Epilepsy is mainly an EEG test. When diagnosing epilepsy, doctors need to determine the type of epilepsy and the severity of the patient’s epilepsy based on the seizure symptoms described by the family and friends of the epilepsy patient, as well as the EEG and some other test results to find out the cause and the location of the lesion. The main diagnostic tests for epilepsy are.
1.Electroencephalography:
2. imaging tests;
3, laboratory tests;
4. Physical examination of the epileptic patient
The doctor needs to determine which tests are needed in the diagnosis of epilepsy according to the specific situation of the patient.
Electroencephalography
In the process of diagnosis and treatment of epilepsy, doctors will ask epileptic patients to undergo EEG examination to determine the type of epilepsy, seizure symptoms, etc. EEG examination of epilepsy has become an important weapon in the diagnosis of epilepsy.
EEG is a specialized technique to study the bioelectric activity of the brain, i.e., the bioelectric activity already present in the brain cells is triggered by electrodes on the scalp and recorded on paper after amplification to form a curve of a certain figure. It reflects the functional state of the brain at any given moment. Under normal conditions, these bioelectrical activities are very small and difficult to record with ordinary instruments. The waveforms recorded by current EEG machines are the result of amplification by a factor of 1 million, and EEG can be expressed in terms of waveform, amplitude, frequency and phase. The EEG changes when there are pathological or functional changes in the brain. This is because abnormal discharges must be present during seizures and can be recorded during interictal periods.
The EEG is the most effective diagnostic aid for epilepsy, and when combined with multiple stimulation methods (hyperventilation, flash stimulation, drugs, sleep, etc.) and special electrodes, abnormal epileptiform waves can be detected in at least 80% of patients. For some epileptic foci without morphological changes, CT, MRI may not show any abnormalities and sometimes the EEG is mainly relied upon to localize them.
EEG has a pivotal value for epilepsy diagnosis, typing, and outcome evaluation. It should be clear that EEG is a non-invasive and painless test. In order to catch the abnormal discharge of brain cells and to clarify the diagnosis, sometimes the test can be repeated several times, so patients and their families do not need to have any concerns. However, once the diagnosis is confirmed, during the treatment period, if there is no special need, it is sufficient to recheck the EEG once in three months to six months. Generally, when the patient’s condition improves, the EEG will also improve. Of course, there are some exceptions, such as the seizures are completely controlled, but the EEG still does not return to normal.
The day before the EEG test, you should wash your hair and do not apply head oil or other fatty cosmetics after washing. Eat normally before the test, do not starve yourself to avoid hypoglycemia affecting the EEG. Patients under treatment do not need to stop their medication; sudden stopping of medication can cause frequent seizures, and that is dangerous. If you have a seizure, you should generally check it about a week after the seizure. It is not very meaningful to check the EEG immediately after the seizure.
Sleep EEG is of great value for epilepsy diagnosis. A sleep EEG is necessary for a formal epilepsy EEG because many patients with epilepsy only have EEG abnormalities during sleep or mainly during sleep. A sleep EEG usually requires the patient to go to bed as late as possible the day before the test, such as after 11:00 p.m. or even 12:00 p.m., and to wake up at 4:00 to 5:00 a.m. on the morning of the test. It is also important not to take a nap at noon, so that the sleep EEG can be easily performed in the afternoon in a well-soundproofed examination room with the necessary medications.
Video EEG is a very advanced EEG technique mainly used for epilepsy diagnosis, in short, it is a video-EEG, which means that the person being examined is videoed at the same time as the EEG is performed. Since the video and EEG are performed simultaneously, the relationship between seizures and EEG changes can be compared and analyzed simultaneously when the patient has a clinical seizure, which is the greatest advantage of video-EEG. This is the biggest advantage of video-EEG. Doctors often use this test to determine whether certain seizures are seizures or not and to identify the type of seizure. Although the cost of the test is higher than that of a normal EEG, it uses an internationally accepted method of examining patients with epilepsy and is equipped with an advanced camera system that synchronizes the EEG signal with the patient’s image signal. Therefore, its diagnostic value for epilepsy is incomparable to that of ordinary EEG. With the development of computer technology, video EEG monitoring can be performed for 24 hours, 48 hours, 72 hours, or even longer, depending on the patient’s condition. Although video EEG monitoring takes longer and is more expensive than general EEG, its value is also significantly greater than that of general EEG. Whenever possible, video-EEG monitoring should be used in patients with epilepsy to provide more valuable diagnostic information.
Video-EEG examinations need to be performed in a hospital setting and monitored by a health care provider. The duration of the test is determined by the patient’s specific situation, and may be continuous for several days. For prolonged monitoring, special fixation methods are required to securely hold the electrodes in place, usually using fire wool adhesive. Depending on the patient, special electrodes, such as pterygoid electrodes, may need to be placed. Sometimes it may be necessary to reduce the dose of the antiepileptic medication the patient is taking, and sometimes to stop the medication altogether, in order to better capture the seizures and reduce the cost of monitoring the patient. In the case of patients with epilepsy, reducing (stopping) the medication may worsen the seizures. However, it has been proven that tapering (discontinuing) medications in a standardized manner is safe and the chances of serious conditions are rare. Even serious cases such as persistent status are managed and controlled in a timely manner due to close monitoring by medical staff.
