Coiling ruptured aneurysms arising from the posterior genu of the cavernous internal carotid artery: A report of two cases

Abstract

Introduction and importance

Exceptionally, aneurysms from the posterior genu of the cavernous internal carotid artery (ICA) can rupture, resulting in subarachnoid hemorrhage (SAH). We reported such a case and provided another case with an unruptured aneurysm as a control to confirm the rarity of the ruptured aneurysm from the posterior genu of the cavernous ICA.

Case presentation

Case 1: This was a 46-year-old female with SAH. Computed tomography angiography (CTA) and digital subtraction angiography (DSA) confirmed that an aneurysm from the posterior genu of the right cavernous ICA had expanded into the intradural space and ruptured; the aneurysm was coiled completely. Postoperatively, she died from cerebral ischemia due to vasospasm. Case 2: This was a 59-year-old female with SAH. CTA and DSA revealed six aneurysms, including two mirror-like aneurysms from the bilateral anterior communicating artery (AcomA), two tandem aneurysms from the posterior genu of the left cavernous ICA, and two aneurysms from the bilateral anterior cavernous ICAs. After coiling the two tandem aneurysms from the posterior genu of the left cavernous ICA, the bilateral AcomA aneurysms were clipped, and rupture of the right AcomA aneurysm was confirmed. Follow-up CTA showed complete clipping of the bilateral AcomA aneurysms. Her Glasgow Outcome Scale score was 5. Endovascular treatment for residual aneurysms is planned for the future.

Clinical discussion

As shown in these two cases, the aneurysm from the posterior genu of the cavernous ICA can rupture, resulting in SAH; however, the rupture of other aneurysms must be excluded.

Conclusion

Once a ruptured aneurysm from the posterior genu of the cavernous ICA was confirmed, EVT was considered an alternative treatment.

Highlights

• •Rarely, the rupture of an aneurysm of the posterior genu of the cavernous ICA can result in SAH.
• •The treatment was necessary.
• •Endovascular treatment was useful to resolve the aneurysm.

1. Introduction

Uncommonly, cavernous internal carotid artery (ICA) aneurysms can rupture into the subarachnoid space, resulting in subarachnoid hemorrhage (SAH) [1]. These aneurysms are often located between loose proximal and distal dural rings and grow into the subarachnoid space [2]. The aneurysm from the posterior genu of the cavernous ICA is often extradural. It is exceptional that it can extend into the subarachnoid space and rupture, resulting in SAH [3,4]. We reported such a case and provided a similar case to confirm the rarity of aneurysm rupture from the posterior genu of the cavernous ICA into the subarachnoid space. Our work is in line with the SCARE criteria, which address the importance of patient privacy, consent, ethical considerations, and the need for clear and concise reporting of surgical procedures and outcomes [5].

2. Presentation of cases

2.1. Case 1

A 46-year-old female presented with sudden onset of headache and aphasia. She had no history of chronic disease or craniocerebral surgical treatment. On physical examination, she was drowsy, could not answer the questions correctly and had a Hunt–Hess grade II SAH. Her limbs had grade V muscle strength. Her neck was stiff. Computed tomography (CT) revealed a diffuse SAH involving the suprasellar, ambient and Sylvian fissure cisterns (Fig. 1A). CT angiography (CTA) revealed that the aneurysm had arisen from the posterior genu of the right cavernous ICA and protruded into the intradural space (Fig. 1B).

Fig. 1.

Pre- and post-EVT images of Patient 1. A: CT image showing subarachnoid hemorrhage in the suprasellar, ambient and Sylvian fissure cisterns. B: CTA image showing an aneurysm (arrow) arising from the posterior genu of the right cavernous ICA and protruding upward; the arrowhead indicates the ruptured bleb. C-D: Three-dimensional DSA reconstruction of the right ICA showing the aneurysm from the posterior genu of the right cavernous ICA (arrow in image C). There was a ruptured daughter bleb from the aneurysm (arrowhead in image D). E: DSA of the right ICA showing that the aneurysm was coiled completely. F: Five days after EVT, CT showed no intracranial hemorrhage or infarction. G: Eight days after EVT, CT revealed severe ischemia of the right hemisphere and mild ischemia of the left hemisphere. H: Bone window CT image showing that the coils did not leave the primary position. Abbreviations: CT: computed tomography; CTA: CT angiography, DSA: digital subtraction angiography, EVT: endovascular treatment, ICA: internal carotid artery, R: right.

