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What is Epilepsy and what are the various types of EpilepsyEpilepsy
and cause of loss of consciousness
Epilepsy
is common. Over 2% of the population have two or more seizures during
their lives and in 0.5% epilepsy is an active problem. Mechanisms Spread of electrical activity between cortical neurones is normally restricted. Synchronous discharge of neurones in normal brain takes place in restricted groups whose limited discharges are responsible for the normal EEG rhythms. During a seizure, large groups of neurones are activated repetitively and hypersynchronously. There is failure of inhibitory synaptic contact between neurones. This causes EEG high voltage spike and wave activity, the electrophysiological hallmark of epilepsy. A partial seizure is epileptic activity confined to one area of cortex with a recognizable clinical pattern .This activity either remain focal or spreads to generate epileptic activity in both hemispheres and thus a generalized seizure. This spread is called secondary generalization of the partial seizure. The focal onset of a seizure may not clinically evident. This means that an apparent tonics clonic seizure may be either a generalized major convulsion or a tonic clonic seizure with began as a partial seizure but with out clinical evidence of its focal origin.
An area of brain is or becomes epileptogenic either because neurones have a predisposition to be hyper excitable, for example following abnormal migration patterns in utero, or because they acquire this tendency. Trauma or brain neoplasms are examples of acquired conditions that alter the seizure threshold of neurones. Seizure threshold Each individual has a threshold for seizure activity. Experimentally some chemicals(e.g. pentylenetetrazol, a toxic gas) induced seizure in all subjects. Individuals who are more in response to various stimuli, for example flashing lights, are said to have low seizure thresholds. This is a concept, not a measurement. The
commoner types of epilepsy 3
Unclassifiable seizures
| Classifications of Epilepsy / Seizure | Symptoms, investigations and management process involved in epilepsy | Understanding Epilepsy Syndromes | |
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