Mycotic aneurysms of the extracranial carotid artery are rare with around 20 cases reported per decade in the last 30 years [1]. We present a case report of a patient with a mycotic aneurysm following otomastoiditis.

Case Presentation

A 60-year-old male patient presented with meningitis. Patient’s history revealed trigeminal neuralgia, diabetes, arterial hypertension and recent ischemic cerebral infarction. One month before admission he was treated for middle ear infection with cultures positive for Pseduomonas aureginosa. CT and MR scans showed bilateral middle ear and mastoid cell effusion, therefore mastoidectomy was performed. No abnormalities were described in the parapharyngeal or retropharyngeal space. After the procedure the patient did not wake up immediately and was transferred to the ICU for ventilatory support. Follow up CT scans showed a retropharyngeal collection, with an 30 × 20 mm left internal carotid artery pseudoaneurysm (mycotic aneurysm) (Fig. 1). At that point the patient was referred to our institution. DSA with external compression of the contralateral internal carotid artery was done to assess cross circulation (Fig. 2). Since cross circulation was seen on DSA, we decided to exclude the mycotic aneurysm from the circulation with clipping of the clinoid ICA and proximally on the neck. The retropharyngeal abscess was drained transnasaly and cultures were taken but no pathogenic bacteria were isolated (Fig. 3). After surgery the patients condition did not improve and 14 days after surgery his condition deteriorated, he was transferred to the ICU where he died of cardiovascular failure.

Fig. 1.

Picture 1 shows a 60-year-old male patient with an 30 × 20 mm left carotis interna pseudoaneurysm (mycotic aneurism). Picture 2 shows the pseudoaneurysm on CT angiography. Pictures 3–8 show contiguous cuts of the epipharyngeal space, showing the pseudoaneurysm in and its relationship to the mastoid cavity

Fig. 2.

DSA pictures prior surgery. Picture 1 shows CAG (carotid arteriography) of the right ACI with external compression of the left ACI. Trough the anterior communicating artery the left middle cerebral artery is filling. Pictures 2 and 3 show CAG left with external compression on the right carotid artery. The pseudoaneurysmal sac is seen and the left posterior communicant artery is not filling. Picture 4 shows the dimension of the pseudoaneurysmal sac as seen on the DSA. The petrous segment of the ACI is also dilated

Fig. 3.

Intraoperative view of the aneurysm before, during and after transnasal endoscopic drainage and resection

Discussion

Extracranial internal carotid artery aneurysm is a rare condition. True aneurysms are full-wall thickness artery lumen dilations of more than 50% of normal diameter, whereas pseudoaneurysms are due to trauma to the arterial wall, creating a false lumen that maintains a connection with the original one [2].

We report of an aneurysm in the upper parapharyngeal space that formed as a complication of otomastoiditis, which is very rare. The infection spread from the temporal bone to the parapharyngeal space causing a mycotic aneurysm of the parapharyngeal ICA just below the carotid canal.

Intracranial carotid artery aneurism following middle ear infection are rare but have been reported in the literature [3]. Amano et al. [4] reports of a case of Vernet’s syndrome caused by an ECAA following acute middle ear infection. Infected (mycotic) ECAA are usually described as enlarging neck masses accompanied by fever and pain [1].

Pathophysiology of mycotic aneurism is not entirely known. The proposed mechanisms are: artery wall infection that occurs during bacteriemia within the atherosclerotic plaque or the carotid bifurcation, infection during vascular trauma e.g. open surgery, endovascular procedures or drug abuse or a local infection that spreads to the artery wall [1].

To evaluate an ECAA, computed tomography and MR angiography are the radiological studies of choice. They provide the clinician with the necessary information about the size of the aneurysm, and the relationship to the surrounding structures. Angiography is used preoperatively to evaluate the flow, possible collateral circulations between external and internal system. Balloon occlusion test is performed when carotid artery sacrifice is being considered [3].

There are no standard treatment protocols for mycotic aneurysms of the nasopharynx. Systemic antibiotics and surgical removal of the infected aneurysm with immediate graft reconstruction is the standard treatment of infected ECAA [1].

The anatomy of the nasopharynx does not allow for open surgical approach. We decided to approach the mycotic aneurysm with an endoscopic transnasal surgical resection with artery ligation proximally and distally.

Endovascular carotid artery stenting is a new minimally invasive approach in the treatment of the artery aneurysms and should also be considered for older patients. There are several different options for endovascular treatment including bare metal stent placement with or without trans-stent coil embolization of the aneurysm sac, exclusion of the aneurysm using a stent-graft, endovascular occlusion of the carotid artery or using a flow diverter [2, 5].

Management of an ICA aneurysm is challenging not only for the surgeon but also for the anesthesiologist. It is crucial to prevent pseudoaneurysm from rupturing during induction to general anesthesia. Careful control of systolic arterial pressure (SAP) is required. Deep sedation and muscle relaxation during laryngoscopy and intubation is advised to prevent SAP spikes. A history of hypertension can make SAP management difficult. SAP should be maintained between 120 and 150 mmHg in unclipped aneurysms [6].

Major complications of an intraoperative aneurysm rupture are cerebral ischaemia, hydrocephalus, cardiopulmonary dysfunction and electrolyte disturbances.

Cerebral ischaemia can be prevented with an extra-intracranial shunt, prior ligation of the ICA [7]. In our case the patient was not a suitable candidate for extra-intracranial shunt due to a septic state and the risk of pseudoaneurysm rupture during shunt placing.

Cardiac dysfunction is common in SAH and correlates with the degree of neurological deficit. Cardiac abnormalities are probably the result of excessive myocardial release of catecholamines from sympathetic nerve terminals triggered by the SAH, resulting in calcium overload and necrosis of myocytes [6].

Conclusion

Infection of the mastoid can spread to the parapharyngeal space of the nasopharynx and damage the carotid artery wall, resulting in an infected aneurysm, that manifests as a nasopharyngeal mass. There are no set guidelines on how to surgically approach those aneurysms. An endoscopic transnasal approach can be beneficial.

Compliance with Ethical Standards

Conflict of interest

The authors declare that they have no conflict of interest.

Ethics Committee Approval

The policy of the Ethics committee at UMC Maribor* is not to review case reports. *Name of the ethics committee: Komisija za medicinsko etiko UKC Maribor.