Coiling embolization was planned under general anesthesia. During endovascular treatment (EVT), digital subtraction angiography (DSA) confirmed that the aneurysm with a ruptured bleb arose from the posterior genu of the right cavernous ICA and grew into the intradural space (Fig. 1C–D). Then, EVT was performed. First, an Echelon-10 microcatheter (Medtronic, Irvine, CA, USA) was catheterized into the aneurysm sac. Then, the aneurysm was completely embolized with coils (Axium Prime 5 mm × 20 cm, 3 mm × 8 cm and 2 × 8 cm (Medtronic, Irvine, CA, USA)) (Fig. 1E).

Postoperatively, the patient gradually recovered. On the 5th postoperative day, she could answer questions correctly, and her Hunt–Hess scale score was Grade I. Brain CT revealed SAH absorption (Fig. 1F). However, on the 8th postoperative day, she fell into a coma, and her Hunt–Hess scale grade was IV. She was transferred to the intensive care unit. Repeated CT showed severe ischemia in the right hemisphere and mild ischemia in the left hemisphere (Fig. 1G); the coils were in position (Fig. 1H). Transcranial Doppler revealed occlusion of the right middle cerebral artery and increased blood flow velocity in the left middle cerebral artery, indicating severe vasospasm of the bilateral hemispheres. It was suggested to her family that she undergo decompressive craniotomy, but they refused. Conservative treatment with mannitol dehydration (250 ml, q6h) and temperature control (34.5 °C–37 °C) with intubation and continuous use of anticonvulsants and muscle relaxants were given [6]. However, she died on the 11th postoperative day.

2.2. Case 2

A 59-year-old female suffered acute headache 20 days before admission. At that time, CT revealed a diffuse SAH involving the suprasellar, ambient and Sylvian fissure cisterns (Fig. 2A), and she was drowsy. The Hunt–Hess scale score was Grade II. She and her family refused surgical treatment, and conservative treatment was given to relieve her symptoms. After 20 days, the patient's condition improved, and only a slight headache remained. She and her family decided on surgical treatment and came to our hospital. On physical examination, she had no positive signs. Her Hunt–Hess scale score was grade I. CT showed SAH absorption (Fig. 2B). CTA revealed a left anterior communicating artery (AcomA) aneurysm and an aneurysm from the left cavernous ICA (Fig. 2C). EVT was performed under general anesthesia.

Fig. 2.

Pre- and post-EVT images of Patient 2. A: CT image showing SAH in the suprasellar, ambient and Sylvian fissure cisterns. B: CT image showing that the SAH had been absorbed. C: CTA showing aneurysms in the left AcomA (arrowhead) and posterior genu of the left cavernous ICA (arrow). D: Three-dimensional DSA of the right ICA showing an AcomA aneurysm (number 1) and an aneurysm from the anterior cavernous ICA (number 2). E: Three-dimensional DSA of the left ICA showing an AcomA aneurysm (number 3), an aneurysm of the anterior cavernous ICA (number 4), and two tandem aneurysms (numbers 5 and 6) of the posterior genu of the left cavernous ICA. F: DSA showing that the upper aneurysm (number 5) of the posterior genu of the left cavernous ICA was completely coiled, the lower aneurysm (number 6) was coiled loosely, and the aneurysm (number 4) was intact. Abbreviations: AcomA: anterior communicating artery, CT: computed tomography; CTA: CT angiography, DSA: digital subtraction angiography, EVT: endovascular treatment, ICA: internal carotid artery, L: left, R: right, SAH: subarachnoid hemorrhage.

