Abstract

Background: Pseudoaneurysm formation at the anastomotic site of extracranial-intracranial (EC-IC) bypass surgery is a rare but potentially severe complication. Due to its unpredictable nature and associated risks, early detection and appropriate management are crucial. However, the rarity of this condition makes diagnosis and treatment challenging. This review explores the pathophysiology, risk factors, diagnostic strategies, and management options for pseudoaneurysms in EC-IC bypass procedures.

Methods: A comprehensive literature search was conducted using the PubMed/MEDLINE database to identify studies related to pseudoaneurysm formation following EC-IC bypass surgery. The search algorithm applied was (((Pseudoaneurysm) AND (Extracranial) AND (Intracranial)) AND ((Bypass) OR (Revascularization) OR (Anastomosis))). Studies were included if they reported on pseudoaneurysm formation at the anastomotic site of EC-IC bypass procedures, including case reports, case series, retrospective studies, and reviews. Exclusion criteria encompassed studies focusing solely on nonanastomotic aneurysms, unrelated cerebrovascular procedures, or insufficient clinical data.

Results: After applying the inclusion and exclusion criteria, a total of five studies were selected for detailed analysis. The extracted data included patient demographics, clinical presentation, imaging modalities used for diagnosis, treatment strategies, and postoperative outcomes.

Conclusion: Pseudoaneurysms at EC-IC bypass sites pose significant diagnostic and therapeutic challenges. Given the potential for delayed complications, early detection, and individualized treatment strategies are essential. Long-term follow-up with serial imaging is necessary to monitor for recurrence and ensure optimal patient outcomes. Greater awareness and reporting of these cases will contribute to improved understanding and management of this rare complication.

Keywords: Anastomotic complications, Bypass reconstruction, Cerebrovascular surgery, Extracranial-intracranial bypass, Pseudoaneurysm, Superficial temporal artery-middle cerebral artery bypass, Superficial temporal artery-vascular pathology

INTRODUCTION

The extracranial-intracranial (EC-IC) bypass is a well-established surgical procedure for treating certain cerebrovascular conditions such as moyamoya disease and complex aneurysms.[ 6 , 9 ] However, one rare but serious complication that can occur at the anastomotic site of this bypass is the formation of a pseudoaneurysm.[ 13 ] A pseudoaneurysm is characterized by the absence of one or more vessel wall layers, replaced by a hematoma contained by surrounding tissue, which may eventually form a fibrous sac.[ 2 , 5 ] These pseudoaneurysms can present unique diagnostic and therapeutic challenges due to their rarity and the complex anatomy involved.[ 3 ] This literature review aims to summarize the pathophysiology, clinical presentation, diagnostic challenges, and management strategies associated with pseudoaneurysms at EC-IC bypass sites, with an emphasis on the importance of early detection and individualized treatment approaches.[ 1 ]

METHODS

A comprehensive literature search was conducted using the PubMed/MEDLINE database to identify studies related to pseudoaneurysm formation following EC-IC bypass surgery. The search algorithm applied was (((Pseudoaneurysm) AND (Extracranial) AND (Intracranial)) AND ((Bypass) OR (Revascularization) OR (Anastomosis))). Studies were included if they reported on pseudoaneurysm formation at the anastomotic site of EC-IC bypass procedures, including case reports, case series, retrospective studies, and reviews. Exclusion criteria encompassed studies focusing solely on nonanastomotic aneurysms, unrelated cerebrovascular procedures, or insufficient clinical data.

RESULTS

After applying the inclusion and exclusion criteria, a total of five studies were selected for detailed analysis. The extracted data included patient demographics, clinical presentation, imaging modalities used for diagnosis, treatment strategies, and postoperative outcomes.

DISCUSSION

This complication occurs primarily due to the complex interaction between extracranial and intracranial vessels at the anastomotic junction.[ 8 ] It is often triggered by factors such as surgical trauma, suture line failure, or infection.[ 5 ] The bypass site is particularly vulnerable because it endures significant hemodynamic stresses, which can exacerbate weaknesses in the vessel wall, leading to pseudoaneurysm development.[ 1 , 6 ]

The technical aspects of the surgery, including the precision of the anastomosis and the quality of the graft material, play a significant role in pseudoaneurysm formation. Inadequate suturing techniques or inappropriate graft materials can induce vessel wall stress, increasing the risk of pseudoaneurysms.[ 7 ] Furthermore, postoperative infections, especially in patients with compromised immune systems or a history of multiple surgeries, have been cited as a major risk factor.[ 5 , 6 ] Chronic inflammatory responses triggered by graft materials or the healing process may also weaken the vessel wall, contributing to pseudoaneurysm formation.[ 5 ] It is important to distinguish pseudoaneurysms from true hemodynamic fusiform aneurysms that may also develop at the anastomotic site. Unlike pseudoaneurysms, which lack all three vessel wall layers and are typically contained by surrounding tissue or a fibrous capsule, true fusiform aneurysms may preserve the media and adventitia but lack the internal elastic lamina.

