To understand what a focal seizure is, one must first understand a little brain anatomy. The brain is divided into two hemispheres: the right and left hemispheres. Each hemisphere is further divided into four lobes: the frontal, temporal, occipital, and parietal lobes.
Seizures can be classified as being either generalized or focal. A generalized seizure involves both hemispheres of the brain while a focal seizure involves only one lobe of one hemisphere. In some instances, a seizure may begin as a focal seizure and progress into a generalized seizure.
One of the first symptoms of a focal seizure is an aura. Not all of those who suffer from focal seizures will experience an aura. However, it is a useful symptom in that it appears anywhere from several seconds to an hour before a seizure strikes.
An aura can manifest as a sudden, overwhelming emotion (i.e., joy or fear), memory, flashing lights, swirling colours, strange odour or taste, sense of déjà vu, or rising sensation in the belly. It can last anywhere from a few seconds to a couple of minutes.
After an aura comes the focal seizure. A common misconception is that all seizures cause convulsions and jerking motions. Contrary to popular belief, seizures can cause a wide range of symptoms.
The symptoms of a focal seizure vary depending on what area of the brain is affected. The different types of focal seizures and their symptoms are described below:
Symptoms of a frontal lobe seizure include convulsions, repetitive body movements (such as rocking or bicycling), abnormal body posturing, head deviation to one side of the body, difficulty speaking, explosive yelling, and laughter.
Symptoms of a temporal lobe seizure include staring into space, lip smacking, repetitive swallowing, repetitive chewing, and unusual finger movements.
Symptoms of an occipital lobe seizure include flashing lights and other visual hallucinations.
Symptoms of a parietal lobe seizure include weakness, dizziness, hallucinations, distortions of space, and sensory disturbances (i.e., heat, numbness, and electrical sensations).
When a person maintains their awareness during a focal seizure, the seizure is described as a simple partial seizure. When a person loses consciousness during a focal seizure, the seizure is described as a complex partial seizure.
Focal seizures are caused by uncontrolled bursts of electrical activity within the brain. For many, the cause for this abnormal brain behaviour remains unknown. For others, their focal seizures may be caused by one of the following:
The risk factors for focal seizures include the following:
Focal seizures typically occur in early childhood or older age (over the age of 65).
Being related to someone who has focal seizures increases one’s own likelihood of having one.
Brain damage due to oxygen deprivation, head trauma, stroke, dementia, drug use, alcohol abuse, or infection can trigger focal seizures in some individuals.
A doctor (typically a neurologist) will diagnose focal seizures based on the patient’s symptoms and the results of various tests. The tests used in diagnosing focal seizures include the following:
The neurologist will talk with the patient about what they felt before, during, and after their seizure. If possible, the doctor will interview anyone who witnessed the patient’s seizure. Video recordings are especially useful for diagnosing focal seizures.
Complications that may arise from having focal seizures are as follows:
The treatment options for focal seizures include the following:
Focal seizures are treated by medicines called anticonvulsants, or antiepileptic drugs (AEDs). There are over 30 different AEDs on the market. The AEDs used to treat focal seizures are referred to as narrow-spectrum AEDs.
If medication does not stop or mitigate one’s seizures, surgery may be considered as a treatment option. Surgery is only applicable for those whose seizures occur in a small part of the brain that can be removed or destroyed without causing serious side effects. Surgery does not have to be an open procedure. MRI-guided stereotactic laser ablation is a minimally invasive technique that uses a laser probe to destroy a small part of the brain.
If medication does not work and surgery is not an option, one may consider VNS. For VNS, a small electrical device is placed under the skin near the collarbone. A wire from the device is then connected to the vagus nerve. Approximately every five minutes, the device sends electrical impulses to the brain via the vagus nerve. VNS helps mitigate the frequency and severity of seizures.
DBS is used to treat focal seizures that do not respond to medication alone. For DBS, a small electrical device is placed under the skin in the upper chest area. A wire from the device is then connected to electrodes. The electrodes are placed onto the specific area of the brain involved in focal seizures. At timed intervals, the device sends electrical impulses to the electrodes in order to stimulate the brain directly. DBS helps mitigate the frequency and severity of seizures.
RNS is a type of device similar to a pacemaker. The device sits over the specific area of the brain involved in focal seizures and actively monitors the brain activity. It will send electrical impulses to the brain when unusual brain activity (i.e., the onset of a seizure) is detected.
Doctors may recommend a ketogenic diet for children suffering from seizures. A ketogenic diet is low in carbohydrates and proteins but high in fats. It is thought that this type of diet changes the levels of certain chemicals in the brain, thus reducing the number of seizures.
The following methods can reduce one’s risk of having a focal seizure:
It should be noted that new-borns are susceptible to brain damage during pregnancy and birth. Mothers can prevent their new-borns from developing seizure disorders by staying healthy during their pregnancies, seeking perinatal care before childbirth, and having healthcare professionals present during the childbirth.