Symptomatic epilepsy is one of the common and severe complications of stroke, but it’s rather difficult to predict.
The proposed formula enables to determine the ability of forming of the incipient epileptic focus when it is impossible to determine focus on visual electroencephalogram (EEG) analysis and before appearance of typical epileptiform activity.
Epileptic focus is typically formed in peri-infarct region. Slow waves registered in projection of infarct area reflect underlying structural abnormalities of the brain and can serve as marker of local neuronal dysfunction in peri-infarct region. The frequency of oscillatory activity is inversely related to the number of synchronously active neurons. Therefore, focal slowing can be regarded as result of abnormal neuronal synchronization. Phenomenon of excessive synchronization is neurophysiologic basis of epileptiform activity and developmental of an epileptiform focus as well.
Proposed formula is based on estimating following factors:
	Degree of rhythmicity (reflect level of neuronal intrahemispheric synchronization) of the slow waves, which constituted focal EEG slowing over the affected region.
	Degree of interhemispheric synchrony of slow oscillation in the peri-infarct region (may reflect development of “mirror” epileptic focus).
This formula expresses an index and can be written as follows:   
S=(∑_(i=1)^n▒((σ ln⁡(σ/σ^' ))/(σ^'  ln⁡σ )) )/n
Where:
S – index of possibility of epileptic focus.
σ’ – root-mean-square deviation (RMSD) of wavelength of slow waves in affected region.
σ – RMSD in symmetrical intact region;
n – number of fragments of approximately equal size containing an equal number of waves.

Positive/higher scores are likely to indicate the formation of epileptic focus whereas negative/lower scores indicate relatively low possibility.

FORECAST APPROACH FOR EARLY DETECTION OF EPILEPTIC FOCUS FORMATION DUE TO POSTSTROKE EPILEPSY