Aneurysmal Subarachnoid Hemorrhage
What Is It?
Aneurysmal subarachnoid hemorrhage (SAH) is bleeding around the brain that occurs when a brain aneurysm
ruptures. The subarachnoid space is the fluid-filled space surrounding the brain, bounded by the wispy arachnoid membrane and filled with cerebrospinal fluid. The major blood vessels that bring blood to the brain pass through this space before diving into the brain itself. These cerebral blood vessels can develop weakened walls that balloon out, called a cerebral aneurysm
. These sacs have a tendency to bleed in some patients. Because they occur most commonly in this fluid-filled subarachnoid space, this bleeding most commonly occurs into cerebrospinal fluid filled subarachnoid space and is thus termed subarachnoid hemorrhage.
While a ruptured aneurysm is the most common cause of a spontaneous subarachnoid bleed, bleeding into this space can occur even more frequently as a result of head trauma. This is discussed elsewhere as traumatic subarachnoid hemorrhage.
More rarely, some aneurysms, depending on their location, size and shape, can also bleed into the brain itself or into the ventricles, the fluid-filled spaces within the brain.
What Types of Symptoms Are Typical?
When an aneurysm ruptures and causes SAH, the most common symptom is severe headache. This headache typically starts very suddenly and is often described as "the worst headache of my life" by the patient.
Accompanying the headache can be other symptoms related to irritation of the coverings of the brain including nausea, vomiting, photophobia (avoidance of bright lights) and a stiff neck (called nuchal rigidity).
While some patients present with normal levels of consciousness, many present with lethargy or more severe impairments in mental status. Many patients present comatose or die suddenly. In fact, aneurysmal subarachnoid hemorrhage is one of the most common causes of sudden death in young adults.
Some patients present with a "sentinel headache", meaning that they will have a sudden, severe headache but without significant neurological deterioration. Some of these patients go on to have another bleed, often more severe, in the first days or weeks following the first bleed. This points to the importance of catching these sentinel bleeds so that patients can be treated quickly while they are in good clinical condition and before another bleed can occur.
How Is The Diagnosis Typically Made?
When a patient presents with the classic presentation of a sudden, severe headache or loss of consciousness with or without a stiff neck or other symptoms, the standard initial test used to evaluate the brain is a CT scan
. In most cases of subarachnoid hemorrhage, the classic pattern of subarachnoid blood can be easily detected on this imaging study.
In rare cases, the blood cannot be seen on CT. If the suspicion is high for an aneurysm rupture some patients will undergo a lumbar puncture (spinal tap). By introducing a needing into the spinal canal, a sample of cerebrospinal fluid is taken to analyze for evidence of blood products.
Once subarachnoid hemorrhage is diagnosed, other studies are used to determine the cause of bleeding. CT angiograms or a traditional cerebral angiogram are both good for visualizing the blood vessels in the head and can usually demonstrate the causative aneurysm, if one is present. MR Angiograms are less commonly used because they have lower resolution of fine detail of the blood vessels. They are sometimes used in un-ruptured cases to look for an obvious aneurysm.
While an aneurysm is the most common cause of a spontaneous subarachnoid bleed, occasionally another lesion such as an arteriovenous malformation is found instead.
What Are Some Common Treatments?
As mentioned above, once an aneurysm ruptures, it is prone to rupturing again, often with more dire consequences for the patient. Therefore, most neurosurgeons recommend prompt treatment of the aneurysm. No treatment is generally used to address the subarachnoid blood which is already there, the treatments aim at treating the aneurysm to prevent further bleeds.
In general, for most standard aneurysms, treatment consists of some means of occluding the aneurysm so that it no longer fills with blood and therefore cannot rupture again. Traditionally this was done surgically by exposing the aneurysm and placing a clip across the opening into the aneurysm from the blood vessel. This clip closes the opening, or neck, and prevents further ruptures.
More recently, another technique has been introduced. Endovascular coiling involves navigating a small catheter into the aneurysm (inserted into a blood vessel in the leg) and filling the aneurysm from the inside with small metallic coils. If done well, this fills most of the aneurysm and causes the blood in it to clot, also blocking it off from the blood circulation in the blood vessel.
The choice of which treatment is most appropriate for each patient is made based on several factors. Each patient is different so these treatment decisions should be made with their own personal treating physician team.
In some cases, SAH can cause acute hydrocephalus which may require a catheter drain (a ventriculostomy) or a shunt.
In some patients, after subarachnoid hemorrhage, the blood can irritate the blood vessels and lead to spasm of the vessels. This vasospasm can lead to stroke which can lead to permanent neurological symptoms or death. Therefore, most patients with SAH are screened closely for the development of vasospasm and may require additional treatments aimed at preventing or treating vasospasm.
Return to the Cerebrovascular Disease page
from the Aneurysmal Subarachnoid Hemorrhage page.
Return to the Nervous System Diseases home page.
This site is not intended to offer medical advice. Every patient is different, and only your personal physician can help to counsel you about what is best for your situation. What we offer is general reference information about various disorders and treatments for your education.