Epilepsy is a common condition of the brain in which a person has a tendency to have recurrent unprovoked seizures.
The brain controls the body’s thoughts, actions, sensations and emotions through nerve cells (neurones) that carry messages between the brain and the body. These messages are transmitted through regular electrical impulses. A seizure occurs when the normal pattern of these impulses is disrupted by sudden excessive bursts of electrical activity in the brain.
The kind of seizure and how the body is affected relates to the part of the brain in which the seizure occurs. Seizures can involve loss of consciousness, a range of unusual movements, odd feelings and sensations, or changed behaviours.
Many people have seizures that are not diagnosed as epilepsy. These seizures often have a known cause or provocation and will not occur again unless the same provoking situation occurs. An example of this is febrile convulsions seen in infants.
The likelihood of being diagnosed with epilepsy at some point in life is about 3 per cent.
The main treatment for epilepsy is medication, which can control seizures in about 70 per cent of people with epilepsy. Surgery and other treatment options may be a possibility for a small number of people if medication fails to control their seizures.
The brain controls the body’s thoughts, actions, sensations and emotions through nerve cells (neurones) that carry messages between the brain and the body. These messages are transmitted through regular electrical impulses. A seizure occurs when the normal pattern of these impulses is disrupted by sudden excessive bursts of electrical activity in the brain.
The kind of seizure and how the body is affected relates to the part of the brain in which the seizure occurs. Seizures can involve loss of consciousness, a range of unusual movements, odd feelings and sensations, or changed behaviours.
Many people have seizures that are not diagnosed as epilepsy. These seizures often have a known cause or provocation and will not occur again unless the same provoking situation occurs. An example of this is febrile convulsions seen in infants.
The likelihood of being diagnosed with epilepsy at some point in life is about 3 per cent.
The main treatment for epilepsy is medication, which can control seizures in about 70 per cent of people with epilepsy. Surgery and other treatment options may be a possibility for a small number of people if medication fails to control their seizures.
There are many different types of seizures. Many people think a ‘seizure’ means a convulsion, where someone becomes unconscious and falls, with stiffness and jerking. However, this is just one type of seizure, and is called a tonic-clonic seizure (previously known as grand mal).
Some people may have episodes where they ‘go blank’ for a few seconds, while others remain fully conscious during a seizure and can describe their experience. For many, consciousness is impaired, and they may be confused and disorientated during and after the seizure.
A seizure may involve both sides of the brain (generalised onset seizure) or a small part of the brain (focal onset seizure). Sometimes seizures start as one type and evolve into another. Some people can have more than one seizure type.
Some people may have episodes where they ‘go blank’ for a few seconds, while others remain fully conscious during a seizure and can describe their experience. For many, consciousness is impaired, and they may be confused and disorientated during and after the seizure.
A seizure may involve both sides of the brain (generalised onset seizure) or a small part of the brain (focal onset seizure). Sometimes seizures start as one type and evolve into another. Some people can have more than one seizure type.
Generalised onset seizures
These seizures begin in both hemispheres of the brain simultaneously. There are several types of generalised onset seizures, including:
- Tonic-clonic seizure – consciousness is lost at the beginning. The muscles stiffen, and the person may fall if standing followed by rhythmic jerking. The person may bite their tongue or become incontinent. They are often confused and very tired afterwards.
- Absence seizure – these occur mostly in children. The person will ‘go blank’ for a brief time, during which they may stare, and their eyelids may flicker. These seizures can mimic daydreaming and go unnoticed.
- Tonic seizure – the body suddenly stiffens briefly, and the person may fall stiffly if standing, often causing injury. Recovery is usually quick.
- Atonic seizure – this is a sudden loss of muscle tone causing the person to fall if standing, or have head drops if sitting. Injuries are common. Recovery is usually rapid.
- Myoclonic seizures – brief, sudden jerks of a muscle or a group of muscles, usually involving the upper body. These can occur in isolation or clusters.
Causes of epilepsy
Anything that causes damage or scarring to the brain may lead to seizures and epilepsy. There are many causes for seizures and not everyone has a clear reason why they have epilepsy. In fact, up to half of people with epilepsy don’t know the cause of their condition.
Known causes of epilepsy can include:
Anything that causes damage or scarring to the brain may lead to seizures and epilepsy. There are many causes for seizures and not everyone has a clear reason why they have epilepsy. In fact, up to half of people with epilepsy don’t know the cause of their condition.
Known causes of epilepsy can include:
- brain injury
- stroke
- brain infection
- structural abnormalities of the brain
- genetic factors.
- Seizures may appear to be triggered by circumstances including lack of sleep or significant stress. Identifying and avoiding individual seizure triggers can help reduce the risk of seizures in people with epilepsy. Keeping a seizure diary or record can highlight seizure patterns and help identify possible triggers.
