Types of Seizures

As we have mentioned in the introductory section of this website, epilepsy is a seizure disorder. The characteristics and frequency of seizures vary greatly. Medical terminology has accordingly broadened in an effort to more precisely identify these different types of seizures. Some are observed predominantly in children, while other types mainly in adults.

Epilepsy is a very serious and often very scary disorder. It can cause great impact on the lives of the people with epilepsy well as those who live around them. One of the first steps to being able to control seizures is to recognise them. It is possible for a person with epilepsy to experience more than one type of seizure. Your physician/neurologist can help provide you with the necessary information.

The following is a brief overview to help you understand the basics of seizures. This is a supplementary guide and should not be a substitute for your own doctor’s advice and information. Links to more information on these and other types of seizures will be provided at the bottom of this page.

Special cells called neurons help to form an electrical and chemical network in the brain. Under normal conditions, electrical signals move along these neurons. They influence the release of different chemicals which further influence the electrical activity of subsequent neurons. Many external and internal influences can cause abnormal activities in the electrical signals of these neurons. A change in the regular brain electrical activity may result in a seizure. Repeated seizure events may be a sign of epilepsy. (Note: while all forms of epilepsy are characterised by some form of seizure disorder, not all seizure disorders are indicative of epilepsy.)

Classification

The modern system of seizure classification draws an essential distinction between partial and generalised seizures. If the excessive electrical discharge is restricted to a given (localised) area in the brain, the seizure is termed partial. If the entire brain is involved, the seizure is generalised.

Before we begin with the different types of seizures, we should first understand a few terms. There are many different causes of epileptic seizures. These causes are often termed idiopathic, cryptogenic, and symptomatic.
Idiopathic means that that there is no identifiable cause for the onset of the seizures.
Cryptogenic refers to an unknown cause, however the doctors believe it may be related to some unidentifiable abnormality in a brain structure.
Symptomatic means that there is a known cause for the seizures and this may be related to damage to brain structures, metabolic disorders, or other known causes.

Knowing this, we can now proceed to the next section describing seizures. Medical terminology has identified many types of seizures. The following are the most common:

Theses are often characterised by abnormal electrical activity that is found localised in one area of the brain. The result may be involuntary movement or unusual sensations (sensory neurons), and attention and behavioural changes.

Simple partial seizures (SPS - formerly known as focal seizures):
These seizures are characterised by strange or unusual sensations, for example odours or visual abnormalities. Other characteristics of SPS include sudden or restless movement, hearing distortion, stomach discomfort, and a sudden sense of fear. Alteration of consciousness or memory is generally not associated with simple partial seizures.

As mentioned before, partial seizures are localised to one region of the brain. Each region of the brain is responsible for certain body functions, sensations, and movements. By observing the motor manifestations and sensory responses during SPS, the neurologist may be able to determine the brain region affected. This may help determining which drugs are best for the treatment of each individual’s epilepsy.

The ICES has categorised simple partial seizures into 4 main categories, motor, sensory, psychic, and autonomic – each category has several types of SPS.

Complex partial seizures (CPS - formerly psychomotor or temporal lobe seizures):
Complex partial seizures are often preceded by an “aura.” They are often identified by the manifestation of complicated motor and sensory action. The person can appear dazed and confused – random walking, mumbling, head turning, or pulling at clothing may be observed. These repeated idiosyncratic motions are often called automatisms and are usually not recalled by the person. There may be some change in consciousness or memory.

In children, this seizure should not be confused with the absence seizures described below. CPS often originate in the temporal or frontal lobes of the brain.

May or may not be convulsive; usually involves a loss of consciousness. There is evidence of abnormal electrical activity in many areas of the brain.

1. Primary generalised seizures
2. Secondary generalised seizures

Generalised absence seizures (formerly petit mal):
Characterised by a complete loss of awareness. The person may stare into space and appear to be daydreaming or of in a daze. Absence seizures are not preceded by a warning (aura) and are followed by normal activity by the individual. There is very minimal movement during the actual seizure so may times it may go unnoticed by others.

These seizures often occur in children. They may, however, develop into other types of seizures, such as complex-partial or tonic-clonic. (Absence seizures may be difficult to distinguish from Complex-partial seizures. Absence seizures are usually more quick in duration and have less recovery time than CPS.)

Absence seizures usually diminish into adulthood. (Opposite of tonic-clonic/grand mal seizures)

1. Typical Absence Seizures: They are non-convulsive and muscle tone is usually preserved. The seizure event usually lasts for less than 10 seconds in duration.
2. Atypical Absence Seizures: They are longer in duration than typical absence seizures. There may or may not be a loss in muscle tone and often tonic/clonic-like movements are observed.

Tonic-clonic seizures (formerly grand mal):
A generalised convulsion occurring in two phases. In the tonic phase, there is stiffening of the muscles, the person loses consciousness and falls, as the body grows rigid. In the clonic phase, body extremities jerk and twitch. The seizure event may often be ended by another tonic phase. After the seizure, consciousness returns slowly. When the person wakes up, they are often confused or disoriented.

This seizure, while perhaps the type of epilepsy most visible in the public mind, is not the most common. Approximately two-thirds of people with epilepsy have complex partial seizures.

A secondary generalised tonic-clonic seizure begins locally (with partial seizure) and it may be preceded by an aura.

