What Is a Saccular Aneurysm?

According to the different characteristics of intracranial aneurysms, they can be divided into different types.

Zhang Hongqi	(Chief physician)	Department of Neurosurgery, Xuanwu Hospital, Capital Medical University
Ye Ming	(Attending physician)	Department of Neurosurgery, Xuanwu Hospital, Capital Medical University

Intracranial aneurysms are mostly abnormal bulges on the walls of intracranial arteries, which is the first cause of subarachnoid hemorrhage. In cerebrovascular accidents, they are second only to cerebral thrombosis and hypertensive cerebral hemorrhage, ranking first three. It can occur at any age, and most often occur in middle-aged and elderly women aged 40 to 60 years. The cause of intracranial aneurysms is not clear. Most scholars believe that intracranial aneurysms are caused by local congenital defects of the intracranial arterial wall and increased intraluminal pressure. Related to the occurrence and development of aneurysms. Intracranial aneurysms occur in the cerebral arterial ring (Willis ring), 80% of which occur in the anterior half of the cerebral arterial ring.

Western Medicine Name

Intracranial aneurysm

Affiliated Department

Surgery-Neurosurgery

Disease site

head

Contagious

Non-contagious

Whether to enter health insurance

Yes

Intracranial aneurysm disease classification

According to the different characteristics of intracranial aneurysms, they can be divided into different types.

Intracranial aneurysms are classified by etiology

Congenital aneurysm

Infectious aneurysm

Traumatic aneurysm

Arteriosclerotic aneurysm

Intracranial aneurysms are classified by morphology

Cystic aneurysm

Spindle aneurysm

Dissecting aneurysm

Irregular aneurysm

Intracranial aneurysms are classified by size

Small aneurysm: <5mm

Medium-sized aneurysms: 5-10mm

Large aneurysm: 11-25mm

Giant aneurysms:> 25mm

Intracranial aneurysms are classified according to the location of the aneurysm

Willis anterior circulation aneurysm

Internal carotid aneurysm

Posterior communicating artery aneurysm

Anterior choroidal aneurysm

Anterior cerebral artery aneurysm

Anterior communicating artery aneurysm

Middle cerebral artery aneurysm

Willis ring posterior circulation aneurysm

Vertebral artery aneurysm

Basilar artery aneurysm

Posterior cerebral artery aneurysm

Intracranial aneurysms are classified according to the structure of the aneurysm wall

True aneurysm

Pseudoaneurysm

Causes of intracranial aneurysms

The cause of aneurysms is not very clear. The causes of aneurysm formation can be summarized as follows:

Congenital factors of intracranial aneurysms

The thickness of the wall of the cerebral artery is 2/3 of that of other parts of the body and the diameter of the artery. The surrounding tissue lacks tissue support, but the blood flow is large, especially at the bifurcation of the artery. The middle layer of the tube wall lacks elastic fibers, and there are fewer smooth muscles. Due to hemodynamic reasons, the bifurcation part is most vulnerable to impact, which is consistent with clinical findings that the bifurcation part has the most aneurysms and protrudes in the direction of blood flow impact. Fissures in the middle layer of the tube wall, residual fetal blood vessels, abnormal or defective congenital arteries (such as internal elastic plate and middle layer dysplasia) are all important factors for aneurysm formation. Congenital arterial dysplasia can develop not only into a cystic aneurysm, but also into a spindle aneurysm.

Acquired factors of intracranial aneurysms

(1) Arteriosclerosis The occurrence of atherosclerosis in the arterial wall causes the elastic fibers to break and disappear, weakening the arterial wall and not being able to withstand great pressure. Sclerosis causes occlusion of the arterial nutrition vessels and degeneration of the vessel walls. 40 to 60 years is the obvious stage of the development of arteriosclerosis, and it is also the age of the onset of aneurysms, which is enough to explain the relationship between the two.

(2) Infectious aneurysms account for about 4% of all aneurysms. Infections in various parts of the body can spread in the form of small emboli and stay on the weekend branch of the cerebral artery through a small amount of blood. A few emboli stay in the bifurcation of the artery. Skull base bone infections, intracranial abscesses, and meningitis can also erode the arterial wall from the outside, causing infectious or fungal aneurysms. The appearance of infectious aneurysms is often irregular.

(3) Traumatic craniocerebral closed or open injury, surgical trauma, due to foreign bodies, instruments, bone fragments, etc., directly damage the arterial wall, or the blood vessel wall is weak due to pulling blood vessels, forming true or pseudo aneurysms.

