A brain tumor is an abnormal mass of cells that grows within the brain or its surrounding structures, where these cells multiply uncontrollably. These growths can be non-cancerous (benign) or cancerous (malignant). A seizure involves a sudden, uncontrolled burst of electrical activity in brain cells, leading to changes in awareness, muscle control, and behavior. While various factors can trigger seizures, brain tumors are a significant cause of new-onset seizures in adults.
How Brain Tumors Lead to Seizures
Brain tumors can induce seizures by disrupting the brain’s normal electrical balance. A tumor can directly irritate surrounding brain cells, causing them to fire signals abnormally and excessively. This irritation leads to disorganized electrical activity that manifests as a seizure.
The physical presence of a tumor can also increase intracranial pressure or cause swelling (edema) in the brain tissue around it. Both increased pressure and edema can compress and displace healthy brain tissue, interfering with its normal function and promoting seizure activity. Additionally, tumors can alter the brain’s chemical environment by increasing excitatory neurotransmitters like glutamate. This imbalance makes brain cells more excitable and prone to seizures.
The specific location of the tumor significantly influences its potential to cause seizures. Tumors in or near the cerebral cortex, especially in the frontal, temporal, or parietal lobes, are more likely to trigger seizures. These cortical regions are highly involved in electrical signaling, making them particularly sensitive to tumor-induced disruptions.
Brain Tumor Types Commonly Associated with Seizures
Many types of brain tumors, both primary and metastatic, can be associated with seizures. The likelihood of seizures often depends on the tumor’s type, location, and growth rate.
Gliomas, particularly low-grade types such as astrocytomas and oligodendrogliomas, are frequently linked to seizures, affecting 60% to 85% of individuals with diffuse low-grade gliomas. These slow-growing tumors often infiltrate brain tissue, disrupting neuronal networks and altering the balance of chemicals that regulate electrical activity, leading to chronic seizure activity.
Meningiomas, which arise from the protective membranes surrounding the brain and spinal cord, are also a common cause of seizures. Although typically benign, meningiomas can cause seizures in about 13% to 60% of cases, often due to their mass effect, associated brain swelling, or invasion of brain tissue.
Gangliogliomas are another primary tumor type strongly associated with seizures. These rare, slow-growing tumors, containing both nerve and supporting cells, are highly epileptogenic and often resistant to medication.
Metastatic brain tumors, which are cancers that have spread to the brain from other organs (e.g., lung, breast, melanoma, or colon), can also cause seizures. Seizures occur in 12% to 35% of patients with brain metastases. The risk is higher if lesions are in the cerebral cortex, particularly the frontal lobe. Melanoma metastases, for instance, show a higher incidence of seizures.
Managing Seizures Caused by Brain Tumors
Managing seizures in individuals with brain tumors involves a two-pronged approach: controlling seizures directly and treating the underlying tumor. Antiepileptic drugs (AEDs) are the primary treatment for controlling seizures. These medications help to regulate abnormal electrical activity in the brain, aiming to reduce the frequency and severity of seizures. Common AEDs used include levetiracetam, lamotrigine, and valproic acid.
Treating the brain tumor itself can significantly improve seizure control. Surgical removal of the tumor is often the most effective way to reduce or eliminate seizures, particularly if it can be safely resected. In some cases, complete removal can lead to seizure freedom.
Other tumor treatments, such as radiation therapy and chemotherapy, can also contribute to seizure reduction by shrinking the tumor or slowing its growth. Radiation therapy, for instance, has been shown to improve seizure control in patients with low-grade gliomas. Ongoing medical monitoring and follow-up are important to adjust medication as needed and assess the effectiveness of tumor treatments.