Common Adult Symptom: An Early Warning Sign of Brain Cancer

A first-time seizure in adulthood may serve as a critical early warning sign for both brain cancer and other non-neurological malignancies, according to a study published on April 27, 2026, in JAMA Neurology.

The research, conducted by an international team, suggests that abnormal electrical activity in the brain can be one of the first indicators of the disease, potentially offering a window for earlier diagnosis and improved patient outcomes.

Seizures as a Diagnostic Indicator

The study analyzed nearly 49,900 Danish adults who experienced a seizure at an average age of 50. Researchers found that a first-time seizure in adulthood was linked to a higher risk of developing neurological cancer within one year of the event. The data also indicated a slightly increased long-term risk of cancer following the initial seizure.

Medical experts note that while seizures are common—affecting approximately 1 in 10 U.S. Adults at some point—they should be treated as serious medical events when they occur for the first time in adulthood.

I think the seizure is the smoke, not necessarily the fire. The fire is probably already ongoing within the brain. You have to treat a first-time seizure as a very serious event.

Dr. Randy D’Amico, director of the Brain and Spine Metastasis Program and associate professor of neurosurgery at Northwell Lenox Hill Hospital

The Link Between Brain Activity and Tumors

The connection between seizures and brain tumors is rooted in the anatomy of the brain. Tumors located in the brain cortex or the swelling associated with such growths can disrupt normal electrical activity. Increased pressure within the brain caused by a tumor can provoke seizures.

The study also highlighted that first-time adult seizures can signal cancers that originate outside the brain. The highest risks among non-neurological cancers included bronchial, tracheal, and lung cancers.

Dr. D’Amico explained that this occurs because certain cancers frequently metastasize to the brain. He noted that lung cancer loves to go to the brain, and even a small metastatic tumor accompanied by swelling can trigger a seizure, often before the primary cancer is detected elsewhere in the body.

Context and Alternative Causes

While the study emphasizes the link between seizures and cancer, medical professionals caution that seizures are not exclusively caused by malignancies. A variety of other physiological factors can trigger abnormal electrical activity, including:

• Fluctuations in blood sugar levels
• Issues with sodium control in the body
• Hypoxia (lack of oxygen to the tissues)
• Inflammation
• Changes in breathing

Despite these alternative causes, the urgency of a first-time seizure remains high. Dr. D’Amico advised that the primary importance of the finding is that a first seizure may signal that something serious is happening. Missing this early window of opportunity can lead to a delayed diagnosis.

Other known symptoms of brain cancer include sudden, severe headaches, dizziness, vision changes, and in some cases, the perception of sweet smells.