Abstract

Background: We report a case of contrast-induced encephalopathy (CIE) following coil embolization of a ruptured anterior communicating artery (AComA) aneurysm with bilateral A1 segment development. The aneurysm was visualized by forcefully injecting contrast medium from a distal access catheter (DAC) positioned distally in the internal carotid artery (ICA).

Case Description: A 50-year-old female was diagnosed with subarachnoid hemorrhage. Computed tomography (CT) angiography revealed an AComA aneurysm with perfusion from well-developed bilateral A1 segments. Emergency coil embolization was performed. Clear visualization of the aneurysm from the right side required advancing the DAC to the C2 segment of the right ICA and forcefully injecting the contrast medium. Postoperatively, CT revealed extensive contrast leakage predominantly in the right cerebral hemisphere. The patient subsequently developed left-sided incomplete hemiparesis and left hemispatial neglect, leading to a diagnosis of CIE. The symptoms improved early with fluid replacement and antiepileptic drug administration.

Conclusion: Forced injection of contrast medium from a DAC positioned distally in the ICA to visualize an aneurysm may have contributed to the onset of CIE. Alternative imaging approaches, such as ipsilateral angiography with contralateral blood flow suppression or contralateral angiography, may enhance aneurysm visualization while reducing the risk of CIE.

Keywords: Aneurysm, Coil embolization, Contrast-induced encephalopathy, Distal access catheter

INTRODUCTION

Contrast-induced encephalopathy (CIE) is a condition in which contrast medium leaks outside the cerebral vasculature, leading to central nervous system symptoms.[ 2 , 13 ] Although cases have been reported in various contrast imaging procedures, such as renal angiography and coronary angiography,[ 1 , 11 ] the incidence of CIE is particularly high in neuroendovascular procedures, making it a complication of special concern for neurointerventionalists.[ 2 , 7 , 9 ] Herein, we report a case of CIE following coil embolization of an anterior communicating artery (AComA) aneurysm with perfusion from well-developed bilateral A1 segments. Owing to the influence of contralateral A1 blood flow, clear visualization of the aneurysm from the ipsilateral side required advancing a distal access catheter (DAC) to the C2 segment of the internal carotid artery (ICA) and forcefully injecting the contrast medium. Postoperative computed tomography (CT) revealed extensive contrast leakage, predominantly on the access side, affecting both cerebral hemispheres. The patient subsequently developed incomplete hemiparesis and cortical symptoms, leading to a diagnosis of CIE. Furthermore, we discuss a possible mechanism underlying the development of CIE, along with potential preventive strategies.

CASE REPORT

History and examination

The patient was a 50-year-old female with no significant past medical history who had experienced sudden onset of headache and was transported to our hospital as an emergency case. Upon arrival, the patient’s Glasgow Coma Scale (GCS) score was E4V5M6 and no neurological deficits were observed. Head CT revealed subarachnoid hemorrhage (SAH) predominantly in the bilateral Sylvian fissures, with a greater extent on the left side. No SAH was detected in the convexity region [ Figures 1a and b ]. CT asngiography revealed a 3-mm AComA aneurysm at the right A1–A2 junction, projecting in the left anteroinferior direction. The A1 segments of both the anterior cerebral arteries were equally well developed [ Figure 1c ]. Emergency coil embolization was performed for the ruptured AComA aneurysm.

Figure 1:

Initial imaging findings before the endovascular surgery. (a) Noncontrast head CT shows subarachnoid hemorrhage predominantly in the bilateral Sylvian fissures, with greater accumulation on the left side. (b) Noncontrast head CT reveals no subarachnoid hemorrhage in the convexity region. (c) CT angiography identifies a 3-mm anterior communicating artery aneurysm projecting anteroinferiorly. The A1 segments of both anterior cerebral arteries are equally well-developed. CT: Computed tomography.

