What is Focal Onset Seizure?
A focal onset seizure starts in just one specific area of one side of the brain. These seizures have two main forms: those that involve movement (motor) and those that don’t (nonmotor). Each form can also be categorized by how aware the person is during the seizure: fully aware, partially aware, or if it’s unknown.
Motor onset seizures show signs such as automatic movements, loss of muscle tone, rhythmic jerking, quick muscle contractions, seizures that cause excessive motion, quick jerking of the limbs, or sustained muscle contraction. Nonmotor onset seizures might affect emotions or senses and could cause changes in behavior, thought process, feelings, or ability to sense things without any major physical movements.
Before a seizure happens, some people experience what is known as an “aura.” These are signs or feelings that a seizure is about to happen, such as changes in vision, a feeling of being unwell in the stomach, strange sensations like déjà vu, numbness or tingling, changes in hearing, or strange tastes or smells.
A seizure is when there is too much or disorganized activity among nerve cells in the brain, causing temporary changes in behavior, movement, or awareness. Epilepsy is when a person has a tendency to have recurring seizures, and these continue to affect the person’s life in different ways. Seizures used to be divided just into partial and generalized types, but a group called the International League Against Epilepsy (ILAE) updated that in 2017 to three categories: generalized onset, focal onset, and unknown onset seizures.
Focal Motor Seizures (also known as Simple Partial Seizures or Complex Partial Seizures) happen because there is a problem in the opposite side of the front part of the brain. Signs can include certain movements of the head, neck, limbs, and body. After these types of seizures, it’s common for the person to experience brief but temporary weakness or inability to use the affected muscles, which is known as Todd paralysis. This shows that the seizure was focal in nature and can help doctors figure out which side of the brain the seizure started from. Sometimes, this might be mistaken for a stroke.
Focal Nonmotor Seizures show signs such as changes in body functions (autonomic signs) like changes in blood pressure, heart rate, sweating, skin color, or upset stomach. Others stop moving entirely (behavioral arrest). Some have changes in how they think or communicate (cognitive signs), like experiencing déjà vu, hallucinations, or visual illusions. Some even have changes in how they feel (emotional signs), like feeling scared, anxious, or even happy. Some nonmotor seizures can even make the person laugh (gelastic seizures) or cry (dacrystic seizures). And then there are those that cause changes in how the person senses things (sensory signs), like changes in vision, feeling tingly or numb, hearing, smell, or even feeling pain.
Sometimes, both types of focal seizures can evolve and become a different type of seizure called bilateral tonic-clonic seizures that affect both sides of the brain and the whole body.
What Causes Focal Onset Seizure?
Certain health issues or conditions can increase a person’s risk of having seizures. It’s essential to try and figure out what’s causing the seizures while identifying what kind of seizure is occurring. According to the International League Against Epilepsy (ILAE), seizures can be caused by six potential categories:
- Genetic (inherited from parents)
- Structural (issues with the brain’s structure)
- Metabolic (problems with the body’s chemical processes)
- Immune (problems with the immune system)
- Infectious (caused by infections)
- Unknown (the cause can’t be identified)
In children, seizures often happen due to a lack of oxygen to the brain around the time of birth. In teenagers, the most common causes are head injuries and infections. In adults, the most common cause is a stroke.
Sometimes, the exact reason for seizures is unknown. However, certain environmental conditions can increase the chance of seizures occurring in people already at risk. Common triggers include lack of sleep, stress, images that cause a reaction in people sensitive to light patterns, drug use, infection, and not taking prescribed medication regularly.
Risk Factors and Frequency for Focal Onset Seizure
Epilepsy is a condition that affects about 52.5 million people around the world. It’s most common in babies and older people, which means it has a two-part pattern of affecting people mainly at those two life stages. The number of people with epilepsy varies based on factors such as their country, ethnicity, race, social and economic status, and how easy it is for them to get healthcare. There are different types of seizures that people with epilepsy can experience. The most common type is called a focal onset seizure with impaired awareness, which happens more frequently than generalized onset seizures.