During EVT, DSA revealed six aneurysms, including two from bilateral mirror-like AcomAs, two from bilateral anterior cavernous ICAs, and two from tandem aneurysms in the posterior genu of the left cavernous ICA (Fig. 2D–E). Coiling was performed for left cavernous ICA aneurysms in two tandem posterior genu, and then the bilateral AcomA aneurysms were clipped. The upper small aneurysm from the posterior genu of the left cavernous ICA was embolized completely with coils (Axium Prime 4 mm × 12 cm, 2 mm × 8 cm and 2 × 6 cm), and the lower large aneurysm was embolized loosely with coils (Axium 9 mm × 30 cm, 7 mm × 30 cm and 5 × 20 cm) (Fig. 2F).

The next day, craniotomy was performed via the left pterion approach, the bilateral AcomA aneurysms were clipped, and the rupture of the right AcomA aneurysm was confirmed intraoperatively (Fig. 3A-B). During craniotomy, exploratory surgery revealed that both the aneurysm of the left anterior cavernous ICA and the upper small aneurysm from the posterior genu of the left cavernous ICA were extradural and unruptured (Fig. 3C–D).

Fig. 3.

Aneurysm clipping and follow-up CTA images of Patient 2. A: Intraoperative image showing left (arrowhead) and right (arrow) AcomA aneurysms. B: Intraoperative image showing bilateral clipped AcomA aneurysms (arrow and arrowhead). C: The intradural region (frame) was explored, and a left cavernous ICA aneurysm could not be found. D: The intradural region (frame) was explored, and aneurysms from the left posterior genu of the cavernous ICA could not be found. They were extradural. The asterisk indicates the posterior clinoid process. E-F: Follow-up CTA showing complete clipping of bilateral AcomA aneurysms (arrow and arrowhead). Abbreviations: A1 and A2: First and second segments of the anterior cerebral artery, AcomA: anterior communicating artery, CTA: computed tomography angiography, ICA: internal carotid artery, L: left.

Postoperatively, the patient recovered gradually. One month later, she returned to work. Her Glasgow Outcome Scale score was 5. Three-month follow-up CTA revealed complete clipping of the bilateral AcomA aneurysms (Fig. 3E–F). EVT for the aneurysms from the bilateral anterior cavernous ICA and residual large aneurysms from the posterior genu of the left cavernous ICA are planned for the future.

3. Discussion

The cavernous ICA begins at the foramen lacerum at the superior margin of the petrolingual ligament and moves into the cavernous sinus (CS), which is surrounded by a venous plexus known as the CS. This segment exits the CS by piercing the dura extending medially from the upper surface of the anterior clinoid process. The cavernous ICA can be divided into five parts: the posterior vertical segment, the posterior bend, the horizontal segment, the anterior bend, and the anterior vertical segment [7].

Similar to other intracranial arteries, aneurysms can occur at the cavernous ICA, and these account for 2 %–9 % of all intracranial aneurysms [8]. Cavernous ICA aneurysms are often saccular and can be associated with its two main branches: the inferolateral trunk arising from the horizontal segment of the cavernous ICA and the meningohypophyseal trunk (MHT) arising from the posterior bend of the cavernous ICA [9]. Most small aneurysms of the cavernous ICA are benign and rarely rupture or grow [10]. Large or giant aneurysms may become symptomatic due to mass effects or rupture. However, the risk of rupture is low, with only 0.2 % of patients with large or giant aneurysms experiencing rupture [12].

By definition, a cavernous ICA is extradural, except at its termination, and it becomes partially intradural by traversing the clinoidal space between the proximal and distal dural rings. Therefore, rupture of the cavernous ICA aneurysm between the loose proximal and distal dural rings will lead to SAH if the aneurysm extends through the dura into the subarachnoid space. It was uncommon for the rupture of aneurysms in other cavernous ICA regions to result in SAH. However, rupture of aneurysms from the posterior bend of the cavernous ICA (also called the posterior genu) can rarely result in SAH.

To date, such cases have rarely been reported [3,4]. We reported such a case and provided a similar case to confirm the rarity of aneurysm rupture from the posterior genu of the cavernous ICA into the subarachnoid space. In Patient 1, no other aneurysms were responsible for the SAH except for the aneurysm from the posterior genu of the cavernous ICA. In addition, a ruptured bleb was found at the tip of the aneurysm, providing evidence for the origin of the SAH. Ruptured aneurysms from the posterior genu of the cavernous ICA into the subarachnoid space should be subjected to aggressive treatment to avoid rebleeding. EVT by traditional coiling with/without stent assistance is a good choice. Flow diverter treatment is also an alternative. In Patient 1, the posterior genu of the cavernous ICA aneurysm was small and saccular. Thus, traditional coiling was sufficient.

