Unruptured Anterior Communicating Artery Aneurysm Research Articles

Retrospective Application of Risk Scores to Unruptured Anterior Communicating Artery Aneurysms

Retrospective Application of Risk Scores to Unruptured Anterior Communicating Artery Aneurysms

Endovascular Treatment of Small Anterior Communicating Artery Aneurysms: Safety and Efficacy in a Contemporary Cohort.

Endovascular treatment (EVT) of small anterior communicating artery (ACoA) aneurysms accompanies a high risk of intraprocedural rupture (IR) because of anatomic location and aneurysm orientation. In this study, we aimed to investigate the safety and efficacy of EVT for small ACoA aneurysms in a contemporary cohort. ACoA aneurysms treated at the Medical University of South Carolina between April 2012 and March 2022 were retrospectively analyzed. Periprocedural baseline characteristics, aneurysm size, and clinical and radiological outcomes were collected. Aneurysms were dichotomized into <4 and ≥4 mm in maximum size. The IR rate, favorable occlusion rate (Raymond-Roy I and II), and the favorable outcome defined as modified Rankin Scale 0-2 were compared. A total of 174 patients were identified, of whom 111 (63.8%) were female, and the median age was 57.7 (interquartile range 50.6-69.6) years. 98 (56.3%) aneurysms were ruptured, and 53 (30.5%) were <4 mm. IR was not observed in unruptured ACoA aneurysms, and there was no significant difference in the IR rates between <4 mm and ≥4 mm ruptured aneurysms (6.5% vs 4.5%, P = .65). Favorable occlusion rate and favorable outcome were observed in 94.7% and 78.2% of patients, respectively. EVT of small ACoA aneurysms is safe and effective.

Predictive value of the anterior communicating artery (ACoA) complex variations for the incidence and rupture of ACoA aneurysms

BackgroundIncrease pressure on arteries branching points and curves (hyperdynamic theory) is the most popular theory to explain the aneurysms formation that augmented by the observation of high incidence of anomalies (either A1 aplasia or hypoplasia) and the anterior communicating artery (ACoA) aneurysms. It still underestimated the correlation between these anatomical anomalies and aneurysm occurrence and its rupture. We aim to estimate the incidence and type of anatomical anomalies of the anterior cerebral circulation, including the A2 segment in patients with ACoA aneurysms and their predictive value for aneurysm occurrence and rupture parallel to the risk of hypertension. Also, we study the impact of these anomalies on the configuration of the aneurysm, including the neck and size.ResultsA1 hypoplasia and aplasia were significantly higher in AcoA aneurysms group than in the control group (P < 0.001 and 0.002, respectively). These anomalies have no significant statistical difference between rupture and unruptured ACoA aneurysms. A2 anomalies were insignificantly different between both groups.ConclusionCongenital anomalies in the A1 segment (hypoplasia and aplasia) have a significant predictive value for AcoA aneurysms formation, with no predictive value for the aneurysm rupture. Concomitantly, A2 anomalies have no significant risk for AcoA aneurysms formation and rupture.

Abstract 167: Surgical treatment for unruptured Anterior communicating artery aneurysm

Introduction We report the results of endovascular surgery as the first‐line treatment for unruptured anterior communicating artery aneurysms. Methods Fifty‐seven patients (F:M, 30:27; mean age, 65.5 years) underwent surgery for unruptured anterior communicating artery aneurysms in our hospital between January 2018 and January 2023. Results The mean aneurysm dome size was 5.29 mm (2–22 mm), and the mean aneurysm neck size was 3.2 mm (1.5–7 mm). Coil embolization was performed for fifty‐four patients using various adjunctive techniques (simple, 7; double catheter, 15; balloon neck remodeling, 7; stent‐assisted, 26 (LVIS Jr., 12; ATLAS, 14). Neck clipping was performed in 3 cases. The surgical results revealed complete coil embolization in 27, neck remnant in 26, and dome filling in 1 patient(s). The reason for 3 patients treated with neck clipping are patient's preference in one, associated with severe Middle cerebral artery stenosis needed TSA MCA anastomosis on one, and difficulty of embolization in one patient. Postoperative thrombotic complications were observed in 1 patient. The modified Rankin scale scores were 0 in 32 (96.5%) patients, 3 in 1 (1.7%) patients, and 6 in 1 (1.7%) patient. Follow‐up was performed in 55 patients, averaging 29.5 months (3–45 months). However, one patient underwent re‐aneurysm embolization for major recanalization of the aneurysm dome, and none of them suffered from rupture of the treated aneurysm. Conclusion Endovascular surgery may be the first choice of treatment for unruptured anterior communicating artery aneurysms.

