Common Causes and Risk Factors of Subarachnoid Hemorrhage

Understanding Subarachnoid Hemorrhage: Primary Causes

Subarachnoid hemorrhage (SAH) is a serious medical condition characterized by bleeding into the space between the brain and the surrounding membrane. The most common causes are intracranial aneurysms and arteriovenous malformations (AVMs), which together account for approximately 60% of all cases. These vascular abnormalities can weaken blood vessel walls, making them prone to rupture under pressure, leading to sudden and potentially life-threatening bleeding in the subarachnoid space.

Aneurysms and AVMs: Leading Contributors

Intracranial aneurysms, which are balloon-like bulges in the arterial walls of the brain, are responsible for the majority of spontaneous SAH cases. When these weakened areas burst—often due to a spike in blood pressure—the result is rapid bleeding into the subarachnoid cavity. Similarly, arteriovenous malformations involve abnormal tangles of blood vessels that bypass normal tissue and create high-pressure zones, increasing the risk of rupture. Both conditions require prompt diagnosis through imaging techniques such as cerebral angiography, CT scans, or MRI.

Other Medical Conditions That May Trigger SAH

While aneurysms and AVMs dominate the landscape of SAH etiology, other underlying health issues can also contribute. Patients undergoing treatment with certain antibiotics, those diagnosed with brain tumors, individuals suffering from venous sinus thrombosis, or people with coagulation disorders and blood diseases may experience non-aneurysmal forms of subarachnoid hemorrhage. Although less frequent, these causes should not be overlooked during clinical evaluation.

The Role of Trauma in Subarachnoid Bleeding

Traumatic subarachnoid hemorrhage occurs as a direct consequence of head injury. Common scenarios include car accidents, falls from height, physical assaults, or sports-related impacts. In these instances, the force of trauma damages blood vessels in the brain, resulting in bleeding within the subarachnoid space. Diagnosis typically relies on a clear history of head trauma combined with neuroimaging findings—especially non-contrast CT scans—that reveal blood distribution patterns consistent with SAH.

Risk Factors and Triggers of Spontaneous SAH

Several modifiable and non-modifiable factors increase the likelihood of spontaneous subarachnoid hemorrhage. Chronic hypertension and atherosclerosis significantly degrade vascular integrity over time, reducing the elasticity of cerebral arteries. This sets the stage for aneurysm formation and eventual rupture. Sudden spikes in blood pressure—triggered by activities like straining during bowel movements, intense emotional stress, or physical exertion—can act as the final catalyst, especially in older adults.

Prevention and Early Detection Strategies

Given the severity of SAH outcomes—including stroke, coma, or death—early detection and management of risk factors are crucial. Regular monitoring of blood pressure, adopting heart-healthy lifestyle choices, and screening high-risk individuals (such as those with a family history of aneurysms) can help prevent catastrophic events. For patients presenting with sudden-onset "thunderclap" headaches—a hallmark symptom of SAH—immediate medical assessment is essential to confirm diagnosis and initiate timely intervention.

Conclusion: A Call for Awareness and Proactive Care

Subarachnoid hemorrhage remains a critical neurological emergency with diverse underlying causes. While aneurysms and vascular malformations are the primary culprits, trauma and systemic illnesses also play significant roles. Recognizing both the causes and triggers enables better prevention, faster diagnosis, and improved patient outcomes. Public awareness, routine check-ups, and access to advanced neuroimaging are vital components in reducing the burden of this life-threatening condition.