Epilepsy

Epilepsy (often referred to as a seizure disorder) is a chronic neurological condition characterized by recurrent unprovoked seizures. The condition is named from the Greek epilepsia ("a taking hold of or seizing"). It is commonly controlled with medication, although surgical methods are used as well.

Types of seizures

Epileptic seizures are classified both by their patterns of activity in the brain and their effects on behaviour.

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In terms of their pattern of activity, seizures may be described as either partial (focal) or generalised. Partial seizures only involve a localised part of the brain, whereas generalised seizures involve the entire cortex. The term 'secondary generalisation' may be used to describe a partial seizure that later spreads to the whole of the cortex and becomes generalised.

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Partial seizures may be further subdivided into both simple and complex seizures. This refers to the effect of such a seizure on consciousness; 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. Although "unconscious" is the word usually associated with complex partial seizures, it might be more appropriate to say that the person is "oblivious." A person having a complex partial seizure may be responsive, but they will have no awareness of it.

Related Topics:
Consciousness - Complex partial seizure

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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 muscles. 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 centred on the temporal lobes 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 anti-convulsants in this case can actually lower the seizure threshold further and worsen the symptoms.

Related Topics:
Motor cortex - Muscle - Temporal lobe - Mystical - Ecstatic - Psychosis - Schizophrenia - Anti-psychotic - Anti-convulsant

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In about half of cases of temporal lobe epilepsy, very strong ictal headacheshttp://www.epilepsy.com/articles/ar_1063754930.html may occur, often misdiagnosed as migraine with aura. However, these headaches may be much more intense, and are sometimes even accompanied by temporary blindness.

Related Topics:
Ictal headache - Migraine - Aura - Blindness

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When these effects appear as a 'warning sign' before a more serious seizure they are known as an aura and may be the result of a partial seizure which later becomes generalised. The subjective experience of an aura will tend to reflect the function of the affected part of the brain.

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Temporal lobe epilepsy may also increase glutamate-mediated neurotoxicity by damagaging GABAergic interneurons (basket cells).

Related Topics:
Glutamate - GABA - Interneuron - Basket cell

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Generalised seizures can be sub-classified into a number of categories, depending on their behavioural effects:

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• Absence seizures (sometimes referred to as petit mal seizures) 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.
• Tonic-clonic seizures (sometimes referred to as grand mal seizures), 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.
• Myoclonic seizures involve sporadic muscle contraction and can result in jerky movements of muscles or muscle groups.
• 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.
• Status epilepticus refers to continuous seizure activity with no recovery between successive tonic-clonic seizures. This 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 (hands 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.