Focal seizures are classified by whether awareness is retained or impaired (altered). If awareness is unknown, then they are simply classified as a focal seizure.
Focal seizures – retains awareness
Sometimes a focal seizure does not alter consciousness and the person is aware of what is going on around them during the seizure. These seizures are known as focal aware seizures.
People often refer to these seizures as 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 evolve 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 – include impaired language or thinking, or features such as déjà vu, hallucinations (visual, smell, taste or hearing), illusions or perceptual distortions
- Focal emotional seizures – characterised by feeling emotions such as joy, sadness, anxiety, fear or panic.
Focal seizures – impaired awareness
In some types of focal seizures, the person has a change in awareness, consciousness, and behaviour. These are called focal impaired awareness seizures. They can also be called focal seizures.
These focal seizures vary greatly, depending on where they start and spread within the brain and are frequently not recognised as seizures by onlookers. Many of these seizures begin with:
- A vacant stare, loss of expression or a vague, confused appearance
- Consciousness or awareness is altered 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 or mumbling
- 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.
Tonic clonic seizures
A tonic clonic seizure is a seizure that has a tonic (muscle stiffening) and a clonic (muscle jerking) phase, typically in this order, but variations such as clonic-tonic-clonic can also be seen. Tonic clonic seizures are the most recognised seizure type and 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 2 minutes or less
- 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 sleep.
A myoclonic seizure is a seizure where a single jerk or series of single jerks (very brief muscle jerks) occur. They frequently affect the upper body, neck shoulders and arms. A person having a myoclonic seizure usually has sudden jerks on both sides of the body at the same time. They vary in severity but can cause someone 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 myoclonus or sudden jerks just as you are falling asleep. These are normal and not seizures.
A tonic seizure involves increased muscle tone 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” (astatic seizure).
Tonic seizures often occur during sleep and in clusters of varying intensity of tonic 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 impairment or more complex epilepsies.
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 impairment or more complex epilepsies.
*Clonic seizures (less common)
A clonic seizure is a seizure involving bilateral rhythmic jerking and may occur alone or in combination with tonic (increased muscle tone) activity typically lasting a few seconds up to a minute. The jerking in a clonic seizure is more sustained and rhythmic than seen in a myoclonic seizure.
During a clonic seizure you will see:
- The person’s muscles begin to spasm and jerk
- With a generalised clonic seizure, the elbows, legs, and head will flex, and then relax – rapidly at first, but the rate of the jerks will gradually subside until they stop altogether
- With a focal clonic seizure, the jerking will be isolated to one area of the body
- As the jerking stops, it is common for the person to let out a deep sigh, then normal breathing resumes.
The most common absence seizure is the typical absence seizure. There are other less common types of absence seizures that are briefly discussed here.
An absence seizure starts and ends abruptly, is very brief with altered 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, it 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. These seizures often occur in people with intellectual impairment and complex epilepsies.
The loss of awareness may be minor with the person continuing an activity, but more slowly or with mistakes.
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.
This is a relatively new classification.
Seizures are broadly categorised as either generalised or focal, but 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.