A spontaneous subarachnoid hemorrhage (SAH) is a sudden, life-threatening medical event caused by bleeding into the subarachnoid space surrounding the brain. This space normally contains cerebrospinal fluid that cushions the brain and spinal cord. The term “spontaneous” indicates the hemorrhage is not the result of external trauma. When a blood vessel ruptures, the rapid influx of blood irritates the brain’s lining and abruptly increases pressure inside the skull. This condition is a form of hemorrhagic stroke requiring immediate emergency medical intervention.
Understanding the Underlying Cause
The majority of spontaneous subarachnoid hemorrhages result from the rupture of a cerebral aneurysm. An aneurysm is a localized, balloon-like bulge that forms on the wall of an artery in the brain, typically at a vessel junction where the wall is naturally weaker. These aneurysms are the cause in approximately 80 to 85% of nontraumatic SAH cases.
The vessel wall at the site of the aneurysm is thin and defective, making it vulnerable to the constant force of arterial blood pressure. Factors such as high blood pressure (hypertension), smoking, and age-related vascular changes can contribute to the formation and growth of these bulges. When the wall of the aneurysm can no longer withstand the pressure, it ruptures, releasing blood directly into the subarachnoid space.
While aneurysms account for most spontaneous cases, other vascular abnormalities can cause the bleeding. Arteriovenous malformations (AVMs), which are tangles of abnormal, fragile blood vessels, are a less common cause, implicated in about 10% of cases. Other rare causes include arterial dissections, vasculitis, or the use of stimulant drugs like cocaine.
Recognizing the Critical Symptoms
The primary symptom of a subarachnoid hemorrhage is a sudden, excruciating headache often described as the “worst headache of my life.” This is known as a “thunderclap headache” because the pain reaches its maximal intensity almost instantaneously, typically within seconds to one minute. The abrupt onset of this severe pain demands immediate emergency care.
Other symptoms often accompany this severe headache due to the blood irritating the protective layers around the brain and increasing intracranial pressure. Patients frequently experience nausea and vomiting. Neck stiffness, or meningismus, is a common finding that develops as the blood irritates the meninges, the membranes covering the brain and spinal cord.
The sudden rise in pressure can also lead to a rapid decrease in the level of consciousness or even a brief loss of consciousness. Other neurological signs may include confusion, sensitivity to light (photophobia), and sudden weakness or numbness. If any of these symptoms appear suddenly, immediate medical attention is required.
Immediate Medical Response and Stabilization
The initial goal upon arrival at the emergency room is to confirm the diagnosis and prevent a re-bleeding event. Diagnostic imaging begins with a non-contrast computed tomography (CT) scan, which is highly effective at detecting blood, particularly within the first six hours of symptom onset. If the CT scan is inconclusive but suspicion remains high, a lumbar puncture may be performed to check the cerebrospinal fluid for blood.
Once SAH is confirmed, the medical team uses a CT angiography (CTA) or a conventional cerebral angiogram to pinpoint the source of the bleeding, usually a ruptured aneurysm. Securing the ruptured vessel is a time-sensitive procedure, performed quickly to minimize the risk of a second hemorrhage. The two primary methods for securing the aneurysm are neurosurgical clipping and endovascular coiling.
Neurosurgical Clipping
Microsurgical clipping involves an open-brain procedure, or craniotomy, where a neurosurgeon places a tiny metal clip across the neck of the aneurysm. This clip completely isolates the aneurysm from the main blood circulation, preventing any further blood flow into the weakened area.
Endovascular Coiling
Endovascular coiling is a less invasive technique where a catheter is threaded from an artery in the groin up to the aneurysm inside the brain. Through this catheter, small, soft platinum coils are deployed into the aneurysm sac, filling it and causing the blood to clot, effectively sealing off the bulge. The choice between clipping and coiling depends on factors like the patient’s overall condition, the aneurysm’s size, shape, and location.
Navigating Recovery and Potential Complications
Following the acute treatment to secure the aneurysm, patients require intensive care unit monitoring due to the risk of secondary complications. One common post-hemorrhage complication is cerebral vasospasm, which is the narrowing of blood vessels in the brain. Vasospasm typically occurs between day four and day fourteen after the initial bleed and can lead to delayed cerebral ischemia, causing a stroke by limiting blood flow to brain tissue.
Another common complication is hydrocephalus, which is the buildup of cerebrospinal fluid (CSF) within the brain’s cavities. The blood from the SAH can interfere with the normal absorption of CSF, causing pressure to increase inside the skull. Acute hydrocephalus often requires the urgent placement of an external ventricular drain to relieve the pressure, and some patients may need a permanent shunt if the condition persists.
The recovery process is often prolonged, involving a lengthy hospital stay and subsequent rehabilitation. Survivors may experience a range of physical, cognitive, and emotional deficits, necessitating physical, occupational, and speech therapy. Long-term follow-up is important, as the overall mortality remains high, and those who survive may still face long-term neurological disability.