Seizure types
Encyclopedia
The numerous epileptic seizure
types are most commonly defined and grouped according to the scheme proposed by the International League Against Epilepsy (ILAE) in 1981. Distinguishing between seizure types is important since different types of seizure may have different causes, prognosis and treatments.
) rather than the underlying pathophysiology
or anatomy
.
In terms of their origin within the brain, seizures may be described as either partial (focal) or generalized. Partial seizures only involve a localized part of the brain, whereas generalized seizures involve the whole of both hemispheres. The term 'secondary generalisation' may be used to describe a partial seizure that later spreads to the whole of the cortex and becomes generalized.
Whilst most seizures can be neatly split into partial and generalized, there exists some that don't fit. For example: the seizure may be generalized only within one hemisphere. Alternatively there may be many focal points (multifocal seizures) that are distributed in a symmetrical or asymmetrical pattern.
; simple seizures cause no interruption to consciousness (although they may cause sensory distortions or other sensations), whereas complex seizures interrupt consciousness to varying degrees. This does not necessarily mean that the person experiencing this sort of seizure will fall unconscious (like fainting). For example, a complex partial seizure
may involve the unconscious repetition of simple actions, gestures or verbal utterances, or simply a blank stare and apparent unawareness of the occurrence of the seizure, followed by no memory of the seizure. Other patients may report a feeling of tunnel vision or dissociation, which represents a diminishment of awareness without full loss of consciousness. Still other patients can perform complicated actions, such as travel or shopping, while in the midst of a complex partial seizure.
The effects of partial seizures can be quite dependent on the area of the brain in which they are active. For example, a partial seizure in areas involved in perception may cause a particular sensory experience (for example, the perception of a scent, music or flashes of light) whereas, when centred in the motor cortex
, a partial seizure might cause movement in particular groups of muscle
s. This type of seizure may also produce particular thoughts or internal visual images or even experiences which may be distinct but not easily described. Seizures centered on the temporal lobe
s are known to produce mystical
or ecstatic
experiences in some people. These may result in a misdiagnosis of psychosis
or even schizophrenia
, if other symptoms of seizure are disregarded and other tests are not performed. Unfortunately for those with epilepsy, anti-psychotic medications prescribed without anticonvulsant
s in this case can actually lower the seizure threshold further and worsen the symptoms.
When the effects of a partial seizure appear as a 'warning sign' before a larger seizure, they are known as an aura
: it is frequently the case that a partial seizure will spread to other parts of the brain and eventually become generalized, resulting in a tonic-clonic convulsion. The subjective experience of an aura, like other partial seizures, will tend to reflect the function of the affected part of the brain.
triggered e.g. by a mild fever.
refers to continuous seizure activity with no recovery between successive seizures. When the seizures are convulsive, it is a life-threatening condition and emergency medical assistance should be called immediately if this is suspected. A tonic-clonic seizure lasting longer than 5 minutes (or two minutes longer than a given person's usual seizures) is usually considered grounds for calling the emergency services.
Epilepsia partialis continua
is a rare type of focal motor seizure (hand
s and face
) which recurs every few seconds or minutes for extended periods (days or years). It is usually due to strokes in adults and focal cortical inflammatory processes in children (Rasmussen's encephalitis
), possibly caused by chronic viral infections or autoimmune processes.
Proposed changes to terminology include:
The hierarchy presented has the structure:
for the ILAE and published in 1970. A significant difference was the distinction between simple and complex partial seizures. In the 1970 classification, the distinction was whether the symptoms involved elementary sensory or motor functions (simple) or whether "higher functions" were involved (complex).
This was changed to consider whether consciousness was fully retained or not. As a result, studies that group patients according to these classifications are not directly comparable from one generation to another. The 1970 classification was important for standardising the modern terms for many seizure types. Prior to this, terms such as petit mal, grand mal, Jacksonian, psychomotor and temporal-lobe seizures were used.
The earliest classification of seizures can be attributed to Babylonian scholars who inscribed their medical knowledge into stone tablets known as the Sakikku (meaning All Diseases). This dates from the reign of the Babylon
ian king Adad-apla-iddina of the Second Dynasty of Isin - estimated to be between 1067 and 1046 BC. Many types of seizures are described, each attributed to a certain demon
or departed spirit
and given a prognosis.
