A seizure is a sudden, brief disruption of brain activity caused by abnormal, excessive, or synchronous neuronal firing. This uncontrolled electrical surge in the brain can lead to temporary changes in movement, sensation, behavior, awareness, or consciousness. While blood tests are part of evaluating a person who has experienced a seizure, they do not directly diagnose the seizure event itself. Instead, blood work helps identify underlying conditions that might provoke a seizure or mimic seizure activity.
What Blood Tests Reveal in Seizure Evaluation
Blood tests help identify underlying causes or conditions that might appear as seizures. Imbalances in electrolytes, such as low or high sodium, calcium, or magnesium, can disrupt the brain’s electrical function and lead to seizures. These tests reveal such metabolic disturbances, which are considered acute symptomatic seizures and do not necessarily indicate epilepsy.
Low blood sugar (hypoglycemia) is another metabolic issue blood tests can detect. When blood glucose levels drop significantly, the brain may not receive enough energy, potentially leading to seizures. Blood tests can also assess kidney or liver dysfunction, which might be associated with seizure activity or influence medication choices. They can also help identify signs of infection or inflammation within the body that could be contributing factors.
After a seizure, specific blood markers might show temporary changes. Serum prolactin levels, a hormone, can elevate after generalized tonic-clonic and complex partial seizures, typically peaking within 15 to 20 minutes and returning to baseline within an hour. This elevation can assist in differentiating an epileptic seizure from a psychogenic non-epileptic event, though it is not always conclusive. Creatine kinase (CK), an enzyme, may also increase after generalized convulsive seizures due to intense muscle activity. Elevated CK levels provide additional information, but a normal CK level does not rule out a recent epileptic seizure.
Why Blood Tests Alone Don’t Diagnose Seizures
Seizures are fundamentally electrical events within the brain. Blood tests, however, do not directly measure this complex electrical activity or provide a real-time snapshot of the brain’s electrical state during an event.
While blood tests can uncover conditions that might cause a seizure or show certain biological responses after one occurs, they do not offer a direct “yes” or “no” diagnosis of the seizure itself. A low sodium level in the blood, for instance, might explain why a seizure happened, but the blood test itself did not detect the seizure. Similarly, post-seizure changes in substances like prolactin or creatine kinase are indicators of a recent event rather than a direct diagnostic tool for the seizure’s occurrence. The brain’s electrical disarray is not reflected in typical blood chemistry in a way that allows for direct diagnosis of the seizure event.
The Comprehensive Approach to Seizure Diagnosis
The diagnosis of a seizure or epilepsy requires a comprehensive evaluation that extends beyond blood tests. A detailed clinical history is essential, including information about what happened before, during, and after the suspected event, often relying on witness accounts. This helps understand the episode’s characteristics. A neurological examination also assesses brain function, including mental abilities, movement, senses, and coordination.
A primary diagnostic tool is the electroencephalogram (EEG), which measures the electrical activity of the brain. Electrodes placed on the scalp record brain waves, allowing identification of abnormal patterns indicating seizure activity or a predisposition to seizures. The EEG helps pinpoint where seizures might originate and determine their type. In some cases, continuous video-EEG monitoring might be used to capture events and correlate them with brain activity.
Brain imaging studies, such as magnetic resonance imaging (MRI) or computed tomography (CT) scans, are also often performed. These imaging techniques provide detailed views of the brain’s structure, helping to identify any underlying causes for seizures, such as tumors, bleeding, or structural abnormalities. Blood tests contribute by identifying potential metabolic causes or co-existing conditions, but they are part of a broader diagnostic picture integrating clinical observations, neurological assessments, and specialized brain studies.