FOCAL ONSET SEIZURES
Focal seizures are classified depending on whether the persons awareness is changed and if there is any movement. Some focal seizures are very subtle and easy to miss.
Focal aware seizures – The person is awake and aware of what is happening
If a seizure does not impair consciousness and the person has full awareness of what is going on around them during the seizure it is called a focal aware seizure.
People often call these seizures their “aura” but they are actually a seizure – which may or may not lead on to a more significant seizure. For instance, the seizure may spread to become a focal impaired awareness seizure or progress into a bilateral tonic clonic seizure.
Examples of focal aware seizures include:
- Focal motor seizures – movements, such as jerking, posturing or stiffening of arm/s or leg/s, twitching of face
- Focal sensory seizures –sensations, such as numbness, tingling or burning feeling in a part of the body
- Focal autonomic seizures – involuntary body changes, such as blushing, looking pale or grey, increased heart rate, butterflies in the stomach, nausea, and perspiring
- Focal cognitive seizures – difficulties with speech or thinking, or features such as déjà vu, hallucinations (visual, smell, taste or hearing), illusions or perceptual distortions
- Focal emotional seizures – feeling emotions such as joy, sadness, anxiety, fear or panic.
Focal seizures – impaired awareness
Some focal seizures cause a change in awareness, consciousness, and behaviour. These are called focal impaired awareness seizures.
These focal seizures vary greatly from person to person, depending on where they start and spread within the brain. They are frequently not recognised as seizures by onlookers. Many of these seizures show features such as:
- A vacant stare, loss of expression or a vague, confused appearance
- Altered or impaired consciousness or awareness and the person may or may not respond
- If they do respond, it is usually inappropriate to the situation
- Sometimes people have unusual and repetitive behaviour such as chewing, fidgeting, walking around, mumbling or vocalising
- The seizure can range from 30 seconds to 3 minutes
- After the seizure, the person is often confused for a short time, and may not remember anything that happened before or during the event.
- Tiredness is common after the seizure.
Both focal aware and focal impaired awareness seizures can simply be called focal seizures.
GENERALISED ONSET SEIZURES
Tonic clonic seizures
This is the most recognised seizure type.
A tonic clonic seizure is a seizure that has a tonic (muscle stiffening) followed by clonic (muscle jerking) phase. Tonic clonic seizures can be frightening to witness. There are slight variations, but a typical tonic clonic seizure will look like:
- A sudden loss of consciousness, sometimes with vocalisation or calling out
- The eyes, head and body may turn in one direction
- The body becomes stiff (tonic), followed by jerking of the muscles (clonic)
- If standing, the person will fall
- Breathing may be shallow or briefly stopped which may cause the lips and face to look greyish/blue
- The person will not respond when spoken to
- Excess saliva may come of the person’s mouth, and there may also be blood if they have bitten their tongue or the inside of their cheek
- There may be loss of bladder or bowel control so the person may wet or soil themselves
- The seizure usually lasts less than 2 minutes
- Immediately after the seizure breathing can be quite laboured and sound like heaving snoring (usually less than a minute)
- After the seizure there is usually a period of confusion, headache, soreness and the person usually needs to sleep it off.
Myoclonic seizures
A myoclonic seizure is a seizure where a single brief muscle jerk or series of single jerks happen. A person having a myoclonic seizure typically has a sudden jerk of the arms and upper body, which can vary in severity, but can cause them to spill or drop what they are holding, or fall off a chair. If severe enough, a myoclonic seizure can also cause a fall.
The seizures are often mistaken for clumsiness before diagnosis.
Note: Even people without epilepsy can experience sudden jerks upon falling asleep, but these are normal and not seizures.
Tonic seizures
A tonic seizure involves increased muscle tone (stiffening) of the body usually very brief, lasting a few seconds. If the person is standing they will suddenly fall stiffly to the ground. This is often termed a “drop attack”.
Tonic seizures often occur during sleep and in clusters of varying intensity of stiffening. The person is unaware during these events. At the beginning of tonic seizures with more intense stiffening, people may make an exhalation or loud sigh sound. With more severe and prolonged tonic seizures the person may look like they have a tremor or shaking.
Tonic seizures often occur in people with intellectual disability or more complex epilepsies.
Atonic seizures
An atonic seizure is a type of seizure that involves the sudden loss of muscle tone. If standing, this can cause a “drop attack” where the person suddenly slumps to the ground. If sitting, a simple head nod (as if the person is trying to fight off sleep) may be seen. These seizures are very brief, less than 2 seconds and may involve the head, body or limbs.
