Medical histories are often supplemented with physical examinations with one or more diagnostic tests. Some of the more common tests are described below.
The electroencephalogram (EEG) is a harmless, noninvasive, diagnostic test that detects faint electrical impulses from the brain and records them on graph paper or nowadays on a computer. It is the primary diagnostic tool for epilepsy. The pattern of brain waves recorded by the EEG can aid doctors in confirming the diagnosis of epilepsy and distinguishing among seizure types.
Computerized Axial Tomography (CT or CAT) scan is a procedure that produces a cross-section image of the inside of the head or body. For cross-section images of the brain, a series of low-radiation X-rays are taken by a camera rotated around the head at different levels. CT scans are more detailed than conventional X-rays. The scan can reveal abnormalities in the skull or brain that are related to seizures and help to localize where seizures may originate. It is the best test to detect calcium deposits (calcification) in the brain.
MRA and MRV Scan
Magnetic Resonance Angiography (MRA) is a technique designed to view the major arteries of the brain. Magnetic Resonance Venography (MRV) is designed to view the major veins of the brain.
Magnetic Resonance Imaging (MRI) is a relatively new, non-invasive procedure that uses a large magnet, radio waves, and a computer to produce two or three-dimensional images of the structural characteristics of the tissue. MRI does not use X-rays; the magnetic fields that are used are not known to be harmful. The images produced by the MRI are very precise and typically reveal details that CT scans cannot.
Positron Emission Tomography (PET) measures emissions from radioactively labeled chemicals that have been injected into the bloodstream and uses the data to produce two or three-dimensional images of the distribution of the chemicals throughout the brain. The positron-emitting radioisotopes used are produced by a cyclotron and chemicals are labeled with these radioactive atoms. The labeled compound called a radiotracer, is injected into the bloodstream and eventually makes its way to the brain. Sensors in the PET scanner detect radioactivity as the compound accumulates in different regions of the brain. A computer uses the data gathered by the sensors to create multicolored two or three-dimensional images that show where the compound acts in the brain.
The greatest benefit of PET scanning is that different compounds can show blood flow and oxygen and glucose metabolism in the tissues of the working brain. These measurements reflect the amount of brain activity in the various regions of the brain and allow us to learn more about how the brain works. More and more PET tracers are being developed to probe different brain functions.
SPECT is similar to PET. The Single Photon Emission Computed Tomography (SPECT) scan is a test that looks mainly at blood flow. SPECT uses gamma-ray emitting radioisotopes and a gamma camera to record data that a computer uses to construct two- or three-dimensional images of active brain regions. SPECT tracers are considered to be more limited than PET scanners in the kinds of brain activity they have the ability to monitor. SPECT tracers are longer lasting than those of PET, which allows for different, longer-lasting brain functions to be examined, but this also requires more time for the SPECT scan to be completed. The resolution of a SPECT is poor (about 1 cm) compared to that of PET.
Magnetoencephalography (MEG) is similar to EEG, but magnetic fields are measured instead of electric fields. The MEG signal is then superimposed onto the patient’s MRI scan for better localization.
Functional MRI (fMRI) relies on the paramagnetic properties of oxygenated and deoxygenated hemoglobin to see images of changing blood flow in the brain associated with neural activity. This allows images to be generated that reflect which structures are activated (and how) during the performance of different tasks. In most fMRI studies, subjects are presented with different visual images, sounds, and touch stimuli, and are asked to make different actions such as pressing a button or moving a joystick. They have to be cooperative in the task. Consequently, fMRI can be used to reveal brain structures and processes associated with perception, thought, and action. The resolution of fMRI is about two or three millimeters at present, limited by the spatial spread of the hemodynamic response to neural activity. It has largely replaced one particular type of PET scanning, that is used for the study of brain activation patterns. PET, however, retains the significant advantage of being able to identify brain metabolism and specific brain receptors associated with particular neurotransmitters through its ability to image radiolabelled receptor ligands.
An MRI of the brain with and without gadolinium enhancement is recommended for visualization of the leptomeningeal angioma. Early in infancy, the abnormal blood vessels on the surface of the brain may not be seen even by MRI. If the initial MRI is normal, it can be repeated at 2-3 years of life to exclude the presence of a leptomeningeal angioma.
