How Epilepsy Is Diagnosed

epilepsy diagnosis

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In order to diagnose epilepsy, your doctor will need to verify that you've had seizures and then figure out what type of seizures they are. This can involve a neurological exam and a variety of tests, the most common of which is an electroencephalogram (EEG). Other tests may include blood tests, a computerized tomography (CT) scan, magnetic resonance imaging (MRI), and a positron emission tomography (PET).

It's important for your doctor to accurately diagnose what type of seizures you're having and where they begin in order to find the most effective treatment.

Physical Exam/Medical History

Your doctor will start by reviewing your medical and family history to see if seizures run in your family and talk to you about the symptoms you've experienced.

Diagnosing epilepsy can be tricky since your doctor probably won't ever witness you having a seizure, so keeping a detailed history about what you were doing before your seizure started, how you felt before, during, and after (as much as you can remember), how long the seizure lasted, and anything that may have triggered it can be extremely helpful. Also note specifics about any sensations, feelings, tastes, sounds. Bring along or get a detailed description from anyone who witnessed your seizure as well; eyewitness accounts are invaluable in diagnosing epilepsy.

You will probably also have a physical exam so that your doctor can check to see if there's an underlying medical condition that's causing your seizures. If you already have a chronic medical condition, be sure to let your doctor know about it since it may be causing your seizures. Even if your underlying condition is not the cause, it could still interfere with any anti-seizure drug your doctor prescribes by causing poor absorption or negative interactions.

Labs and Tests

There are a number of labs and tests that your doctor may use to help diagnose epilepsy.

Neurological Tests

In order to determine how your seizures may be affecting you, your doctor may perform some neurological tests to assess your behavior, as well as your intellectual and motor abilities. This can also help determine what type of epilepsy you have.

A neurological exam may involve testing your reflexes, balance, muscle strength, coordination, and your ability to feel. If you are diagnosed with epilepsy, your doctor will likely conduct a brief neurological exam every time you have a check-up to see how your medication is affecting you.

Blood Tests

You will likely have some blood tests, like a complete metabolic panel to make sure that your kidneys, thyroid, and other organs are functioning properly and that they're not the cause of your seizures. You may also have a complete blood count (CBC) to check for infections that may be responsible for the seizures. A blood test can also look at your DNA for genetic conditions that might explain your seizures. 

Electrocardiogram (ECG)

Because it's possible to be diagnosed with epilepsy when you may actually have a condition known as syncope (see "Differential Diagnoses" below), your doctor may want to do an electrocardiogram (ECG) to check your heart.

An ECG can also rule out a cardiac arrhythmia (abnormal heartbeat) that may have caused syncope.

An ECG is a quick and painless test that measures and records the electrical activity in your heart for several minutes using electrodes that are attached to your chest. Your doctor can then tell if your heart is beating regularly and whether or not it's being worked too hard.

Electroencephalogram (EEG)

An electroencephalogram (EEG) is the most common diagnostic tool doctors use for epilepsy because it picks up abnormal brain waves. That said, an abnormal EEG merely supports a diagnosis of seizures; it cannot rule them out since some people have normal brain waves after seizures.

Others have abnormal brain activity even when they're not having a seizure. Abnormal brain waves may also be seen when you've had a stroke, head trauma, or when you have a tumor.

It can be helpful to have an EEG within 24 hours of having your first seizure, if at all possible. Your doctor may have you come in for your EEG very early in the morning when you're still drowsy or have you stay up late the night before in order to increase the chance of recording seizure activity.

For this procedure, electrodes are attached to your scalp using a washable glue. The electrodes have wires connecting them to an EEG machine, which records your brain's electrical activity, typically while you're awake. The electrodes are simply for detection and don't conduct any electricity, so it's a completely painless procedure. An EEG may last from 20 minutes to two hours, depending on your doctor's orders.

Brain waves are recorded as squiggly lines called traces, and each trace represents a different area in your brain. Your neurologist is looking for patterns, called epileptiform, that show a tendency toward epilepsy. These can manifest as spikes, waves, or spike-and-wave discharges.

If abnormal activity shows up on your EEG, the trace can show where in your brain the seizure originated. For instance, if you're having generalized seizures, which means they involve both sides of your brain, there will likely be spike-and-wave discharges spread throughout your brain. If you're having focal seizures, meaning that they involve just one area of your brain, there will be spikes and sharp waves in that specific location.

Your doctor may want you to have a high-density EEG rather than a classic EEG. This just means that the electrodes are placed closer together, which can help pinpoint more accurately where in your brain your seizures are starting.