Safety and Efficacy of Flow Diverters for Treatment of Unruptured Anterior Communicating Artery Aneurysms: Retrospective Multicenter Study

BackgroundThe anterior communicating artery (AComm) region is the most common site of intracranial aneurysms, with increased rupture risk compared with other locations. Overall, flow diverters present as a safe and...

Foreign Body Reaction After Endovascular Treatment with Pipeline Embolization Device (P8-5.031)

<h3>Objective:</h3> The following case elucidates a rare complication of a foreign body reaction to the hydrophilic coating fragments of the pipeline embolization device. <h3>Background:</h3> Intracranial aneurysms (IAs) are pathological dilatations of intracranial arteries. Unruptured IAs have a prevalence of 3% in the adult population worldwide. Endovascular treatment (EVT) is a common first line preventive repair for unruptured intracranial aneurysm. <h3>Design/Methods:</h3> NA <h3>Results:</h3> 50-year-old female presented to the ED with acute onset left-sided weakness of the upper and lower extremities and left-sided facial numbness 20 days following treatment of an unruptured anterior communicating artery aneurysm with Pipeline Flex Embolization Device (PED). Patient’s significant medical history includes multiple sclerosis (MS), rheumatoid arthritis, Crohn’s disease managed with Humira, and diabetes. The CT head without contrast showed confluent edema within the right MCA watershed region, suspicious for infarct. However, the CTA of head showed no vessel occlusion with a patent PED. Brain MRI identified numerous enhancing lesions throughout the right cerebral hemisphere with internal cavitations and significant perilesional vasogenic edema with regional mass effect without midline shift. Empiric antibiotics and antifungal were initiated to cover both typical and atypical causes due to Humira use for Crohn’s disease. Labs, blood cultures and CSF results were insignificant. Pulse-dose steroid for 5 days was started, after 72-hr negative blood cultures. Over time, the patient’s symptoms improved, and she regained her strength back. A repeat brain MRI after the course of steroids showed diminished enhancement, size, and number of brain lesions. The patient was discharged home on a long Prednisone taper and long-term intravenous vancomycin, ceftriaxone, and oral metronidazole. <h3>Conclusions:</h3> Foreign body reactions are rare complications of EVT. It is important to be aware of possible foreign body emboli in patients with the enhancing brain lesions located in the same vascular territory where the recent endovascular procedure was performed. <b>Disclosure:</b> Dr. Aung has nothing to disclose. Mr. Kaufman has nothing to disclose. Dr. Moroz has nothing to disclose. Dr. Axelband has nothing to disclose. Mr. Oselkin has nothing to disclose.

557 Results of Microsurgical Clipping of Unruptured Anterior Communicating Artery Aneurysms (ACOMa) Using the Pretemporal Minimal Durotomy Approach

INTRODUCTION: Recent reports suggest the superiority of microsurgical clipping of ACOMa compared to endovascular treatments. We present our experience with the pretemporal minimal durotomy (minimal brain exposure) approach in 168 patients. METHODS: Data of 168 patients were prospectively collected and retrospectively reviewed. The pretemporal approach with the removal of the posterior roof of the orbit and the anterior clinoid process with a minimized subfrontal durotomy allowed broad exposure to the ACOMa complex and minimal exposure to the surrounding brain. The technique allowed early proximal control and 360-degree visualization of the aneurysm and its surroundings. RESULTS: The average aneurysm size was 6.4 mm. Total clip occlusion was achieved in 100%, confirmed by intraoperative indocyanine green videography and post-operative computer tomography angiography/cerebral angiography. At discharge, 93.5% were modified Rankin Scale (mRS) 0-2, and 99.0% were mRS 0-2 at 1 year follow up. There was zero mortality, and one patient with a giant aneurysm had a stable residual on follow-up. CONCLUSIONS: Microsurgical clipping of ACOM aneurysms using the pretemporal minimal durotomy approach results in more durable outcomes than endovascular technique with excellent functional outcomes and should be strongly considered as a first treatment option, especially in aneurysms that have anatomic endovascular disadvantages that have a high likelihood of recurrence.

