Subarachnoid hemorrhage and intracranial aneurysm I.
I. What is subarachnoid hemorrhage?
Subarachnoid hemorrhage (SAH) is a type of cerebral hemorrhage, named after the cerebral blood vessels that rupture and distribute blood diffusely in the subarachnoid space on the surface of the brain, and is divided into traumatic subarachnoid hemorrhage and spontaneous subarachnoid hemorrhage. Traumatic subarachnoid hemorrhage, as the name implies, is bleeding from a ruptured intracranial blood vessel caused by trauma. Spontaneous subarachnoid hemorrhage, on the other hand, is commonly caused by the presence of primary lesions in the intracranial vessels, such as intracranial aneurysms, cerebrovascular malformations, etc., which require timely surgical removal, and if treated conservatively, the primary lesions are likely to bleed again, leading to further aggravation and even life-threatening conditions. Therefore, to be precise, spontaneous subarachnoid hemorrhage is only a form of bleeding manifestation of cerebrovascular disease, but not cerebrovascular disease.
Intracranial aneurysms are the most common cerebrovascular disease causing spontaneous subarachnoid hemorrhage, accounting for more than 80% of cases. Spontaneous subarachnoid hemorrhage due to ruptured intracranial aneurysms is known as “aneurysmal subarachnoid hemorrhage” and is the most serious cerebrovascular accident with a mortality rate of 45%. Currently, the global average incidence is about 1 in 10,000 per year.
The presentation of aneurysmal subarachnoid hemorrhage is typical, with 80% of patients describing it as “the most severe headache ever”, 70% with nausea and vomiting, 50% with loss of consciousness, and 30% with neck pain. Most severely, 12% of patients die before reaching the hospital emergency room.
What is intracranial aneurysm?
Intracranial aneurysm is a “time bomb” lurking in the human brain, which is an abnormal cystic bulge in the wall of cerebral blood vessels. It can also be said that the “blistering” or “bulging” of the cerebral artery wall is intracranial aneurysm, and the incidence of intracranial aneurysm in human body is about 7%. Just as a “blister” or “bulge” in a bicycle inner tube is prone to air leakage, an intracranial aneurysm is much weaker than a normal cerebral artery and is also prone to rupture, resulting in cerebral hemorrhage, which often appears as This kind of cerebral hemorrhage caused by ruptured intracranial aneurysm is often called “subarachnoid hemorrhage”, which has the highest mortality rate among all cerebral hemorrhages, and the global mortality rate is still as high as 45% even with the rapid development of medical technology. What is more frightening is that intracranial aneurysms are often asymptomatic and life-threatening when they rupture and bleed, so aneurysms are like “time bombs” in the brain that can explode at any time with disastrous consequences. Bleeding from a ruptured intracranial aneurysm usually occurs in brief spurts, with 12% of patients dying instantly after the first “rupture” and the bleeding stopping temporarily in survivors. Thereafter, if the aneurysm is not treated promptly, it will “rupture” a second time, called a secondary hemorrhage, with an incidence of 20-30% in the first month after the first hemorrhage and a mortality rate of 70% in patients with a secondary hemorrhage, and a third hemorrhage in patients who survive both hemorrhages, with little hope of survival.
III. How to detect intracranial aneurysm?
Intracranial aneurysm is a “time bomb” lurking in the human brain, with an incidence of about 7% in the human body, usually with no symptoms before rupture and bleeding, but life-threatening once it bleeds. Therefore, patients who have had spontaneous subarachnoid hemorrhage or are suspected of having an intracranial aneurysm must be examined and treated immediately.
The “gold standard” for diagnosing intracranial aneurysms is digital cerebral angiography (DSA), an invasive test that involves puncturing the femoral artery at the base of the thigh or the flexural artery at the wrist, advancing a catheter along the large blood vessels in the body to the carotid artery in the neck, injecting contrast through this catheter, and using digital silhouette technology to obtain A clear image of the cerebral vessels is obtained using digital silhouette technology. In addition to this, with the advancement of CT and MRI technology, CT angiography (CTA) and MRI angiography (MRA) have become important auxiliary examinations. The greatest advantage of both compared to digital cerebral angiography is that they are less invasive, but the disadvantage is that the image clarity is relatively poor.
The detection of intracranial aneurysm is usually divided into three cases. First, an unruptured intracranial aneurysm is incidentally detected by nuclear magnetic angiography during a normal physical examination. Second, intracranial aneurysm compresses or stimulates intracranial nerve tissue, corresponding neurological symptoms appear, and the physician suspects that the patient has intracranial aneurysm and performs digital angiography or CT angiography to discover intracranial aneurysm. Third, subarachnoid hemorrhage after intracranial aneurysm rupture, and the intracranial aneurysm is detected by emergency digital angiography. Currently in China, most patients with intracranial aneurysms are found by cerebral angiography (DSA) and other examinations only after subarachnoid hemorrhage occurs from the first rupture. After subarachnoid hemorrhage is detected, the aneurysm must be treated surgically as soon as possible to avoid secondary bleeding and save the patient’s life.
4.How to treat intracranial aneurysm?
The purpose of intracranial aneurysm treatment is to avoid rupture and bleeding, and if rupture and bleeding have already occurred, secondary rupture and bleeding must be avoided so as to save the patient’s life. Therefore, the timing of intracranial aneurysm treatment currently follows two principles: first, intracranial aneurysms that have ruptured and bleeding or have neurological symptoms are treated as soon as the patient’s physical condition allows; second, patients who have not ruptured or have no symptoms are treated according to the doctor’s recommendation.
