2025 年 19 巻 1 号 論文ID: cr.2024-0118
Objective: We report a case in which coil embolization was performed for an angiographically occult ruptured anterior communicating artery aneurysm (Acom AN).
Case Presentation: A 91-year-old man was admitted to our hospital because of sudden deterioration of consciousness. Computed tomography (CT) revealed a diffuse subarachnoid hemorrhage in the basal cisterns, and CT angiography identified a 5-mm Acom AN. The next day, a catheter angiogram slightly visualized the neck portion of the Acom AN, despite no apparent visualization of the aneurysmal sac. We suspected intraluminal thrombosis of ruptured Acom AN, and intraaneurysmal coil embolization was performed to prevent re-rupture. By referring to the size and projection of the aneurysmal sac on CT angiography, a microcatheter was guided into the neck portion, and 3 platinum coils were successfully placed within the aneurysm without any complications. Eight days after coil embolization, recanalization of the aneurysm was suspected on magnetic resonance imaging (MRI). Another MRI obtained 17 days after coil embolization revealed gradual recanalization of the aneurysm, which was confirmed on catheter angiogram obtained 22 days after coil embolization. Additional intraaneurysmal coil embolization resulted in complete occlusion. Subsequently, the patient had an uneventful course without rebleeding and was transferred to a rehabilitation center.
Conclusion: We performed intraaneurysmal coil embolization for an angiographically occult ruptured Acom AN by referencing the neck position, aneurysm projection, and aneurysm size on CT angiography. Thus, angiographically occult aneurysms can be treated with endovascular coil embolization despite the need for close follow-up studies to detect recanalization.
Catheter angiography is the gold standard for identifying hemorrhagic sources of spontaneous subarachnoid hemorrhage (SAH). However, hemorrhagic sources have not been identified in approximately 10%–20% of patients with SAH.1) In such cases, repeat angiography can be used to identify blister-like microaneurysms and dissecting lesions. Once intraluminal thrombosis occurs, ruptured aneurysms are rarely detected using catheter angiography.2) Aneurysm with intraluminal thrombosis cannot be identified on catheter angiography. This kind of angiographically occult aneurysm is relatively rare.3–5) Here, we report a case in which coil embolization was performed for an angiographically occult ruptured anterior communicating artery aneurysm (Acom AN) under the guidance of computed tomography (CT) angiography.
A 91-year-old man suddenly collapsed during outdoor activities and was admitted to the emergency department. On admission, the patient exhibited a mild deterioration of consciousness. CT revealed a diffuse subarachnoid cistern in the basal cistern (Fig. 1A), and a CT angiogram identified Acom AN with a 5-mm dome, a 3-mm neck, and a bleb at the tip, originating from the anterior communicating artery and A2 segment of the left anterior cerebral artery (Fig. 1B). The following day, intraaneurysmal coil embolization was performed. A left internal carotid artery angiogram demonstrated faint delineation of the neck of the Acom AN; however, the aneurysm body was not clearly visualized (Fig. 2A). Therefore, intraluminal thrombosis in the ruptured Acom AN was suspected. We had a discussion on treatment strategy. There were 3 options: no interventions, surgical neck clipping, and endovascular coil embolization. Using CT angiogram images, we were able to establish the working angle based on the CT angiogram image and estimate the aneurysm projection. Surgical neck clipping was discouraged for 90-year-old patients due to its invasiveness. Also, there remains concern for re-rupture by no interventions at acute phase and follow-up strategy. We considered that we were able to navigate the microcatheter to the AN neck and perform deployment of coils to the AN dome. Then, we tried to perform coil embolization to prevent re-rupture of angiographical occult ruptured Acom AN. The treatment strategy was thoroughly planned for angiographical occult AN. The major issues in coil embolization of angiographical occult AN is perforation of AN and migration of intraluminal thrombus. To avoid these critical complications, we tried to conduct safe coil embolization by the following schemes: First, the tip of the microcatheter was placed at the AN neck, not in the invisible AN dome. Second, undersized and soft coils were selected so as not to induce perforation of ruptured AN and avoid migration of intraluminal thrombosis. Undersized and soft coils were gently delivered to the AN dome from the microcatheter whose tip was placed at the AN neck. Third, we set the goal of 1st treatment as prevention of re-rupture at the acute phase. Further intraluminal thrombosis is expected by placement of coils. Then, the goal of the 1st treatment was body filling of the ruptured AN.
