The American Heart Association/American Stroke Association (AHA/ASA) published Guidelines for the Management of Patients with Unruptured Intracranial Aneurysms (hereinafter referred to as the Guidelines) on June 18 in the journal Stroke. The guideline writing group systematically reviewed the literature from January 1977 to June 2014, and made a series of recommendations on the natural history, epidemiology, risk factors, screening and diagnosis, imaging, and regression to surgical and endovascular treatment of patients with unruptured intracranial aneurysms (UIAs) in the context of an evidence-based scenario. Details are as follows: I. Risk factors for aneurysm progression, growth, and rupture 1. Smoking may increase the risk of UIA formation; therefore, patients with UIA should be made aware of the importance regarding smoking cessation. (Class I recommendation, Level B evidence) 2. Hypertension may play a role in the growth and rupture of intracranial aneurysms (IA); therefore, patients with UIA should have their blood pressure monitored and be treated for hypertension. (Class I recommendation, Level B evidence) 3. Aneurysm growth may increase the risk of rupture; therefore, patients with UIA who are receiving conservative treatment should be regularly imaged and followed. (Class I recommendation, Level B evidence) II.CLINICAL PRESENTATIONS 1. Patients with aneurysmal subarachnoid hemorrhage (aSAH) who have coexisting UIA should be carefully evaluated. (Class I recommendation, Level B evidence) 2. Early treatment is usually indicated in patients presenting with UIA causing cerebral nerve palsy. (Class I recommendation, Level C evidence) 3. The effectiveness of routine treatment of UIA to prevent ischemic cerebrovascular disease is uncertain (Class IIb recommendation, Level C evidence) III. Diagnostic/Imaging Examinations 1. If surgical or endovascular treatment of the patient is being considered, digital subtraction angiography (DSA) is helpful in identifying and evaluating cerebral aneurysms when compared with noninvasive imaging. (Class IIa recommendation, Level B evidence) 2. DSA is reasonable and most sensitive in the follow-up of patients with treated aneurysms. (Class IIa recommendation, Level C evidence) 3. CT angiography (CTA) and magnetic resonance angiography (MRA) are useful in detecting and following up UIAs.(Class I recommendation, Level B evidence) 4. MRA can be used as an alternative test for following up patients with treated aneurysms, and DSA can be performed when necessary when the decision is made to proceed with treatment. (Class IIa recommendation, Level C evidence) 5, For patients with coiled and tortuous aneurysms (especially those with wide necks or dome diameters or residual fillings), follow-up evaluation should be performed (Class I recommendation, Level B evidence); the time and duration of follow-up are uncertain, and this aspect needs to be further explored. 6, The importance of supervised imaging after endovascular treatment of UIA that lacks high-risk features for recurrence is unclear, but supervised imaging is likely to be warranted. (Class IIa recommendation, level C evidence) IV. Screening 1. Patients with ≥2 family members with IA or SAH should be screened for aneurysm CTA or MRA. Particularly high risk factors predictive of aneurysm development in such families include a history of hypertension, smoking, and being female. (Class I recommendation, Level B evidence) 2. Patients with a history of autosomal dominant polycystic nephropathy, especially with a family history of IA, should be screened for ATA or MRA (Class I recommendation, Level B evidence); it is reasonable to perform CTA or MRA in patients with combined aortic constriction and in patients with primitive dwarfism (Class IIa recommendation, Level B evidence). V. MEDICAL HISTORY 1. aHistory of ASAH is either an independent risk factor contributing to an elevated risk of distant hemorrhage secondary to heterogeneous small unruptured aneurysms. (Class IIb recommendation, level B evidence) 2. If a patient is observed to have an enlarged aneurysm during follow-up, it should be treated as long as there is no coexisting disease that would contraindicate treatment. (Class I recommendation, Level B evidence) 3. If a family history of ruptured intracranial aneurysm exists in a patient with UIA, treatment should be offered to such patients, even if the patient’s lesion is smaller than a spontaneous ruptured intracranial aneurysm. (Class IIa recommendation, Level B evidence) VI. Surgical Intervention 1. When considering the choice of surgical clamping as a treatment modality, attention should be paid to a variety of factors, including the patient’s age, aneurysm size, and location. (Class I recommendation, Level B evidence) 2. Considering that aneurysm closure and incomplete closure carry different risks of hemorrhage and lesion enlargement, it is recommended that imaging studies be performed after surgical intervention to determine aneurysm closure. (Class I recommendation, Level B evidence) 3. Considering the risk of postoperative aneurysm recurrence and neoplastic aneurysm, long-term follow-up after surgical intervention is recommended, which is especially important for patients with incompletely closed aneurysms on first treatment. (Class IIb recommendation, Level B evidence) 4.Surgical intervention for UIA is recommended in medical centers