A coexisting pseudoaneurysm hidden behind a saccular distal middle cerebral artery aneurysm in long-standing postirradiation vasculopathy: illustrative case

Abstract

BACKGROUND

Delayed cerebrovascular complications after childhood cranial irradiation may include progressive vasculopathy and aneurysmal disease. However, attributing a ruptured aneurysm directly to prior irradiation can be difficult in patients with complex preexisting cerebrovascular pathology. The authors describe a diagnostic pitfall in a patient with long-standing postirradiation vasculopathy who presented with hemorrhagic distal middle cerebral artery (MCA) aneurysmal lesions.

OBSERVATIONS

A 51-year-old man who had undergone whole-brain irradiation for pineal germinoma at 8 years of age presented with intracerebral and subarachnoid hemorrhage. He had a long history of progressive cerebrovascular disease, including recurrent ischemic strokes, prior intracerebral hemorrhage, intracranial arterial stenosis, and a previously treated internal carotid artery aneurysm. MR angiography and initial digital subtraction angiography demonstrated a newly detected saccular distal MCA aneurysm, which was treated with coil embolization. Hematoma enlargement occurred the following day. Repeat angiography showed complete obliteration of the treated saccular aneurysm but revealed a coexisting pseudoaneurysm in the same vascular territory. Parent artery occlusion achieved definitive hemostasis without additional clinically apparent neurological deterioration.

LESSONS

In patients with long-standing postirradiation vasculopathy, a conspicuous saccular aneurysm may obscure a coexisting pseudoaneurysm. Repeat angiography should be considered when hemorrhage progresses despite apparent aneurysm obliteration.

https://thejns.org/doi/10.3171/CASE26561

Cerebrovascular complications are recognized late effects of childhood cranial irradiation and may include both large- and small-vessel disease. Intracranial arterial stenosis, moyamoya-like changes, ischemic stroke, hemorrhage, cerebral microbleeds, and aneurysmal lesions can emerge years to decades after treatment.^1–5 However, in patients with complex preexisting cerebrovascular pathology, a direct causal relationship between prior irradiation and a newly detected aneurysmal lesion may be difficult to establish.

Pseudoaneurysms are particularly challenging because they may be small, dynamically evolving, partially thrombosed, or associated with delayed contrast filling.^6,7 In the setting of acute intracranial hemorrhage, a conspicuous saccular aneurysm may lead to anchoring bias and obscure a coexisting pseudoaneurysm in the same vascular territory. Failure to recognize such a lesion can result in incomplete treatment of the true bleeding source.

We report an illustrative case of a patient with long-standing postirradiation vasculopathy who presented with intracerebral hemorrhage (ICH) and subarachnoid hemorrhage (SAH) from distal middle cerebral artery (MCA) aneurysmal lesions. An initial angiographic study identified a saccular aneurysm, but hematoma enlargement after coil embolization prompted repeat angiography, which revealed a coexisting pseudoaneurysm requiring parent artery occlusion (PAO). This case highlights the risk of anchoring bias in hemorrhagic distal aneurysmal lesions and the importance of repeat angiography when clinical or radiological findings are discordant with apparent aneurysm obliteration.

Illustrative Case

A 51-year-old man was brought to our hospital from a long-term care facility because of sudden deterioration in consciousness and vomiting. He had undergone whole-brain irradiation with a total dose of 60 Gy at 8 years of age for pineal germinoma, followed by ventriculoperitoneal shunt placement for hydrocephalus. During adulthood, he developed progressive cerebrovascular disease, including recurrent ischemic strokes, prior ICH, diffuse intracranial arterial stenosis, and an unruptured left internal carotid artery (ICA) aneurysm that had been treated with coil embolization at 39 years of age, as previously reported.^4,5 His preevent functional status was a modified Rankin Scale (mRS) score of 5. He was fully dependent for activities of daily living because of severe dysarthria, dysphagia, and left hemiparesis, but he was able to communicate by nodding.

