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Intracranial electrographic analysis of preictal spiking and ictal onset in uni- and bitemporal epilepsy Volume 17, numéro 2, June 2015

TEST YOURSELF

(1) What are the indications for invasive monitoring with intracranial electrodes in people with drug-resistant mesial temporal lobe epilepsy (mTLE)?


(2) What are the characteristics of preictal spikes?


(3) How do preictal spikes and ictal onset patterns (IOPs) during intracranial EEG monitoring assist in the distinction between uni-temporal and bitemporal epilepsy?

 

 

 

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Answers

(1) Invasive monitoring in drug-resistant mTLE is indicated when there is discordance of the findings from non-invasive evaluation and laterality of the seizure focus is not clearly established. Bilateral placement of intracranial electrodes across the temporal lobes is necessary in order to establish a uni-temporal or, in the case of bitemporal epileptogenicity, a dominant epileptic source, which could be amenable to resective temporal lobe epilepsy surgery.


(2) Preictal spikes are characterized by the presence of rhythmic spikes or sharp-wave discharges, lasting at least five seconds, with a repetition rate of 1-2 Hz which occur prior to ictal onset in the same location. Preictal spikes are distinct from ictal onset patterns which consist of sustained rhythmic, localized discharges at variable oscillation frequencies that further evolve in amplitude and frequency.


(3) Preictal spiking may be present more often in uni-temporal epilepsy than in bitemporal epilepsy. On the other hand, in bitemporal epilepsy, preictal spikes are less frequently noted and IOPs are more often in the low-frequency range.

 

 

 

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