Seizure
An epileptic seizure, occasionally referred to as a fit, is defined as a transient symptom of "abnormal excessive or synchronous neuronal activity in the brain". The outward effect can be as dramatic as a wild thrashing movement or as mild as a brief loss of awareness...
types are most commonly defined and grouped according to the scheme proposed by the International League Against Epilepsy (ILAE) in 1981. Distinguishing between seizure types is important since different types of seizure may have different causes, prognosis and treatments.
International classification of seizure types (1981)
This classification is based on observation (clinical and EEGEEG
EEG commonly refers to electroencephalography, a measurement of the electrical activity of the brain.EEG may also refer to:* Emperor Entertainment Group, a Hong Kong-based entertainment company...
) rather than the underlying pathophysiology
Pathophysiology
Pathophysiology is the study of the changes of normal mechanical, physical, and biochemical functions, either caused by a disease, or resulting from an abnormal syndrome...
or anatomy
Anatomy
Anatomy is a branch of biology and medicine that is the consideration of the structure of living things. It is a general term that includes human anatomy, animal anatomy , and plant anatomy...
.
- I Partial seizuresFocal seizuresPartial seizures are seizures which affect only a part of the brain at onset. The brain is divided into two hemispheres, each consisting of four lobes - the frontal, temporal, parietal and occipital lobes...
(Older term: focal seizures)- A Simple partial seizureSimple partial seizureSimple partial seizures are seizures which affect only a small region of the brain, often the temporal lobes and/or hippocampi. People who have simple partial seizures retain consciousness...
s - consciousness is not impaired- 1 With motor signs
- 2 With sensory symptoms
- 3 With autonomic symptoms or signs
- 4 With psychic symptoms
- B Complex partial seizureComplex partial seizureA complex partial seizure is an epileptic seizure that is associated with bilateral cerebral hemisphere involvement and causes impairment of awareness or responsiveness, i.e. loss of consciousness.-Presentation:...
s - consciousness is impaired (Older terms: temporal lobe or psychomotor seizures)- 1 Simple partial onset, followed by impairment of consciousness
- 2 With impairment of consciousness at onset
- C Partial seizures evolving to secondarily generalized seizures
- 1 Simple partial seizures evolving to generalized seizures
- 2 Complex partial seizures evolving to generalized seizures
- 3 Simple partial seizures evolving to complex partial seizures evolving to generalized seizures
- A Simple partial seizure
- II Generalized seizuresGeneralised epilepsyGeneralised epilepsy, also known as primary generalised epilepsy or idiopathic epilepsy, is a form of epilepsy characterised by generalised seizures with no apparent cause...
- A Absence seizureAbsence seizureAbsence seizures are one of several kinds of seizures. These seizures are sometimes referred to as petit mal seizures ....
s (Older term: petit mal)- 1 Typical absence seizures
- 2 Atypical absence seizures
- B Myoclonic seizures
- C Clonic seizures
- D Tonic seizures
- E Tonic–clonic seizures (Older term: grand mal)
- F Atonic seizureAtonic seizureAtonic seizures , are a type of seizure. They consist of a brief lapse in muscle tone that are caused by temporary alterations in brain function. The seizures are brief - usually less than fifteen seconds. They begin in childhood and may persist into adulthood...
s
- A Absence seizure
- III Unclassified epileptic seizures
In terms of their origin within the brain, seizures may be described as either partial (focal) or generalized. Partial seizures only involve a localized part of the brain, whereas generalized seizures involve the whole of both hemispheres. The term 'secondary generalisation' may be used to describe a partial seizure that later spreads to the whole of the cortex and becomes generalized.
Whilst most seizures can be neatly split into partial and generalized, there exists some that don't fit. For example: the seizure may be generalized only within one hemisphere. Alternatively there may be many focal points (multifocal seizures) that are distributed in a symmetrical or asymmetrical pattern.
Partial seizures
Partial seizures may be further subdivided into both simple and complex seizures. This refers to the effect of such a seizure on consciousnessConsciousness
Consciousness is a term that refers to the relationship between the mind and the world with which it interacts. It has been defined as: subjectivity, awareness, the ability to experience or to feel, wakefulness, having a sense of selfhood, and the executive control system of the mind...