(4) There are other rare causes such as tumors that can cause aneurysms. Skull base abnormal vascular network disease, cerebral arteriovenous malformations, intracranial vascular dysplasia and cerebral artery occlusion can also be accompanied by aneurysms.

In addition to the above reasons, a common factor is the impact of hemodynamics. The arterial wall is caused by the aforementioned congenital factors, arteriosclerosis, infection or trauma, and the impact of blood flow is the cause of aneurysm formation. Sometimes the following conditions can be seen clinically to develop into an aneurysm: Residual aneurysm pedicle: a small part of the thin wall remains when the aneurysm is clamped. swelling at the bifurcation of the artery: such as the swelling at the junction of the internal carotid artery and the posterior communication branch. A part of the arterial wall protrudes outward. These can develop into aneurysms in 2 to 10 years.

Pathogenesis of intracranial aneurysms

After an aneurysm develops, it often progresses further and an enlarged aneurysm appears. Hypertension is an important acquired factor that causes aneurysms to gradually expand.

The rupture of the aneurysm is actually only bleeding from the tumor wall. This rupture is different from imagined aneurysm bursts (such as intraoperative aneurysm rupture). In this case, the bleeding is often very turbulent, and the patient often falls into a coma within a few minutes and died quickly due to brain stem damage.

Anxiety, nervousness, agitation, sudden rise in blood pressure, urination, exertion, late pregnancy, childbirth, manual labor, sexual life, etc. are just the factors that induce aneurysm rupture. In more cases, bleeding occurs suddenly when there is no obvious cause.

After an aneurysm ruptures and bleeds, the bleeding site is stopped by blood clot coagulation and vasospasm contraction, and the promotion of cerebrospinal fluid, the rupture site stops bleeding. 1 to 2 weeks after the bleeding, fibrinolysis phenomenon is excessive, which weakens the fibrous network at the rupture site and liquefies blood clots. At this time, fibrosis at the rupture opening of the arterial wall is not firm, so rebleeding is prone to occur.

Intracranial aneurysm pathophysiology

Intracranial aneurysms occur at the bifurcation of the cerebral arteries and their main branches. About 85% of the aneurysms are located in the anterior carotid system of the anterior ring of the Willis artery, namely the intracranial segment of the internal carotid artery, the anterior cerebral artery, the anterior communicating artery, the middle cerebral artery, and the posterior half of the posterior communicating artery.

If the arterial wall is asymmetric cystic dilatation, it is called a cystic aneurysm, and a small cystic aneurysm with a narrow neck is also called a berry aneurysm. Most congenital aneurysms are sac-like or berry-like, and they can also be leaf-like. Other forms include gourd-like, spherical, and sausage-shaped. The tumor wall is generally smooth like a sac, most of which are composed of congenital weak blood vessel walls, often located at the bifurcation of larger arteries. The aneurysm and the tumor-bearing artery are narrow at the junction, called the tumor neck (pedicle) or basal. The width of the neck is very inconsistent; the most prominent part of the far side opposite the neck is the tumor bottom (apex), which is between The site between the tumor bases is called the tumor body (sac). Xiaofu is a small bulge on the tumor sac, often the place where the aneurysm ruptures or remains after rupture.

Intracranial aneurysms vary widely in size, usually 0.5 to 2 cm. The rupture of an aneurysm has a certain relationship with its size. It is generally believed that a ruptured aneurysm is larger and an unruptured aneurysm is smaller. The critical size of aneurysm rupture is 0.5 to 0.6 cm in diameter. Aneurysms with a diameter of more than 0.5cm gradually increase the chance of bleeding. When the diameter exceeds 3.0cm, the symptoms of increased intracranial pressure replace the symptoms of bleeding.

Clinical manifestations of intracranial aneurysms

Before intracranial aneurysm patients rupture and bleed, 90% of patients have no obvious symptoms and signs. Only a few patients have special manifestations due to aneurysms affecting adjacent nerves or brain structures. Aneurysm symptoms and signs can be roughly divided into pre-rupture symptoms, bleeding symptoms during rupture, localized signs, and symptoms of increased intracranial pressure.

Intracranial aneurysm aura symptoms

40% to 60% of aneurysms have certain aura symptoms before rupture. This is because aneurysms often have a sudden expansion or a small amount of local leakage before they rupture. Among them, oculomotor nerve palsy is the most lateral and localized sign of aura rupture.

Intracranial aneurysm bleeding symptoms

80% to 90% of patients with aneurysms are found because of subarachnoid hemorrhage caused by rupture and bleeding, so the most common symptoms of bleeding are spontaneous subarachnoid hemorrhage.