Under general anesthesia and systemic heparinization, a super compliant occlusion balloon catheter Transform 3 × 5 mm (Stryker, Kalamazoo, MI, USA) was prepared in case of intraoperative rupture. A 6-Fr guiding sheath (Fubuki Dilator Kit; Asahi Intecc, Aichi, Japan) was placed at the distal cervical portion of the left internal carotid artery. To prevent perforation of the ruptured Acom AN and migration of intraluminal thrombosis, the tip of the microcatheter was placed at the AN neck and the coils were gently placed into the aneurysmal dome. A Phenom 17 preshaped 45° microcatheter (Medtronic, Minneapolis, MN, USA) was guided into the aneurysmal neck using a CHIKAI 0.014 microguidewire (Asahi Intecc) (Fig. 2B and 2C). Framing was initially performed using a Target 360 Ultra Soft coil 3 mm × 4 cm (Stryker). Angiogram after framing confirmed no complications, including thrombus migration and perforation. Subsequently, Avenir Finishing coils 2.5 mm × 3 cm and 1.5 mm × 2 cm (Wallaby Medical, Laguna Hills, CA, USA), which were smaller in size than the framing coil, were placed as filling coils without deviating from the framing coil. The embolization was completed after confirming no visualization of aneurysmal dome and no complications (Fig. 2D). The final angiogram confirmed no filling of the aneurysm dome and no evidence of perforations and thrombus migration (Fig. 2E). The postoperative CT confirmed no evidence of hemorrhagic complications (Fig. 2F). The diffusion-weighted magnetic resonance (MR) imaging on the next day after surgery showed no evidence of infarctions in the anterior cerebral artery territory (Fig. 2G). The patients did not show postoperative neurological deterioration. A lumbar drain was inserted, and fasudil hydrochloride was administered intravenously. Aspirin (100 mg/day) was administered orally. MR angiogram performed the day after coil embolization did not demonstrate recanalization of the aneurysm (Fig. 3A and 3B). However, recanalization of the aneurysm was suspected on MR imaging 8 days after coil embolization. Follow-up MR imaging obtained 17 days after coil embolization demonstrated obvious recanalization of the aneurysm (Fig. 3C–3F). Additional intraaneurysmal coil embolization was performed 22 days after the initial treatment. Under local anesthesia and systemic heparinization, a 6-Fr guiding sheath (Fubuki Dilator Kit; Asahi Intecc) was placed in the distal cervical segment of the left internal carotid artery. Catheter angiography confirmed recanalization of the anterior communicating artery aneurysm, with coils filling the lower portion of the aneurysm. The residual dome was 4.1 × 3.7 × 4.0 mm in size (Fig. 4A). Using a 6-Fr Navien 115 cm (Medtronic) as a distal access catheter through the guiding sheath, a Phenom 17 preshaped 45° microcatheter (Medtronic) was guided into the aneurysm using a Synchro select soft 0.014 microguidewire (Stryker). An Axium Prime 3D coil 3 mm × 4 cm (Medtronic) was used to fill in the residual aneurysmal dome. The aneurysm was occluded with a total of 10 platinum coils (Fig. 4B), and the final angiogram confirmed complete obliteration of the aneurysm (Fig. 4C). The patient did not exhibit any new postoperative neurological symptoms. The patient was transferred to a rehabilitation center 2 months after surgery (modified Rankin Scale score, 4).
Angiographically occult aneurysms are a general concern in the management of spontaneous SAH. There are several causes of angiographically occult aneurysms, including cerebral vasospasm, intraluminal thrombus, compression by a hematoma, subarachnoid hemorrhage of unknown etiology, and misdiagnosis.6) In the present case, the catheter angiogram faintly showed the neck of the ruptured Acom AN, whereas the CT angiogram on admission clearly showed a ruptured Acom AN. We estimated that the intraluminal thrombus was the cause of failure to visualize the ruptured aneurysm on the catheter angiogram. Ishikawa et al. investigated the mechanisms of intraluminal thrombosis by performing pathological examinations of ruptured aneurysms.7–9) Based on the location of clot formation, hemostatic patterns were categorized into (1) an outside pattern, in which the surface of the aneurysm rupture point was sealed from the outside by the clot; (2) inside pattern, in which the thrombus was attached to the rupture point from inside the aneurysm; (3) inside-outside pattern, in which the thrombus extended from the inside to the outside of the rupture point; and (4) membrane pattern, in which the rupture point was changed to a fibrin wall-like membrane without distinct thrombus formation. The most common type is the outside pattern; it shows relatively less thinning of the aneurysm wall around the rupture site, whereas the inner pattern shows significant thinning and fragmentation of the surrounding aneurysm walls. Complete intraluminal thrombosis has also been observed in approximately 2% of cerebral aneurysms.7–9) Collectively, angiographically occult aneurysms caused by intraluminal thrombosis should be considered in the diagnosis of spontaneous SAH.