; simple seizures cause no interruption to consciousness (although they may cause sensory distortions or other sensations), whereas complex seizures interrupt consciousness to varying degrees. This does not necessarily mean that the person experiencing this sort of seizure will fall unconscious (like fainting). For example, a complex partial seizure
Complex partial seizure
A complex partial seizure is an epileptic seizure that is associated with bilateral cerebral hemisphere involvement and causes impairment of awareness or responsiveness, i.e. loss of consciousness.-Presentation:...
may involve the unconscious repetition of simple actions, gestures or verbal utterances, or simply a blank stare and apparent unawareness of the occurrence of the seizure, followed by no memory of the seizure. Other patients may report a feeling of tunnel vision or dissociation, which represents a diminishment of awareness without full loss of consciousness. Still other patients can perform complicated actions, such as travel or shopping, while in the midst of a complex partial seizure.
The effects of partial seizures can be quite dependent on the area of the brain in which they are active. For example, a partial seizure in areas involved in perception may cause a particular sensory experience (for example, the perception of a scent, music or flashes of light) whereas, when centred in the motor cortex
Motor cortex
Motor cortex is a term that describes regions of the cerebral cortex involved in the planning, control, and execution of voluntary motor functions.-Anatomy of the motor cortex :The motor cortex can be divided into four main parts:...
, a partial seizure might cause movement in particular groups of muscle
Muscle
Muscle is a contractile tissue of animals and is derived from the mesodermal layer of embryonic germ cells. Muscle cells contain contractile filaments that move past each other and change the size of the cell. They are classified as skeletal, cardiac, or smooth muscles. Their function is to...
s. This type of seizure may also produce particular thoughts or internal visual images or even experiences which may be distinct but not easily described. Seizures centered on the temporal lobe
Temporal lobe
The temporal lobe is a region of the cerebral cortex that is located beneath the Sylvian fissure on both cerebral hemispheres of the mammalian brain....
s are known to produce mystical
Mysticism
Mysticism is the knowledge of, and especially the personal experience of, states of consciousness, i.e. levels of being, beyond normal human perception, including experience and even communion with a supreme being.-Classical origins:...
or ecstatic
Religious ecstasy
Religious ecstasy is an altered state of consciousness characterized by greatly reduced external awareness and expanded interior mental and spiritual awareness which is frequently accompanied by visions and emotional/intuitive euphoria...
experiences in some people. These may result in a misdiagnosis of psychosis
Psychosis
Psychosis means abnormal condition of the mind, and is a generic psychiatric term for a mental state often described as involving a "loss of contact with reality"...
or even schizophrenia
Schizophrenia
Schizophrenia is a mental disorder characterized by a disintegration of thought processes and of emotional responsiveness. It most commonly manifests itself as auditory hallucinations, paranoid or bizarre delusions, or disorganized speech and thinking, and it is accompanied by significant social...
, if other symptoms of seizure are disregarded and other tests are not performed. Unfortunately for those with epilepsy, anti-psychotic medications prescribed without anticonvulsant
Anticonvulsant
The anticonvulsants are a diverse group of pharmaceuticals used in the treatment of epileptic seizures. Anticonvulsants are also increasingly being used in the treatment of bipolar disorder, since many seem to act as mood stabilizers, and in the treatment of neuropathic pain. The goal of an...
s in this case can actually lower the seizure threshold further and worsen the symptoms.
When the effects of a partial seizure appear as a 'warning sign' before a larger seizure, they are known as an aura
Aura (symptom)
An aura is a perceptual disturbance experienced by some migraine sufferers before a migraine headache, and the telltale sensation experienced by some people with epilepsy before a seizure. It often manifests as the perception of a strange light, an unpleasant smell or confusing thoughts or...
: it is frequently the case that a partial seizure will spread to other parts of the brain and eventually become generalized, resulting in a tonic-clonic convulsion. The subjective experience of an aura, like other partial seizures, will tend to reflect the function of the affected part of the brain.