Brain calcification is most easily seen with a head CT but this is not usually an early finding. Other typical findings on brain imaging include brain atrophy (decreased brain mass) and enlarged deep draining veins on the affected side. Angiography is NOT routinely performed in the evaluation of children with SWS but may be required in atypical cases to evaluate for other associated vascular malformations. PET and SPECT imaging is not routinely indicated except when surgery for seizures is being considered. If seizures occur, then an electroencephalogram (EEG) is obtained to evaluate brain function and seizure foci.
Medications for Epilepsy
Drug therapy is the most common treatment for epilepsy. Common terms, meaning the same thing, include anticonvulsants, anti-epileptic drugs, or anti-seizure drugs.
Anticonvulsant medications come in a wide variety of preparations, including liquids, tablets, controlled-release tablets, chewable tablets, sprinkles, etc. They also come in different strengths and formulations. Keep medications in a cool, dry place that is out of reach of young children. The humidity of a bathroom or kitchen may damage the medication. Liquid medications may require refrigeration. Anticonvulsant medications should be taken at the same time(s) each day. If you or your child misses a dose, administer it as soon as possible. If more than one dose is missed, follow your regular schedule and take the missed dosage at bedtime. If an entire day is missed, consult with your physician. Never give more than the prescribed amount of medication, regardless of seizures. Do not discontinue or reduce medication without consulting with your physician. Drug level monitoring is essential for some medications. Some physicians will want monitoring done every six months. Others may prefer shorter or longer intervals.
Anticonvulsants may interact with other medications. Be sure your physician is aware of all other medications that you or your child is taking. Non-prescription medications, such as cough or cold remedies may interact with anticonvulsants. Anticonvulsants may also interfere with the effectiveness of oral contraceptives.
Be sure to alert a physician (including your dentist) of your medications before undertaking any medical procedure such as surgery. A medical identification bracelet should be worn.
Do not wait until the anticonvulsant medication is in short supply before ordering more. Generally, it is best to keep several weeks supply on hand. When traveling across international borders, obtain a note from your physician regarding the medical condition and the need for medication.
As anticonvulsant medications may result in drowsiness or lack of concentration, schools should be advised of children on the medications.
The ketogenic diet is a medical diet that is used to treat individuals with seizures that have not been controlled by conventional medications. The diet must be given under medical supervision. The diet is a high-fat, low-carbohydrate diet that drives the body to produce ketones. The body prefers to use glucose (carbohydrates) as its source of fuel, which is stored in the body in the form of glycogen. When there is not enough glucose or when the glycogen stores are depleted, the body will use fat as its major energy source. The process of burning fat instead of glucose will produce ketones. Ketones have been shown to reduce seizures in some individuals. The ketogenic diet is not widely used as a means of controlling seizures in Sturge-Weber Syndrome.
Surgery is considered when seizures are frequent and when drugs have been ineffective and under some circumstances when there is increasing developmental delay. Normally physicians will have tried different drugs, either alone or in combinations before considering surgery as an option. Seizure surgery is never undertaken lightly. Surgery should be considered when an individual has uncontrolled partial seizures, particularly when dangerous or serious drug side effects are present.
Surgery for uncontrolled seizures includes removal of a focus; callosotomy; and hemispherectomy. Removal of a focus is done by removing the portion of the brain that is causing the seizure. A callosotomy is done by disconnecting the two halves of the brain. This procedure helps to prevent seizures that start in one hemisphere of the brain from traveling to the other side. While callosotomy does not typically eliminate seizures, they help reduce their severity. A hemispherectomy is done by removing all or most of a diseased hemisphere (one side) of the brain. A hemispherectomy is effective in reducing or eliminating seizures.
Therapeutic vagus nerve stimulation (VNS) is chronic, intermittent electrical stimulation of the mid-cervical segment of the left vagus nerve. The stimulation occurs automatically at set intervals, during waking and sleep.
Stimuli are fast-frequency, brief pulses of alternating polarity, which are delivered in pulse trains, with pauses between trains. The electrical pulses are generated by a pacemaker-like device that is implanted below the clavicle and is delivered by a read wire that is coiled around the vagus nerve. Stimulation parameters are programmed within a range of values that are known not to cause nerve injury based on animal experiments. Programming is performed by a medical professional using a laptop computer and magnetic transducer (wand) placed over the implanted generator. In addition to receiving the trains of stimuli that are programmed to occur at regular intervals, the patient can trigger a single train of stimuli by placing a hand-held magnet over the generator and then removing the magnet. The patient can stop all stimulation for as long as he or she wishes by holding or tapping the magnet over the generator.