(1) Causes and onset: Some patients often have obvious causes before aneurysm rupture, such as heavy physical labor, cough, hard stool, running, drinking, emotional excitement, anxiety, sexual life, etc. Some patients may have no obvious cause, even in sleep. Sudden onset in most patients, usually with headaches and disturbances of consciousness as the most common and prominent manifestations.

(2) Focal neurological symptoms caused by hemorrhage: The neurological symptoms caused by subarachnoid hemorrhage are meningeal irritation, which is manifested by a strong neck and positive Kirschner's sign. Anterior cerebral artery aneurysm bleeding often invades the frontal lobe of the cerebral hemisphere, causing dementia, decreased memory, incontinence, hemiplegia, aphasia, and so on. Hemorrhage of the middle cerebral artery aneurysm often causes temporal lobe hematoma, which manifests as hemiplegia, blindness, aphasia, and temporal lobe hernia. Ipsilateral oculomotor nerve paralysis may occur when the posterior communication artery aneurysm ruptures and bleeds.

(3) Systemic symptoms: A series of systemic symptoms can occur after rupture and bleeding:

A. High blood pressure: After the onset, the blood pressure of the patient usually rises suddenly, usually temporarily, and usually returns to normal after a few days to 3 weeks.

B. Elevated body temperature: Most patients do not exceed 39 ° C, mostly around 38 ° C. Elevated body temperature usually occurs within 24 to 96 hours after the onset of illness, and usually returns to normal within 5 days to 2 weeks.

C. Brain-heart syndrome: clinical manifestations are transient hypertension, disturbance of consciousness, dyspnea, acute pulmonary edema, epilepsy within 1 to 2 days after onset, and acute myocardial infarction can occur in severe cases (mostly in the first week after onset) Within)). The more severe the disturbance of consciousness, the higher the chance of an abnormal ECG.

D. Gastrointestinal bleeding: A small number of patients may show signs of upper gastrointestinal bleeding, manifested as vomiting coffee-like or tar-like stools.

(4) Rebleeding: Once an aneurysm ruptures, bleeding will repeatedly occur, and the rebleeding rate is 9.8% to 30%. According to statistics, the time of rebleeding is usually 7 to 14 days after the last bleeding, accounting for 10% in the first week, 11% can rebleed within 1 year, and 3% can rupture and rebleed in a longer time.

(5) Localized symptoms: Before aneurysm rupture, symptoms may be directly pressed on adjacent structures. These symptoms are of local significance in diagnosis. Common localized symptoms are:

Cranial nerve symptoms: This is one of the most common localized symptoms caused by aneurysms. The oculomotor nerve, trigeminal nerve, pulley nerve, and abductor nerve are the most common.

Visual symptoms: This is caused by the aneurysm compressing the visual pathway. Aneurysms in the anterior half of the Willis ring, such as aneurysms of the anterior cerebral artery and aneurysms of the anterior communication artery, can compress the optic cross and cause bilateral temporal hemianopia or oppression of the optic beam to cause co-hemiopia.

Migraine: Typical migraines caused by aneurysms are rare, and their incidence is 1% to 4%. Headaches usually occur suddenly, often on one side of the orbit, and most are pulsatile. Compression of the common carotid artery on the ipsilateral side can temporarily relieve the pain.

(6) Symptoms of increased intracranial pressure: It is generally believed that an unruptured giant aneurysm with an aneurysm diameter of more than 2.5 cm or a ruptured aneurysm with intracranial hematoma can cause increased intracranial pressure. The change of fundus edema caused by giant aneurysm is different from the change of fundus edema caused by rupture and bleeding. The former is disc edema caused by increased intracranial pressure, and the latter is mostly disc edema and retina caused by subarachnoid hemorrhage. Bleeding.

(7) Special manifestations: Aneurysms sometimes show some special manifestations. For example, internal carotid artery aneurysms or anterior communicating artery aneurysms can present with symptoms of saddle-like tumors such as headache, bilateral temporal blindness, acromegaly, and hypopituitarism. Individual cases can also be transient cerebral ischemia as the main manifestation; a small number of patients can develop acute mental disorders after aneurysm rupture and bleeding, manifested as acute insanity, disorientation, excitement, hallucinations, incoherence, and irritability.

(8) Clinical classification: Hunt and Hess classify patients with intracranial aneurysms into five grades according to their clinical manifestations to assess the risk of surgery:

Grade I: Asymptomatic, or mild headache and mild neck stiffness.

