Epilepsy Awareness Program - Types of Seizures
AS there are many different types of epilepsy, there are many different types of seizures, which fall into two major categories: Partial seizures which take place in one particular part of the brain and Generalized seizures which affect the whole brain.
There are many different types of seizures. People may experience just one type or more than one. The kind of seizure a person has depends on which part and how much of the brain is affected by the electrical disturbance that produces seizures.
Seizures take many forms. Before your doctor can prescribe the right treatment, he or she must figure out which type (or types) you have.
Based on the type of behavior and brain activity, seizures are divided into two broad categories: generalized and partial (also called local or focal). Classifying the type of seizure helps doctors diagnose whether or not a patient has epilepsy.
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.
International classification of seizure types (1981):
Partial seizures (Focal seizures): Partial seizures may be divided into simple and complex seizures. This refers to the effect of such a seizure on consciousness; simple seizures cause no interruption to consciousness, whereas complex seizures interrupt consciousness to varying degrees.
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
Partial seizures may be classified into the following:-
** Simple partial seizures - consciousness is not impaired
1 With motor signs
2 With sensory symptoms
3 With autonomic symptoms or signs
4 With psychic symptoms
** Complex partial seizures - consciousness is impaired (temporal lobe or psychomotor seizures)
1 Simple partial onset, followed by impairment of consciousness
2 With impairment of consciousness at onset
** 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
Generalized seizures: Primarily generalized seizures can be sub-classified into a number of categories, depending on their behavioural effects:-
** Absence seizures (Petit mal): 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. It is classified as:
1 Typical absence seizures
2 Atypical absence seizures
** 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
** Tonic seizures:
** Tonic–clonic seizures (Grand mal): involve an initial contraction of the muscles (tonic phase) which may involve tongue biting, urinary incontinence 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 seizures: 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 narcolepsy or cataplexy.
Unclassified epileptic seizures
(End of international 1981 classification)
Other Types of Seizure
Mixed seizures: Mixed seizure is defined as the existence of both generalized and partial seizures in the same patient.
Continuous seizures: Status epilepticus 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 non-epileptic seizure, or non-epileptic event, is a seizure that isn't caused by epilepsy but looks the same. These may be caused by a change or difference in electrical activity in the brain, but not an electrical disruption of the type that triggers an epileptic seizure. There are two types of non-epileptic seizures, called psychogenic and physiologic. A psychogenic non-epileptic seizure can be brought on by some sort of emotional stressor or trauma. It's a legitimate seizure and should be treated that way, but it is not caused by a problem in the brain.
A physiologic non-epileptic seizure can be triggered by some sort of change in the brain — typically a change in the supply of blood or oxygen rather than electrical activity. Some possible causes of physiologic non-epileptic seizures include: Rapid drop in blood pressure, Low blood sugar levels and Irregular heartbeat.Can be classified as:
• First-time seizures: It is the first seizure a person has, The underlying cause may be determined to be epilepsy, but often the cause can't be determined. These isolated seizures are not rare events. A first seizure typically occurs before age 25, with most taking place in those younger than 15. First seizures seem to strike males a little more often than females, and they may not have a specific or detectable cause. A first seizure can affect part of or the entire brain.
• Febrile seizures: These seizures are caused by high fevers, and occur most commonly in infants and young children. Febrile seizures are quite common, affecting 1 in 25 children. While frightening, these seizures don't cause brain damage or otherwise harm children. During the seizure, the child may be unconscious, shake, and convulse. Febrile seizures can last longer than 15 minutes or less than a few seconds, but most commonly last one to two minutes.Febrile seizures typically strike when a child is between 6 months and 5 years old, but they most often occur during the toddler years. These types of seizures may recur during childhood but are usually outgrown.
• Pseudoseizures: or Psychogenic nonepileptic seizures (PNES) are paroxysmal episodes that resemble and often misdiagnosed as epileptic seizures; however, PNES are psychological (ie, emotional, stress-related) in origin. Paroxysmal nonepileptic episodes can be either organic or psychogenic. Syncope, migraine, and transient ischemic attacks (TIAs) are examples of organic nonepileptic paroxysmal symptoms.
• Eclampsia: These seizures occur in pregnant women and are not caused by epilepsy or other brain disorders. The cause of eclampsia is not known, but it often follows the pregnancy condition called preeclampsia, in which the woman’s blood pressure gets abnormally high. Eclampsia occurs in about 1 out of every 2,000 to 3,000 expectant women. The seizures cause convulsions or changes in personality such as agitation.
Some people with epilepsy can detect when a seizure is approaching. This sensation has been called an “aura,” and can be for example as: feeling of pins and needles or a strange taste or smell.
Seizures can be triggered by many factors, including:
•Missing a dose of medication
•Taking illicit drugs
•Increased stress level
•Overheating or overexertion (hyperthermia)
See Also: Neurophysiology Health Corner
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