Epidemiology
Because subarachnoid hemorrhage resulting from a ruptured aneurysm is a serious condition, it is extremely disabling and fatal. Therefore, the treatment of unruptured aneurysms found incidentally or in multiple aneurysms subarachnoid hemorrhage has been aggressively pursued in Western countries for decades. Unruptured aneurysms are usually classified as follows: asymptomatic aneurysms, symptomatic aneurysms, and unruptured aneurysms in cases of subarachnoid hemorrhage (cases of multiple aneurysms). Although the high risk of death and disability from aneurysmal subarachnoid hemorrhage can be eliminated by prophylactic interventional embolization or craniotomy clamping of unruptured aneurysms. However, the natural medical history, the surgical risk of embolization and clamping of unruptured aneurysms, and the risk factors for aneurysm rupture remain unclear. Previous studies lacked sufficient number of cases and follow-up time. Chuan He, Department of Neurosurgery, Xuanwu Hospital, Capital Medical University
To date, only few prospective follow-up studies and several small retrospective studies have evaluated the natural history of unruptured aneurysms. The results of the two largest prospective studies on the risk of rupture of unruptured aneurysms (Class B Class II/III recommendations) are shown in the icons below.
Study Name
Patient
SAH
Total years of follow-up
Annual rupture rate
Risk factors
ISUIA
1692
51
6544
0.8%
1, 2
Juvela
142
34
2577
1.3%
1,3,4
Risk factors: 1, aneurysm diameter; 2, aneurysm location; 3, smoking; and 4, age.
In addition, the results of the prospective and retrospective study portions of the International Study of Unruptured Aneurysms (ISUIA) differed, with a relatively higher annual incidence of aneurysm rupture in the prospective study portion than in the retrospective study (0.8 vs 0.3%). Although, the ISUIA included a large number of patients, the difference in results between the prospective and retrospective study parts suggests a selection bias in the ISUIA. Therefore, the results of ISUIA may not truly reflect the natural history of the unruptured aneurysm population, and the results should be treated with caution.
In summary, the following recommendations for the treatment of unruptured aneurysms are provided for informational purposes only and do not yet have sufficient scientific evidence.
Recommended Principles for Treatment of Unruptured Aneurysms
The following recommendations for treatment of unruptured aneurysms are provided
1) Aneurysms of 5-7 mm or greater.
2) Aneurysms under 5 mm include the following characteristics.
A. Symptomatic aneurysms.
B. Posterior circulation, anterior communicating, and posterior communicating aneurysms.
C. Aneurysms with a large Dome neck, aspect ratio, irregular shape, and small sac-like protrusion morphology.
3) In addition, even if the aneurysm does not have the above characteristics, patients with psychiatric symptoms such as intense agitation or depression caused by the aneurysm should be considered for treatment with adequate information.
Embolization or Closure
1. Aneurysm neck.
Traditionally, embolization of “wide neck” aneurysms with a neck of 4 mm or more or a dome/neck ratio <2 has been relatively difficult. However, with the widespread use of 3d spring coils and the development of balloon-assisted and stent-assisted techniques, embolization of "wide neck" aneurysms has become possible. < p="">
In addition to the dome/neck ratio, the aspect ratio is also an important factor in determining the likelihood of embolization; aneurysms with the same dome/neck ratio and an aspect ratio <1 are more difficult to embolize and may require balloon or stent assistance. < p="">.
2. Aneurysm site.
Cranial clamping of anterior bed-surface collateral aneurysms and vertebrobasilar aneurysms is relatively difficult, and interventional embolization is recommended. Middle cerebral artery bifurcation aneurysms, distal anterior cerebral artery aneurysms, and distal posterior cerebral artery aneurysms (farther than p2) have more distant embolization access, finer vessel diameters, higher risk of thrombosis and bleeding from ruptured vessels due to microcatheters, and in addition cannot be assisted by balloons or stents, so interventional embolization needs to be considered carefully.
In addition to the aneurysm site, the pointing of the aneurysm and the anatomical features of the nearby brain tissue also have an impact on craniotomy clamping. In anterior communicating aneurysms, the risk of craniotomy is higher in cases where the apex of the aneurysm is pointing posteriorly, and the risk of injury to the penetrating hypothalamic artery is higher. Aneurysms of the middle cerebral artery bifurcation site, with a short horizontal segment of the middle cerebral artery (short M1), have a higher risk of craniotomy injury to the lateral bean-y artery. Aneurysm of the superior segment of the bed of the internal carotid artery, located ventral to the internal carotid artery and in a low position, makes craniotomy exposure difficult.
3. Aneurysm size.
The smaller the aneurysm, the more difficult it is to get the microcatheter in place to enter the aneurysm. It is relatively easy to get the microcatheter in place for aneurysms over 3.5 mm in diameter, while the risk of rupture during embolization of aneurysms below 3 mm is higher. In addition, the stability of the microcatheter during spring-ring entry into the aneurysm also requires careful consideration. The smaller the aneurysm, the less room for microcatheter oscillation, the greater the pressure on the aneurysm wall, and the greater the possibility of microcatheter head dislodgement or even spring-ring dislodgement, thus making embolization more difficult. In view of the above reasons, for aneurysms below 2 mm, it is recommended to first consider a 1.5 mm diameter spring coil, with the aid of a stent if necessary. However, even with a 1.5mm diameter spring coil, 1.7-1.8mm aneurysms are the lower limit of aneurysm size that can be embolized.
