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Seizure. 2016 Aug;40:59-70. doi: 10.1016/j.seizure.2016.06.010. Epub 2016 Jun 18.

Decision analysis of intracranial monitoring in non-lesional epilepsy.

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Massachusetts Institute of Technology Department of Brain and Cognitive Sciences, Cambridge, MA, USA.
Massachusetts General Hospital Department of Neurology, Boston, MA, USA. Electronic address:
Massachusetts General Hospital Department of Neurology, Boston, MA, USA.
Massachusetts General Hospital Department of Neurosurgery, Boston, MA, USA.



Up to one third of epilepsy patients develop pharmacoresistant seizures and many benefit from resective surgery. However, patients with non-lesional focal epilepsy often require intracranial monitoring to localize the seizure focus. Intracranial monitoring carries operative morbidity risk and does not always succeed in localizing the seizures, making the benefit of this approach less certain. We performed a decision analysis comparing three strategies for patients with non-lesional focal epilepsy: (1) intracranial monitoring, (2) vagal nerve stimulator (VNS) implantation and (3) medical management to determine which strategy maximizes the expected quality-adjusted life years (QALYs) for our base cases.


We constructed two base cases using parameters reported in the medical literature: (1) a young, otherwise healthy patient and (2) an elderly, otherwise healthy patient. We constructed a decision tree comprising strategies for the treatment of non-lesional epilepsy and two clinical outcomes: seizure freedom and no seizure freedom. Sensitivity analyses of probabilities at each branch were guided by data from the medical literature to define decision thresholds across plausible parameter ranges.


Intracranial monitoring maximizes the expected QALYs for both base cases. The sensitivity analyses provide estimates of the values of key variables, such as the surgical risk or the chance of localizing the focus, at which intracranial monitoring is no longer favored.


Intracranial monitoring is favored over VNS and medical management in young and elderly patients over a wide, clinically-relevant range of pertinent model variables such as the chance of localizing the seizure focus and the surgical morbidity rate.


Decision Analysis; Epilepsy Surgery; Intracranial EEG; Non-lesional Epilepsy

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