Endovascular treatment

The procedure was performed under general anesthesia. After systemic heparinization, a 6-Fr Fubuki dilator kit (Asahi Intecc, Seto, Japan) was inserted into the right femoral artery and advanced into the cervical segment of the right ICA at the C3 vertebral level. Initial angiography from the guiding sheath in the right ICA revealed distal regions of the right middle and anterior cerebral arteries; however, the aneurysm was not clearly visible [ Figure 2a ]. When the left common carotid artery was manually compressed and angiography was repeated from the right ICA, the AComA aneurysm was visualized but remained unclear [ Figure 2b ]. Given the inadequate evaluation of the aneurysm using contrast injection from the guiding sheath in the cervical ICA, as well as concerns about head movement due to manual compression and radiation exposure to the assistant operator, intraoperative angiography was performed using a distally advanced DAC. A Vecta 71 DAC (stryker) was selected and guided to the C4 segment of the ICA for angiography; however, the aneurysm remained poorly visualized [ Figure 2c ]. Consequently, the DAC was advanced further to the ICA C2 segment, where forceful injection of contrast medium finally provided clear visualization of the aneurysm [ Figure 2d ]. The AComA aneurysm had a neck of 1.6 mm, a dome measuring 2.5 × 2.5 mm, and a height of 2.8 mm. A 3 × 5 mm (Stryker) balloon catheter was guided to the terminal portion of the right ICA, and a Phenom 17 (straight medtronic) microcatheter was positioned within the aneurysm [ Figure 2e ]. Subsequent contrast injection from the DAC resulted in poor aneurysm visualization [ Figure 2f ], requiring an even stronger contrast injection for further imaging. The aneurysm was framed using a Target Tetra 2.5 mm × 3.5 cm (stryker) coil and filled with an OPTIMA coil system complex-10 super soft 1.5 mm × 2 cm (century medical) and an OPTIMA coil system complex-10 super soft 1 mm × 1 cm (century medical) [ Figure 2g ]. The procedure was completed with a volume embolization ratio of 44.0%, leaving minimal inflow of contrast into the aneurysm neck [ Figure 2h ]. During coil embolization, seven contrast injections were performed over 1 h through the Vecta 71 catheter positioned in the ICA C2 segment, with an estimated contrast volume of approximately 40 mL. The total intraoperative volume of nonionic low-osmolar contrast medium (iopamidol 300, molecular weight 777.09 Da) stored at 38°C used was 150 mL.

Figure 2:

Imaging findings during the endovascular surgery. (a) Angiography from the guiding sheath (black arrowhead) in the right ICA does not visualize the aneurysm (white arrowhead). (b) Angiography from the guiding sheath (black arrowhead) in the right ICA, performed under manual compression of the left common carotid artery, shows the anterior communicating artery aneurysm, but visualization remains unclear (white arrowhead). (c) Angiography from the DAC (arrow) positioned at the ICA C4 segment results in poor visualization of the aneurysm (white arrowhead). (d) Angiography from the DAC (arrow) positioned at the ICA C2 segment provides good visualization of the aneurysm (white arrowhead) but requires a strong contrast injection. (e) A transform 3 mm × 5 mm is guided to the terminal portion of the right ICA, and a Phenom 17 microcatheter is placed inside the aneurysm. (f) After placement of the Transform and Phenom 17 microcatheter, angiography from the DAC (arrow) again shows poor aneurysm visualization (white arrowhead). (g) The aneurysm is embolized using a total of three coils. (h) The final angiography from the DAC (arrow) shows slight contrast inflow into the aneurysm neck (white arrowhead). DAC: Distal access catheter, ICA: Internal carotid artery.

Postoperative course

Postoperative XperCT showed no increase in the SAH in the bilateral Sylvian fissures [ Figure 3a ]. However, high-density areas were predominantly observed in the right subarachnoid space of both cerebral hemispheres [ Figure 3b ]. Immediate postoperative CT revealed high-density areas in the subarachnoid spaces of both hemispheres, which were more prominent on the right side [ Figure 3c ]. Dual-energy CT (DECT) revealed a reduction in the high-density areas [ Figure 3d ], suggesting that these findings were due to contrast medium leakage. General anesthesia was maintained, and the patient was managed with aggressive intravenous hydration and administration of an antiepileptic drug (Levetiracetam 1000 mg/day). The following day, a noncontrast head CT showed a decreasing trend in the high-density areas in both hemispheres compared to the previous day. However, high-density areas persisted in the subarachnoid space of the right cerebral hemisphere with an indistinct appearance of the cerebral sulci [ Figure 3e ]. Upon awakening from general anesthesia on postoperative day 1, the patient exhibited a GCS score of E3V5M5, along with impaired consciousness, left-sided incomplete hemiparesis, dysarthria, and hemispatial neglect. On postoperative day 2, noncontrast head CT revealed further resolution of the high-density areas in both hemispheres [ Figure 3f ]. Magnetic resonance angiography performed on postoperative day 2 revealed good visualization of the intracranial vessels without evidence of an aneurysm [ Figure 3g ]. Diffusion-weighted imaging detected small, scattered cerebral infarctions in the right frontal cortex [ Figure 3h ]. Fluid-attenuated inversion recovery imaging showed high signal intensity in the subarachnoid spaces of both hemispheres [ Figure 3i ], whereas T2*-weighted imaging (T2 star) did not reveal any low-signal intensity changes in the cerebral sulci of either hemisphere [ Figure 3j ]. The MRI findings did not corroborate the patient’s clinical symptoms, and based on CT findings, a diagnosis of CIE was made. Intravenous hydration and levetiracetam (1000 mg/day) were continued. The patient’s symptoms improved by postoperative day 2, and she was discharged on postoperative day 29 with a modified Rankin scale score of 0.

