Subarachnoid hemorrhage (SAH)

Subarachnoid hemorrhage (SAH) is a type of stroke caused by bleeding in the subarachnoid space — the area between the brain and the thin tissues covering it. This space is filled with cerebrospinal fluid (CSF), which helps cushion the brain. A subarachnoid hemorrhage is typically a medical emergency, as it can lead to severe brain damage and even death if not treated promptly.

Causes of Subarachnoid Hemorrhage:

The main causes of subarachnoid hemorrhage include:

1. Ruptured Aneurysm:

   • The most common cause of SAH is the rupture of an intracranial aneurysm, which is a bulging area in a blood vessel in the brain. When the aneurysm bursts, blood leaks into the subarachnoid space.

   • Aneurysms usually form at branches of major arteries in the brain, particularly at the Circle of Willis (a ring of arteries at the base of the brain).

2. Head Injury:

   • Traumatic brain injuries (such as from falls, car accidents, or sports) can also lead to bleeding in the subarachnoid space.

3. Arteriovenous Malformation (AVM):

   • A condition where blood vessels in the brain are abnormally connected, leading to increased pressure and the potential for rupture.

4. Cerebral Amyloid Angiopathy:

   • A condition where amyloid protein deposits in the brain's blood vessels, weakening them and making them more prone to rupture.

5. Blood Clotting Disorders:

   • Conditions such as hemophilia or the use of blood thinners can increase the risk of bleeding in the brain.

6. Other Causes:

   • Brain tumors, aneurysms from high blood pressure, and some infections can also cause SAH.

Symptoms of Subarachnoid Hemorrhage:

The symptoms of a subarachnoid hemorrhage can appear suddenly and are often severe:

1. Sudden, Severe Headache:

   • Often described as the worst headache of the patient's life. This is the most common symptom and occurs in 90-95% of cases.

   • The headache may start suddenly and worsen rapidly.

2. Neck Stiffness:

   • Due to irritation of the meninges (the layers of tissue covering the brain and spinal cord).

3. Nausea and Vomiting:

   • Occurs due to increased intracranial pressure.

4. Loss of Consciousness:

   • Some people may lose consciousness immediately after the hemorrhage, ranging from brief fainting to prolonged coma.

5. Seizures:

   • Can occur due to irritation of the brain caused by the blood.

6. Photophobia:

   • Sensitivity to light.

7. Double Vision or Blurred Vision:

   • Vision disturbances due to pressure on parts of the brain responsible for sight.

8. Weakness or Numbness:

   • Often on one side of the body (hemiparesis).

9. Speech Difficulties:

   • Problems with speaking or understanding speech.

Diagnosis of Subarachnoid Hemorrhage:

Diagnosis is typically made with the following tests:

1. CT Scan (Computed Tomography):

   • The first line of imaging used to detect bleeding in the brain. A non-contrast CT scan is highly effective for identifying acute subarachnoid hemorrhage.

   • The scan can quickly show blood in the subarachnoid space.

2. Lumbar Puncture (Spinal Tap):

   • If the CT scan is negative but suspicion remains high, a lumbar puncture is performed. It involves collecting cerebrospinal fluid (CSF) from the lower back. Blood in the CSF is a strong indicator of a subarachnoid hemorrhage.

3. MRI (Magnetic Resonance Imaging):

   • MRI can sometimes help detect areas of brain damage caused by the hemorrhage, though it’s not as fast as CT in the acute phase.

4. Cerebral Angiography:

   • This test involves injecting a contrast dye into the arteries and taking X-ray images to identify the source of the hemorrhage, such as an aneurysm or arteriovenous malformation (AVM).

Treatment of Subarachnoid Hemorrhage:

Treatment depends on the underlying cause of the hemorrhage, the severity, and the overall health of the patient:

1. Emergency Care:

   • Patients with SAH require immediate hospitalization, often in an intensive care unit (ICU).

   • The first goal is to control intracranial pressure (ICP) and manage symptoms like pain, nausea, and vomiting.

2. Surgical Treatment:

   • Aneurysm Clipping: Involves placing a small clip around the neck of the aneurysm to stop the blood flow and prevent further rupture.

   • Endovascular Coiling: A less invasive option where a catheter is inserted through the groin and directed to the aneurysm. Coils are inserted into the aneurysm to block it and promote clotting.

   • Surgical Removal of AVMs: If an arteriovenous malformation is the cause, it may be surgically removed.

3. Supportive Treatment:

   • Managing Intracranial Pressure (ICP): Drugs may be used to reduce swelling in the brain and relieve pressure.

   • Pain Relief: Strong pain medications like opioids may be administered to control headaches.

   • Preventing Seizures: Anticonvulsant medications may be given if seizures occur.

   • Blood Pressure Control: Keeping blood pressure within safe limits is crucial to prevent further bleeding.

4. Rehabilitation:

   • Following the acute phase, patients may need extensive rehabilitation to recover lost neurological functions, depending on the extent of brain damage.

Complications of Subarachnoid Hemorrhage:

1. Rebleeding:

   • The initial hemorrhage can lead to rebleeding, which can worsen the condition. This is more common in the first 24 hours.

2. Vasospasm:

   • Narrowing of the blood vessels in the brain, which can reduce blood flow and lead to delayed cerebral ischemia, a condition where brain tissue doesn’t get enough oxygen.

3. Hydrocephalus:

   • Accumulation of cerebrospinal fluid in the brain due to blockage of normal CSF flow. This may require a shunt to drain excess fluid.

4. Severe Brain Damage:

   • Permanent damage to the brain tissue due to lack of oxygen or excessive pressure.

5. Infections:

   • There is a risk of infections, particularly if surgery is involved.

Prevention of Subarachnoid Hemorrhage:

1. Managing Risk Factors:

   • Hypertension (high blood pressure) is the leading modifiable risk factor for aneurysm rupture, so keeping blood pressure under control is crucial.

   • Smoking cessation: Smoking is a major risk factor for aneurysm formation and rupture.

   • Limiting alcohol and avoiding illicit drug use (e.g., cocaine) are important to prevent increases in blood pressure and vessel damage.

2. Screening for Aneurysms:

   • Individuals with a family history of brain aneurysms or other risk factors might undergo screening through cerebral angiography or other imaging techniques to detect aneurysms before they rupture.

3. Treating Aneurysms Before Rupture:

   • If an aneurysm is detected and is at risk of rupture, preventive surgery (such as clipping or coiling) can help avoid a subarachnoid hemorrhage.

Prognosis:

• Early intervention significantly improves outcomes, but subarachnoid hemorrhage still carries a high mortality rate (about 40-50% of cases).

• Of the survivors, about 30-40% will experience significant disabilities, including cognitive, physical, and speech impairments.

• Rehabilitation is critical in improving long-term outcomes for those who survive the initial hemorrhage.