29 September 2010

What are the different kinds of seizures

About 2.5 million people in North America have active epilepsy, leaving them susceptible to seizures. However, not all epileptic seizures are the same. They can range in intensity from non-serious to seriously life-threatening.

During a seizure, a person may lose a certain degree of consciousness, called impaired consciousness, and may also experience an episode of intense, widespread motor activity called a convulsion. A convulsion can occur without loss of consciousness, but not normally.

A seizure happens when the way the brain functions is somehow abnormal causing the impaired consciousness or convulsions. When they happen at the same time, you'd call them a convulsive or sensory seizure.

Epilepsy is diagnosed when brain disfunction is disturbed for a relative while or if someone is particularly prone to seizures. You have to have at least two seizures that are not caused by something else, like a disease, before the diagnosis is made.

Now, as for the different types:

- A partial seizure is one that is localized in a specific set of brain structures, where as a generalzied seizure involves widespread abnormal brain activity such as happening in the cerebral cortex of both brain hemispheres.
- A tonic-clonic seizures are the most common, and often called grand mal seizures. They are generalized convulsive seizures where one also loses consciousness. They occur in phases: The tonic phase is when there's a stiffening of muscles, then the clonic phase is when there's relaxation -- the result are muscle spasms of contraction/relaxation of muscles.
- A myoclonic seizure is when you have muscle twitching or limb jerking. It's generally due to problems with cortical activity in the brain. It's localized. But sometimes, myoclonic jerks can involve upper limbs or the entire body being thrown about.

Some nonepileptic seizures occur. They include those tonic-clonic seizures that happen after withdrawal from sedatives or hypnotic drugs. If the seizures come in a chain of patterns, then it's called status epilepticus. Other nonepileptic seizures can happen because of bacterial meningitis, renal or hepatic failure, hypoxic encephalopathy, fever, brain tumors or cerebrovascular accidents. Nonepileptic seizures are usually not a concern once underlying cause is treated.

On the other hand, epileptic seizures are primary from epilepsy. Their origins are in the gray matter of the brain, or, actually, the cortical tissue that forms the hippocampus, which is necessary for memory. The neurons in the cortex that give rise to excitatory outflow are the pyramidal cells, which are kind of pyramid shaped.

The pattern of a seizure is usually pretty predictable. It starts with a prodrome, or warning symptoms like a mental, motor or sensory phenomena called an aura, which a person might remember happened last time a seizure occurred. Then, the seizure happens and depends on type, as explained above.

A partial seizure will either have a focal motor without march, in which the seizure comes from neurons in the motor cortex that leads to twitching on the hand or a side of the face and doesn't spread across. Or, it may have a focal motor with march, which happens when the twitching spreads to the upper arm, shoulder and face. If the spread is limited, then it's called a simple partial seizure.

Complex partial seizures can result of a change in consciousness after a simple partial seizure, with resulting "automatisms," like lip smacking, sucking, chewing, fumbling, incoherent talking, etc, which have no apparent purpose. When these occur, it's highly possible they arise from the temporal lobe.

If the partial seizure progresses, it may end up becoming a generalized tonic-clonic seizure with a full episode including loss of consciousness.

A generalized seizure doesn't have any specific focus, so generally includes seizures that vary a lot. Absence seizures are a type of generalized seizure in that they involve an appearance of absence, like a blank stare for about two to ten seconds along with lip smacking, chewing, etc. A simple absence is common in childhood or adolescence epilepsy. An absence variant is associated with Lennox-Gastaut, which usually results from mental retardation in children.

The tonic-clonic, or grand mal seizures, are a maximal seizure response in the brain. It is generalized because it involves both hemispheres and is usually has a prodrome. The prodrome could be depression, irritability, sometimes euphoria (as Dostoyevsky expressed saying that seizures began with ecstasy). The seizure, again, has a tonic phase of about 10-20 seconds with muscle flexing, with sometimes an epileptic cry. Tthen a 1/2 to 2-minute clonic phase of relaxation. Then these phases are followed by a terminal phase for 5 minutes when the patient goes into something like a coma, going totally limp and quite.

Diagnosis involves an electroencephalograph, or EEG, as well as CT scans or magnetic resonance imaging (MRI) (which are more effective than CT scans). The EEG will determine characteristic interictal (period of time between seizures) abnormalities. A MRI could identify structural abnormalities in the cortex.

Medical treatment and seizure-coping strategies may involve pharmaceutical agents as well as simple stress-reduction techniques, plus routine EEGs and seizure monitoring with CT or MRI.


Nowak et al.

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