Real-Time Monitoring of Aneurysm Catheterization During Stent-Assisted Coiling for Irregularly Shaped Intracranial Aneurysms: The Scope Technique

Stent-assisted coiling (SAC) using the jailing technique is a well-established treatment for wide-neck intracranial aneurysms. However, low-volume packing, which is a key factor for aneurysm recanalization, can occur in patients with irregularly shaped aneurysms. We have devised a real-time monitoring system for aneurysm catheterization that allows the intentional placement of the jailed coil-delivery microcatheter and deployed stent, referred to as the "scope" technique. Herein, we present a case of irregularly shaped anterior communicating artery (ACoA) aneurysm successfully treated with SAC using this technique. A 72-year-old woman diagnosed with an unruptured wide-neck ACoA aneurysm that was eccentric to the parent ACoA and overhanging posteriorly underwent SAC using this technique. Bilateral transradial quadraxial systems (6-Fr Simmons guiding sheath/6-Fr intermediate catheter/3.2-Fr intermediate catheter/microcatheter) were established via right and left internal carotid artery. The stent-delivery microcatheter was advanced into the left A2 via the right A1, leaving a 0.014″ microguidewire for visualization under fluoroscopic guidance. To place the coil-delivery microcatheter in the middle of the aneurysm after stent deployment, the coil-delivery microcatheter was cannulated into the aneurysm via the left A1, intendedly through the posterior side of the stent-delivery microcatheter in the down-the-barrel view of the parent ACoA (the scope technique). After stent deployment, SAC of the aneurysm was successfully achieved. Using this technique, the coil-delivery microcatheter was cannulated into the aneurysm, while monitoring its positional relationship with the stent-delivery microcatheter in real time. This technique is a useful treatment option for irregularly shaped and wide-neck aneurysms.

The risk factors of postoperative infarction after surgical clipping of unruptured anterior communicating artery aneurysms: anatomical consideration and infarction territory.

An anterior communicating artery is a common location for both ruptured and unruptured intracranial aneurysms, and microsurgery is sometimes necessary for their successful treatment. However, postoperative infarction should be considered during clipping due to the complex surrounding structures of anterior communicating artery aneurysms. This study aimed to evaluate the risk factors of postoperative infarction after surgical clipping of unruptured anterior communicating artery aneurysms and its clinical outcomes. The data of patients who underwent microsurgical clipping of an unruptured anterior communicating artery aneurysm in our hospital between January 2008 and December 2020 were retrospectively analyzed. The patients' demographic data, anatomical features of the anterior communicating artery complex and aneurysm, surgical technique, characteristics of postoperative infarction, and its clinical course were evaluated. Notably, among 848 patients, 66 (7.8%) and 34 (4%) patients had radiologic and symptomatic infarctions, respectively. Univariate and multivariate logistic regression analyses showed that hypertension (odds ratio (OR), 1.99; [Formula: see text]), previous stroke (OR, 3.89; [Formula: see text]), posterior projection (OR, 5.58; [Formula: see text]), aneurysm size (OR, 1.17; optimal cut-off value, 6.14mm; [Formula: see text]), and skull base-to-aneurysm distance (OR, 1.15; optimal cut-off value, 11.09mm; [Formula: see text]) were associated with postoperative infarction. In the pterional approach, a closed A2 plane was an additional risk factor (OR, 1.88; [Formula: see text]). Infarction of the subcallosal and hypothalamic branches was significantly associated with symptomatic infarction ([Formula: see text]). Hypertension, previous stroke, posteriorly projecting aneurysms, aneurysm size, and highly positioned aneurysms are independent risk factors for postoperative infarction during surgical clipping of an unruptured anterior communicating artery aneurysm. Additionally, a closed A2 plane is an additional risk factor of postoperative infarction in patients undergoing clipping via the pterional approach.

Fast Transition from Open Surgery to Endovascular Treatment of Unruptured Anterior Communicating Artery Aneurysms–A Retrospective Analysis of 128 Patients

Anterior communicating artery aneurysms (ACoAAs) are challenging to treat both surgically and endovascularly. In this study, we evaluate the treatment-related morbidity and clinical outcome of microsurgical clipping and endovascular treatment for a consecutive series of unruptured ACoAAs while the treatment paradigm was in transition from surgical to endovascular first. We retrospectively reviewed clinical and radiologic data of adult patients who underwent microsurgical clipping or endovascular treatment of an unruptured ACoAA at a high-volume academic neurovascular center (Helsinki University Hospital) during 2012-2019. During this period, a transition from microsurgical clipping to endovascular treatment took place. Regarding outcome, we focused on treatment-related complications, discharge-to-home rates, functional performance (modified Rankin Scale score), and obliteration rates. Of 128 treated ACoAAs, 81 (64%) were treated surgically and 47 (36%) endovascularly. There was no difference in major complications, intracranial hemorrhagic complications or ischemic complications, discharge-to-home rates, or functional performance between the surgically and endovascularly treated patients. With time, a decrease in major complications was observed in the surgical cases (from 29% to 17%), whereas the major complication rate increased in the endovascularly patients (from 0% to 25%). Cerebral ischemia was the most frequent complication in both groups. The risk for permanent neurologic deficit remained low in both groups (9% for endovascular and 5% for surgery). We did not find any major differences regarding complications and outcomes after the treatment paradigm shift from clipping to endovascular of unruptured ACoAAs. Prospective studies evaluating durability of treatments are needed to compare overall effectiveness.

