3T-MRI in patients with pharmacoresistant epilepsy and a vagus nerve stimulator: a pilot study.

Purpose: For safe 3T-MRI of patients with VNS (vagus nerve stimulator), specific conditions are mandatory. However, application of these conditions can lead to a loss of image quality. In this work, we evaluated the diagnostic value of 3T-MRI in VNS patients with pharmacoresistant epilepsy.

Methods: Using a transmit-and-receive head coil and adapting our sequences to allow for low SAR (specific absorption rate), we examined 15 patients with pharmacoresistant epilepsy. Diagnostic quality was assessed by comparison of the SNR (signal to noise ratio) and CNR (contrast to noise ratio) of the hippocampus, the grey-white matter contrast and epileptogenic lesions to images of patients without VNS acquired with our routine 3T-MRI protocol and the 32-channel head coil.

Results: 3T-MRI is feasible in VNS-patients. Image quality is adequate for detection and follow-up of epileptogenic lesions such as ganglioglioma or PNH (periventricular nodular heterotopia). Due to a significant reduction of SNR and CNR, the diagnostic value for subtle lesions may be decreased. Overall, the feasibility of 3T-MRI is beneficial in the diagnostic workup and follow-up of epilepsy-patients with VNS.