Most Common Causes of Subarachnoid Hemorrhage: Understanding the Risks and Triggers
Subarachnoid hemorrhage (SAH) is a life-threatening type of stroke characterized by bleeding into the space that surrounds the brain, known as the subarachnoid space. This condition demands immediate medical attention due to its high mortality and morbidity rates. While several factors can contribute to SAH, two primary causes stand out: ruptured cerebral aneurysms and traumatic head injuries.
Ruptured Cerebral Aneurysms: The Leading Cause
A ruptured brain aneurysm accounts for approximately 80% of all spontaneous subarachnoid hemorrhages. An aneurysm is a weak, bulging spot on the wall of a brain artery that develops over time due to structural defects in the vessel wall. As this weakened area expands, it becomes increasingly vulnerable to rupture.
Several triggers can increase the likelihood of an aneurysm bursting. These include sudden spikes in blood pressure, intense emotional stress, physical exertion, and chronic hypertension. Activities such as heavy lifting, straining during bowel movements, or even severe coughing may also provoke a rupture in susceptible individuals.
Who Is at Risk?
Certain risk factors make some people more prone to developing cerebral aneurysms. These include:
- Family history of aneurysms
- Smoking
- High blood pressure (hypertension)
- Age over 40
- Polycystic kidney disease
- Certain connective tissue disorders
While many aneurysms remain asymptomatic until they rupture, early detection through imaging—especially in high-risk patients—can be lifesaving.
Traumatic Brain Injury and Secondary SAH
Trauma-induced subarachnoid hemorrhage, also known as traumatic SAH, occurs following a significant blow to the head. This form of bleeding results from damage to the delicate blood vessels on the surface of the brain or within the meninges—the protective layers surrounding the brain.
Traumatic SAH is commonly seen in accidents such as motor vehicle collisions, falls from height, or sports-related impacts. Unlike spontaneous SAH, which typically presents with a sudden "thunderclap" headache, traumatic cases are usually diagnosed in the context of other brain injuries like contusions or skull fractures.
Symptoms and Diagnosis
The hallmark symptom of spontaneous SAH is a sudden, severe headache described by patients as "the worst headache of my life." Other signs include nausea, vomiting, neck stiffness, sensitivity to light, and altered mental status. In severe cases, loss of consciousness or seizures may occur.
Diagnosis typically begins with a non-contrast CT scan, which can detect blood in the subarachnoid space with high accuracy. If the scan is inconclusive, a lumbar puncture may be performed to analyze cerebrospinal fluid for signs of bleeding.
Prevention and Long-Term Outlook
While not all cases of SAH can be prevented, managing modifiable risk factors plays a crucial role. Controlling blood pressure, quitting smoking, avoiding excessive alcohol consumption, and undergoing screening for aneurysms in high-risk individuals can significantly reduce the chances of a catastrophic event.
Early intervention improves outcomes dramatically. Patients who survive the initial hemorrhage require close monitoring and often need neurosurgical or endovascular treatment to prevent rebleeding, such as aneurysm clipping or coiling.
Understanding the root causes of subarachnoid hemorrhage empowers both patients and healthcare providers to take proactive steps toward prevention, early diagnosis, and effective treatment—ultimately saving lives and improving long-term neurological recovery.