Definition

The brain is covered by three layers, which from the inside out consist of the pia mater, arachnoid mater, and dura mater. Subarachnoid Hemorrhage (SAH) is bleeding in the subarachnoid space, the area between the pia and arachnoid layers.

Causes

Bleeding usually occurs due to the rupture of an abnormal bulge on a blood vessel (aneurysm) in the brain. Sometimes bleeding can be caused by trauma, abnormal tangles of brain blood vessels (arteriovenous malformations), or other vascular and health issues.

In non-traumatic subarachnoid hemorrhage, about 80% are caused by the rupture of an aneurysm. Rupture of arteriovenous malformations (AVM) is the second most recognizable cause of SAH, accounting for about 10% of SAH cases.

Aneurysms can be associated with several congenital diseases such as coarctation of the aorta, Marfan syndrome, Ehlers-Danlos syndrome, fibromuscular dysplasia, and polycystic kidney disease. Acquired factors suspected to be related to aneurysm formation include:

• Atherosclerosis, which is the blockage of blood vessels by cholesterol clots
• Hypertension or high blood pressure
• Old age
• Smoking

Other causes of SAH include:

• Infection
• Cancer
• Injury (e.g., skull base fracture)
• Vasculitis (inflammation of blood vessel walls)

Risk factor

SAH can occur at any age, and some people are even born with cerebral aneurysms that can lead to this condition. According to the National Institute of Neurological Disorders and Stroke, women are at a higher risk of brain aneurysms than men. The risk of AVM rupture is higher during pregnancy. Risk factors for aneurysm formation include high blood pressure, smoking, heavy alcohol consumption, drug use, a family history of brain aneurysms, certain connective tissue disorders, and a previous history of brain aneurysms.

Symptoms

The main symptom of SAH is a sudden severe headache (in 48% of cases). The headache is sometimes accompanied by nausea, vomiting, and temporary loss of consciousness. Other symptoms include:

• Dizziness
• Pain around the eyes
• Double vision
• Sensitivity to light
• Loss of vision
• Sensory and motor disturbances
• Seizures
• Signs of meningeal irritation (e.g., neck stiffness)
• Ptosis, or drooping eyelids
• Bruits, or abnormal sounds from blood vessels due to turbulent blood flow
• Speech disturbances
• Localized nerve function impairment
• Decreased consciousness

Diagnosis

To diagnose subarachnoid hemorrhage, a doctor will conduct a brief medical history interview, a physical examination, and supporting tests.

During the physical examination, results may be normal or show the following signs:

• Increased blood pressure
• Elevated body temperature
• Increased heart rate
• Swelling of the optic nerves
• Retinal hemorrhage
• Localized or generalized nerve function impairment

For diagnostic tests, the doctor may recommend several examinations:

• CT scan: This test can detect bleeding in the brain. The doctor may inject contrast dye to see the blood vessels in detail (CT angiogram).
• MRI: This test can also detect bleeding in the brain. Dye is injected into the blood vessels to visualize the arteries and veins in more detail (MR angiogram) and to observe blood flow.
• Cerebral angiography: The doctor inserts a long, thin tube (catheter) into an artery in the leg and threads it to the brain. Dye is injected into the brain's blood vessels to make them visible on X-rays. Cerebral angiography is typically recommended for more detailed imaging or if subarachnoid hemorrhage is suspected but not clear or visible on other tests.

About 22% of subarachnoid hemorrhages caused by aneurysms are not seen on initial imaging tests. If initial tests do not show bleeding, the doctor may recommend:

• Lumbar puncture: In this test, the doctor inserts a needle into the lower back to take a sample of cerebrospinal fluid, which surrounds the brain and spinal cord. Blood in the cerebrospinal fluid indicates subarachnoid hemorrhage.
• Repeat imaging tests: Tests can be repeated a few days after the initial test.

Management

The first step in managing SAH is to stabilize the patient's condition. After determining the cause through examination, the next step is to address the cause of SAH. If the bleeding is due to a ruptured brain aneurysm, the doctor may recommend:

• Surgery: The surgeon makes an incision in the scalp to locate the brain aneurysm. A metal clip is placed on the aneurysm's neck to stop blood flow to the bulge.
• Endovascular embolization: This procedure blocks blood flow to abnormal blood vessels, such as in brain aneurysms. The doctor inserts a catheter into an artery in the groin and threads it to the brain. The catheter guides a platinum coil that is placed in the aneurysm. The coil fills the aneurysm, blocking and stopping blood flow into the bulge.
• Other endovascular procedures: Certain aneurysms can be treated with advanced endovascular embolization techniques like stent-assisted or balloon-assisted coiling.

Endovascular procedures may need to be repeated. Patients require regular follow-ups to monitor their condition after the procedure. They may also need physical, occupational, and speech therapy.

Complications

If untreated, subarachnoid hemorrhage can cause permanent brain damage or even death. Some complications of SAH include:

• Hydrocephalus
• Re-bleeding
• Blood vessel narrowing leading to poor blood flow
• Seizures
• Heart function impairment

Prevention

The only way to prevent this condition is by addressing its causes and risk factors. Early detection and treatment of brain aneurysms can prevent recurrent bleeding in the subarachnoid space.

Subarachnoid hemorrhage is associated with significant morbidity and mortality. Treating hypertension, quitting smoking, and avoiding excessive alcohol consumption can reduce the risk of bleeding. Proper use of blood thinners can also reduce the frequency of SAH.

Wisely used surgical and endovascular therapies reduce the risk of first-time or recurrent bleeding in vascular abnormalities, including AVM and brain aneurysms. For unruptured aneurysms, preventive measures may include tying off the aneurysm to reduce blood flow, causing it to shrink gradually.

When to see a doctor?

The sooner treatment is initiated to control bleeding, the better the recovery process. Immediately visit the emergency department if you experience the following symptoms:

• Seizures
• Severe headache
• Nausea, vomiting, or light sensitivity accompanying a headache
• Double vision
• Neck stiffness
• Speech disturbances
• Inability to fully open the eyelids
• Confusion and difficulty concentrating

If you have an aneurysm, consult your doctor to prevent the risk of SAH.

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