Grade : Moderate to severe headache, stiff neck, no neurological deficit except for cerebral palsy.

Grade III: lethargy, confusion, or mild focal neurological deficits.

Grade : Stiff, moderate to severe hemiparalysis, may have early decortical tonicity and autonomic nervous system dysfunction.

Grade V: Deep coma, decortical rigidity, dying state.

Intracranial aneurysm diagnosis

SAH Intracranial aneurysm for subarachnoid hemorrhage (SAH)

In the acute phase of bleeding, the positive rate of SAH diagnosis by CT is extremely high, and it is safe, fast, and reliable. Elevated lumbar puncture pressure with bloody cerebrospinal fluid is often the direct evidence for diagnosis of subarachnoid hemorrhage after aneurysm rupture. However, when intracranial pressure is high, lumbar puncture should be performed carefully.

Intracranial aneurysm to determine the etiology and lesion site

Cerebral angiography is the "gold standard" for the diagnosis of intracranial aneurysms. It can clearly determine the location, shape, size, number of aneurysms, the presence of vasospasm, and the final surgical plan. The first angiography is negative and should be repeated after 3 to 4 weeks. CTA can replace cerebral angiography to a certain extent and provide more information for the treatment decision of aneurysms.

Differential diagnosis of intracranial aneurysms

Patients with intracranial aneurysm onset of spontaneous subarachnoid hemorrhage

In addition to intracranial aneurysm rupture and bleeding, cerebral arteriovenous malformations, dural arteriovenous fistulas, cavernous hemangioma, moyamoya disease, and spinal vascular malformations can also cause spontaneous subarachnoid hemorrhage. Cerebral angiography and CT or MRI of the skull can make a definitive diagnosis of the corresponding disease.

Patients with highly suspected intracranial aneurysms who have not ruptured with an intracranial aneurysm

Non-bleeding aneurysms should be distinguished from high-density tumors and cysts during plain and enhanced CT scans of the skull. If extra-dense nodules or masses are found, tumors, cysts, tuberculomas, hematomas, aneurysms, etc. should be considered . MRI has important discriminative value. The aneurysm cavity airflow signal is significantly different from other tumors, and thrombus T1 high signal and hemosiderin deposition are also more characteristic. ^[1]

Intracranial aneurysm disease treatment

Non-surgical treatment of intracranial aneurysms after rupture and bleeding

(1) Prevention of rebleeding: including absolute bed rest, analgesia, anti-epilepsy, stabilizers, cathartic drugs to keep patients quiet and avoid emotional excitement. Application of anti-fibrinolytic agents (aminocaproic acid, antithrombin acid, aphthalasin, etc.). Prior to the treatment of aneurysms, controlling blood pressure is one of the important measures to prevent and reduce the rebleeding of aneurysms, but too low blood pressure can cause insufficient cerebral perfusion and cause damage. It is usually reduced by 10% to 20%.

(2) Reduce intracranial pressure: increased intracranial pressure may occur after subarachnoid hemorrhage, and mannitol can be applied. However, the application of mannitol to increase blood volume, increase the average blood pressure, and occasionally rupture the aneurysm.

(3) Cerebrospinal fluid drainage: In the acute stage after aneurysm bleeding, there may be a large amount of blood on the brain surface and in the brain to increase intracranial pressure. Some may block the interforaminal or brain aqueducts due to small hematomas or clots, causing acute brain Accumulated water and dysconsciousness need urgent ventricle drainage. Lumbar puncture and lumbar drainage can also be used as a method for drainage of cerebrospinal fluid, but patients with cerebral hernia may appear under high intracranial pressure.

(4) Prevention and treatment of cerebral vasospasm: After an aneurysm ruptures and bleeds, blood entering the subarachnoid space easily causes cerebral vasospasm. Cerebral vasospasm begins to occur 3 to 4 days after bleeding, peaks at 7 to 10 days, and begins to subside at 10 to 14 days. At present, the treatment of cerebrovascular spasm is mainly carried out in three aspects: the application of calcium antagonists; the removal of bloody cerebrospinal fluid; and an appropriate increase in blood pressure.

Surgical treatment of intracranial aneurysms

Surgical treatment of aneurysms includes craniotomy and endovascular intervention.

(1) Aneurysm neck clamping or ligation: The purpose of surgery is to block the blood supply to the aneurysm to prevent rebleeding; to keep the tumor-bearing and blood-supplying arteries open and to maintain normal blood flow in the brain tissue.

