What Do We Know About Epilepsy?
What Is Epilepsy?
Epilepsy is one of the most common and disabling brain disorders. It causes seizures. Seizures can occur cyclically but with repetitive onset of sudden attacks. It happens when there is abnormal electrical activity in your brain cells called neurons. This abnormality involves the excessive, hypersynchronous firing of neurons in your brain. Hypersynchronous means there is firing of neurons together that propagates from one group of neurons to the next leading to a strong build-up of activity.
Put in another way, an epileptic seizure is caused by abnormal neuronal firing. The term epilepsy is defined as a condition in which you have recurrent and unprovoked seizures. If you've had two or more seizures in your lifetime, there is a good chance that you may be epileptic. An epilepsy syndrome is a group of characteristics that consistently occur together. Patients may have similar seizure types, age of onset, triggering factors, genetics, EEG findings, natural history, prognosis, and response to antiepileptic drugs.
We will be looking at how common epilepsy is, its classification, diagnosis, a few epilepsy syndromes, and its treatment in this article.
How Common Is Epilepsy?
Epilepsy is relatively common. It has an incidence of about 50 new cases per year per 100,000 population. About 1% of the population is affected. One-third of patients have drug-resistant epilepsy. Roughly 75% of epilepsies start during childhood.
Classification: Generalized, Focal, and Epileptic Spasms
Seizures are separated into three categories: generalized, focal and epileptic spasms. Focal seizures originate in and are limited to one cerebral hemisphere. Generalized seizures begin in and affect both hemispheres. A seizure can start off focally and later generalize.
There are four types of generalized seizures: generalized tonic-clonic (GTC), absence, myoclonic, and atonic.
In GTC seizures, you lose consciousness. You also experience bilateral symmetric convulsive movements, stiffening followed by jerking, of all limbs.
With absence seizures, you may stare or sometimes blink your eyes or nod your head. You become unresponsive to external stimuli.
Myoclonic seizures involve sudden, brief, lighting fast, movements. These short-lived involuntary muscle contractions may affect one or several of your muscles. Hence, myoclonic seizures can be generalized or focal. You may not lose consciousness while this is happening.
Atonic seizures cause you to lose your body tone. Often it results in a head drop or fall.
The characteristics of focal seizures depend on the area of the cortex affected. For instance, a focal seizure arising from the occipital lobe may involve visual phenomena. One arising from the precentral gyrus may present with rhythmic clonic or tonic motor activity. When the postcentral gyrus is involved, there may be sensory symptoms such as paresthesias (tingling or prickling sensation). When you lose consciousness during a focal seizure, the seizure is classified as dyscognitive. Seizures originating in temporal lobe are often dyscognitive.
Some seizures are preceded by an aura. This is a focal seizure where you retain awareness and describe motor, sensory, autonomic, or psychic symptoms. An aura occurs seconds or minutes before a focal dyscognitive or generalized seizure. Patients with temporal lobe epilepsy most often experience these.
The origin of epileptic spasms is uncertain. They involve sudden extension or flexion of the hands and feet, lasting for several seconds. They typically occur in a series with several in a cluster.
Epileptic spasms can happen at any age. When they begin in the first year of life, they are part of a syndrome called infantile spasms (West syndrome).
Classification of Seizures and Epilepsies
Diagnosis is based on your medical history and physical examination. Additional testing may be needed to confirm the diagnosis.
You may be asked to have an electroencephalogram (EEG) recording. This measures the brain's electrical activity as brain waves. It can detect abnormal electrical activity like focal spikes or waves. These are consistent with focal epilepsy. It can also detect diffuse bilateral spike waves, which is consistent with generalized epilepsy.
You may also be asked for neuroimaging tests, such as computed tomography and magnetic resonance imaging. These techniques are particularly helpful in detecting central nervous system structural damage.
Genetic testing may be ordered if a specific syndrome is suspected.
A Few Epilepsy Syndromes With Potential Identifiable Causes
Benign familial neonatal epilepsy is an epilepsy syndrome whereby seizures start in the first week of life. Seizures are focal clonic or focal tonic and often accompanied by apnea. They often stop after a few days or weeks. BFNE is linked to mutations in two potassium channel, KCNQ2 and KCNQ3. These voltage-gated potassium channels regulate the M-current, a muscarine-activated neuronal current. The M-current stabilizes the resting membrane potential. Its dysfunction leads to increased neuron excitability and consequently seizures.
West syndrome is characterized by epileptic spasms, an EEG pattern called hypsarrhythmia, and intellectual disability. It begins mainly in the first year of life. Most cases of this syndrome have an identifiable cause including hypoxia-ischemia, CNS infection, intracranial hemorrhage, and developmental brain anomaly or inborn metabolic error.
Febrile Seizures Plus
Children with febrile seizures plus have febrile seizures beyond the age at which febrile seizures usually stop, about 5 years. They may also develop other seizure types including GTC, absence and myoclonic. In some of the families, mutations have been identified in neuronal sodium channels, SCN1A or SCN2A, or their beta subunit, SCN1B, and GABA receptors, GABRG2.
Dravet syndrome is a rare epilepsy syndrome in which children suffer from seizures before 18 months of age. The initial seizure often occurs with a fever and may be hemiclonic (jerking only on one side of the body). About 70% to 80% of patients have a mutation in the SCN1A gene, resulting in sodium channels that don't function.
Drugs called anticonvulsants (also called antiepileptic drugs) are usually used to decrease or stop seizures. With an arsenal of over 20 drugs, many newly diagnosed patients can be successfully treated. Drugs used to treat epilepsy work by reducing the electrical activity of the brain. They can do this by preventing neuronal firing by blocking sodium channels (carbamazepine) or calcium channels (valproate) or enhancing potassium channel function (retigabine). They may inhibit excitation carried out by the neurotransmitter glutamate (topiramate). Lastly, they may promote inhibition carried out by GABA (benzodiazepines).
A doctor's decision to choose one drug over the other is based on seizure type, age, other medical conditions, and potential side effects.
Levetiracetam has become popular in recent years as a first-line treatment. Its efficacy, easy titration, and well-recognized side effect profile have made it a popular choice.
If drugs do not help with your symptoms, there may be other options. An electrical device may be implanted in your chest to help decrease seizures. Surgery may be required to remove any damaged parts of your brain that are causing seizures. Hormone medicines may be given to women if seizures are related to hormonal changes.
Other Conditions Associated With Epilepsy
Epilepsy can be accompanied by other conditions. These comorbidities include depression, anxiety, learning disabilities, attention-deficit hyperactivity disorder, intellectual disability and autism.
Epilepsy is a brain disorder that causes seizures due to too much electrical activity in your brain. Symptoms of a seizure can vary and can be different for everyone. Symptoms can include unexplained fear or sadness, loss of consciousness, trouble responding to questions and confusion. Physical symptoms can include jerking and twitching, tingling and numbness, tongue biting, passing out or loss of bladder control. Diagnosis involves examining your medical history and a physical examination. Other tests may be ordered including an EEG. Drugs called anticonvulsants are used to treat seizures with relatively good outcomes.
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