A word about EEG is necessary.  EEGs can both be very useful and at the same time extremely frustrating.  An EEG is not the way to diagnose epilepsy. Epilepsy is diagnosed on the clinical history.  The EEG can help confirm the diagnosis and also the type of epilepsy and whether or not it may be difficult to control.


A baseline EEG takes between thirty and sixty minutes.  Electrodes are applied to the scalp and a recording machine then picks up the electrical discharges or wave forms that normal brains produce. Abnormal wave forms stand out from the normal pattern and enable comment to be made.  The Technician will get the patient to hyperventilate and also expose them to a series of high frequency flashing lights and this may stimulate abnormal wave forms on the EEG.


Longer EEG recordings can be undertaken.  These can involve the patient staying awake all night and then logically just going to sleep first thing in the morning when they are asked to lie down in a darkened room.  Ambulatory EEG recordings can also be carried out over a number of days which of course are even more likely to pick up abnormalities.  Your examining Neurologist should advise you which EEG recordings ought to be undertaken under which circumstances.


It is worth remembering that 60% of people who definitely have epilepsy will have a normal resting EEG.  Likewise 10% of normal people without epilepsy will have abnormal EEGs.  The pick-up rate however of abnormalities in people who will turn out to have epilepsy will go up significantly with repeat recordings or doing longer recordings.  The gold standard of epilepsy diagnosis however would be the detection of typical spike and wave discharges on the EEG or clear-cut EEG changes during a seizure that occurs during an EEG recording. 


Sometimes the attacks complained by patients, particularly those after brain injury, can be so odd and strange that their veracity is once again doubted and prolonged EEG recordings have frequently helped me both clinically and in medico-legal cases to get to the real truth which obviously has a fundamental impact on the diagnosis of epilepsy nd then on the damages awarded.


The reverse also applies.  If an individual has attacks that are captured by an EEG with no changes whatsoever, then they are likely to be so-called non-epileptic attacks which are based deep in the psychological state and will usually respond to appropriate psychological management.