What Is Subarachnoid Hemorrhage? Understanding Causes, Symptoms, and Modern Treatments
Subarachnoid hemorrhage (SAH) refers to the sudden leakage of blood into the subarachnoid space—the area between the brain and the thin tissues that cover it. This condition is not a disease in itself but rather a critical clinical manifestation of underlying neurological disorders. SAH can be broadly categorized into two types: spontaneous and traumatic. While traumatic SAH results from head injuries, spontaneous SAH—often referred to as aSAH—is typically caused by the rupture of intracranial aneurysms, which account for approximately 80% of cases.
Common Causes of Spontaneous Subarachnoid Hemorrhage
Intracranial aneurysms are the leading cause of non-traumatic SAH. These are weak, bulging spots on the walls of brain arteries that can burst under pressure. The second most frequent cause is cerebral or spinal vascular malformations, such as arteriovenous malformations (AVMs), which involve abnormal connections between arteries and veins.
Other less common causes include:
- Severe hypertensive arteriosclerosis
- Moyamoya disease, a rare cerebrovascular disorder
- Brain tumors that undergo hemorrhagic transformation
- Blood disorders like hemophilia or thrombocytopenia
- Meningitis-induced vessel inflammation
- Complications from anticoagulant therapy, such as warfarin or novel oral anticoagulants
Sudden Onset: Recognizing the Symptoms
One of the hallmark features of SAH is its abrupt onset. Patients often describe the headache as the worst they've ever experienced—a "thunderclap headache" that peaks within seconds to minutes. This severe pain is usually accompanied by several other alarming symptoms:
Nausea and vomiting are common due to increased intracranial pressure. A significant number of patients experience altered consciousness, ranging from confusion to loss of consciousness. Additionally, meningeal signs such as neck stiffness, photophobia, and positive Kernig's or Brudzinski's signs are frequently observed during physical examination.
Some individuals may also present with psychiatric disturbances, including agitation or hallucinations, while others suffer seizures at the time of bleeding. Early recognition of these symptoms is crucial, as timely intervention can dramatically improve outcomes.
Diagnostic Imaging: From CT Scans to Angiography
Non-Contrast Head CT: The First-Line Diagnostic Tool
The non-contrast computed tomography (CT) scan of the brain is the gold standard for initial diagnosis of spontaneous SAH. It is fast, widely available, and highly sensitive—detecting blood in the subarachnoid space in over 95% of cases when performed within the first 6 to 12 hours after symptom onset.
If the CT scan is inconclusive but clinical suspicion remains high, a lumbar puncture may be performed to analyze cerebrospinal fluid (CSF) for the presence of xanthochromia (yellowish discoloration due to broken-down red blood cells).
Advanced Imaging for Identifying the Source
Once SAH is confirmed, identifying the underlying cause becomes paramount. CT angiography (CTA) with 64-slice or higher resolution scanners offers excellent sensitivity and specificity in detecting aneurysms and vascular malformations. It is non-invasive and provides detailed 3D reconstructions of cerebral vasculature.
However, catheter-based digital subtraction angiography (DSA) remains the definitive "gold standard" for diagnosing vascular abnormalities. It allows for both precise visualization and potential endovascular treatment in the same session, making it indispensable in comprehensive stroke centers.
Treatment Strategies Based on Clinical Grading
The management of aneurysmal SAH (aSAH) depends heavily on the patient's neurological status at presentation. The Hunt-Hess grading scale is commonly used to assess severity, ranging from Grade I (mild headache, slight neck stiffness) to Grade V (deep coma, moribund appearance).
For patients classified as Hunt-Hess Grade I to III, early intervention is strongly recommended—typically within the first 72 hours—to prevent rebleeding, which carries a high mortality rate. Treatment options include surgical clipping or endovascular coiling.
Endovascular coiling has become the preferred approach for most ruptured aneurysms due to its minimally invasive nature. Unlike traditional craniotomy, this technique involves threading a catheter through the femoral artery up to the brain, where platinum coils are deployed to seal off the aneurysm. Benefits include shorter hospital stays, reduced risk of infection, and faster recovery times.
Patients in Hunt-Hess Grade IV or V, who are critically ill upon arrival, often require stabilization in the intensive care unit (ICU) before any definitive procedure. This includes managing intracranial pressure, optimizing oxygenation, and correcting systemic complications such as hyponatremia or cardiac arrhythmias.
In recent years, advancements such as flow diverters and stent-assisted coiling have further improved outcomes for complex aneurysms, offering hope even for previously untreatable cases.
Early diagnosis, rapid imaging, and prompt treatment are essential in reducing mortality and improving long-term neurological function in patients suffering from subarachnoid hemorrhage. As medical technology continues to evolve, multidisciplinary stroke teams are better equipped than ever to manage this life-threatening condition effectively.