There are currently two main treatment methods for intracranial aneurysms: first, craniotomy aneurysm clamping, which opens the skull, separates the brain tissue, exposes the aneurysm and then uses a special metal clip (aneurysm clip) to clamp the neck of the aneurysm (the part where the aneurysm body is connected to the cerebral blood vessels) so that the blood flow in the cerebral blood vessels will not enter the aneurysm again and prevent the aneurysm from rupture again. This method has been used for more than 50 years. The advantage is that the aneurysm is occluded under direct vision and the hematoma can be removed in patients with a large amount of bleeding. The disadvantage is that it opens the cranial cavity and is very traumatic, making the procedure extremely difficult for critically ill patients. Secondly, interventional surgical aneurysm embolization is performed by puncturing the femoral artery through the root of the thigh, bringing the catheter along the internal vessels to the location of the intracranial aneurysm, embolizing the aneurysm sac (the internal space of the aneurysm body) using a special titanium wire (spring coil), and finally withdrawing the catheter so that the blood flow from the cerebral vessels will not enter the aneurysm again and prevent the aneurysm from rupture and bleeding again. This method is a new technology in the past 20 years, and has the advantages of no craniotomy, little trauma, fast recovery of patients after surgery, and no significant increase in surgical difficulty for seriously ill patients. However, the cost of treatment is higher, embolization of complex-shaped aneurysms is difficult, and the hematoma cannot be removed. In general, both open aneurysm clamping and interventional aneurysm embolization have their own advantages and disadvantages. Specifically for each patient, the most favorable treatment method must be decided by a neurosurgeon with extensive experience in both interventional embolization and open clamping, or a neurointerventional physician with experience in interventional embolization and a neurosurgeon with experience in open clamping.
V. How is subarachnoid hemorrhage treated?
Subarachnoid hemorrhage following rupture of an intracranial aneurysm can have catastrophic consequences. The first principle of treatment is to deal with the cause of bleeding to avoid secondary bleeding, that is, to deal with intracranial aneurysm. However, after treatment of an intracranial aneurysm, the patient is also faced with the problem of what to do with the blood that has entered the subarachnoid space after the first hemorrhage. If a portion of the blood is in a more concentrated location and forms a hematoma, the hematoma can be removed by craniotomy. However, most of the blood tends to be diffusely distributed on the brain surface and is difficult to remove surgically. Currently, the common clinical treatment method is lumbar puncture for cerebrospinal fluid release, because the subarachnoid space on the brain surface is filled with cerebrospinal fluid, and releasing cerebrospinal fluid through lumbar puncture can bring out part of the blood from the brain surface, while the residual part of the blood can only be absorbed gradually by the body, which may take weeks or even months.
Therefore, even if the intracranial aneurysm has been successfully treated without secondary hemorrhage, the blood diffusely distributed in the subarachnoid space can still cause continuous damage to the brain tissue, leading to death in severe cases. Therefore, patients still need further hospitalization after aneurysm management, lumbar puncture to release cerebrospinal fluid, control cranial pressure, prevent cerebral vasospasm, etc.
What are the sequelae of intracranial aneurysm rupture and bleeding?
Ruptured intracranial aneurysm bleeding will bring a series of brain tissue damage. If the first bleeding is small and the second bleeding is avoided after intracranial aneurysm treatment, the patient can often return to normal life without any sequelae. However, if there is a lot of bleeding and damage, the patient may still be left with disability. The sequelae of ruptured intracranial aneurysm are usually cognitive impairment of varying degrees, and in severe cases, persistent coma or even vegetation, while relatively few of them manifest as limb paralysis.
Ruptured intracranial aneurysm hemorrhage can lead to hydrocephalus because the blood affects the normal absorption of fluid in the brain. Continued unrelieved hydrocephalus can cause further brain damage in mild cases or may be life-threatening in severe cases. Therefore, regular review is needed after intracranial aneurysm surgery, and ventriculo-abdominal shunt surgery should be performed if necessary.
How to review after intracranial aneurysm treatment?
There is a risk of recurrence and rebleeding for treated aneurysms, regardless of interventional embolization or craniotomy clamping. It may be either the regrowth of the original aneurysm (0.9-2.9%) or the new aneurysm of other cerebral vessels (1-2%). Therefore, patients with aneurysms must be reviewed regularly for a long time after surgery in order to detect and treat them in time. The method of review varies according to the treatment method.
For open aneurysm clamping, digital cerebral angiography and enhanced CT cerebral angiography are usually repeated.
For interventional aneurysm embolization, digital cerebral angiography and enhanced nuclear magnetic angiography are usually reviewed.
In addition to aggressive review, there are limited methods to prevent recurrence of intracranial aneurysm. Blood pressure control and smoking cessation may reduce the risk of intracranial aneurysm occurrence and rupture bleeding.
VIII. How to prevent intracranial aneurysm?
The mechanism of intracranial aneurysm is not fully understood, and there is no good prevention method, but blood pressure control and smoking cessation may reduce the occurrence of intracranial aneurysm and the risk of bleeding.
For intracranial aneurysms that are already “latent” in the human brain, it is important to detect them in time before they rupture and bleed. Because digital angiography is invasive and carries some risk, non-invasive MRI or CT angiography is more routinely used.
It is important to note that not all unruptured aneurysms require immediate surgical management, and the decision to treat an unruptured intracranial aneurysm after detection must be made by a neurosurgeon with extensive experience in both interventional embolization and cranial clamping, or by mutual agreement between a neurointerventionalist with experience in interventional embolization and a neurosurgeon with experience in cranial clamping.