Focal or partial seizures begin in only one part of the brain. A person may experience muscle contractions, unusual sensations, and other symptoms. Possible causes range from epilepsy to dehydration.

They are key symptoms of epilepsy, but they can also occur due to other causes. There are two types of focal, or partial, seizures: simple and complex.

This article looks at the types, causes, symptoms, and treatment of focal seizures.

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The human brain contains neurons, or brain cells, that use electrical signals to communicate with each other.

During a seizure, which is temporary, a person experiences an atypical surge of electrical activity in their brain. People can experience physical symptoms before, during, and after a seizure.

Unlike generalized seizures, focal seizures originate in only one part of the brain. In contrast, generalized seizures originate across the entire brain rather than in one area.

All seizures occur due to atypical electrical discharges within the brain. However, there are types of seizures that differ according to how they affect the brain.

Health experts classify seizures into three categories:

  • generalized
  • focal
  • unknown

These types of seizures vary depending on where they originate in the brain.

TypeGeneralizedFocalUnknown
OriginThese affect both sides of the brain and include tonic-clonic and absence seizures.Focal seizures affect only one side of the brain and may cause twitching, confusion, and changes to the senses. These can progress to generalized seizures.This type of seizure does not have an identifiable origin. This may be due to seizures occurring when a person is sleeping or when they are on their own.

Learn more about the types of seizures.

Because a focal seizure begins in one part of the brain, its symptoms can vary depending on the area it affects. Also, a person will usually have symptoms on only one side of their body.

However, if the focal seizure becomes a generalized seizure, they may begin to experience convulsions on both sides.

Symptoms that may occur during a focal seizure include:

  • muscle contractions
  • unexpected sensations
  • atypical head or eye movements
  • automatisms, such as skin-picking or lip-smacking
  • vision changes or auras

People who remember having a seizure often describe an aura at its onset.

An aura is a confusing feeling or the perception of an unexpected light or smell just before a seizure begins. Therefore, auras usually indicate the start of atypical electrical activity in the brain prior to a seizure.

Following the aura, the individual may have odd sensations, changes in their motor abilities, or visual disturbances, usually on one side of their body.

However, bystanders may notice different symptoms in these individuals, such as staring, rapid eye blinking, or body stiffening, followed by confusion and tiredness after the event.

There are three types of focal seizures.

Simple focal seizures

Doctors also refer to simple focal seizures as focal aware seizures, which do not involve the loss of consciousness.

During a simple focal seizure, a person remains alert throughout the event and remembers it when it finishes. This seizure typically lasts less than 1–2 minutes.

Complex focal seizures

Doctors also refer to complex focal seizures as focal impaired awareness seizures.

When a person has a complex focal seizure, their consciousness is impaired, and they may only be aware of and remember some details of the seizure.

The seizure may last up to 10 minutes and can involve involuntary, repetitive movements known as automatisms, although most last around 1–2 minutes.

Secondary generalized seizures

Some focal seizures can start in one part of the brain and move to another, essentially turning into generalized seizures. These can last around 5 minutes.

Seizures can have many different causes and triggers, some of which doctors still do not know.

Potential causes of focal seizures include:

Potential triggers of focal seizures include:

  • sleep deprivation
  • an illness
  • high or low blood sugar
  • dehydration
  • electrolyte abnormalities
  • seeing flashing lights
  • alcohol or drug use
  • stress
  • low blood sugar
  • certain medications

Doctors also classify focal seizures into two additional types depending on their cause. One type is an unprovoked seizure, which occurs without a known cause. The other is an acute symptomatic seizure, which results from a triggering event or injury.

Doctors can diagnose a seizure according to a person’s account of the event. However, a bystander’s report can be more reliable, so clinicians prefer to hear both accounts, if possible.

A healthcare professional will try to figure out whether the seizure was focal or generalized. They will also attempt to distinguish the seizure episode from other events that look similar to seizures.

Doctors will also take note of any potential seizure triggers and will assess a person’s likelihood of another seizure.

If there is a risk of recurrent seizures, the doctor might decide if an individual would benefit from medication.

