Background

Giant intrapetrous internal carotid aneurysms (ICA) are rare. Only a few studies generally consisting of case reports or small case series have been documented [8, 9, 11, 13, 14, 16, 18]. Traditional surgical clipping is not frequently utilized due to their complex location within the petrous bone, and extracranial-intracranial (EC-IC) bypass with proximal ligation of the internal carotid artery (ICA) is still the conventional treatment [1, 2]. However, mini-invasive endovascular techniques have greatly evolved in the last two decades, allowing effective intervention for both ruptured and unruptured aneurysms, even in more complex anatomical and clinical conditions [6, 17]. Although endovascular treatment is a feasible treatment option for giant petrous ICA aneurysm, high residual and recurrence rates were observed in earlier reports [9, 15]. In this article, we reported a case of successful surgical trapping with bypass intervention of a giant intrapetrous ICA aneurysm presenting as otorrhagia and coil exposure caused by a penetrated coil after repeated endovascular treatment, which has never been documented before.

Case presentation

History and examination

A 58-year-old man presenting with persistent otorrhagia was admitted to our hospital because of the recurrence of a giant petrous ICA aneurysm. The patient had a history of two embolization treatments of the aneurysm in the local hospital 9 years and 1 year ago. Digital subtraction angiography (DSA) post coiling embolization of the aneurysm demonstrated that the aneurysm was completely filled with coils (Figs. 1 and 2). However, the patient suffered mild bloody discharge in his right ear for approximately 9 years after the first endovascular treatment, and conservative management with administration of oral antibiotics was applied during the previous 9 years until the patient was admitted to our medical center, as the aneurysm was visualized again on angiographic imaging. An electronic otoscope examination revealed the coil exposure in his right EAM (Fig. 3). The patient was planned for bypass with ICA occlusion as he did not pass the balloon test occlusion (BTO).

Fig. 1
figure 1

Right carotid angiogram shows a giant right petrous carotid aneurysm (a and b). Postprocedural right carotid angiogram obtained after deployment of coils reveals the aneurysm was completely filled with coils for the first time (c and d)

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Fig. 2
figure 2

Right carotid angiogram shows recurrence of the aneurysm (a and b). A repeat embolization with stent-assisted coiling was performed 8 years later after the first embolization (c and d)

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Fig. 3
figure 3

CT and electronic otoscope examinations showed coils escaped into the external auditory meatus (a, b and c)

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Operation and postoperative course

The patient was taken to the hybrid operating room. Then, a 15-cm segment of the radial artery was harvested, and end-to-end and end-to-side anastomosis were respectively performed at the main superficial temporal artery and middle cerebral artery. After the bypass surgery, we have intended to trap the aneurysm with endovascular means, but the guide wire could not pass though due to the block of old stents and coils around the neck of aneurysm. Therefore, the aneurysm was trapped by clipping just proximal to the takeoff point of the ophthalmic artery and occluding proximal to the aneurysm with endovascular coil embolization. DSA after the trapping showed complete disappearance of the aneurysm with patent bypass (Fig. 4a, b). The patient was discharged with no event, and the coils in the ECA were still present.

Fig. 4
figure 4

Right carotid angiogram shows recurrence of the aneurysm for the second time (a, arrow). End-to-end and end-to-side anastomosis were respectively performed using the arterial graft at the main STA and MCA (M2); intraoperative angiography confirmed the patency of the bypass (b, arrow) and full suppletion of the entire right middle cerebral artery territory (b). The operation of the removal of the coils was performed with the transpetrosal approach. Many coils were seen in the external auditory meatus (d and e). After removing these coils from the external auditory meatus and then removing the surrounding bone, more underlying coils appeared (f). We removed most of them, and a small portion of the coils deep inside could not be completely removed. CTA showed good patency of the bypass 3 months later (c, arrow), and a small portion of the residual coils were still there (c, arrow head)

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Three months later, the patient returned to our department to address the coils in his ear. Partial coil removal together with auditory canal occlusion was performed through the transpetrosal approach (Fig. 4d–f). The postoperative course was uneventful, and the patient continues to be asymptomatic.

Discussion

Asymptomatic petrous ICA aneurysm can be managed conservatively because of the protection of the surrounding bony structure, but patients with symptoms, especially bleeding, should undergo more aggressive treatment [3, 19]. Proximal ligation of the ipsilateral ICA was the most frequently utilized treatment of these aneurysms in the early 1960s [20]. However, the morbidity and mortality associated with internal carotid ligation were significant [16]. ICA occlusion with bypass appears to be a better strategy, and although the procedure is challenging, an acceptable outcome was observed [1, 10]. With the advances in endovascular techniques, several authors have reported their results in treating petrous ICA aneurysm with coiling embolization. The treatment has been effective, but aneurysm residue and recanalization were common, especially for giant petrous ICA aneurysms [9]. Complete occlusion was only achieved in approximately half of the large and giant cerebral aneurysms by endovascular embolization [22]. These studies demonstrated that although short-term management was effective, the recurrence or coil compaction was the major problem leading to retreatment, which would increase morbidity. Embolization may be incomplete for giant aneurysms, and even if coiling is successful, the aneurysm may recanalize and regrowth or coils may suffer compaction, requiring further microsurgery [21]. In the present case, the aneurysm had recurred twice after complete embolization. Endovascular treatment would obviously have been an ineffective further treatment.

The advancement of modern endovascular technology allows mini-invasive endovascular intervention in more complex anatomical conditions [4, 5, 7, 14]. However, the endovascular approach has increased the risk of some certain complications such as aneurysmal perforation by guidewire, microcatheter, and/or coils. Ruptured aneurysms seem to be more susceptible to perforations related to endovascular intervention than unruptured ones [6]. In the present case, we were primarily concerned about the exposed coils. Giant petrous ICA aneurysms are always associated with a chronic osseous erosion and a thin aneurysmal wall. Therefore, aneurysmal wall penetration by coils is possible, although it is extremely rare that the surrounding bony structure would be penetrated at the same time. Thus, a CT scan of the petrous bone is suggested to evaluate the situation around the aneurysm before any coiling for a petrous ICA aneurysm is performed. In this case, if the patient received flow-diverter or liquid embolic treatment for the recurrent aneurysm rather than repeated coiling, both the recanalization and the subsequent rupture might have been avoided. However, the existence of the escaped coils made it impossible to perform endovascular treatment, as those escaped coils required removal because they could have become a source of infection leading to intracranial infection in the future. Of course, we have to trap the aneurysm first to secure the removal safely. Accordingly, we planned the operation in stages.

Conclusion

The patient is lucky to not have had a carotid blow out through his ear during the 9 years of conservative management. We offered the surgical treatment immediately after the patient was admitted to our medical center, and the treatment of EC-IC bypass with ICA occlusion was effective. It is relatively safe to remove the coils inside the aneurysm after the aneurysm is trapped. A giant petrous ICA aneurysm is still challenging, and the optimal treatment has yet to be determined. Both microsurgical treatment and endovascular treatment are effective for some cases but not perfect [12]. Therefore, it is important to make an appropriate choice between these two options.