This page covers focal onset seizures, which start in one part of the brain.
What happens during a focal onset seizure will depend on which part (lobe) of the brain is affected.
What are focal onset seizures?
When abnormal electrical activity occurs in one part of the brain – the focus of the activity – the result is a focal onset seizure.
This means that what happens during a focal onset seizure will depend on where in the brain it happens and which functions that part of the brain controls.
Focal onset seizures can cause:
- Motor symptoms – movement is affected
- Sensory symptoms – sensation is affected
Sometimes, in focal onset seizures, the child’s consciousness can be affected.
At other times, they can be fully aware throughout.
Focal onset seizures can spread and affect the whole brain, resulting in a generalised seizure known as a ‘focal to bilateral tonic-clonic seizure’.
Temporal lobe epilepsy
‘Lobe’ simply means ‘rounded or sticking-out area’. ‘Temporal’ comes from the Latin for time.
The temporal lobes control smell, auditory perception (what we hear), language, feelings, emotion and memory.
The temporal lobes sit behind the ears and are the second-largest lobes.
Temporal lobe epilepsy is the most common type of epilepsy to cause focal onset seizures, and can start at any age.
In temporal lobe epilepsy, the child may experience a sudden strange mix of feelings, emotions, or thoughts that they find difficult to describe.
These may include a feeling of déjà vu (the sense that things have happened before), butterflies in the stomach, nausea and odd smells or tastes.
These sensations may occur alone or may be a warning of further seizure activity that will affect their consciousness.
These complex seizures may cause unusual movements, such as lip-smacking, plucking at clothes, finger-fumbling, unusual speech or wandering off in a confused state.
They may also develop into tonic-clonic seizures and tend to be followed by confusion.
Frontal lobe epilepsy
Frontal lobe epilepsy is the second most common type of focal onset epilepsy after temporal lobe epilepsy.
The frontal lobes are a large area of the brain responsible for:
- Emotional behaviour
- Personality
- Planning
- Problem-solving
- Some high-level cognitive functions (mental processes involved in knowledge and reasoning)
- Control of movement
Frontal lobe seizures will vary depending on which part of the frontal lobes is affected.
When a frontal lobe seizure begins, there may be no symptoms until it spreads to other areas of the brain, or most of it, causing a tonic-clonic seizure.
They usually start suddenly and end just as quickly, and often occur in clusters.
They may produce weakness in certain muscles, including those used to speak.
They may also cause sudden movements in the limbs, such as the flinging out of an arm.
Frontal lobe seizures usually happen during sleep and can be quite dramatic as the child may turn their head, grimace, thrash around or make cycling movements with their legs.
Frontal lobe seizures can be misdiagnosed as nonepileptic seizures, sometimes called ‘dissociative seizures’, seen in non-epileptic attack disorder (NEAD).
NEAD seizures don’t have a physical cause and may be caused by overwhelming stress, causing the brain to shut down.
Find out more about non-epileptic seizures.
Find out more about helping with the assessment.
Parietal lobe epilepsy
The parietal lobes are located in the upper back area of the skull. They are responsible for:
- Interpreting information from our senses
- Spatial orientation – understanding where we are in relation to our environment and objects around us
- Artistic and musical appreciation
Parietal lobe seizures are rare. They usually cause strange sensations and are also known as ‘sensory seizures’.
These may include a tingling or warmth, often down one side of the body only.
Some people say their arms and legs feel bigger or smaller than usual, and areas of their body might go numb.
Parietal lobe epilepsy can be misdiagnosed because the symptoms can be unusual and even show a normal EEG result during a seizure.
Occipital lobe epilepsy
The occipital lobe is at the back of the brain. It’s responsible for processing visual information and recognising shapes and colours.
Occipital lobe seizures are less common than other focal onset seizures.
The seizures affect sight, with symptoms including:
- Seeing patterns
- Flashing lights or colours
- Images that appear to repeat before the eyes
- Eyes moving or jerking uncontrollably from side to side
- Eyelids fluttering
- Possibly some pain in the eyes
Partial blindness may also occur and severe headaches often occur during or after a seizure.
Occipital lobe epilepsy is often mistaken for migraines, because of the severe headaches and related symptoms affecting vision.
Occipital lobe epilepsy can also spread to the temporal or frontal lobes, also making it hard to recognise because the characteristics of the seizure change.