During EEG, the metal object that is stuck to the scalp of the person being examined is the electrode. Special electrodes are for ordinary electrodes, and we often refer to the electrodes stuck on the scalp as ordinary electrodes. In general, a certain number of ordinary electrodes can be sufficient for routine EEG. In a few cases, especially when the results of conventional EEG are still uncertain, special electrodes need to be placed to further clarify the diagnosis. The most commonly used special electrode in clinical practice is the pterygoid electrode, which can better capture the firing in deeper parts of the brain (medial temporal lobe). The nasopharyngeal electrode, which used to be used in the past, is also a special electrode, although it is rarely used nowadays.
Regarding the placement of pterygoid electrodes, either acupuncture milli-needles or soft wire pterygoid electrodes can be used; the former is mostly used during short EEG examinations, while the latter is commonly used for prolonged EEG monitoring. When placing the pterygoid electrodes, the doctor will find a suitable entry point on the face in front of both ears and slowly insert the needles after local anesthesia, and the patient will experience a very brief period of mild discomfort. Do not mistake that the pterygoid electrodes are inserted into the skull, not to mention the risk of brain damage. Practice has proven that the standardized placement of pterygoid electrodes under the premise of mastering the indications is safe and effective.
The correct understanding and judgment of EEG results is a very professional thing and requires strong professional knowledge. Generally speaking, the test results can be broadly classified into normal EEG and abnormal EEG. There is a difference in the degree of abnormal EEG. Abnormal EEG can appear in patients as well as in other brain disorders (such as stroke, traumatic brain injury, brain tumor), and even in a few cases in normal people without any uncomfortable symptoms. Therefore, it cannot be assumed that an abnormal EEG is epilepsy.
In patients with epilepsy, it is often difficult to perform an EEG right at the time of the seizure. Fortunately, most patients with epilepsy who have a standard EEG when they are not having seizures often have abnormal discharge activity, such as “epileptiform discharges,” which strongly suggest a tendency to have a seizure on the spot, and the physician can make a diagnosis of epilepsy when combined with the patient’s clinical presentation. In a few cases, the EEG with “epileptiform discharges” may be considered epilepsy, but this must be combined with the specific clinical presentation.
On the other hand, some patients with epilepsy may have normal EEG results due to infrequent abnormal brain discharges or specific discharge sites. In this case, doctors often recommend that the EEG be rechecked later during follow-up, or even that multiple EEG examinations be performed before the diagnosis is confirmed. For some patients with an unclear diagnosis, if the patient’s condition allows, the physician will sometimes arrange for a prolonged video-EEG, which can last for several days until the seizure is captured, at which point the results are a more reliable seizure EEG.
It is true that there are clinical cases of seizures with normal EEGs, where the patient has had several definite episodes (seizures), but the EEG results are normal. In this case, the diagnosis of epilepsy cannot be ruled out. Due to the limitations of the scalp EEG examination technique itself, the differences in the location, intensity, and frequency of wire discharges, and the degree of standardization of the examination operation, some patients with epilepsy can have a normal EEG, especially when only one examination has been performed. When this occurs, the chances of detecting abnormal discharges can be improved by supplementing the EEG with a sleep EEG, adding certain special electrodes, and increasing the number of tests.
It is important to note that doctors do not rely on EEG results alone to make a diagnosis of epilepsy. Clearly abnormal EEG results can support the diagnosis, but normal EEG results cannot rule out a diagnosis of epilepsy, but normal EEG results cannot rule out a diagnosis of epilepsy. In addition to the EEG, other conditions should be considered in combination. One important point is the description of clinical seizure phenomena. In other words, the offending condition experienced by the patient and witnessed by the bystander collection is the more important evidence! This is why it is repeatedly emphasized that it is extremely important to provide a reliable and detailed clinical history, especially of the seizures.
Imaging
Some epilepsy is caused by structural brain abnormalities, such as brain tumors, hydrocephalus, vascular malformations, etc. These abnormalities are usually confirmed with neuroimaging. In simple terms, neuroimaging is the use of special imaging techniques to “take pictures” of the nervous system (including the brain) to see if there are structural or functional abnormalities. It can be broadly divided into structural imaging, which includes the familiar brain TC and MRI, and functional imaging, which includes SPECT and PET.
Not all are necessarily needed. For most newly diagnosed patients, imaging is necessary because it may reveal the “root cause” of the seizure, such as a brain tumor or vascular malformation. If these causes are found, surgical treatment may be needed rather than just medication. Some patients with chronic epilepsy who are not responding well to medication may also require detailed imaging to find the location of the lesion before surgery is considered. Patients with previous lesions in the brain, especially those that may have changed, also need regular review of the images during follow-up to observe changes.