Signs and Symptoms of Focal Onset Seizure
When someone is showing signs of a seizure, it’s crucial to find out if this is caused by actual seizures. During a seizure, a person may lose consciousness, have trouble communicating, or be in a state of confusion afterwards. Therefore, it’s important to get information from someone who saw the episode, not just from the patient’s memory. Making a timeline of what happened is key for diagnosing and classifying the seizure. A doctor should ask about warning signs, including feeling light-headed, dizzy, a stomach upset, changes in taste or smell, changes in vision, or a ringing sound in the ears. Doctors should also check whether the patient lost consciousness or became less aware during the episode.
Bear in mind, awareness during a seizure does not mean the patient knows a seizure has occurred, but they can interact with their surroundings during the seizure. It’s important to note any physical movements, like jerking, twitching, or stiffness of the face or limbs. Other symptoms during a seizure can include loss of bladder or bowel control, biting the tongue, drooling, and forced eyes movement. A detailed clinical history and timeline can help locate the source of the seizure.
- Seizures starting from the temporal lobe can cause changes in body functions or psychological symptoms, including indigestion, hearing things that aren’t there, and smelling things that aren’t there.
- Seizures starting from the frontal lobe show prominent physical signs like twitching or stiffness of the face or limbs.
- Seizures starting from the parietal lobe show symptoms such as odd sensations, visual disturbances, not knowing where a body part is, feelings of spinning, and disturbances in language.
- Seizures beginning from the occipital lobe can show as visual disturbances or illusions.
When checking a patient with seizures, it’s important to observe their consciousness level. If the patient is awake, their speech, memory, and ability to follow commands can be assessed. It’s also important to look for signs of further seizure activity, like abnormal face or limb movements, forced eyes movement, biting the tongue, and loss of bladder or bowel control. Weakness on one side of the body could be a sign of a condition known as Todd’s paralysis.
Testing for Focal Onset Seizure
Electroencephalography (EEG) is a critical tool to accurately diagnose seizures and pinpoint the origin of a seizure. If the EEG shows abnormal electrical activity in the brain, a magnetic resonance imaging (MRI) scan of the brain is crucial to find and check any structural changes. It’s important to note that EEG’s effectiveness improves if it spans a complete 24-hour period since this allows the capture of day-to-day changes in seizure activity.
Barring any specific medical reasons to the contrary, an MRI is generally carried out following a first seizure. This enables doctors to examine the brain, blood vessels, and protective layers covering the brain (meningeal structures). MRI scans use various imaging methods to provide a highly detailed image of the brain, far more accurate than CT scans. This is because CT scans can’t always provide clear images of certain areas in the brain due to the presence of bony structures.
Certain standard blood and urine tests are also necessary to identify possible triggers of seizure related to the body’s metabolism or exposure to toxins. These tests may include checks for electrolyte balance, full blood count, liver and kidney function, lactate levels, creatinine phosphokinase (a muscle enzyme), and toxicology tests. If an infection or autoimmune process in the brain is suspected, then a lumbar puncture (taking fluid from the spinal column) followed by cerebrospinal fluid analysis is performed to pinpoint the root cause.
It is also essential to differentiate between true epileptic seizures and psychogenic nonepileptic seizures (PNES), which were previously known as pseudoseizures. PNES appear outwardly like epileptic seizures, but they don’t show abnormal brain activity on the EEG. These seizures are often associated with a history of abuse or trauma and can be considered a type of emotional disorder. Interestingly, PNES is quite common, affecting 20-30% of patients in epilepsy centers, and these patients may be exposed to side effects from epilepsy medications if mistakenly diagnosed with epilepsy. Moreover, the diagnosis can be further complicated as a percentage of patients (between 5-40%) with PNES also have epilepsy.
Treatment Options for Focal Onset Seizure
When treating someone who’s having a seizure, the first step is to stop the ongoing seizure activity. This is generally done using medications such as benzodiazepines, levetiracetam, valproic acid, phenytoin, and fosphenytoin. If a patient continues to have seizures even after these medications are administered, additional medications given through an IV, such as propofol, midazolam, and ketamine, may be given. Once the seizures have stopped, long-term medications to prevent future seizures may be introduced. These choices can depend on various factors such as the type of seizures, medication side effects, patient’s age, other medications they are on, and the presence of other illnesses.