Aneurysm presence at the anterior communicating artery bifurcation is associated with caliber tapering of the A1 segment.

Vessel tapering results in blood flow acceleration at downstream bifurcations (firehose nozzle effect), induces hemodynamics predisposing to aneurysm initiation, and has been associated with middle cerebral artery (MCA) aneurysm presence and rupture status. The authors sought to determine if vessel caliber tapering is a generalizable predisposing factor by evaluating upstream A1 segment profiles in association with aneurysm presence in the anterior communicating artery (ACoA) complex, the most prevalent cerebral aneurysm location associated with a high rupture risk. Three-dimensional rotational angiographic studies were analyzed for 68 patients with ACoA aneurysms, 37 nonaneurysmal contralaterals, and 53 healthy bilateral controls (211 samples total). A1 segments were determined to be dominant, codominant, or nondominant based on flow and size. Equidistant cross-sectional orthogonal cuts were generated along the A1 centerline, and cross-sectional area (CSA) was evaluated proximally and distally, using intensity-invariant edge detection filtering. The relative tapering of the A1 segment was evaluated as the tapering ratio (distal/proximal CSA). Computational fluid dynamics was simulated on ACoA parametric models with and without tapering. Aneurysms occurred predominantly on dominant (79%) and codominant (17%) A1 segments. A1 segments leading to unruptured ACoA aneurysms had significantly greater tapering compared to nonaneurysmal contralaterals (0.69 ± 0.13 vs 0.80 ± 0.17, p = 0.001) and healthy controls (0.69 ± 0.13 vs 0.83 ± 0.16, p < 0.001), regardless of dominance labeling. There was no statistically significant difference in tapering values between contralateral A1 and healthy A1 controls (0.80 ± 0.17 vs 0.83 ± 0.16, p = 0.56). Hemodynamically, A1 segment tapering induces high focal pressure, high wall shear stress, and high velocity at the ACoA bifurcation. Aneurysmal, but not contralateral or healthy control, A1 segments demonstrated significant progressive vascular tapering, which is associated with aneurysmogenic hemodynamic conditions at the ACoA complex. Demonstration of the upstream tapering effect in the communicating ACoA segment is consistent with its prior detection in the noncommunicating MCA bifurcation, which together form more than 50% of intracranial aneurysms. The mechanistic characterization of this upstream vascular tapering phenomenon is warranted to understand its clinical relevance and devise potential therapeutic strategies.

Rupture Risk Assessment for Anterior Communicating Artery Aneurysms Using Decision Tree Modeling.

BackgroundAlthough anterior communicating artery (ACoA) aneurysms have a higher risk of rupture than aneurysms in other locations, whether to treat unruptured ACoA aneurysms incidentally found is a dilemma because of treatment-related complications. Machine learning models have been widely used in the prediction of clinical medicine. In this study, we aimed to develop an easy-to-use decision tree model to assess the rupture risk of ACoA aneurysms.MethodsThis is a retrospective analysis of rupture risk for patients with ACoA aneurysms from two medical centers. Morphologic parameters of these aneurysms were measured and evaluated. Univariate analysis and multivariate logistic regression analysis were performed to investigate the risk factors of aneurysm rupture. A decision tree model was developed to assess the rupture risk of ACoA aneurysms based on significant risk factors.ResultsIn this study, 285 patients were included, among which 67 had unruptured aneurysms and 218 had ruptured aneurysms. Aneurysm irregularity and vessel angle were independent predictors of rupture of ACoA aneurysms. There were five features, including size ratio, aneurysm irregularity, flow angle, vessel angle, and aneurysm size, selected for decision tree modeling. The model provided a visual representation of a decision tree and achieved a good prediction performance with an area under the receiver operating characteristic curve of 0.864 in the training dataset and 0.787 in the test dataset.ConclusionThe decision tree model is a simple tool to assess the rupture risk of ACoA aneurysms and may be considered for treatment decision-making of unruptured intracranial aneurysms.