During the physical examination, they will look for signs that may indicate a condition that causes seizures, such as a stroke, brain infection, or other chronic syndromes, including neurofibromatosis or tuberous sclerosis.

Healthcare professionals may also order blood tests, imaging scans, and spinal taps. There are also options for neuroimaging, such as MRI scans.

Finally, they may recommend electroencephalography (EEG), a procedure that monitors brain activity.

Doctors prescribe medications to treat focal seizures and help prevent future occurrences. When possible, they will try to treat the underlying cause.

Medications

Doctors prescribe antiepileptic medications to prevent seizures.

Several options are available for focal seizures, including:

  • lamotrigine (Lamictal)
  • levetiracetam (Keppra)
  • topiramate (Topamax)
  • valproate (Depakote)
  • zonisamide (Zonegran)
  • carbamazepine (Tegretol)
  • oxcarbazepine (Oxtellar XR)
  • phenytoin (Dilantin, Phenytek)
  • lacosamide (Vimpat)

Ketogenic diet

Following a ketogenic diet that limits carbs and focuses on high fat and certain proteins may help reduce focal seizures in some people with their epilepsy.

A doctor may recommend this treatment if at least two epilepsy medications have been ineffective. This dietary therapy is mainly suggested for treating children, but healthcare professionals may recommend it for some adults.

Surgery

When other treatments are not providing beneficial outcomes, a person may need a surgical procedure to separate or remove the part of the brain causing the seizures.

An individual can discuss these options with a doctor. This surgery is not suitable for pregnant people.

Vagus nerve stimulation

If a person finds medications are ineffective and they are not a surgical candidate, another therapy for epilepsy is vagus nerve stimulation (VGS).

In this procedure, a neurosurgeon implants an electric stimulator to the left vagus nerve in the neck, which can help reduce electrical activity in the brain. In turn, this can reduce the intensity and severity of a person’s seizures.

This surgery is only suitable for people with focal seizures that begin in certain areas of the brain. A doctor will do extensive preoperative testing to determine if it could be effective.

However, this treatment can take as long as 2 years to be effective, so a person will continue to take antiepileptic drugs if they still have seizures or EEG abnormalities during this time.

While it is not always possible to prevent focal seizures, a person can reduce their occurrence if there is an identifiable cause or trigger. In this case, individuals can treat the underlying disease or do their best to avoid the trigger.

Alcohol consumption, severe sleep deprivation, and high or low blood sugar are regular triggers for seizures in the majority of people with epilepsy. Some people may have more specific triggers, such as flashing lights.

The outlook for someone who has had a focal seizure depends on its underlying cause. However, effective treatments are available to help sustain a person’s quality of life.

Additionally, getting sufficient sleep, eating a nutritious diet, and taking medication under a doctor’s guidance can benefit those who experience seizures. It is also crucial to avoid alcohol and activities that may cause head trauma.

Here are some frequently asked questions and answers on focal seizures.

How common are focal seizures?

Focal seizures are the most common type of seizure that affects both adults and children. Approximately 36% of people who experience seizures have a subtype of focal seizures called complex focal seizures that involve impaired consciousness.

What are continuous focal seizures?

It is possible to have continuous focal seizures. If a person with epilepsy experiences a focal seizure for 5 minutes or more or a series of seizures with short breaks in between, they are experiencing a continuous focal seizure. Another way to experience continuous focal seizures is by having a rare condition called epilepsia partialis continua.

How do focal seizures in children differ from those in adults?

When epilepsy is the cause, children may experience additional symptoms to adults, including cognitive dysfunction, behavioral issues, hyperactivity, and even psychosis. As with adults, the specific symptoms will depend on the location of the seizure in the brain.

Focal seizures, or partial seizures, occur when there is a disruption of electrical impulses that begin in one part of the brain.

A person may be aware they are having a seizure — health experts call this a simple focal seizure. In contrast, those who may be unaware of the seizure are often experiencing a complex focal seizure.

Some focal seizures occur after a person encounters a trigger, but some may happen without a known cause. Treatment often involves antiepileptic medication, dietary changes, vagus nerve stimulation, or surgery. The outlook depends on the underlying cause of the seizure.