Magnetoencephalography (MEG)

The neurons in your brain create electrical currents that, in turn, create small magnetic fields that can be measured with a magnetoencephalography (MEG). A MEG is often done at the same time as an EEG or used with magnetic resonance imaging (MRI) and can be especially helpful in pinpointing the area of your brain that your seizures are coming from.

Similar to an EEG, a MEG is non-invasive and painless, using metal coils and sensors to measure your brain function. It may be more accurate than an EEG in detecting the location of your seizures because your skull and the tissue surrounding your brain don't interfere with the readings, whereas they affect an EEG's readings. However, the two tests complement one another since each may pick up abnormalities the other does not.

Imaging

Your doctor may want to do one or more imaging tests of your brain to check for any abnormalities and to pinpoint where in your brain the seizures originate.

Magnetic Resonance Imaging (MRI)

MRI uses a magnetic field and radio waves to give a detailed image of your brain and is considered the best imaging method for epilepsy because it's especially sensitive to detecting a variety of causes of seizures. It can rule out structural brain abnormalities and lesions that may be causing your seizures, as well as areas that have developed abnormally and changes in your brain's white matter.

Computerized Tomography (CT) Scan

A computerized tomography (CT) scan utilizes X-rays and can be used to find obvious problems in your brain such as a hemorrhage, cysts, large tumors, or obvious structural abnormalities. A CT scan may be used in the emergency room to rule out any conditions that need immediate treatment, but an MRI is considered more sensitive and usually used in non-emergency situations.

Positron Emission Tomography (PET)

When you have a PET scan, a low dose of radioactive material is injected into your vein to record how your brain uses sugar. This scan is usually done in between seizures to identify any areas in your brain that aren't metabolizing sugar well, an indicator of the seizure's origin. This test is especially helpful when you have focal seizures.

Single-Photon Emission Computerized Tomography (SPECT)

A single-photon emission computerized tomography (SPECT) test is a specialized test that's usually only used if other tests haven't been able to locate where your seizures start. When you have a seizure, more blood flows to the area of your brain in which it originates.

A SPECT test is the same as a CT scan, except that like a PET scan, you're injected with a low dose of radioactive material right before the scan itself is done. The radioactive material shows the blood flow activity in your brain, helping to pinpoint the origin of your seizures.

Differential Diagnoses

There are other conditions that can look like a seizure that your doctor may need to rule out before diagnosing you with epilepsy.

Syncope

Syncope occurs when you lose consciousness due to a lack of blood flow to the brain, which can cause your muscles to jerk or stiffen, similar to a seizure. It can be misdiagnosed as epilepsy, particularly if no one witnessed the event. The most common cause of syncope is vasovagal syncope, but there are other causes as well, including long QT syndrome.

Vasovagal syncope, also called the simple fainting spell or reflex syncope, occurs because of a neurological reflex that's often triggered by factors like pain, fright, an upsetting situation, stress, or the sight of blood. Sometimes the trigger is unknown, but it usually happens when you're standing. Your body overreacts and your blood pressure and heart rate plummet, causing you to faint. Once you're lying down, gravity allows the blood to return to your heart and you regain consciousness quickly.

Long QT syndrome is an inherited disorder of the cardiac electrical system, which controls the heartbeat. People who have long QT syndrome can develop sudden, unexpected episodes of a peculiar variety of ventricular tachycardia, a potentially dangerous rapid heart rhythm, that commonly leads to sudden syncope and can even lead to sudden cardiac arrest. Long QT syndrome can be effectively treated once it's diagnosed.

One difference between a seizure and syncope is that when you wake up after syncope, you are alert immediately whereas, with a seizure, you're often sleepy and disoriented for a few minutes or longer. It's very rare to have both syncope and a seizure at the same time.

If your doctor suspects that vasovagal syncope is the cause of what seemed to be a seizure, you may have a tilt table test to help diagnose it. In a tilt table test, you lie down on a table that's slowly tilted upward into a standing position while your blood pressure and heart rate are monitored to see how they respond to gravity. This may cause you to faint.

Some people with vasovagal syncope have warning signs that they're about to faint such as sweating, nausea, blurry vision, or weakness, but some people don't.

Transient Ischemic Attack (TIA)

A transient ischemic attack (TIA) is often referred to as a mini-stroke and it's far more likely in older adults. During a TIA, blood flow to your brain is temporarily blocked and your symptoms may be similar to that of a stroke. However, unlike a stroke, it usually resolves within a few minutes without any lasting damage. A TIA may be a warning sign that you're going to have a stroke in the future and always needs medical attention.

A TIA can be mistaken for a seizure. Occasionally, people have shaky limbs during a TIA, though this isn't common. Both TIAs and a type of seizure known as aphasic seizures can cause aphasia (being unable to speak or understand others). One difference is that with a TIA, this happens suddenly and doesn't get worse, whereas in an aphasic seizure, it typically progresses. Both TIA and seizures can also cause you to suddenly fall to the ground, which is called a drop attack.

