A brain tumor is an abnormal growth of cells within the brain or central nervous system. A stroke occurs when blood flow to the brain is interrupted, causing cell death. This disruption can be a blockage (ischemic stroke) or a burst blood vessel (hemorrhagic stroke). Although uncommon, a brain tumor can directly or indirectly lead to a stroke. Recognizing this connection is important, as the tumor’s presence changes how the stroke is diagnosed and managed.
Mechanisms Leading to Blockage
A brain tumor can cause an ischemic stroke by physically obstructing blood vessels or by creating a systemic environment that promotes clotting. The tumor mass can grow large enough to press against an adjacent artery, mechanically narrowing the vessel. This physical compression restricts blood flow and can lead to a complete blockage, causing brain cells to lose oxygen and nutrients.
A more complex mechanism involves the tumor’s influence on the body’s clotting system, creating hypercoagulability. Malignant tumor cells, especially in aggressive cancers like glioblastoma, release procoagulant factors (such as tissue factor) into the bloodstream. These factors activate the coagulation cascade, leading to the formation of small clots (thrombi) within blood vessels, a phenomenon known as Trousseau syndrome.
These small clots can break free, travel through the bloodstream, and lodge in a cerebral artery, causing an embolic stroke. This type of stroke is driven directly by the underlying cancer, not by traditional risk factors. Imaging often shows multiple scattered lesions affecting different vascular territories simultaneously, suggesting a cancer-related cause. Tumor treatments like surgery or radiation therapy can also increase ischemic stroke risk by injuring blood vessel walls.
Mechanisms Leading to Bleeding
A brain tumor can also lead to a hemorrhagic stroke. This occurs when blood vessels within or near the tumor rupture, often due to structural fragility. Aggressive tumors can directly invade and weaken the walls of existing blood vessels. This infiltration compromises the vessel wall integrity, making it susceptible to rupture and bleeding.
Many tumors stimulate the growth of their own blood supply through angiogenesis. These newly formed tumor vessels are frequently abnormal, structurally unsound, and lack the proper tissue layers. This fragility makes them prone to spontaneous rupture. Intratumoral hemorrhage (bleeding within the tumor mass) is common in certain types, including glioblastoma and metastatic tumors.
Tumors like glioblastoma and oligodendrogliomas are known for their propensity to hemorrhage. When bleeding occurs, the accumulating blood forms a hematoma that rapidly increases pressure within the skull. This can cause sudden neurological decline similar to a severe stroke. The hemorrhagic stroke results directly from the tumor’s pathology, either through aggressive invasion of normal vessels or the rupture of its own dysfunctional vasculature.
Identifying the Tumor-Related Stroke
Diagnosing a stroke in a patient with a known or suspected brain tumor requires a specialized diagnostic approach. Advanced neuroimaging, typically a computed tomography (CT) scan or magnetic resonance imaging (MRI), is used first to differentiate between an ischemic blockage and a hemorrhagic bleed. MRI, especially with diffusion-weighted imaging (DWI), is sensitive for detecting acute ischemic stroke lesions while also visualizing the tumor mass.
A pattern of multiple small infarcts scattered across different vascular territories, sometimes called the “three-territory sign,” strongly indicates cancer-associated hypercoagulability. This suggests the stroke is not due to common causes. Further imaging, such as MR angiography, assesses blood vessels for signs of compression or direct invasion by the tumor.
Laboratory tests provide supportive evidence, particularly for ischemic strokes caused by Trousseau syndrome. Elevated levels of D-dimer can signal systemic hypercoagulability linked to the malignancy. Clinicians must rule out traditional stroke causes, such as atrial fibrillation or severe atherosclerosis, before confirming the tumor as the underlying source.
Treatment Strategies and Outcomes
Treatment for a tumor-related stroke is complex, requiring management of the acute stroke while simultaneously addressing the underlying cancer. Standard ischemic stroke treatment involves blood thinners or clot-busting drugs. However, this carries significant risk in tumor patients due to the high likelihood of bleeding, which can turn an ischemic stroke into a fatal hemorrhagic one.
For a hemorrhagic stroke caused by the tumor, management focuses on controlling the bleeding and reducing intracranial pressure. This may involve surgery to evacuate the hematoma (blood clot) and relieve pressure on the brain. In both scenarios, the definitive long-term treatment requires addressing the tumor itself through surgical removal, radiation therapy, or chemotherapy. This eliminates the source of vessel compression or pro-clotting factors.
A stroke occurring with a malignant brain tumor is associated with a poorer prognosis and a higher risk of recurrence compared to strokes from non-cancer causes. The combined effect of the neurological injury and the severity of the underlying cancer contributes to this challenging outcome. This dual diagnosis necessitates a coordinated approach involving oncologists, neurologists, and neurosurgeons.