Cerebral vasospasm after coil embolization for unruptured anterior communicating artery aneurysm: illustrative case.

BACKGROUNDCompared with several reports of cerebral vasospasm after clipping for unruptured cerebral aneurysm, only one study to date has reported cerebral vasospasm after coil embolization. Herein, the authors report a rare case of cerebral vasospasm after coil embolization for unruptured cerebral aneurysm.OBSERVATIONSA 58-year-old woman with an unruptured anterior communicating artery aneurysm was referred to our department. Stent-assisted coil embolization was performed for the aneurysm, and no obvious adverse events were observed on cerebral angiography obtained immediately after the operation. However, the patient developed mild headache and slight restlessness soon after the operation and new-onset disorientation, left hemispatial neglect, and left hemiplegia the day after the operation. Emergency brain magnetic resonance imaging and cerebral angiography indicated vasospasm in the right middle cerebral artery, and intra-arterial injection of fasudil hydrochloride hydrate was performed to dilate the middle cerebral artery. Blood flow in the middle cerebral artery immediately improved, and she was discharged without neurological deficits 8 days after the operation.LESSONSImmediate intervention is necessary to prevent cerebral infarction in patients with cerebral vasospasm, which may occur even after coil embolization for unruptured cerebral aneurysm.

Scintillating scotoma following optic nerve compression caused by an unruptured anterior communicating artery aneurysm: a case report

BackgroundScintillating scotoma caused by optic nerve compression by aneurysm is rare. We report a case of scintillating scotoma following optic nerve compression caused by an unruptured anterior communicating artery aneurysm.Case presentationA 64-year-old woman visited our department with a scintillating scotoma. Magnetic resonance imaging demonstrated no new lesions, although her previously diagnosed anterior communicating artery aneurysm had increased in size. Thus, we performed neck clipping. The operative view showed that the aneurysm compressed the right optic nerve. Her symptoms disappeared after the operation. These findings suggest that scintillating scotoma may be caused by compression of the optic nerve by the anterior communicating artery aneurysm.ConclusionAlthough scintillating scotoma is a common condition, aneurysms should be considered as a potential cause.

Comparison of hydrogel coils versus bare platinum coils for the treatment of anterior communicating artery aneurysms.

INTRODUCTION:While endovascular coiling has been shown to be a safe treatment option for intracranial aneurysms, there remains concern regarding increased recurrence and retreatment rates. Preliminary studies evaluating hydrogel coated coils have demonstrated decreased recurrence rates compared to bare metal coils.METHODS:A retrospective chart review was done on all patients with anterior communicating artery aneurysms (ACoAAs) treated with endovascular coiling between 2014 and 2018. Treatment groups were divided into hydrogel coated coils or bare metal coils. Patients were categorized into the hydrogel group when ≥ 70% of the coil length was hydrogel coated.RESULTS:Eighty-four ACoAAs were treated with coil embolization between 2014 and 2018. Postoperative imaging was available for 68 patients. Twenty-six patients were categorized into the hydrogel treatment group. Aneurysm recurrence was seen in 7.7% (2/26) of patients treated with hydrogel coated coils compared to 33.3% (14/42) of those treated with bare metal coils (P = 0.03). Subanalysis of patients with ruptured aneurysms revealed decreased recurrence rates in patients treated with hydrogel coated coils at 5.9% (1/17) compared to patients treated with bare metal coils at 39.4% (13/33) (P = 0.01).CONCLUSIONS:Hydrogel-coated coils may reduce recurrence rates in the treatment of both ruptured and unruptured ACoAAs.

A comparative analysis of the endoscopic endonasal and pterional approaches for clipping anterior communicating artery aneurysms on three-dimensional printed models.

A comparative analysis of the endoscopic endonasal and pterional approaches for clipping anterior communicating artery aneurysms on three-dimensional printed models.

