Listed below are some of the common tests that Children’s epilepsy team performs to learn more about the cause of seizures.
CT Scans (Computerized Tomography Scans)
- This test looks at activity in the brain. It is the most useful study for diagnosing epilepsy. Small pads are applied to the scalp with a sticky paste. These pads pick up the electrical impulses made by brain waves. There are no side effects associated with EEGs, and the test is painless. The test lasts about an hour and, for most of the time, you will be asked to lie calmly with your eyes closed. For some tests you will be asked to breathe deeply, look at flashing lights, or sleep. Try to keep as still and relaxed as possible, as the equipment is very sensitive to movement.
MRI (Magnetic Resonance Imaging)
- Used to show details of the brain, this is a series of x-rays. You will be asked to lie down with just your head inside the scanner. You will need to keep very still. Sometimes a strap is placed across the forehead to help prevent movement. The test takes about 5 to 20 minutes. Sometimes, a CT scan “with contrast” is ordered. This involves injection of a small amount of contrast material into your vein, followed by more pictures.
- This test is similar to a CT scan, but uses radio waves instead of x-rays, so you will not be exposed to any radiation. You will lie down on a table which slides into the scanner. You will hear a knocking sound during the test, which usually takes 30 to 90 minutes. Because you must lie still during the entire test, many children require sedation.
- This is a test to obtain spinal fluid. The fluid is checked for abnormalities, which can be linked to seizures. The lumbar puncture only causes minor discomfort because local anesthetic is used to numb the skin. You will be asked to sit up, curl up or lie down, while a small sterile needle is inserted into the lower back region. A few drops of fluid from the spinal canal are collected and sent to the lab for analysis.
Epilepsy Diagnostic Tests for Pre-Surgical Evaluation
A pre-surgical evaluation is generally composed of a series of tests that will be tailored to your child’s specific needs. These are some of the tests that might be used to provide more information about your child’s seizures:
Video Electroencephalography (EEG): This requires an admission to the hospital. Typically, the goal is to capture between 3-5 typical seizures. This usually requires that the patient’s seizure medications are lowered and then restarted again prior to admission. Children do require an IV- in case rescue medications, such as ativan are required to stop their seizures. The Video EEG is used to figure out electrically where the seizures are coming from. Typically the study takes between 5-7 days. For about 10% of children the video EEG can take more than one week to gather the needed data.
Magnetic Resonance Imaging (MRI) Scan: A high resolution image of the brain is performed to look at the structure of the brain and help determine if there is a structural reason for seizures to be happening, such as a developmental abnormality or tumor. For many children sedation is required to obtain a high-quality MRI without movement.
Positron Emission Tomography (Pet) Scan: This study is sometimes performed under sedation, where tagged glucose is given by IV, between seizures to look for areas of the brain that are not metabolically symmetric. The region surrounding the seizure onset zone is identified because it uses less sugar than other parts of the brain.
Neuropsych Testing: A battery of tests performed by a specially trained psychologist to determine the strengths and relative weaknesses of the different parts of the brain. Examining patterns in cognitive functioning provides a better idea of where the seizures are coming from, and what would happen if a particular region of the brain was removed.
Magnetoencephalography (MEG): Measures the magnetic fields produced by the brain. Magnetic signals, unlike electrical signals picked up on EEG, are not distorted by the skull and spinal fluid and provide complementary data to the EEG. This study is an outpatient procedure done between seizures.
Single Photon Emission Computed Tomography (SPECT): An isotope is given via IV between seizures and during a seizure to look for an area of increased blood flow in the brain that is the seizure focus. The picture taken between the seizures and the one taken during a seizure are subtracted from each other and then overlaid on the MRI to help localize the seizure onset zone. This study requires a hospitalization and video EEG to perform the injection at the beginning of a seizure, and a second outpatient study to obtain the data between seizures. Some children will require sedation for the imaging portion of the study.
Functional MRI: Looks at blood flow in the brain during specific tasks to help figure out where language and movement is located.
Wada Test: Intra-arterial injection of anesthetic to the brain to determine where language and memory are located.