Describes a state of recurring seizures between which consciousness does not return in between the seizure events. If a seizure does not stop within 5-10 minutes, call for help. The individual may be in danger of going into status epilepticus. This is a potentially life-threatening event. For any seizure event that appears to be different than those normal for the individual or lasts abnormally long help should be called. This demands immediate medical care, as it can lead to severe brain damage and even loss of life.

To return the person back to normal, benzodiazepines such as diazepam or lorazepam (see drugs section) may be administered by the hospital.

There are many potential triggers for status epilepticus and in many cases, there is no apparent trigger. Potential triggers should be discussed with your physician as these will vary from person to person.

Myoclonic Seizure:
There is no loss of consciousness during this type of seizure. It is often associated with single or repetitive jerking motions of the muscles (myoclonus). Myoclonic seizures are primarily observed in young children and infants. They are more rare in adults.

Atonic Seizure:
Often called drop attacks/seizures. These seizures are characterised by sudden loss of muscle tone, resulting in an inability to sit or stand. (Also known as akinetic seizures). Atonic seizures are usually rare in adults.

They are often identified in children with Lennox-Gastaut Syndrome (link to Lennox-Gastaut section). While the actual seizures cause little injury to the child, most resulting harmful injuries after the event are usually related to the child falling or injuring his/herself when they lost muscle tone. To help prevent more serious injuries, some parents may choose to have their child wear a protective helmet as well as restrict their involvement in certain activities if they are prone to atonic seizures.

Note: Astatic seizures involve loss of muscle tone resulting in the inability to stand. Atonic seizures are not always astatic in nature.

Photosensitive seizures:
Often, you may notice warnings on electronic devices, lighting equipment (such as strobe lights), or video games. They may having warnings that the product may induce photosensitive epileptic seizures.

Photosensitive seizures are rare, even for people with epilepsy (less than 5%). These are not a distinct type of seizure, rather the result of a light-related stimulus that may induce the triggering of a seizure. Photosensitive seizures are often classified under the heading of “reflex epilepsy.”

They usually occur around the ages 8-20 with a higher frequency of cases during puberty. They may be triggered by both natural and artificial light – oscillating or moving patterns.

To avoid unnecessary risks, it is advised for children and adults with photosensitive seizures to sit more than 2m away from the television. This is due to the frequency of the refresh rate of the television monitor. While the incidence of television-induced photosensitive seizures is lower in North America than in Europe (due to the differences in refresh rates), people with epilepsy should still remain cautious. Computer monitors present very little risk for inducing photosensitive seizures. There are two types of monitors, CRT (cathode-ray tube) and LCD (liquid crystal display). Most CRT monitors have refresh frequencies greater than 70Hz (70 flashes/second). LCD monitors do not have full-screen refreshing and may be better in some instance for photosensitive people. However, since most people use newer model monitors, the problem of inducing photosensitive seizures is more related to software than the monitors themselves. Computer games and other programs with flashing lights and varying patterns may trigger a seizure.

Infantile Spasms/West’s Syndrome:
These are found in some epileptic infants less than a year old. The spasms may occur as single events or in clusters – each spasm lasting a very brief (1-3 seconds). The infant often has an appearance of nodding – as if they are flexing and extending back and forth at the head or waist (often call salaam convulsions/attacks). Infantile spasms occur when the infant is sleeping, drowsy, or upon wakening. The infant may give a cry out loud after the spasm which may often be mistaken for colic.

There are two groups of infantile spasms: cryptogenic (no known cause) and symptomatic (known cause).. For the cases of symptomatic infantile spasms, there are many different causes.

Infantile spasms are often observed in children with West’s Syndrome. Note: although Infantile spasms and West’s syndrome are often used interchangeably, not all infantile spasms are related to West’s syndrome. West’s syndrome was first described in 1841 by an English physician who observed symptoms of infantile spasms in his own son. This is related to a more specific type of infantile spasms.

Lennox-Gastaut Syndrome:
Lennox-Gastaut Syndrome affects children between the ages of 1 to 8, with predominance in male children. It is characterised by frequent, often violent seizures. Some of the seizure types associated with this syndrome are: tonic, atonic, atypical absence, myoclonic, and status epilepticus. Status epilepticus has been observed in approximately 50% of children with Lennox-Gastaut.

Like West’s Syndrome, Lennox-Gastaut Syndrome is divided into two types, cryptogenic and symptomatic. Cryptogenic cases (around 30%) usually appear to have no brain defect. Symptomatic cases make up the remaining 70% in which there appears to be some underlying brain damage.

The causes of this syndrome are varied. Possible causes include brain injury or malformation, brain infection, genetics, and many other unknown influences (especially in cryptogenic cases). Many children with Lennox-Gastaut experience developmental delay as well as many behavioural problems as a result.

To date, there is no known cure for Lennox-Gastaut Syndrome. These children are often found to have a higher frequency of drug resistance than unaffected epileptic children. They are often placed on a polytherapy of drugs. The Ketogenic Diet is often recommended for children with Lennox-Gastaut Syndrome as a way to control their epileptic seizures in addition to the prescribed medication.

Other Epilepsy Syndromes:

Febrile Spasms

Juvenile Myoclonic Epilepsy (JME)

Benign Rolandic Epilepsy (BRE)

There are many more types of seizures (epileptic and non-epileptic) than are listed above. We have described the most common types.

The International League Against Epilepsy (ILAE) was formed in 1909. Their goal is:

• To advance and disseminate knowledge about epilepsy
• To promote research, education and training
• To improve services and care for patients, especially by prevention, diagnosis and treatment.

For additional information: you can read through Epilepsy Canada’s brochure on Seizures and First Aid