Generalized seizures
Primarily generalized seizures can be sub-classified into a number of categories, depending on their behavioural effects:- Absence seizureAbsence seizureAbsence seizures are one of several kinds of seizures. These seizures are sometimes referred to as petit mal seizures ....
s involve an interruption to consciousness where the person experiencing the seizure seems to become vacant and unresponsive for a short period of time (usually up to 30 seconds). Slight muscle twitching may occur. - Myoclonic seizures involve an extremely brief (< 0.1 second) muscle contraction and can result in jerky movements of muscles or muscle groups.
- Clonic seizures are myoclonus that are regularly repeating at a rate typically of 2-3 per second. in some cases, the length varies.
- Tonic–clonic seizures involve an initial contraction of the muscleMuscleMuscle is a contractile tissue of animals and is derived from the mesodermal layer of embryonic germ cells. Muscle cells contain contractile filaments that move past each other and change the size of the cell. They are classified as skeletal, cardiac, or smooth muscles. Their function is to...
s (tonic phase) which may involve tongueTongueThe tongue is a muscular hydrostat on the floors of the mouths of most vertebrates which manipulates food for mastication. It is the primary organ of taste , as much of the upper surface of the tongue is covered in papillae and taste buds. It is sensitive and kept moist by saliva, and is richly...
biting, urinary incontinenceUrinary incontinenceUrinary incontinence is any involuntary leakage of urine. It is a common and distressing problem, which may have a profound impact on quality of life. Urinary incontinence almost always results from an underlying treatable medical condition but is under-reported to medical practitioners...
and the absence of breathing. This is followed by rhythmic muscle contractions (clonic phase). This type of seizure is usually what is referred to when the term 'epileptic fit' is used colloquially. - Atonic seizureAtonic seizureAtonic seizures , are a type of seizure. They consist of a brief lapse in muscle tone that are caused by temporary alterations in brain function. The seizures are brief - usually less than fifteen seconds. They begin in childhood and may persist into adulthood...
s involve the loss of muscle tone, causing the person to fall to the ground. These are sometimes called 'drop attacks' but should be distinguished from similar looking attacks that may occur in cataplexyCataplexyCataplexy is a sudden and transient episode of loss of muscle tone, often triggered by emotions. It is a rare disease , but affects roughly 70% of people who have narcolepsy...
.
Mixed seizures
Mixed seizure is defined as the existence of both generalized and partial seizures in the same patient. For example, someone who periodically has myoclonic seizures may have a tonic-clonic seizureTonic-clonic seizure
Tonic–clonic seizures are a type of generalized seizure that affects the entire brain...
triggered e.g. by a mild fever.
Continuous seizures
Status epilepticusStatus epilepticus
Status epilepticus is a life-threatening condition in which the brain is in a state of persistent seizure. Definitions vary, but traditionally it is defined as one continuous unremitting seizure lasting longer than 5 minutes, or recurrent seizures without regaining consciousness between seizures...
refers to continuous seizure activity with no recovery between successive seizures. When the seizures are convulsive, it is a life-threatening condition and emergency medical assistance should be called immediately if this is suspected. A tonic-clonic seizure lasting longer than 5 minutes (or two minutes longer than a given person's usual seizures) is usually considered grounds for calling the emergency services.
Epilepsia partialis continua
Epilepsia partialis continua
Epilepsia partialis continua is a rare type of brain disorder in which a patient experiences recurrent motor epileptic seizures that are focal , and recur every few seconds or minutes for extended periods .-Presentation:During these seizures, there is repetitive focal myoclonus or Jacksonian...
is a rare type of focal motor seizure (hand
Hand
A hand is a prehensile, multi-fingered extremity located at the end of an arm or forelimb of primates such as humans, chimpanzees, monkeys, and lemurs...
s and face
Face
The face is a central sense organ complex, for those animals that have one, normally on the ventral surface of the head, and can, depending on the definition in the human case, include the hair, forehead, eyebrow, eyelashes, eyes, nose, ears, cheeks, mouth, lips, philtrum, temple, teeth, skin, and...
