What is the primary diagnostic tool for epilepsy?

The primary diagnostic tool for epilepsy is the electroencephalogram (EEG). This is because the EEG specifically measures the electrical activity of the brain, allowing clinicians to identify abnormal brain waves that are characteristic of epilepsy. During an EEG, electrodes are placed on the scalp to capture and record the electrical impulses in the brain, which helps in detecting seizure activity, even when the patient is not actively seizing during the test.

Other imaging modalities like MRI and CT scans provide structural information and can help rule out other conditions that might cause seizures, such as tumors or structural anomalies in the brain. However, they do not measure the electrical activity that is critical for diagnosing epilepsy. Similarly, a PET scan allows for metabolic assessment but does not provide real-time monitoring of brain electrical activity. Thus, while these tools can be useful in a comprehensive evaluation, the EEG remains the most essential and primary method for diagnosing epilepsy specifically.