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Seizures are caused by a period of abnormal electrical activity in the brain. During the seizure, there is normally an increase in electrical activity. When it is over, it is followed by a decreased activity which is the brain’s way of recovering.
Seizures are often short and self-limiting. Approximately 10%¹ of the population will have one seizure during their lifetime. Due to their brief nature, they are not dangerous in themselves but indirectly can cause harm, e.g., trauma from falling or crashing your car.
Status epilepticus occurs when a seizure lasts longer than five minutes and would be considered a medical emergency.
If seizures are recurrent and unprovoked, you will be diagnosed with epilepsy. It is a relatively common condition; approximately 7.5 out of 1000 people are diagnosed².
Seizures are often classified by which parts of the brain are affected. They are:
Generalized, which involves the whole brain
Focal, which is limited to one part of the brain but can progress to any area
Unknown, unable to specify
Symptoms vary depending on where the seizure is occurring and its duration in the brain.
Because the structures in the brain are closely linked to their function, doctors can figure out which part of the brain is electrically abnormal by the symptoms you exhibit. For example, if you feel a preceding ‘aura’ described as fogginess or light-headedness, your temporal lobes might be implicated.
Generally speaking, symptoms of seizures include:
Changes in your level of consciousness
An uncontrolled movement, such as jerking and/or complete paralysis of your limbs
Changes relating to your sense, such as disturbed vision, smell, and hearing
Tongue biting and urinary incontinence after losing consciousness are other hallmark symptoms that suggest seizure activity.
Seizures often occur for no reason, but there can be structural brain abnormalities, hormonal factors, and/or triggering stimuli. Seizures in children are typically less serious because a large proportion outgrows their seizures and disappear in adolescence.
If seizures begin as an adult, they are grouped into the adult-onset category. These types of seizures are often more serious and require further investigation.
Seizures can occur due to disturbances in the brain, but they can also be due to changes in the body.
Intrinsic causes, i.e., basic predisposition (genetic, but otherwise healthy) or structural (e.g., trauma, infection, tumor)
Extrinsic causes, i.e., factors that are occurring in the body, such as low oxygen levels, electrolyte disturbances, drug withdrawal, and medications
Let’s take drug withdrawal, for example. Stopping alcohol consumption suddenly after chronic usage can be extremely dangerous because it can lead to seizures. Alcohol is a drug that dampens the electrical activity in our brains.
However, research³ has found that the concentration of GABA, the major inhibitory chemical in the brain, is reduced as well as its receptors. Therefore, if you decide to stop drinking and do not reduce the amount of alcohol slowly, the brain essentially does not have the inhibitory mechanisms to compensate.
This results in increased activity in the brain.
It is reported that the most common causes are stroke (23%), idiopathic with no identifiable cause (22%), and infections within the central nervous brain (21%). Generally, other studies support these findings.
While there may be small differences, these can be attributed to variations in populations, e.g., average age, sample size, and rate of infections.
This is the most common cause for adults over the age of 60. Stroke is the medical terminology for tissue death in the brain due to an interruption of blood flow, such as from a clot.
The symptoms correlate to which blood vessel is affected and the severity of the clot, i.e., whether it is fully blocked, partially blocked, or unblocked within several hours. Most strokes will produce seizures that are restricted to the affected area.
This is the most common type of seizure in adults under 40 years of age, where healthcare professionals cannot find a specific cause. Despite negative findings in the investigations, your doctor might suggest beginning medication if seizures are recurrent.
Seizures can occur after viral or bacterial infections in your brain or spine. There is a long list, but one example is herpes simplex virus type 1 (HSV-1). Commonly, herpes causes cold sores, but rare occasions can cross into the central nervous system to cause seizures.
Certain stimuli can make having a seizure more likely, but do not directly cause epilepsy.
A review article⁴ published in the Epilepsia medical journal indicated that 53–65% of adults report that certain triggers precede their seizure. Furthermore, another study reported in the review found that 2+ triggers are found in 70–90% of patients with seizures, suggesting that there is an additive effect between triggers.
This can be brought on by multiple factors, which can generally be classified into:
Physical, e.g., fatigue, lack of sleep, illness, poor nutrition
Mental, e.g., major life events, work, relationships
Stress is reported to be the most common trigger for seizures. It acts in various ways, but ultimately stress can increase electrical activity in the brain, increasing its vulnerability.
A study⁵ conducted in 1984 investigated the relationship between seizures and stress by asking participants to write in a diary for three months. Participants were more likely to have a seizure during stressful days.
There is a lot of evidence to support this claim. Another study involving military personnel with different occupations (e.g., combative, administrative) found that more stressful jobs increased the likelihood of seizures.
Flashing lights can produce instant seizures. It is hard to quantify how many people in the population are vulnerable to photo-induced seizures because those who do not have seizures are generally not tested.
Air Force studies, however, are the exception. In many countries, pilots are tested before commencing their training.
One study⁶ investigated 5,893 pilots and their EEG abnormalities in response to photostimulation over 20 years.
It found that 2.4% of the asymptomatic pilots had abnormal electrical responses in the brain due to photic stimulation, making them ‘photosensitive’ and vulnerable to seizures. The study also found that 1 in 10,000 people will have seizures from visual stimuli.
Hyperventilation increases the frequency of seizures that are classified as absence seizures. As the name suggests, this is a brief loss of consciousness that affects the whole brain.
When we hyperventilate, we breathe out a lot of carbon dioxide, which is important for acid-base regulation in our body. Because carbon dioxide is an acid, getting rid of it increases your body's pH — this is medically known as respiratory alkalosis. This response has been found to underpin over 90% of people with absence seizures⁷.
High-intensity exercise is one example of hyperventilation that occurs regularly. In a study⁸ by the Norwegian Epilepsy Center, 8% of its adult patients reported that over 50% of their seizures occurred before, during, or after exercise.
This small proportion of the participants demonstrates that while exercise can be a trigger for people with epilepsy, it is a relatively rare one and does not outweigh the benefits of exercise in most cases.
Not taking medications leads to poorer health outcomes. The benefits outweigh the risks if prescribed anti-epileptic medications (e.g., carbamazepine).
If you want to stop your medication, it should be gradually tapered off to avoid the chance of seizure, and only after consultation with your doctor.
Doctors are often able to identify the causes of adult-onset seizures. Therefore, it is very important to visit your local doctor if you are concerned that you have had a seizure.
It is often hard to remember the event if you have had a seizure. That being the case, taking someone with you when going to the doctors that witnessed the event is a great way to convey what actually happened.
There are many reasons that seizures occur, but sometimes the reason for it will be unknown. If you have a seizure for the first time, visit your doctor to discuss the matter with them and establish the best treatment course. The three most common causes are stroke, idiopathic, and CNS infection.
Numerous types of triggers can cause a seizure to occur in adults. These include infections, illnesses, stress, and health conditions like stroke. It’s always good to check in with a health professional, as uncontrolled seizures can be dangerous.
The epidemiology of epilepsy (2020)
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