Treatment results and long-term outcomes of endovascular treatment of 96 unruptured anterior communicating artery aneurysms: A large single-center study

ObjectiveData on endovascular treatment of unruptured anterior communicating artery (AcomA) aneurysms remain limited. Therefore, to clarify the outcomes of treatment for unruptured AcomA aneurysms, we retrospectively analyzed a single-center series of 96 unruptured AcomA aneurysms treated endovascularly. MethodsEndovascular treatment of 100 unruptured AcomA aneurysms was performed at our institution between May 2009 and May 2019; of these, 96 consecutive aneurysms (95 patients) were included in this retrospective study. Recanalization and retreatment rates were investigated for 76 aneurysms through follow-up using time-of-flight magnetic resonance angiography or digital subtraction angiography for ≥ 2 years after treatment. ResultsThe rate of total procedure-related complications was 19.8%. The rates of thromboembolic complications, hemorrhagic complications, and intraprocedural aneurysm bleeding were 12.5%, 6.3%, and 3.1%, respectively, with no poor outcomes (modified Rankin Scale score 2–6) resulting from thromboembolic and hemorrhagic complications at 180 days after treatment. The permanent morbidity rate was 1.0%. Multivariate analysis revealed that maximum diameter (>10 mm), neck size (>4 mm), and stent use were independently associated with symptomatic cerebral infarction. Endovascular retreatment was conducted for two aneurysms (2.6%), and the cumulative recanalization rate was 5.3% (4/76) over a mean follow-up period of 48.2 ± 23.7 months. ConclusionThis study indicates that although there is a relatively high possibility of overall procedure-related complications with endovascular treatment for unruptured AcomA aneurysms, most complications are temporary and mild, with a permanent morbidity rate of approximately 1.0%.

Commentary on: Result of coiling versus clipping of unruptured anterior communicating artery aneurysms treated by a hybrid vascular neurosurgeon.

Commentary on: Result of coiling versus clipping of unruptured anterior communicating artery aneurysms treated by a hybrid vascular neurosurgeon.

Radial Artery Access for Cerebral Angiography: 2-Dimensional Operative Video.

A number of studies have demonstrated that the radial artery is a safer access site than the femoral artery for endovascular procedures.1-4 In the prospective randomized studies comparing transradial and transfemoral approaches for cardiac procedures, there was a 60% reduction in access site complications as well as significant decreases in all-cause mortality with the transradial approach as compared to transfemoral, which has led to the adoption of a radial first strategy.5-7 Neurointerventional studies have demonstrated similar safety benefits as well as improved patient preference.8-14 In this video, a patient presented with an unruptured anterior communicating artery aneurysm and consented to a transradial artery diagnostic cerebral angiogram. This technical video demonstrates the key preprocedural preparation, room setup, patient positioning, steps for radial artery, and distal radial artery puncture and sheath placement. Distal transradial artery access is our preferred approach for diagnostic cerebral angiography because of an improved safety profile and procedural ergonomics. In cases in which a larger radial artery is advantageous such as for neurointerventions requiring larger systems, a standard transradial approach may be performed.9 In this video, a full 6-vessel cerebral angiogram is performed, followed by our arteriotomy closure technique using our standard equipment including a 10-cm 5 French Glidesheath Slender (Terumo, Japan), 100-cm hydrophilic coated 5 French Simmons 1 catheter (Merit OEM), 0.035 hydrophilic coated guidewire, and SafeGuard closure device (Merit, Salt Lake City, Utah).

Geometrical and Hemodynamic Characteristic Changes of Small Anterior Communicating Artery Aneurysms during Follow-ups in a Retrospective Analysis.

Small intracranial aneurysms have a low risk of rupture. However, ruptured anterior communicating artery (ACoA) aneurysms are usually smaller in clinical practice. The retrospective study aimed to investigate the geometrical and hemodynamic changes of small unruptured ACoA aneurysms during serial follow-ups. We retrospectively collected patients with small unruptured ACoA aneurysms that were not repaired, who had serial follow-ups from the Electronic Medical Record System in four tertiary hospitals. The geometrical parameters of ACoA aneurysms were measured using a three-dimensional reconstructed model. Intra-aneurysmal hemodynamic parameters were computed using a high-resolution computational fluid dynamics model. Geometrical and hemodynamic changes of the aneurysms were evaluated at each follow-up. Five patients with small unruptured ACoA aneurysms that were not repaired were identified and included in this analysis. Aneurysms rupture occurred in two patients with aneurysm growth. The formation and enlargement of an irregular bleb at the aneurysm neck or dome were observed before the rupture. Ruptured aneurysms showed high wall shear stress (WSS) in the high inflow zone of aneurysm neck while low WSS and high oscillatory shear index (OSI) in the flow-recirculating region of aneurysm dome. Three unruptured aneurysms maintained a stable morphology and a physiological level of WSS. Aneurysm growth, low WSS, and high OSI at the dome and/or high WSS at the neck potentially contribute to the rupture of small ACoA aneurysms. These aneurysms should be considered for the treatment regardless of the small size.