Some patients with specific types of epilepsy may not require imaging, for example, benign epilepsy in children and myoclonic epilepsy in adolescents, because these types of epilepsy are not caused by abnormal structures in the brain.
This is generally indicated in patients with secondary epilepsy, i.e., epilepsy that has a clear etiology, such as trauma or infection. Such cases can often be identified on imaging as the responsible lesion and guide treatment.
Both are the most common structural imaging examinations, and both are imaging techniques used to look at brain structures. In China, brain CT is more common and generally available at county hospitals. It is a convenient and less expensive test that can be used to get a cursory look at the structures in the brain and is not as clear as a brain MRI. Brain MRI usually provides more information than brain CT and is a clearer imaging test. Some abnormalities are not visible on CT, but can be clearly shown on MRI, for example, focal cortical dysplasia. The high cost and low availability of the test are the disadvantages of MRI.
As with ordinary X-rays, patients do receive radiation exposure during brain CT examinations, but the amount of radiation is low and generally safe for the patient. Clinically, some patients have not been found to have any abnormalities even after repeated CT examinations.
MRI examinations are not exposed to X-rays, so there is no need to be concerned about harmful rays.
CT and MRI examinations: CT has become an important tool in the diagnosis of epilepsy due to epilepsy. The positive rate of CT examination of brain lesions in non-selective epileptic patients is generally above 50% according to the bulk case data report. MRI is more valuable than CT for the diagnosis of epilepsy cause. First, it is clearer than CT images, with high resolution and wide scanning range; second, MRI provides energy status and blood flow in the brain that CT cannot; third, the scan does not use harmful substances such as X-rays and can be used repeatedly in patients of all ages.
Other tests such as MRA and DSA also have clinical significance in some cases.
Laboratory tests
In patients with clinical suspicion of various intracranial infections or congenital metabolic diseases causing epilepsy, biochemical tests should be performed to clarify the cause of epilepsy, and lumbar puncture for cerebrospinal fluid examination should be performed if necessary.
Blood biochemical examination: according to the age and condition, different items are selected for differential diagnosis. Generally, there are blood calcium, magnesium, sodium, blood glucose, blood bilirubin, blood gas analysis, blood lactate, blood ammonia, liver function, etc.
Abnormal changes in arterial partial pressure of oxygen, arterial partial pressure of carbon dioxide, blood glucose, nonlipidated fatty acids, ATP, chromium, phosphorus, glutamate, glutamine, lactate, and GABA are often present during seizures. For example, increased oxygen demand, accelerated glucose metabolism, decreased brain phosphocreatine concentration and increased creatine concentration during seizures; decreased brain 5-hydroxytryptamine, decreased dopamine content and increased cholinesterase activity during seizures.
Cerebrospinal fluid examination: mainly to exclude intracranial infection, intracranial hemorrhage and other diseases. In addition to routine, biochemical, bacterial culture smear, etiological examination of mycoplasma, toxoplasma, cytomegalovirus, herpes simplex virus, cysticercosis, etc. and cytological examination of abnormal white blood cells should be performed.
Blood concentration test: Generally refers to the concentration of the drug in the whole blood. Generally, the intensity of drug action is proportional to the concentration of the drug in the plasma. The test can clarify the metabolism of the drug in the patient’s body, which can be used as a basis for adjusting the drug and its dose and judging the patient’s choice of medication.
Blood tests: The entire results of blood tests, including the number of red blood cells, the number of white blood cells and the number of platelets. The test can clarify whether antiepileptic drugs cause granulocytopenia, reversible thrombocytopenia, or even whether they cause diseases such as aplastic anemia and toxic hepatitis.
Physical examination
During the visit, the physician will perform a physical examination of the epileptic patient. This is because seizures can be caused by either the neurological system itself or by secondary involvement of other systemic lesions in the brain. A complete physical examination and necessary ancillary laboratory tests can help the doctor understand whether the patient’s liver, kidneys, or other organs are functioning properly. This can help the doctor determine the cause of the seizures and the appropriate anti-seizure medication in the future.
For example, in a patient with seizures, a simple test reveals that the patient has a low level of intelligence, and a physical examination reveals skin depigmentation and facial angiofibromas, so the doctor can initially determine that the patient may have a neurocutaneous syndrome (tuberous sclerosis).
As you can see, a formal epilepsy diagnosis needs to be done in steps and levels, so it is important to be patient and cooperate with the doctor and not be impatient. In some cases, it is difficult to make a clear diagnosis with just one visit, especially at the level of epilepsy syndrome, which may require multiple rechecking of the EEG, further supplemental seizures, and dynamic observation of treatment effects during long-term follow-up to make it clear, which is one of the reasons why doctors often tell patients and family members that they need to come to the hospital for regular follow-up.