Atonic seizures often occur in people with intellectual disability or more complex epilepsies.
Absence seizures
The most common absence seizure is the typical absence seizure. There are other less common types of absence seizures that are briefly discussed here.
A typical absence seizure starts and ends abruptly, is very brief with no awareness during the seizure. Absence seizures usually begin in childhood (but can occur in adolescents and adults) and are easily missed, or misinterpreted as daydreaming or inattentiveness.
Typically, they will look like:
- the seizure starts suddenly with the person stopping their activity
- you will see staring, loss of facial expression and unresponsiveness
- sometimes eye blinking or upward eye movements are seen
- the seizure can last from two to 20 seconds and ends abruptly
- the person usually recovers immediately and resumes their previous activity, with no memory of what happened during the seizure
These seizures can happen numerous times a day causing learning to be disrupted. They generally respond well to medication.
The below group are less common absence seizure types:
*Atypical absence seizures
The seizure does not start and end as suddenly as a typical absence, it can be more gradual. They are often seen with other features such as loss of muscle tone of the head, trunk or limbs (often seen as a gradual slump) and subtle jerking. The loss of awareness may be minor with the person continuing an activity, but more slowly or with mistakes.
These seizures often occur in people with intellectual disability and complex epilepsies.
*Myoclonic absence
Rhythmic myoclonic jerks of the shoulders and arms and lifting of the arms during the seizure can be seen. The myoclonic jerks are usually seen in both arms, but may be one-sided or not symmetrical. Puckering (jerking) of the lips, twitching of the corners of the mouth, or jaw jerking can also be seen. Sometimes rhythmic jerks of the head and legs may occur. Seizures last 10-60 seconds and typically occur daily. The level of awareness varies from complete loss of awareness to retained awareness.
*Absence with eyelid myoclonia
These are absence seizures accompanied by brief, often rhythmic, fast myoclonic jerks of the eyelids at the same time with an upward movement of the eyeballs and of the head. This can look like fluttering of the eyelids and simultaneous rolling back of the eyes. These seizures are typically very brief and occur many times a day. Mostly awareness is retained.
UNKNOWN ONSET SEIZURES
There are seizures that cannot be clearly diagnosed as focal or generalised, and may even be considered both. The “Unknown Onset” classification is used when a seizure is unable to be classified due to either:
- not enough information or
- an unusual nature of the seizure, or
- the inability to classify the seizure as either focal or generalised onset.
Unknown onset seizures are not truly separate types of seizures, but temporary labels for seizure types for which the onset is unknown. As more information becomes available over time or through further testing, the seizure type may be changed to a generalised or focal onset seizure.
For instance a person reports having a tonic clonic seizure, but the start of the seizure was not seen. Therefore it is uncertain if it was a focal or generalised onset.
Epileptic spasms are classified in unknown onset
Epileptic spasms (which include infantile spasms) are seen in infants and appear like:
- A sudden bending or lunging forward (flexion) of the upper body followed by stiffening
- Often the arms are flung out as the knees are pulled up and the body bends forward
- Less often, the head can be thrown back (extension) as the body and legs stiffen in a straight-out position
- Movements can be more subtle and limited to grimacing or head nodding
- These spasms are longer than a myoclonic jerk, but shorter than a tonic seizure.
Each seizure lasts only a second or two but they usually occur in clusters, several in a row.
What is a syndrome?
There are many different types of epilepsy classifications. Many people are now given a specific diagnosis or name for their epilepsy, rather than just told that ‘you have epilepsy’. Some types of epilepsy are further classified as syndromes and are defined based on a unique combination of symptoms.
An epilepsy syndrome is a type of epilepsy that depends upon:
- family history
- what age the seizures start
- seizure type(s)
- cause, and other linked diseases/conditions
- how the syndrome progresses over time
- presence or absence of brain abnormalities
- EEG findings
- brain scan findings (such as CT, MRI, PET)
- seizures response to medication.
A diagnosis of a particular epilepsy syndrome is useful in deciding the possible treatment options, what course the condition may take, and the possible genetic risk of passing it on to offspring.
Some types of epilepsy syndromes are:
- Childhood absence epilepsy (CAE)
- Self-limited epilepsy with centrotemporal spikes
- Dravet syndrome
- West syndrome (Infantile spasms)
- Doose syndrome (Myoclonic Astatic Epilepsy (MAE))
- Rasmussen’s syndrome
- Lennox-Gastaut syndrome (LGS)
- Landau-Kleffner syndrome (LKS)
- Sturge-Weber syndrome (SWS)
- Juvenile myoclonic epilepsy (JME).
and many more.
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