On arrival, his Glasgow Coma Scale score was 11 (E4V2M5). Neurological examination showed worsening consciousness and severe bilateral limb weakness, more pronounced on the left side, compared with his preevent baseline. Noncontrast CT demonstrated a right frontal ICH with associated SAH (Fig. 1A and B). MR angiography (MRA) showed a newly detected distal right MCA aneurysmal lesion located near the hematoma (Fig. 1C). This lesion had not been present on surveillance MRA obtained 1 year earlier or on earlier imaging performed at the time of the previously treated left ICA aneurysm (Fig. 1D and E). These findings suggested de novo formation of a distal MCA aneurysmal lesion within a previously irradiated vascular territory.

FIG. 1.

Initial images and identification of a de novo aneurysmal lesion. Axial (A) and coronal (B) noncontrast head CT scans obtained on admission showing a right frontal ICH with associated SAH. MR angiogram (C) obtained on admission demonstrating a distal right MCA aneurysm (arrow) located within the ICH. MR angiogram (D) obtained 1 year earlier showing no aneurysm in the distal right MCA (arrow), supporting the de novo appearance of the distal MCA aneurysmal lesion. MR angiogram (E) obtained at 39 years of age demonstrating a left ICA aneurysm (arrowhead) but no aneurysm in the distal right MCA (arrow). No recurrence of the previously treated left ICA aneurysm is observed in panels C and D. Anteroposterior (F and H) and lateral (G and I) diagnostic digital subtraction angiograms confirming a saccular aneurysm in the distal right MCA (arrows in F and G), corresponding to the lesion identified on the MR angiogram. In the venous phase, a small focus of contrast pooling is retrospectively recognized (arrows in H and I); however, this finding was not appreciated at the time of the initial evaluation.

Digital subtraction angiography (DSA) demonstrated a 4 × 2–mm saccular aneurysm arising from a distal right MCA branch, corresponding to the lesion detected on MRA (Fig. 1F–I). No other definite bleeding source was identified prospectively. Because the saccular aneurysm was considered the most likely source of hemorrhage, endovascular coil embolization was performed under general anesthesia and systemic heparinization. An 8-Fr Optimo balloon guiding catheter (Tokai Medical Products) was positioned in the right ICA, and a Guidepost intermediate catheter (Tokai Medical Products) was advanced into the right MCA. A 45° steam-shaped Excelsior SL-10 microcatheter (Stryker Neurovascular) was navigated into the aneurysm using a 0.010-inch TENROU S10 microguidewire (Kaneka Medical Products). Two Numen MicroFinish detachable coils (MicroPort NeuroTech) were deployed, achieving complete angiographic obliteration of the saccular aneurysm (Fig. 2). The patient had been receiving cilostazol before onset because of prior ischemic strokes. Aspirin loading of 200 mg was administered before the initial endovascular treatment, and coil embolization was performed without stent placement.

FIG. 2.

Endovascular treatment of the saccular aneurysm and retrospective identification of a pseudoaneurysm. Initial anteroposterior (A) and lateral (B) view intraoperative digital subtraction angiograms obtained during the first procedure demonstrating a 4 × 2–mm saccular aneurysm in the distal MCA projecting upward (arrow). Magnified anteroposterior (C) and lateral (D) views showing the aneurysm selected as the presumed bleeding source (arrow). Postembolization anteroposterior (E) and lateral (F) arterial-phase angiograms demonstrating complete obliteration of the treated saccular aneurysm. Postembolization anteroposterior (G) and lateral (H) delayed-phase angiograms showing faint contrast pooling in the distal vessel beyond the treated aneurysm, retrospectively corresponding to a pseudoaneurysm that was not appreciated during the initial evaluation.

