Imaging Biomarkers of Anti-Epileptic Drug Action: Insights from Magnetic Resonance Imaging

Background: Approximately one third of patients with epilepsy are refractory to medical treatment. Adverse effects associated with Anti-Epileptic Drugs (AEDs) are considered to affect quality of life often more than seizures themselves. Neuroimaging techniques, particularly Magnetic Resonance Imaging (MRI), have proven instrumental in clinical decision making in relation to epilepsy surgery, but may also provide further insights into the mechanisms underlying treatment response and side effects associated with AEDs. Objective and Method: We searched PubMed and Scopus databases for original articles and reviews published in the last two decades, which addressed the effects of AEDs on structural MRI, functional MRI and Magnetic Resonance Spectroscopy (MRS) measures. Results: The majority of investigations implemented task-based fMRI, and probed the influence of widely used anti-epileptic drugs on tasks assessing language, executive functions and emotion recognition. Collectively, MRI allows detecting reproducible AED-related effects on regions and networks relevant to disease pathomechanisms, thus elucidating the anatomo-functional substrates of cognitive side effects. MRS analyses shed light on the molecular correlates of AED action, and may provide indicators of treatment response. Conclusion: MRI techniques have considerably improved our understanding of the effects of AEDs at a regional and network level, and provide biomarkers with potential to improve routine clinical decision making in epilepsy.