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These result from an electrochemical disorder in the brain. Brain cells use chemical reactions to produce electrical discharges. Each brain cell either excites or inhibits other brain cells with its discharges. When the balance of excitation and inhibition in a region of brain is moved too far in the direction of excitation, then a seizure can result.
The type of seizure depends upon several factors. One of the most important factors is where in the brain the abnormal electrical discharge occurs. The diagram below shows the four lobes of the brain (frontal, temporal, parietal and occipital) and where key regions of the brain are located. Strength and sensation are laid out along the border of the frontal and parietal lobes, with strength more toward the front (frontal) and skin sensation more toward the back (parietal) of the strip.
The undersurface of the temporal lobe is particularly prone to have seizures. The temporal lobes include the parts of the brain most commonly involved in adult epilepsy. Such temporal structures are given Greek names, such as "amygdala" (almond) and "hippocampus" (seahorse). The amygdala and hippocampus are targets for surgical removal in surgery for epilepsy (see discussion later). These structures are also involved in expression of emotionality and in ability to form memories.
In simple terms, if an abnormal electrical discharge originates in motor cortex: the patient will experience a motor seizure; if in sensory cortex: a sensory perception; if in visual cortex: lights, flashes, or jagged lines. Seizures in deep temporal lobe structures present with arrest of activities, loss of memory or awareness, and automatic (robot-like) behavior. If a seizure spreads to all regions of brain, then a "grand mal convulsion" results, with loss of consciousness, stiffening and jerking.
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