) which recurs every few seconds or minutes for extended periods (days or years). It is usually due to strokes in adults and focal cortical inflammatory processes in children (Rasmussen's encephalitis
Rasmussen's encephalitis
Rasmussen's encephalitis, also known as chronic focal encephalitis , is a rare inflammatory neurological disorder, characterized by frequent and severe seizures, loss of motor skills and speech, hemiparesis , encephalitis , and dementia...
), possibly caused by chronic viral infections or autoimmune processes.
Future classifications
In 1997, the ILAE began work on revising the classification of seizures, epilepsies and epileptic syndromes. This revision remains in gestation and has not superseded the 1981 classification.Proposed changes to terminology include:
- Replace partial with the older term focal to describe seizures that originate in one part of the brain (though not necessarily a small or well defined area). The word partial was regarded as ambiguous.
- Drop the terms simple partial and complex partial - grouping based on the effect to consciousness is no longer regarded as useful.
- Replace cryptogenic with probably symptomatic.
The hierarchy presented has the structure:
- Self limiting seizure types
- Generalized seizures
- Tonic-clonic seizures (includes variations beginning with a clonic or myoclonic phase)
- Clonic seizures (with and without tonic features)
- Typical absence seizures
- Atypical absence seizures
- Myoclonic absence seizures
- Tonic seizures
- Spasms
- Myoclonic seizures
- Massive bilateral myoclonus
- Eyelid myoclonia (with and without absences)
- Myoclonic atonic seizures
- Negative myoclonus
- Atonic seizures
- Reflex seizures in generalized epilepsy syndromes
- Seizures of the posterior neocortex
- Neocortical temporal lobe seizures
- Focal seizures
- Focal sensory seizures
- Focal motor seizures
- Gelastic seizures
- Hemiclonic seizures
- Secondarily generalized seizures
- Reflex seizures in focal epilepsy syndromes
- Generalized seizures
- Continuous seizure types
- Generalized status epilepticus
- Generalized tonic-clonic status epilepticus
- Clonic status epilepticus
- Absence status epilepticus
- Tonic status epilepticus
- Myoclonic status epilepticus
- Focal status epilepticus
- Epilepsia partialis continua of Kojevnikov
- Aura continua
- Limbic status epilepticus (psychomotor status)
- Hemiconvulsive status with hemiparesis
- Generalized status epilepticus
Earlier classifications
The 1981 classification was a revision of the one devised by Henri GastautHenri Gastaut
Henri Gastaut was a French neurologist.Henri Gastaut was educated in neurology and neuroanatomy at the University of Marseille, graduating M.D. in 1945. In 1953 he became head of the neurobiological laboratories. He was appointed professor of anatomical pathology in 1954 and director of the...
for the ILAE and published in 1970. A significant difference was the distinction between simple and complex partial seizures. In the 1970 classification, the distinction was whether the symptoms involved elementary sensory or motor functions (simple) or whether "higher functions" were involved (complex).
This was changed to consider whether consciousness was fully retained or not. As a result, studies that group patients according to these classifications are not directly comparable from one generation to another. The 1970 classification was important for standardising the modern terms for many seizure types. Prior to this, terms such as petit mal, grand mal, Jacksonian, psychomotor and temporal-lobe seizures were used.
The earliest classification of seizures can be attributed to Babylonian scholars who inscribed their medical knowledge into stone tablets known as the Sakikku (meaning All Diseases). This dates from the reign of the Babylon
Babylon
Babylon was an Akkadian city-state of ancient Mesopotamia, the remains of which are found in present-day Al Hillah, Babil Province, Iraq, about 85 kilometers south of Baghdad...
ian king Adad-apla-iddina of the Second Dynasty of Isin - estimated to be between 1067 and 1046 BC. Many types of seizures are described, each attributed to a certain demon
Demon
call - 1347 531 7769 for more infoIn Ancient Near Eastern religions as well as in the Abrahamic traditions, including ancient and medieval Christian demonology, a demon is considered an "unclean spirit" which may cause demonic possession, to be addressed with an act of exorcism...
or departed spirit
Spirit
The English word spirit has many differing meanings and connotations, most of them relating to a non-corporeal substance contrasted with the material body.The spirit of a living thing usually refers to or explains its consciousness.The notions of a person's "spirit" and "soul" often also overlap,...
and given a prognosis.