In Patient 2, who had multiple aneurysms, it was difficult to determine which aneurysm was ruptured. Because two aneurysms from the posterior genu of the left cavernous ICA were difficult to treat by clipping, they were coiled first. As in Patient 1, the upper aneurysm from the posterior genu of the left cavernous ICA protruded into the intradural space; therefore, dense coiling was performed. The lower aneurysm was located in the extradural space; thus, loose coiling was performed. The bilateral AcomA aneurysms are small and wide-necked, and the proximal anterior cerebral arteries are tortuous; thus, EVT was not easy. Therefore, a craniotomy can be used to clip bilateral AcomA aneurysms, and whether the aneurysms of the posterior genu of the left cavernous ICA are ruptured can be explored and confirmed. During craniotomy, the right AcomA aneurysm was confirmed to be a ruptured aneurysm; thus, aneurysms from the posterior genu of the cavernous ICA can rarely be the origin of an SAH.

The causes of the aneurysm rupture from the posterior genu of the cavernous ICA into the intradural and subarachnoid spaces are not completely clear but are likely associated with the dural anatomy at this location. The posterior genu of the cavernous ICA can sometimes bulge upward into and deform the dura of the roof of the CS just lateral to the posterior clinoid process, which may produce a potential point of weakness of the ICA at the posterior genu, where the MHT originates (Fig. 4). In addition, a possible route of intradural extension of the aneurysm is through the meningeal sheath, which wraps the subarachnoid space of cranial nerve III as it enters the CS [3]. Certainly, growing aneurysms can directly erode the dura into the intradural and subarachnoid spaces. Another etiological hypothesis for this finding is that initially, a large adenoma may have eroded the dural boundary. Subsequently, shrinkage of this adenoma left a residual dural defect, allowing communication between the CS and the subarachnoid space [4]. However, no evidence of pituitary adenoma was observed in our patients.

Fig. 4.

CTA anatomy of the posterior genu of the cavernous ICA. The posterior genu of the cavernous ICA on CTA is indicated by the arrows in panels A (superior inferior view) and B (lateral view). The asterisks indicate the location of the aneurysm from the posterior genu of the cavernous ICA, which can protrude upward and into the intradural subarachnoid space. Abbreviations: CTA: computed tomography angiography, ICA: internal carotid artery.

Regrettably, in Patient 1, after EVT, the patient died from delayed cerebral ischemia due to vasospasm that had been confirmed by transcranial Doppler. In addition, on CT, the area of cerebral ischemia was wide and bilateral, and the coils were in position, providing further evidence of vasospasm.

4. Conclusion

Exceptionally, an aneurysm of the posterior genu of the cavernous ICA can rupture into the subarachnoid space, resulting in SAH; however, the rupture of other aneurysms should be excluded. Once the aneurysm of the posterior genu of the cavernous ICA was confirmed to be ruptured, EVT was useful for resolving the aneurysm.

Consent for publication

Written informed consent was obtained from the patient for publication of this case report and accompanying images. A copy of the written consent is available for review by the Editor-in-Chief of this journal on request.

Provenance and peer review

Not commissioned, externally peer-reviewed.

Ethical approval

Ethical approval is not needed for case reports in our institution (The First Hospital of Jilin University).

Funding

No funding.

Author contribution

Jinlu Yu contributed to the study conception and design. Zhuo Chen wrote the draft of the manuscript. All authors read and approved the final manuscript.

Guarantor

Jinlu Yu, Department of Neurosurgery, The First Hospital of Jilin University. E-mail: jlyu@jlu.edu.cn

Research registration number

Not applicable. This is a case reports not a research study.

Conflict of interest statement

All authors declare that they have no conflicts of interest.

Data availability statement

The datasets used and/or analyzed in the current study are available from the corresponding author upon reasonable request.