Charlotte Figi, an eight-year-old girl from Colorado with Dravet syndrome, a rare and debilitating form of epilepsy, came into the public eye in 2013 when news broke that medical marijuana was able to do what other drugs could not: dramatically reduce her seizures. Now, new scientific research provides evidence that cannabis may be an effective treatment for a third of epilepsy patients who, like Charlotte, have a treatment-resistant form of the disease.
Last month Orrin Devinsky, a neurologist at New York University Langone Medical Center, and his colleagues across multiple research centers published the results from the largest study to date of a cannabis-based drug for treatment-resistant epilepsy in The Lancet Neurology. The researchers treated 162 patients with an extract of 99 percent cannabidiol (CBD), a nonpsychoactive chemical in marijuana, and monitored them for 12 weeks. This treatment was given as an add-on to the patients’ existing medications and the trial was open-label (everyone knew what they were getting).
The researchers reported the intervention reduced motor seizures at a rate similar to existing drugs (a median of 36.5 percent) and 2 percent of patients became completely seizure free. Additionally, 79 percent of patients reported adverse effects such as sleepiness, diarrhea and fatigue, although only 3 percent dropped out of the study due to adverse events. “I was a little surprised that the overall number of side effects was quite high but it seems like most of them were not enough that the patients had to come off the medication,” says Kevin Chapman, a neurology and pediatric professor at the University of Colorado School of Medicine who was not involved in the study. “I think that [this study] provides some good data to show that it's relatively safe—the adverse effects were mostly mild and [although] there were serious adverse effects, it's always hard to know in such a refractory population whether that would have occurred anyway.”
Last month Orrin Devinsky, a neurologist at New York University Langone Medical Center, and his colleagues across multiple research centers published the results from the largest study to date of a cannabis-based drug for treatment-resistant epilepsy in The Lancet Neurology. The researchers treated 162 patients with an extract of 99 percent cannabidiol (CBD), a nonpsychoactive chemical in marijuana, and monitored them for 12 weeks. This treatment was given as an add-on to the patients’ existing medications and the trial was open-label (everyone knew what they were getting).
The researchers reported the intervention reduced motor seizures at a rate similar to existing drugs (a median of 36.5 percent) and 2 percent of patients became completely seizure free. Additionally, 79 percent of patients reported adverse effects such as sleepiness, diarrhea and fatigue, although only 3 percent dropped out of the study due to adverse events. “I was a little surprised that the overall number of side effects was quite high but it seems like most of them were not enough that the patients had to come off the medication,” says Kevin Chapman, a neurology and pediatric professor at the University of Colorado School of Medicine who was not involved in the study. “I think that [this study] provides some good data to show that it's relatively safe—the adverse effects were mostly mild and [although] there were serious adverse effects, it's always hard to know in such a refractory population whether that would have occurred anyway.”
Despite these limitations, both commentary authors agree the study is an important step in establishing CBD as a safe and effective epilepsy treatment. “This is a first step, and it's great,” Detyniecki says. Despite the large number of adverse events, he says that overall “there were no surprising side effects—we can conclude that CBD appears to be safe in the short term.”
Evidence suggesting that CBD is effective against treatment-resistant epilepsy may be growing but scientists still know very little about how it works—other than the likelihood that it is “completely different than any other seizure drug we know,” as Devinsky puts it. That’s a good thing, he notes: “One fear is that because of the way that the drugs are tested and screened, we've ended up with a lot of ‘me-too’ drugs that are all very similar.”
Researchers, including those who were involved in the study published last December, hope to address these limitations in currently running blind and placebo-controlled clinical trials testing CBD on Dravet sufferers as well as Lennox–Gastaut syndrome, another drug-resistant form of epilepsy. In the meantime most clinicians and researchers, including those involved in the trial, advise “cautious optimism” when considering CBD as an epilepsy treatment.
Evidence suggesting that CBD is effective against treatment-resistant epilepsy may be growing but scientists still know very little about how it works—other than the likelihood that it is “completely different than any other seizure drug we know,” as Devinsky puts it. That’s a good thing, he notes: “One fear is that because of the way that the drugs are tested and screened, we've ended up with a lot of ‘me-too’ drugs that are all very similar.”
Researchers, including those who were involved in the study published last December, hope to address these limitations in currently running blind and placebo-controlled clinical trials testing CBD on Dravet sufferers as well as Lennox–Gastaut syndrome, another drug-resistant form of epilepsy. In the meantime most clinicians and researchers, including those involved in the trial, advise “cautious optimism” when considering CBD as an epilepsy treatment.
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