with high procedure volumes (>20 cases per year). (Class I recommendation, Level B evidence) 5. Specialized intraoperative devices or techniques may be considered during UIA procedures to avoid vascular injury or residual aneurysms. (Class IIb recommendation, Level C evidence) VII. Endovascular Treatment Guideline Key Points 1. Endoluminal flow diversion represents an emerging class of treatments that may be considered for implementation in specific patients (Class IIb recommendation, Level B evidence). Newer techniques for the treatment of unruptured cerebral aneurysms, including fluid embolization, may also be considered in selected patients (Class IIb recommendation, Level B evidence). However, the long-term prognosis of these new techniques is unknown; therefore, until trials confirm the improved safety and efficacy of these new techniques, it is recommended that treatment be chosen in strict accordance with the FDA’s instructions (Class IIa recommendation, Level C evidence). 2. Coated coil therapy is not superior to bare coil therapy. (Class III recommendation, Level A evidence) 3. UIA endovascular treatment is recommended in medical centers with high procedure volumes. (Class I recommendation, Level B evidence) 4. The risks of radiation exposure procedures should be clearly communicated during the informed consent process for endovascular therapy. (Class I recommendation, Level C evidence) VIII.Efficacy of surgical clamping versus coil embolization 1.Surgical clamping is an effective treatment modality for patients with UIA who are being considered for treatment. (Class I recommendation, Level B evidence) 2. Coil embolization is an effective treatment modality for selected patients with UIA who are being considered for treatment. (Class IIa, Level B) 3. If patients with unruptured cerebral aneurysms are pre-treated, they should be thoroughly informed of the risks and benefits of endovascular and microsurgical procedures as alternatives. (Class I recommendation, Level B evidence) 4. Coil embolization with surgery has lower mortality and morbidity than surgical clamping in specific patient groups, but overall recurrence rates are higher. (Class IIb recommendation, level B evidence) IX. Follow-up of patients with aneurysms 1. For patients with UIA who receive noninvasive treatment (without surgical or endovascular intervention), MRA or CTA imaging follow-up is recommended. The optimal duration and interval of follow-up are not known. (Class I recommendation, Level B evidence) 2. For patients with UIA who receive noninvasive treatment (not undergoing surgical and endovascular interventions), the first follow-up visit may be considered 6 to 12 months after the first disease episode, and subsequent follow-up visits may be yearly or every other year. (Class IIa recommendation, Level C evidence) 3. For patients with UIA who receive non-invasive treatment and have no contraindications to MRI, it is recommended that time-of-flight (TOF) MRA be used in preference to CTA for long term follow-up.(Class IIb recommendation, Level C evidence) Summary of key points of the guideline 1. A variety of factors should be considered in determining the optimal treatment plan for unruptured intracranial aneurysms (UIAs) including the size, location, and other morphologic features of the aneurysm. Lesion size, location, and other morphologic features; lesion changes documented by serial imaging; patient age; history of aneurysmal subarachnoid hemorrhage (aSAH); family history of cerebral aneurysms; the presence of multiple aneurysms; and the presence of concomitant pathologic changes, such as arteriovenous vascular malformations, cerebral or hereditary pathology that may result in an elevated risk of bleeding. (Class I recommendation, Level C evidence) 2. If patients with unruptured cerebral aneurysms are pre-treated, they should be exhaustively informed of the risks and benefits of endovascular surgery and microsurgery as alternatives to prevent and treat UIAs and prevent bleeding. (Class I recommendation, Level B evidence) 3. The effect of UIA treatment is poor in medical centers with a low volume of surgeries, and UIA treatment is recommended in medical centers with a high volume of surgeries. (Class I recommendation, Level B evidence) 4. Retrospective and prospective studies from multiple countries and international collaborations have confirmed that microsurgical clip ligation can control aneurysm regeneration for a longer period of time, but coil embolization is superior to microsurgical clip ligation in terms of surgical prevalence and mortality rate, hospitalization time, and cost of treatment. Therefore, endovascular surgery may be considered as an alternative to surgical clip treatment for selected patients with UIAs, and it is particularly suitable for patients who present with basal apical lesions or in the elderly high-risk patient population. (Class IIb recommendation, Level B evidence) 5. Factors associated with the risk of UIA treatment include old age, coexisting disease, and aneurysm size and location. Therefore, in elderly patients or asymptomatic patients with UIA with suspected coexisting disease who are at low risk of bleeding (lesion size, location, morphologic features, family history, and other factors can influence bleeding risk), observation of disease progression is a reasonable option. (Class IIa recommendation, Level B evidence).