Figure 3:

Imaging findings after the endovascular surgery. (a) Immediate postoperative XperCT shows no increase in subarachnoid hemorrhage in the bilateral Sylvian fissures. (b) Immediate postoperative XperCT reveals high attenuation in the subarachnoid spaces of both cerebral hemispheres, predominantly on the right side. (c) Immediate postoperative CT also shows high attenuation in the subarachnoid spaces of both cerebral hemispheres, more prominent on the right side. (d) Subtraction imaging from immediate postoperative dual-energy CT shows a reduction in the high attenuation in the subarachnoid spaces of both hemispheres. (e) Noncontrast head CT on postoperative day 1 shows a reduction in the high attenuation in the subarachnoid space of the right cerebral hemisphere compared to the immediate postoperative findings, but the cerebral sulci remain indistinct. (f) Noncontrast head CT on postoperative day 2 shows resolution of the previously observed high attenuation in the right cerebral hemisphere’s subarachnoid space. (g) Brain MRA on postoperative day 2 shows good visualization of the intracranial vessels. (h) Diffusion-weighted imaging reveals scattered cerebral infarctions in the right frontal cortex. (i) Fluid-attenuated inversion recovery imaging shows high signal intensity in the subarachnoid spaces of both cerebral hemispheres. (j) T2*-weighted imaging does not show any low-signal intensity changes in the cerebral sulci of either hemisphere. CT: Computed tomography, MRA: Magnetic resonance angiography.

DISCUSSION

This case involved SAH due to the rupture of an AComA aneurysm perfused by well-developed bilateral A1 segments, followed by the onset of CIE after coil embolization. Owing to the influence of blood flow from the contralateral A1, angiography using a guiding catheter placed in the cervical ICA or a DAC positioned proximally in the ICA resulted in poor visualization of the aneurysm. Although the total contrast medium injection from the DAC was relatively low at approximately 40 mL, to achieve clear visualization of the aneurysm, the DAC was positioned distally in the ICA and contrast was injected with greater force. In this case, the pressurized injection of contrast from a distally placed DAC may have contributed to the development of CIE. In neuroendovascular procedures, the need to advance the DAC distally for angiography depends on the vascular anatomy of the target vessels. This case suggests that such an approach may increase the risk of CIE. It serves as a cautionary example, emphasizing the need for careful consideration of contrast injection strategies to minimize complications during endovascular treatment.

CIE is a rare neurological complication associated with exposure to contrast media during angiographic procedures.[ 2 , 13 ] The proposed mechanisms include blood– brain barrier (BBB) disruption due to endothelial cell damage caused by the high osmolarity and chemical toxicity of contrast agents and the direct neurotoxic effects of contrast media.[ 6 , 14 ] The incidence of CIE varies depending on the target vessel and the procedure type. On coronary angiography, its occurrence is relatively low, ranging from 0.05% to 0.4%.[ 1 ] However, in mechanical thrombectomy, the incidence is reported to be 1.7%,[ 2 ] whereas in coil embolization, it ranges from 0.66% to 2.9%.[ 7 , 9 ] The higher incidence of neuroendovascular procedures is thought to be due to the frequent direct injections of large amounts of contrast medium into a single cerebral vessel. Chu et al. defined the diagnostic criteria for CIE as the appearance of neurological symptoms inconsistent with the primary disease, and the presence and persistence of hyperattenuation in the brain parenchyma or subarachnoid space observed on CT.[ 2 ] The hyperattenuation observed on CT is thought to result from contrast leakage and typically resolves relatively quickly.[ 8 ] In some cases, distinguishing CIE from SAH based on imaging alone can be challenging. However, in the present case, DECT was useful for early diagnosis. DECT is a technique that utilizes two different X-ray tube voltages to generate images, enabling the detection of hyperattenuation caused by contrast media using iodine-based density imaging.[ 12 ] This allows precise differentiation between intracranial hemorrhage and contrast leakage on noncontrast CT.[ 10 ] In this case, DECT was performed immediately postoperatively, allowing early determination that the hyperattenuation in the right cerebral hemisphere’s subarachnoid space was due to contrast leakage. This early diagnosis facilitated the prompt initiation of fluid therapy and antiepileptic treatment, leading to a rapid improvement in the patient’s neurological symptoms. Because no lesions corresponding to postoperative neurological symptoms were detected on MRI, the final diagnosis was CIE-related neurological symptoms.

