EEG IN VARIOUS DISEASES :::
1.Increased intracranial pressure :: During this condition $-waves with an amplitude upto 100 microvolts and frequency of 3 cycles per second may be observed
2.Cerebral tumors : Tumors cause progressive destruction of cortical tissues and as a result abnormally large slow $-waves arise from the damaged cerebral cortex
3. Epilepsy :: It is a disorder characterised by an abnormal and severe discharge of EEG It is usually associated with loss of consciousness convulsions and autonomic hyperactivity There are three main types of epilepsy grand mal petit mal and psychomotor
Grand mal epilepsy is characterised by generalised convulsions along with abrupt loss of consciousness The EEG pattern shows high voltage waves occuring about 8 to 12 times per seconds during the tonic phase and slower waves during clonic phase
Petit-mal epilepsy is characterised by clonic convulsions and jerking The EEG pattern shows alternating round and pointed (spiked) waves occuring in pairs (doublets) 3 times per second in petit- mal epilepsy there occurs episodes of impairment of consciousness usually associated with bilateral clonic motor acitivity such as eyelid blinking petit -mal is a disease of childhood and attack which starts for the first time after childhood is more likely to be minor epilepsy it is always idiopathic and may disappear after childhood or be replaced by grand mal epilepsy in adult life 
psychomotor type of epilepsy is characterised by the automatic movements i.e. chewing smacking of lip etc alongwith a dreamy feeling of unreality The EEG pattern shows low frequency of rectangular waves with the frequency of 2-4 cycles per second
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