====== Interictal epileptiform discharge ======

The [[interictal]] epileptic discharges (IEDs) occurring in [[Stereotactic electroencephalography]] (SEEG) recordings are in general abundant compared to [[ictal]] discharges, but difficult to interpret due to complex underlying network interactions.

Analysis of IEDs is considered a valuable addition to routine review of SEEG recordings, with the potential to increase the success rate of epilepsy surgery
((Meesters S, Ossenblok P, Colon A, Wagner L, Schijns O, Boon P, Florack L,
Fuster A. Modeling of intracerebral interictal epileptic discharges: Evidence for
network interactions. Clin Neurophysiol. 2018 Apr 11;129(6):1276-1290. doi:
10.1016/j.clinph.2018.03.021. [Epub ahead of print] PubMed PMID: 29679878.
)).

[[Seizure]]s are infrequent events in the majority of patients, making recording of ictal [[EEG]] time-consuming and labor intensive. The mainstay of diagnosis, therefore, remains detection of [[interictal]] (ie, between seizures, from the Latin icere, to strike) epileptiform discharges. Continuous video-EEG monitoring, facilitate recording of ictal events, also greatly increases the time available to detect interictal epileptiform discharges (IEDs). 

Epileptiform discharges within the first 30 min of EEG recording are predictive for the occurrence of ictal EEG patterns and for ictal interictal uncertainty on subsequent continuous EEG (cEEG), for acute convulsive seizures during the ICU stay, and for a worse functional outcome after 6 months of follow-up
((Koren J, Herta J, Draschtak S, Pötzl G, Pirker S, Fürbass F, Hartmann M, Kluge
T, Baumgartner C. Prediction of rhythmic and periodic EEG patterns and seizures
on continuous EEG with early epileptiform discharges. Epilepsy Behav. 2015 May
15. pii: S1525-5050(15)00213-9. doi: 10.1016/j.yebeh.2015.04.044. [Epub ahead of 
print] PubMed PMID: 25982266.
)).
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After surgery for intractable mesiotemporal lobe epilepsy (mTLE) seizures recur in 30-40%. One predictor for seizure recurrence is the distribution of seizure onset and [[interictal epileptiform discharge]]s (IED). 

Preoperative bilateral ictal foci are a negative predictor for seizure outcome. Contrarily, IED exceeding the affected temporal lobe in the ipsilateral hemisphere or even bilateral IED had favorable seizure outcome if seizure onset is strictly limited to the affected temporal lobe. Reoperation for seizure persistence constitutes a promising therapeutic option
((Schmeiser B, Zentner J, Steinhoff BJ, Brandt A, Schulze-Bonhage A, Kogias E,
Hammen T. The role of presurgical EEG parameters and of reoperation for seizure
outcome in temporal lobe epilepsy. Seizure. 2017 Sep 6;51:174-179. doi:
10.1016/j.seizure.2017.08.015. [Epub ahead of print] PubMed PMID: 28888215.
)).
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Early postoperative IEDs are more frequently seen in selective amygdalohippocampectomy (SAH). than in corticoamygdalohippocampectomy (CAH). Unlike in patients with CAH, the presence of IEDs after selective amygdalohippocampectomy (SAH) was not a predictor of seizure recurrence. The type of surgery should be considered while utilizing postoperative Interictal epileptiform discharges (IEDs) for evaluating the prognosis
((Yu HY, Hsu SPC, Lin CF, Shih YH, Yen DJ, Kwan SY, Chen C, Chou CC. Prognostic 
significance of postoperative spikes varied in different surgical procedures for 
mesial temporal sclerosis. Seizure. 2017 Oct 3;52:71-75. doi:
10.1016/j.seizure.2017.09.018. [Epub ahead of print] PubMed PMID: 29017080.
)).