Several factors have been associated with the development of CIE, including a high volume of contrast injection, frequent contrast injections, and the use of low-temperature contrast agents (23°C).[ 4 ] In this case, a nonionic, lowosmolar contrast agent stored at 38°C was used, and during the coil embolization procedure, the contrast agent was injected 7 times over 1 h through the DAC. The contrast volume required to induce CIE varies among individuals[ 14 ] but has been estimated to range from 50 to 300 mL.[ 4 ] In this case, the total contrast volume injected from the distal ICA through the DAC was 40 mL, which is lower than the reported risk threshold. However, the patient still developed CIE. This suggests that the positioning of the DAC may have contributed to the onset of CIE. Large-bore DACs have recently become widely used in the endovascular treatment of cerebral aneurysms, as they improve the maneuverability of microcatheters and enable high-density coil embolization. However, in this case, angiography performed from a DAC positioned at the right ICA C4 segment resulted in poor visualization of the aneurysm owing to the influence of the contralateral A1 blood flow. To achieve a clearer visualization of the aneurysm, the DAC was advanced to the C2 segment, requiring a more forceful injection of the contrast agent. High-pressure injection from a distally positioned DAC may have delivered undiluted, high-concentration contrast medium directly to the target vessel, potentially increasing the risk of CIE. Fuga et al. conducted a study on 396 patients with unruptured aneurysms who underwent coil embolization and reported that contrast injection from a DAC positioned in the intracranial ICA was an independent predictor of CIE.[ 3 ] In this case, the patient did not have other reported risk factors for CIE, such as renal dysfunction or a history of stroke,[ 2 ] suggesting that contrast injection from the DAC positioned at the right ICA C2 segment may have increased the risk of CIE. However, experimental studies in animals have demonstrated that the BBB can be disrupted after SAH,[ 15 ] raising the possibility that the aneurysm rupture itself may have contributed to the development of CIE in this case. In addition, although the contrast volume injected from the DAC was 40 mL, the total contrast volume used throughout the procedure was 150 mL, which cannot be excluded as a contributing factor to CIE.

Although CIE symptoms are usually transient and reversible, they may persist permanently in some cases, leading to poor clinical outcomes.[ 5 , 6 ] Therefore, developing effective preventive strategies to avoid CIE is essential. Reducing the total contrast volume and the number of angiographic injections as much as possible is critical in preventing CIE. In cases where the DAC must be positioned distally, as in this case, the increased risk of CIE should be recognized, and angiography should be limited to the minimum necessary quantity. In the coil embolization of AComA aneurysms with bilateral A1 segments of similar development, temporary occlusion of the contralateral blood flow using a balloon catheter during angiography may improve aneurysm visualization. This technique could eliminate the need for distal catheter placement and forceful contrast injection, potentially reducing the risk of CIE. In addition, performing angiography from the contralateral side may also improve visualization of aneurysms that were previously difficult to assess. However, angiography from the contralateral side does not allow for simultaneous visualization of the vascular structures on the access side; therefore, caution is necessary.

CONCLUSION

Forced injection of contrast medium from a DAC positioned distally in the ICA to visualize an aneurysm may have contributed to the onset of CIE. Alternative imaging approaches, such as ipsilateral angiography with contralateral blood flow suppression or contralateral angiography, may enhance aneurysm visualization while reducing the risk of CIE.

Ethical approval:

Institutional review board approval is not required.

Declaration of patient consent:

The authors certify that they have obtained all appropriate patient consent.

Financial support and sponsorship:

Nil.

Conflicts of interest:

There are no conflicts of interest.

Use of artificial intelligence (AI)-assisted technology for manuscript preparation:

The authors confirm that there was no use of artificial intelligence (AI)-assisted technology for assisting in the writing or editing of the manuscript and no images were manipulated using AI.

Disclaimer

The views and opinions expressed in this article are those of the authors and do not necessarily reflect the official policy or position of the Journal or its management. The information contained in this article should not be considered to be medical advice; patients should consult their own physicians for advice as to their specific medical needs.

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