Pathophysiology of seizure onset in human focal epilepsy and its relevance to epilepsy surgery

Student thesis: Doctoral ThesisDoctor of Philosophy


Epilepsy is a major source of disability amongst all age groups. Most epilepsies are well controlled on antiepileptic drugs. However, significant proportions of patients are not controlled on medical treatment and may be successfully treated with resective surgery. Unfortunately, as many as 30% of patients remain with disabling seizures after resective surgery. In the present thesis I aim at identifying seizure onset patterns on intracranial EEG that are predictors of surgical outcome.

Methods: I have studied all patients operated after intracranial recordings implantation between 1999 and 2010 with a follow up period longer than 1 year. I identified the first, the second ictal patterns and the presence of preceding epileptiform discharges, and correlated their presence with surgical outcome. As the initial pattern was bilateral in 33% of patients, I used single pulse electrical stimulation (SPES) to identify bilateral connections that could be responsible for bilateral changes at seizure onset.

Results: Focal fast activity as first ictal pattern was associated with favourable outcome. Diffuse electrodecremental event as first ictal pattern was associated with poor outcome. A preceding focal, widespread or bilateral epileptiform discharge was not associated with neither favourable nor poor outcome. As second ictal pattern, fast activity was associated with poor outcome whereas diffuse electrodecremental event with good outcome. Delayed second ictal patterns (≥10sec) appear to be associated with good outcome in temporal lobe epilepsy. Hippocampus and amygdala have a low incidence of contralateral connections (5.0%). Fusiform gyrus showed the highest incidence of contralateral functional connections (≤7.1%). Bi-temporal connectivity is related neither to bilateral seizure onset nor postsurgical outcome.

Conclusion: The prognostic value of ictal patterns depends where they occur during seizure evolution. Early bilateral changes at seizure onset cannot solely be explained by functional bilateral connections.
Date of Award2016
Original languageEnglish
Awarding Institution
  • King's College London
SupervisorAntonio Valentin Huete (Supervisor) & Gonzalo Alarcon (Supervisor)

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