Abdalhamid Lagnf1, Hassan Souidan1, Abdelrahman M.Alsherbini1, Rene Andrade Machado2, Mona Elsayed1
1Neurology, Detroit Medical Center/Wayne State University, 2Children's Hospital of Wisconsin
Objective:
To evaluate the relationship between certain scalp interictal epileptiform discharges (IEDs) and the underlying seizure pathology.
Background:
Ictal characteristic patterns in focal epilepsy have been observed to be highly associated with certain pathologies and identifying such patterns can act as a predictor for possible underling etiology and to guide further investigations in work up of epilepsy.
Design/Methods:
Retrospective analysis of the interictal, ictal, and postictal epileptiform discharges recorded from scalp EEG based on frequency, amplitude, distribution, and morphology.
Results:
Independent or asynchronous bursts of IEDs in the form of spike trains consisting of monomorphic alpha frequencies with crescendo amplitudes, at times preceded or followed by 2-3Hz slow waves, were associated with FCD. IEDs of spike trains with crescendo amplitudes and frequencies 5-6 Hz small spikes followed by 6-8Hz higher amplitudes spikes with sharp peaks per second, then followed by 1-3 Hz slow waves, and at times showed broad field to the contralateral side were associated with heterotopia. An isolated spike-slow wave discharge confined to the temporal electrodes without broad field ipsilaterally were associated with MTS of possible dentate and proper hippocampus origin. IEDs of spike-slow wave discharges with broad field to the ipsilateral side were associated with MTS of possible hippocampal and para-hippocampal origin. Irregular 1-2 Hz spikes/sharp waves-slow waves and appearing as irregular “M shape” correlated with neocortical gliosis. Spike/sharp-slow wave complexes with broad field ipsilaterally and contralaterally while sustaining higher amplitudes ipsilaterally, might indicate kindling.
Conclusions:
Scalp EEG provides information about different epileptic parameters. IEDs are heterogeneous in terms of pattern and underlying mechanisms. EEG is not only a method to prove the presence of an epileptic focus, but can also correlate with the underlying etiology, and can be a useful tool to guide medical and surgical interventions.