On the following day, however, repeat CT showed enlargement of the ICH (Fig. 3A and B). MRA confirmed disappearance of the treated ­saccular aneurysm but did not reveal another structural lesion suggestive of a bleeding source (Fig. 3C). Given the radiological progression despite apparent aneurysm obliteration, repeat DSA was performed. The repeat study showed persistent occlusion and collapse of the treated saccular aneurysm but newly demonstrated a small pseudoaneurysm in the same distal MCA territory (Fig. 4A–C). Retrospective review of the initial angiographic study revealed subtle delayed contrast pooling distal to the treated saccular aneurysm, suggesting that the pseudoaneurysm had been present but was overlooked because of its small size, delayed filling, and the more conspicuous adjacent saccular aneurysm.

FIG. 3.

Images obtained after the first intervention. Axial (A) and coronal (B) head CT scans obtained the day after the first procedure showing expansion of the ICH. MR angiogram (C) obtained on the same day demonstrating the disappearance of the treated aneurysm and no alternative structural lesion suggesting a bleeding source.

FIG. 4.

Repeat angiograms and definitive treatment of the pseudoaneurysm. Repeat 3D (A), anteroposterior (B), and lateral (C) digital subtraction angiograms demonstrating no recanalization of the treated saccular aneurysm (arrowhead) and clearly delineating a peripheral pseudoaneurysm that had not been appreciated on the initial evaluation (arrow). Anteroposterior (D) and lateral (E) views of PAO performed using additional coils (arrow). Anteroposterior (F and H) and lateral (G and I) postprocedural angiograms demonstrating complete disappearance of both aneurysms, with no residual contrast pooling in the venous phase.

Because the pseudoaneurysm was small, distal, and morphologically fragile, selective coil embolization of the lesion itself was considered unsuitable. PAO was therefore performed under general anesthesia. An 8-Fr Optimo balloon guiding catheter was again positioned in the right ICA, and a Guidepost intermediate catheter was advanced into the right MCA. A 90° steam-shaped Excelsior SL-10 microcatheter was navigated to the distal parent artery using a 0.014-inch CHIKAI Nexus microguidewire (Asahi Intecc). Two additional Numen MicroFinish detachable coils were deployed to achieve PAO (Fig. 4D and E). Final angiography demonstrated complete disappearance of both ­aneurysmal lesions without residual delayed contrast pooling (Fig. 4F–I). Endoscopic hematoma evacuation was also performed. After PAO, cilostazol alone was continued without additional dual antiplatelet therapy.

No further hemorrhage occurred after PAO. Diffusion-weighted MRI obtained 5 days after PAO demonstrated a small focal infarction in the right frontal lobe within the distal right MCA territory (Fig. 5A and B). However, no additional clinically apparent neurological deterioration was observed, and the patient’s neurological status returned to his preevent baseline, with an mRS score of 5 at discharge. Follow-up CT demonstrated resolution of the ICH, and follow-up MRA showed no evidence of recurrence of the treated lesions or new aneurysmal lesion formation (Fig. 5C– E).

FIG. 5.

Posttreatment and follow-up images. Axial diffusion-weighted MR images (A and B) obtained 5 days after PAO demonstrating a small focal infarction in the right frontal lobe within the distal right MCA territory (circle). Follow-up axial (C) and coronal (D) head CT scans obtained 2 months after the procedures showing resolution of the intracerebral hematoma. Follow-up MR angiogram (E) demonstrating no evidence of recurrence or new aneurysmal lesion.

Informed Consent

The necessary informed consent was obtained in this study.

Discussion

Observations

This illustrative case highlights the rare coexistence of two distinct aneurysmal morphologies—a saccular aneurysm and a ­pseudoaneurysm—within the same distal MCA territory in a patient with long-standing postirradiation vasculopathy. Initial MRA and DSA demonstrated a saccular aneurysm, which was considered the most likely bleeding source and was treated with coil embolization. However, hematoma enlargement occurred despite apparent angiographic obliteration of the saccular aneurysm. Repeat angiography revealed a coexisting pseudoaneurysm in the same distal vascular territory, and PAO achieved definitive hemostasis. The case therefore emphasizes not only the diagnostic pitfall of pseudoaneurysm detection, but also the need to consider multiple aneurysmal lesions with different morphologies in hemorrhagic distal arterial territories.