Treatment strategy for angiographically occult aneurysms is controversial. Surgical neck clipping appears to be the best treatment strategy to assess the status of ruptured aneurysms; however, this procedure is considered extremely invasive in a 90-year-old patient. Postoperative systemic complications, including respiratory failure and cardiac events, could be fatal for older patients who underwent surgical neck clipping.10) Repeated catheter angiography without any surgical or endovascular intervention is also a viable treatment option.11) If we select close observation, there is a concern for re-rupture of the ruptured aneurysm. Until the completion of interventions for the ruptured aneurysm, termination of sedation and initiation of rehabilitation is discouraged. For super older patients, a long period of bed rest could result in severe systemic complications, such as pulmonary embolism and frailty. The natural history of ruptured aneurysms with intraluminal thrombosis remains poorly understood. Honda and Anda conducted a literature review on cases of subarachnoid hemorrhage in which the bleeding source was not identified on the initial catheter angiogram. They reported that identification of the bleeding source by repeated catheter angiography was achieved in 4%–21% of initially angiographical occult aneurysms.5) Chohan et al. documented the case of a ruptured basilar artery aneurysm, which was angiographically occult.12) The authors did not perform any surgical interventions. This ruptured basilar artery aneurysm resulted in re-rupture 26 days after 1st rupture. This case indicates that ruptured aneurysms with apparently complete intraluminal thrombosis could result in re-rupture. Collectively, endovascular intraaneurysmal coil embolization can be a treatment option for angiographically occult ruptured aneurysms especially for older cases, despite the need of caution for intraoperative rupture and thrombus migration.
When performing coil embolization for angiographically occult aneurysms, it is essential to accurately estimate the aneurysm’s morphology. In the present case, delivery of the microcatheter into the ruptured Acom AN was successful with the assistance of CT angiogram. Thus, we performed endovascular intraaneurysmal coil embolization for this angiographically occult ruptured Acom AN. CT angiogram is useful for predicting the location, vessels, and projection of the aneurysm, and for establishing the working angle.13) However, CT angiogram evaluates the lumen of the blood vessel and may not accurately assess the shape of an aneurysm that could be thrombosed. MR imaging could help estimate the accurate morphology of this ruptured aneurysm with intraluminal thrombosis. Yoshida et al. evaluated the external diameter of occluded arteries and thrombosed aneurysms using basiparallel anatomic scanning (BPAS)-MR imaging in a case of acute occlusion and recanalization of vertebral artery dissection following subarachnoid hemorrhage.14) In the present case, MR imaging after confirming angiographically occult aneurysm may further help understand the aneurysm morphology. Understanding of accurate morphology and intrananeurysmal status could facilitate the safe endovascular coil embolization for angiographically occult aneurysms.
Coil embolization for angiographical occult aneurysm harbors specific risk of operative complications. One of the critical operative risks is perforation of the ruptured aneurysms. Since the aneurysm dome is invisible on catheter angiogram, deployment of coil was based on the estimation using CT angiogram. In addition, to avoid perforation of the ruptured aneurysm, soft and small coils were placed in the dome of the ruptured aneurysm. Tight packing of the aneurysmal sac is unnecessary. Another critical operative risk is migration of intraluminal thrombosis. Deployment of platinum coils could migrate intraluminal thrombosis to parent vessels, leading to ischemic complications. Balloon-assisted coil embolization may help minimize the risk of thrombus migration. The disadvantage of this strategy is to restrict microcatheter maneuverability, increasing pressure on the aneurysmal wall and elevating the risk of intraoperative rupture. Furthermore, aneurysm morphology is critical for safe intraaneurysmal coil embolization for angiographical occult aneurysms. Critical issues for safe intranaeurysmal coil embolization is to ensure that the coils are deployed without resistance against the aneurysmal wall and avoidance of intraluminal thrombus migration. Then, tiny angiographical occult aneurysms harbor high risk of perforation. Also, angiographical occult aneurysms with a broad neck harbor the risk of thrombus migration. Therefore, we can have a chance to conduct safe intraaneurysmal coil embolization for angiographical occult aneurysms with a relatively narrow neck and not tiny ones. Then, we performed intra-aneurysmal coil embolization without any adjunctive technique by gentle deployment of soft and small platinum coils. There is still a risk of re-rupture after embolization of angiographically occult aneurysm. Even if intraaneurysmal coil embolization for angiographical occult aneurysm was performed, only body filling of the aneurysm could be achieved. Then, close postoperative follow-up is mandatory to detect the recanalization of angiographically occult aneurysms. Once recanalization of the treated angiographically occult aneurysm is evident, retreatment should be planned immediately. In the present case, follow-up MR imaging identified recanalization of the angiographical occult aneurysm, which was further treated by additional coil embolization. Taken together, intranauerysmal embolization for angiographically occult aneurysm can be a useful option in cases where neck clipping or conservative management is unlikely to achieve a favorable outcome.
We present an angiographically occult ruptured Acom AN that was treated with intraaneurysmal coil embolization with the assistance of CT angiography. Despite successful coil embolization of the angiographically occult aneurysm, there was a risk of intraoperative rupture and migration of the intraluminal thrombus. In addition, close follow-ups are imperative because body filling can be achieved.
We would like to thank Editage (www.editage.jp) for English language editing.
This study was supported by the Japan Society for the Promotion of Science Grant-in Aid for Scientific Research A (22K16675).
The authors declare that they have no conflicts of interest.