If you're an older adult and you've never had a seizure before, your doctor will likely test you to rule out or confirm a TIA.

Migraine

Both migraine and epilepsy involve episodes of brain dysfunction and share some symptoms, including a headache, nausea, vomiting, visual aura, tingling, and numbness. Having a personal or family history of migraine can be a big clue that helps your doctor differentiate between the two concerns.

While a headache is a trademark symptom of a migraine, 40 percent to 45 percent of people with epilepsy get them after having a seizure too, and the pain may feel similar to a migraine. Additionally, up to a third of people with migraine don't feel head pain with at least some of their migraines.

Many people with migraine have a visual aura that lets them know a migraine is coming. Visual aura can occur with epilepsy that originates in the occipital lobe of the brain too. Epileptic visual auras tend to only last a few minutes though while migraine visual auras can last up to an hour.

Somatosensory symptoms like numbness, tingling, pain, and feeling like one or more of your limbs are "asleep" can also occur in both epilepsy and migraine. Like visual auras, they spread slowly and can last for up to an hour in migraine, whereas they come on quickly and only last a few minutes with epilepsy.

Losing consciousness and motor activity like muscle stiffening or jerking is very unusual in migraine, so these symptoms are far more likely to be epilepsy. Confusion or sleepiness that lasts for some time after an episode is more common in epilepsy, but can occur in certain types of migraine too.

Panic Attacks

If you're prone to having panic attacks, you likely have an underlying anxiety disorder. Symptoms of a panic attack are sweating, increased heart rate, a sense of impending doom, chest pain, lightheadedness, and shortness of breath. A panic attack can also result in shakiness and tremors. Rarely, the hyperventilation that often accompanies an attack can cause you to lose consciousness briefly. All of these can be mistaken for signs of a seizure.

Panic attacks are especially likely to be mistaken for seizures when you aren't feeling anxious or stressed before an attack occurs. Seizures can also be mistaken for panic attacks since anxiety disorders commonly co-occur with epilepsy and fear can occur after a seizure, especially in temporal lobe epilepsy.

One way to tell the difference between a panic attack and a seizure is that a panic attack can last from minutes to hours, whereas seizures occur abruptly and typically last less than two minutes. Motor automatisms like lip smacking or blinking, unresponsiveness, and sleepiness after an episode are also unlikely in a panic attack, but common with seizures.

Psychogenic Nonepileptic Seizures

While psychogenic nonepileptic seizures (PNES) look just like regular seizures, there is no abnormal electrical brain activity that ties them to epilepsy. The cause of these seizures seems to be psychological rather than physical, and they're categorized as a subtype of conversion disorder under the somatic symptoms and related disorders in the Diagnostic and Statistical Manual of Mental Disorders, 5th edition (DSM-5). Video EEG monitoring is usually used to diagnose PNES.

There are several differences between epileptic seizures and psychogenic nonepileptic seizures:

Symptom/SignEpileptic SeizuresPNES
Seizure Duration1 to 2 minutesMay be longer than 2 minutes
EyesUsually openOften closed
Motor ActivitySpecificVariable
VocalizationUncommonCommon
Rapid HeartbeatCommonRare
Blue Tinge to the SkinCommonRare
Post-Seizure SymptomsSleepiness, confusion, headacheTypically back to normal quickly

 

Narcolepsy With Cataplexy

Narcolepsy is a sleep disorder that causes episodes of extreme sleepiness in which you may fall asleep for a few seconds to a few minutes throughout the day. This can happen at any time, including when you're walking, talking, or driving. It's rare, affecting an estimated 135,000 to 200,000 people in the United States.

When you have narcolepsy with cataplexy, called type 1 narcolepsy, you also experience sudden partial or complete loss of muscle tone that can result in slurred speech, buckled knees, and even falls. This can be mistaken for an atonic seizure, which also causes you to lose muscle tone.

One way to differentiate between the two is that cataplexy usually occurs after you've experienced a strong emotion, like laughter, fear, surprise, anger, stress, or excitement. Your doctor can do a sleep study and a multiple sleep latency test (MSLT) to diagnose narcolepsy.

Paroxysmal Movement Disorders

There are several paroxysmal movement disorders that may look like epilepsy because of the involuntary twitching, writhing, or repetitive movements that can occur at different times. The cause of these disorders isn't understood, but they can happen for no reason, run in your family, or occur when you have another condition such as multiple sclerosis (MS), stroke, or a traumatic brain injury. Anti-seizure medication can be helpful for certain types of these disorders and they're often diagnosed based on your history and possibly a video-monitored EEG.

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