Pseudoaneurysms at EC-IC bypass sites pose significant diagnostic challenges due to their rarity and nonspecific symptoms.[ 2 ] Patients may present with a range of symptoms, from headaches and cranial nerve deficits to more severe issues, such as hemorrhage or cerebral ischemia, depending on the size and location of the pseudoaneurysm.[ 2 , 9 ] Diagnostic delays are common, often due to subtle initial symptoms and a low index of suspicion for this rare complication.[ 3 ]

Pseudoaneurysm formation is a notable complication of superficial temporal artery-middle cerebral artery (STAMCA) bypass surgery, as demonstrated in multiple cases. The first case involved a patient with moyamoya disease who developed a pseudoaneurysm at the STA-MCA anastomotic site. Remarkably, this pseudoaneurysm spontaneously developed and subsequently involuted, an unusual and poorly understood occurrence in vascular surgery. This case highlights the unpredictability of pseudoaneurysm behavior and the critical importance of vigilant follow-up.[ 13 ] The second case involved a rapidly developing pseudoaneurysm at the STA-MCA anastomotic site shortly after surgery, posing significant diagnostic and therapeutic challenges due to its rapid formation. Patient-related factors such as underlying vessel pathology or hemodynamic instability may predispose individuals to this complication, emphasizing the critical need for early detection and intervention given the narrow window for effective treatment.[ 12 ] Another instance is a 43-year-old male who initially underwent STAMCA bypass surgery for transient right hemiparesis and left carotid occlusion.[ 11 ] Although he recovered uneventfully for 5 years, he later suffered a massive intracerebral hemorrhage caused by a pseudoaneurysm at the anastomotic site. While emergency intervention controlled the hemorrhage, histological examination confirmed the presence of the pseudoaneurysm, highlighting that severe complications can arise long after the procedure.[ 11 ] Similarly, a patient treated for transient ischemic attacks due to left common carotid artery occlusion underwent endarterectomy and STA-MCA bypass, only to later develop a pseudoaneurysm at the anastomotic site. This case represents one of the earliest documented occurrences of such a complication post bypass and underscores the technical challenges and vascular risks inherent in combined carotid and STA-MCA interventions.[ 4 ] From the authors’ experience, among nine direct bypass anastomosis operations with a 5-year follow-up, one notable case involved a 13-year-old female with adult-onset moyamoya disease who underwent a left STA-MCA bypass. At the 6-month follow-up, computed tomography (CT) imaging revealed a dilation resembling a pseudoaneurysm at the anastomotic site. The patient opted for conservative management and declined revision surgery. Subsequent CT scans showed no progression of the pseudoaneurysm before the patient was lost to follow-up.

Another notable case involved a 60-year-old man with vertebrobasilar ischemia who underwent an STA-superior cerebellar artery bypass. Postoperative angiography revealed a small pseudoaneurysm at the anastomosis site, which later progressed to symptomatic aneurysmal growth approximately a year after surgery.[ 10 ] The patient required multiple surgical interventions, including bypass revision and aneurysm ligation, eventually achieving stabilization. In addition, ventriculoperitoneal shunting resolved associated parkinsonism.[ 10 ] This case underscores the complex and evolving nature of pseudoaneurysm-related complications and highlights the critical importance of long-term surveillance in managing these patients.[ 10 ]

Digital subtraction angiography remains the gold standard for diagnosing pseudoaneurysms.[ 8 ] However, multi-modality imaging, including CT angiography and magnetic resonance angiography, is often required for a complete characterization of the pseudoaneurysm and to plan appropriate interventions.[ 1 , 8 ] In some cases, pseudoaneurysms may not be detected on initial imaging and are only identified upon further exploration, highlighting the need for vigilance and repeated angiography in patients with unexplained postoperative symptoms.[ 1 ]

Managing a pseudoaneurysm at an EC-IC bypass site is complex and must be tailored to the patient’s clinical condition, the size and location of the pseudoaneurysm, and the underlying vascular pathology.[ 9 ] Surgical intervention is often necessary, especially when there is a risk of rupture or significant neurological compromise.[ 9 ] Pseudoaneurysm resection followed by bypass reconstruction is the most commonly used surgical approach,[ 5 ] though in some cases, more conservative measures such as endovascular coiling or stenting may be effective.[ 2 ]

Outcomes for patients undergoing treatment for pseudoaneurysms at EC-IC bypass sites are variable. Success largely depends on the timing of intervention, the complexity of the surgery, and the patient’s overall condition.[ 5 ] Major complications, including pseudoaneurysm recurrence, graft occlusion, or new-onset neurological deficits, are not uncommon.[ 5 ] Long-term follow-up with serial imaging is essential to ensure the durability of the repair and to monitor for delayed complications.[ 9 ]

CONCLUSION

Pseudoaneurysms at EC-IC bypass sites, though rare, present significant diagnostic and management challenges. Their formation is influenced by factors such as surgical technique, postoperative infection, and hemodynamic stress. Early diagnosis is crucial but often difficult due to nonspecific symptoms and the rarity of the condition. Individualized treatment, typically involving surgical intervention, is essential for preventing serious complications, while long-term follow-up is necessary to monitor for recurrence. This review underscores the importance of vigilance, precise surgical techniques, and tailored management strategies to improve patient outcomes.

Ethical approval:

Institutional Review Board approval is not required.

Declaration of patient consent:

Patient’s consent is not required as there are no patients in this study.

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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