Cranial irradiation during childhood is associated with delayed cerebrovascular complications that may emerge years to decades after treatment. These complications include large-vessel disease, such as intracranial arterial stenosis, moyamoya-like vasculopathy, and aneurysmal lesions, as well as small-vessel disease, such as lacunar infarctions, cerebral microbleeds, white matter injury, and hemorrhage.^1–3 In the present case, the patient had undergone whole-brain irradiation at 8 years of age and subsequently developed progressive cerebrovascular disease, including seven ischemic strokes, prior ICH, diffuse intracranial arterial stenosis, multiple cerebral microbleeds, white matter lesions, brain atrophy, and a previously treated ICA aneurysm. This ultra-long-term clinical course, reported separately as a case of progressive postirradiation cerebrovascular disease, suggested long-standing vasculopathy involving both large and small vessels more than 40 years after childhood cranial irradiation.^4,5 The newly detected distal MCA aneurysmal lesions arose within a previously irradiated vascular territory and were absent on surveillance imaging performed 1 year earlier. These findings support a possible association with postirradiation vasculopathy.

However, the causal relationship between prior cranial irradiation and an individual aneurysmal lesion cannot be proven in a single case. This patient had complex preexisting cerebrovascular pathology, and other mechanisms, including degenerative, dissecting, hypertensive, inflammatory, infectious, or nonspecific fragile distal arteriopathy, cannot be completely excluded. Therefore, the lesion is best regarded as a suspected radiation-associated aneurysmal lesion occurring in the setting of long-standing postirradiation vasculopathy rather than as a definitive radiation-induced aneurysm.

Radiation-associated intracranial aneurysms are rare but have been increasingly recognized in the literature.^4,6–11 They may develop after a long latency period and can occur within irradiated vascular territories. Reported morphologies include saccular, fusiform, dissecting, and pseudoaneurysmal lesions, suggesting heterogeneous arterial wall pathology after irradiation.^4,7–11 Previous reports have also suggested that such aneurysms may have a higher rupture risk than sporadic aneurysms and may be difficult to treat because of vessel wall fragility and coexisting vasculopathy.^7–9 In the present case, the coexistence of a saccular aneurysm and a pseudoaneurysm in the same distal MCA territory was unusual and clinically important. Although this dual morphology may be compatible with heterogeneous vascular injury in a previously irradiated field, it should not be interpreted as radiation specific. The main contribution of this case is therefore not simply the delayed recognition of the pseudoaneurysm, but the coexistence of two morphologically distinct aneurysmal lesions in the same hemorrhagic distal arterial territory, which created a diagnostic and therapeutic pitfall.

The coexistence of a conspicuous saccular aneurysm and a subtle pseudoaneurysm created the central diagnostic pitfall in this case. Intracranial pseudoaneurysms are often difficult to diagnose because they may be small, morphologically unstable, partially thrombosed, or characterized by delayed contrast filling.^12,13 Noninvasive imaging, including MRA, may fail to depict such lesions, particularly in the acute hemorrhagic setting. In this case, MRA demonstrated the saccular aneurysm but did not show the pseudoaneurysm. Initial DSA also led to prospective identification of the saccular aneurysm as the presumed bleeding source. Retrospective review, however, revealed subtle delayed contrast pooling distal to the treated aneurysm, suggesting that the pseudoaneurysm had been present at the initial evaluation but was overlooked. The more conspicuous adjacent saccular aneurysm likely contributed to anchoring bias. This case therefore underscores the need for systematic review of arterial, capillary, and delayed phases of angiography when evaluating hemorrhagic distal aneurysmal lesions.