(2) Isolation of aneurysms: Aneurysm isolation is the simultaneous clamping of aneurysm-containing arteries at the distal and proximal ends of the aneurysm to isolate the aneurysm from the blood circulation.

(3) Aneurysm wrapping: using different materials to strengthen the aneurysm wall, although the tumor cavity is still congested, it can reduce the chance of rupture. The current clinical applications are fascia and cotton.

(4) Intravascular interventional therapy: For patients with aneurysms, craniotomy is extremely high-risk, craniotomy fails, or due to systemic and local conditions that are not suitable for craniotomy, etc., endovascular embolization can be used. For those who do not have aneurysms, they can also choose embolization treatment. The purpose of intravascular interventional surgery is to use femoral artery puncture to place a thin microcatheter in the aneurysm sac or the neck of the aneurysm, and then send a soft titanium alloy spring coil into the aneurysm sac through the microcatheter and It is full, causing blood flow in the aneurysm sac to disappear, thereby eliminating the risk of bleeding again. ^[2-3]

Prognosis of intracranial aneurysm disease

The prognosis of intracranial aneurysms is related to the age of the patient, whether there are other diseases before the operation, the size, location, nature of the aneurysm, the clinical classification status before the operation, the choice of the operation time, the presence of vasospasm and its severity, especially the aneurysm Patients with subarachnoid hemorrhage accompanied by vasospasm and intracranial hematoma are important factors affecting the prognosis. The experience and technical proficiency of the surgeon, whether microsurgery is used for the operation, whether there is an increase in intracranial pressure after surgery (the decompression is sufficient or not), etc., are all closely related to the prognosis. Patients are older and have poor prognosis with heart, kidney, liver, lung and other important organ diseases and hypertension. Preoperative high Hunt-Hess classification and surgical mortality of posterior circulation aneurysms are higher.

Intracranial aneurysm disease prevention

There is currently no way to prevent the occurrence of intracranial aneurysms. For people with high-risk factors, it is recommended to perform regular cerebrovascular imaging examinations so that lesions can be found and treated appropriately before aneurysm rupture and bleeding. Risk factors should be controlled in order to reduce the incidence of aneurysms.

Intracranial aneurysm disease care

Preoperative care of intracranial aneurysms

(1) Explain to the conscious person the need for surgery and the matters that need to be coordinated with the patient during the operation to eliminate their fear. For the conscious person, do the family's psychological care before surgery so that they understand the purpose and meaning of the operation The content of preoperative preparation to achieve the purpose of cooperating with the operation.

(2) Keep the patient absolutely bedridden, avoid all external stimuli, prevent blood pressure from rising due to restlessness, and increase the possibility of rebleeding. Observe vital signs and changes in consciousness at any time, and detect bleeding early.

(3) Give a reasonable diet, do not eat foods that are likely to cause constipation, and maintain smooth stool. It is appropriate to maintain indoor ventilation to prevent patients from sneezing or coughing hard due to cold, so as to avoid increasing intracranial pressure and reflexive increase of intracranial pressure and rupture of intracranial aneurysms.

(4) For those with epilepsy, pay attention to ensure their safety, prevent injuries during seizures, keep the airway open, give oxygen, record the time of convulsions, and give antiepileptic drugs according to doctor's orders.

Postoperative care of intracranial aneurysms

(1) General care: Raise the head of the bed 15-30 ° to facilitate venous return, reduce cerebral edema, and reduce intracranial pressure.

(2) Observation of the condition: observe vital signs and try to keep blood pressure at a stable level; pay attention to observe the size of the pupils of the patients and observe the changes of consciousness dynamically.

(3) Nursing of puncture points: After the femoral artery puncture site is pressurized and bandaged, closely observe the pulsation of the foot arteries of the punctured limb, the temperature, color and peripheral blood flow of the lower limbs. form.

(4) Nursing of epilepsy: reduce irritation, prevent seizures, install bed stalls, prepare rescue medication, prevent accidents, and minimize the damage during seizures as much as possible.

(5) Prevention and nursing of complications: pay attention to observe the incision healing, the presence of scalp fluid, whether the drainage tube of the head is unobstructed, the amount and characteristics of the drainage; observe the physical activity, sensory condition and lack of nerve function Symptoms should be reported to the doctor immediately if there are any abnormalities so that they can be handled promptly.

Intracranial aneurysm discharge guidance

Educate patients to maintain emotional stability, to have a regular life, to avoid strenuous exercise and cough, to maintain smooth urination, and to prevent changes in blood pressure. Follow up regularly, if there is any change in condition, immediately go to the hospital for examination and treatment.