Epilepsy is a disorder of brain function characterized by repeating fits or seizures. The symptoms can be as mild as thought disorders, or as severe as a physical convulsion and unconsciousness. Epilepsy affects one in a hundred people.
Derived from the Greek, epilepsy means 'to be designated by forces from without'. It is a symptom of brain malfunction that can be caused by diverse disease processes (such as brain tumors or infection) by head injury, or by genetic inheritance, although in many cases no cause can be found.
The expression of epilepsy is usually an intermittent, paroxysmal, excessive and disorderly discharge of cerebral neurons. This is due to instability of the cell membranes resulting from excessive depolarization and repolarization. Membrane stability and polarization are maintained by ionic fluxes across the membrane. When this ionic balance is disturbed or when the intrinsic mechanisms for maintaining membrane stability are affected, there is a tendency for a seizure to occur. Individuals may have, by genetic determination or acquired condition, a lower threshold to spontaneous firing of certain neurons.
There are two types of seizure, partial and generalized. Partial seizures begin in a local area of the brain. In the simple partial seizures consciousness is not impaired but there are specific symptoms dependent which part of the brain has been affected.
In complex partial seizures consciousness is impaired. There can be a brief clouding of consciousness or a more prolonged episode of automatism. When the abnormal neuronal discharge that initiates the fits remains localized it may elicit a conscious sensation or series of sensations that the person learns to interpret as a warning or aura. The nature of the aura is determined by which part of the brain is affected. Although the person interprets the aura sensations as a warning of the fit to come, it is actually an initial seizure manifestation.
The generalized seizures can be either convulsive or non-convulsive.
They range in severity from a simple 'absence' (also known as petit mal seizures), to 'grand mal' seizures (which are characterized by a tonic-clonic pattern of spasm). The seizure is generalized from the sunset. Sudden unconsciousness with or without motor phenomena, is the usual mode of seizure sunset. However, there may be jerks (myoclonic jerks) in clear consciousness which also occurs.
The suggestion is that the generalized seizure is caused by a system of neurons, coming from the brainstem, which integrate the activities of both hemispheres. Alternatively it is suggested that in generalized epilepsy there is a diffuse and reliably mild state of chronic cortical hyperexcitability which increases the responsiveness of the cortical neurons. This leads on to spike and wave discharges associated with the generalized seizure.
Modern medicine provides many medications which can control epileptic seizures, and active research continues into the many factors which cause epilepsy.