Repeat angiography was decisive. Hematoma enlargement after complete coil occlusion of the saccular aneurysm created a discrepancy between the apparent angiographic result and the clinical-radiological course. Repeat DSA clarified the residual bleeding risk by demonstrating the coexisting pseudoaneurysm. This sequence suggests that, when hemorrhage progresses despite apparent treatment of an aneurysm, clinicians should maintain a low threshold for repeat angiographic evaluation rather than assuming that the treated lesion was the only bleeding source. This principle may be particularly important in patients with postirradiation vasculopathy, in whom diffuse arterial wall injury, stenotic changes, and fragile distal vessels can complicate interpretation and management.

The endovascular strategy in this case was determined by lesion morphology. The saccular aneurysm was well defined and could be selectively catheterized and treated with coil embolization. In contrast, the pseudoaneurysm was small, distal, and morphologically fragile, making selective coil embolization of the pseudoaneurysm itself unsuitable. PAO was therefore selected and achieved definitive disappearance of both aneurysmal lesions without additional clinically apparent neurological deterioration. Previous reports on intracranial pseudoaneurysms and radiation-associated aneurysms have similarly emphasized that treatment must be individualized according to morphology, location, collateral circulation, and the feasibility of vessel preservation.^8,9,11–13 In distal fragile pseudoaneurysms, PAO remains a practical option when selective reconstruction or intrasaccular treatment is unsafe or technically unfeasible.

Microsurgical treatment is another important option for distal MCA pseudoaneurysms. Clipping, trapping, or excision with or without revascularization, such as superficial temporal artery–MCA bypass, may provide definitive treatment depending on the lesion location, collateral circulation, and eloquence of the distal territory.^10,12,14,15 Open surgical exploration may also allow pathological examination of the aneurysmal wall, which could support or refute radiation-induced vascular injury. In the present case, however, endovascular PAO was selected because the pseudoaneurysm was located in a distal MCA branch, the lesion was morphologically fragile, the patient had severe preexisting neurological disability, and immediate hemorrhage control was required. The small focal infarction on postprocedural diffusion-weighted MRI underscored the ischemic risk of parent vessel sacrifice, although no additional clinically apparent neurological deterioration occurred.

This case has several limitations. The causal relationship between prior cranial irradiation and the newly detected distal MCA lesions cannot be proven histopathologically or mechanistically. The pseudoaneurysm was retrospectively visible in the initial angiographic study, and earlier recognition might have altered the initial treatment strategy. In addition, because this is a single case, the findings should not be generalized as a radiation-specific phenomenon. Nevertheless, the case illustrates a clinically important diagnostic pitfall in hemorrhagic distal aneurysmal lesions.

Lessons

In patients with long-standing postirradiation vasculopathy, newly detected aneurysmal lesions within a previously irradiated vascular territory should be interpreted cautiously as suspected radiation-­associated lesions rather than as definitive radiation-induced lesions. A conspicuous saccular aneurysm may obscure a coexisting pseudoaneurysm in the same hemorrhagic distal arterial territory. When hemorrhage progresses despite apparent aneurysm obliteration, repeat DSA should be performed with careful attention to subtle delayed contrast pooling. Treatment should be tailored to lesion morphology; PAO remains a useful option for small, distal, fragile pseudoaneurysms when selective embolization is unsafe.

Disclosures

The authors report no conflict of interest concerning the materials or methods used in this study or the findings specified in this paper.

Author Contributions

Conception and design: Matsumoto, Yasunori Yoshida, Tomogane. Acquisition of data: Matsumoto, Tomogane, Yamaura. Analysis and interpretation of data: Tomogane. Drafting the article: Matsumoto, Tomogane. Critically revising the article: Matsumoto, Yamaura. Reviewed submitted version of manuscript: Yasunori Yoshida, Okada, Masuda, Minami, Yasuhisa Yoshida. Approved the final version of the manuscript on behalf of all authors: Matsumoto. Administrative/technical/material support: Yasunori Yoshida, Tomogane.

Correspondence

Hiroaki Matsumoto: Cerebrovascular Research Institute, Yoshida Hospital, Kobe, Hyogo, Japan. hiroaki-matsu@umin.ac.jp.