Surgical Management of MR-Negative Epilepsy

Surgical management of patients with refractory epilepsy in the context of normal MR imaging is an increasingly more common and challenging scenario presenting to epilepsy surgery centres. Historical seizure freedom rates after surgical intervention, however, were modest with the odds of seizure freedom remaining significantly higher in the presence of a lesion on MR. As a result, many patients with normal MR imaging may not have even been considered for an initial surgical evaluation. Upon completion of comprehensive presurgical investigations, patients ultimately considered candidates, uniformly require the additional step of intracranial EEG, often in the form of extensive subdural implantation to adequately define the Seizure Onset Zone (SOZ) and determine surgical candidacy. Recent reports of Stereotactic EEG (SEEG) for intracranial investigations has now demonstrated that it is the safest, best tolerated and most effective method of intracranial implantations in defining the SOZ in patients with normal MR imaging. Seizure freedom may be possible in over half of properly selected patients with normal MR imaging after SEEG guided treatments, approaching the outcome of lesional epilepsy patients subjected to similar intracranial EEG evaluations.