The rate of recanalization after embolization of giant aneurysms (25 mm or more) is high, with a maximum reported rate of 99%. If embolization is chosen, long-term postoperative follow-up and lifelong treatment with repeated embolization are required. Below the giant type aneurysm (below 25 mm) consider that interventional embolization can be performed.
4. Intra-aneurysmal thrombosis.
Intra-aneurysmal thrombosis is usually present in large (10 mm) and giant aneurysms (25 mm), especially those over 15 mm. The immediate consequence of intra-aneurysmal thrombosis is that the spring coil becomes trapped within the thrombus and cannot be densely filled, with a high rate of postoperative recanalization. In addition, there is a relatively high risk of thromboembolism during embolization.
5. Symptoms of aneurysm compression.
Compression symptoms of aneurysms are related to the size of the aneurysm. After interventional embolization of aneurysms, there is usually a reduction or no change in compression symptoms, but there is a possibility of worsening compression symptoms in the short term after embolization of large and giant aneurysms. In addition, aneurysm enlargement and recanalization rates are higher after large and giant aneurysm treatment, accompanied by worsening compression symptoms. Therefore, open or interventional aneurysm isolation is the best option for large and giant aneurysms with severe compression symptoms. If the vascular occlusion test cannot be passed, isolation is accompanied by the need for vascular bypass surgery. With the development of interventional materials, dense mesh stents may be an alternative to vascular bypass.
Symptoms of aneurysm compression are related to the site of the aneurysm. Posterior communicating aneurysm compression resulting in motor nerve palsy is usually fully recovered after embolization, while the prognosis after embolization of compression symptoms of aneurysms in other sites is not clearly concluded yet. According to clinical experience, the recovery of motor nerve compression symptoms is more likely, while the recovery of sensory nerve compression symptoms is more difficult, especially in the case of large anterior bed prominence paracentral aneurysm compression symptoms of the optic nerve, interventional embolization needs to be considered carefully.
6. Embolization access.
Femoral artery puncture is the common access for intracranial aneurysm embolization, so if there is occlusion, severe stenosis or extreme tortuosity in the internal iliac artery, abdominal aorta, carotid artery or vertebral artery vessels, embolization is difficult to complete. Flexural artery puncture access may be considered when necessary, however, embolization of left hemisphere aneurysms by right flexural artery puncture is equally difficult.
Aneurysm embolization is usually recommended with a 6F guiding catheter that is capable of meeting the requirement for passage of a second microcatheter or balloon in the event of an intraoperative accident such as aneurysm rupture. In addition, the use of two 5F guiding catheters may be considered when necessary to meet multi-system passage requirements. An 8F guiding catheter may also be considered for cases where support is inadequate.
7. Age
Compared to open aneurysm clamping, interventional aneurysm embolization is less invasive and has a faster recovery. Interventional aneurysm embolization is preferred for patients of advanced age, and according to previous studies, aneurysm embolization is preferred for patients over 65 years of age. However, for patients over 80 years old, embolization access is often poor due to vascular sclerosis, and even angiography is difficult to complete. It is recommended to consider appropriate treatment according to vascular conditions after CTA examination.
8. History of contrast allergy.
The symptoms of the history of contrast allergy are first clarified to determine the degree of allergy.
Mild, rash and fever, etc.
Moderate, severe vomiting, tracheospasm, facial or laryngeal edema, vasovagal reflexes resulting in decreased blood pressure.
Severe, hypotensive shock, respiratory arrest, cardiac arrest, and seizures.
There are no contraindications for patients with a history of mild allergy. However, statistics show that patients with a history of mild allergy are six times more likely to develop moderate to severe allergy relative to the average patient, and although some studies claim that prophylactic application of hormonal medications can reduce the incidence of severe allergy, there is no definitive evidence that they are necessarily effective. For patients with a history of mild allergy, in addition to the prophylactic application of hormonal medications, it is also important to prepare cardiopulmonary resuscitation instruments and medications such as epinephrine.
Patients with a history of moderate or severe contrast allergy are contraindicated for interventional aneurysm embolization.
9. anticoagulation and antiplatelet drugs.
Systemic heparinization is required during interventional aneurysm embolization, which increases the risk of post-surgical wound bleeding. In addition, if complications such as thrombosis of the aneurysm-carrying artery occur during aneurysm embolization, thrombolytic drugs are required, which can also lead to an increased risk of bleeding from the surgical incision. Therefore, interventional aneurysm embolization is recommended to be performed after the surgical incision has healed sufficiently, depending on the patient’s condition. For patients with multiple aneurysms, interventional aneurysm embolization after open clamping aneurysm should also follow these principles.
There are no clear guidelines for the waiting time for interventional aneurysm embolization after surgical procedures, and if we refer to the guidelines for the use of t-PA intravenously, t-PA is contraindicated for 3 months after intracranial and spinal cord surgery.
Although the 3-month interval is not required to be followed for emergency embolization of ruptured aneurysms, interventional aneurysm embolization is recommended 3-6 months after surgical procedures for unruptured and asymptomatic aneurysms.
For patients on long-term antiplatelet drugs such as aspirin and anticoagulants such as Warfarin, open aneurysm clamping is a higher risk and interventional aneurysm embolization is considered first.