For focal onset seizures, where the seizures start in one part of the brain, the initial go-to drugs are typically carbamazepine and lamotrigine. Other drugs that could be used include valproate, oxcarbazepine, and levetiracetam. More drugs like gabapentin, topiramate, and clonazepam might be used alongside these, if necessary. If these combinations fail to stop the seizures or cause severe side effects, the patient might be referred to a specialist center.
Besides medications, there are other ways to manage seizures for those who don’t respond well to drugs. These include a special diet (called the ketogenic diet), having a device implanted to stimulate a nerve (vagus nerve stimulator), or undergoing brain surgery. The ketogenic diet is high in fats and low in carbohydrates and protein, and might be beneficial in children with stubborn seizures despite trying at least two different drugs. It might also work well in certain genetic disorders. Brain surgery can be considered when seizures can be traced back to a specific part of the brain that can be safely removed. During this process, the surgeons may use a technique called neural mapping to identify the exact area in the brain responsible for starting the seizures.
Another option is Vagus nerve stimulation (VNS), a procedure where a device is placed inside the body and attached to a nerve in the neck called the vagus nerve. This device helps control irregular electrical activity in the brain that might trigger a seizure. VNS therapy can reduce the frequency, intensity, and duration of the seizures, and is often considered in people who don’t respond to medications and aren’t suitable for surgery.
What else can Focal Onset Seizure be?
There are several conditions that have similar symptoms to focal onset seizures. These include:
- Psychogenic nonepileptic seizures
- Movement disorders
- Migraine disorders
- Psychiatric disorders
- Headache disorders
When someone experiences symptoms similar to seizures, it’s important to have a video EEG (vEEG) monitoring test. This test helps doctors see if the brain activity that causes seizures is present during these symptoms. If the vEEG doesn’t show this kind of brain activity, then other diagnoses should be considered.
What to expect with Focal Onset Seizure
In people experiencing focal onset seizures, it’s important to treat any identifiable causes to lower the chance of more seizures occurring. Common factors that can be controlled or changed include lack of sleep, not drinking enough fluids, not taking prescribed medication as directed, drug or alcohol use, and exposure to images that stimulate the brain excessively. People typically have a higher risk of experiencing more seizures if the cause of the seizure isn’t found. As a result, it’s crucial for those with these seizures to take long-term anti-seizure medication.
Possible Complications When Diagnosed with Focal Onset Seizure
If an individual with seizures that start in one area of the brain (known as focal onset seizures) doesn’t receive treatment, a condition called focal status epilepticus might occur. This condition can lead to immediate serious complications such as falling into a coma, brain damage, irregular heart rhythm, failure of the respiratory system, choking, and even death.
Focal seizures are more likely to turn into status epilepticus (SE), particularly if they evolve into generalized-tonic-clonic seizures, compared to seizures that start off generalized. The seizures in status epilepticus can be either convulsive or nonconvulsive. Convulsive SE is a medical emergency since two minutes of continuous seizure activity can sometimes cause permanent damage or even death. The long-term effects of nonconvulsive SE are not as clear.
The potential long-term complications from focal onset seizures include depression, anxiety, cognitive impairment (trouble thinking, understanding, learning or remembering), insomnia (trouble sleeping), bone fractures, and even an early death. If someone has had focal onset epilepsy, it’s very important to screen for these conditions.
Immediate Complications:
- Coma
- Brain damage
- Cardiac arrhythmia (irregular heart rhythm)
- Respiratory failure (breathing stops or becomes very difficult)
- Aspiration (choking)
- Potential death
Long-term Complications:
- Depression
- Anxiety
- Cognitive impairment
- Insomnia
- Bone fractures
- Premature mortality (early death)
Preventing Focal Onset Seizure
If you or a family member have focal onset seizures, it’s important to learn certain safety measures to lessen the chance of getting hurt during a seizure. Various sorts of driving restrictions might apply to you depending on where you live. It’s a crucial part of your medical care for your doctor or healthcare provider to consistently talk to you about these driving rules, especially if your seizures aren’t well-controlled.
For your safety, use caution when you’re cooking, using heavy machines or power tools, climbing high structures, or working at heights. Also, try to avoid taking baths or swimming alone without supervision. Following these precautions will help keep you safe and can reduce the risk of accidents associated with seizure episodes.