Clinic-based stimulation mapping can localize adverse sensory phenomena to a single contact and enable targeted reprogramming without loss of efficacy.

Responsive Neurostimulation (RNS) is an FDA-approved closed-loop therapy for drug-resistant focal epilepsy. Beyond seizure reduction, outpatient stimulation mapping can identify stimulation-related sensory effects and guide programming. We present a case in which contact-specific mapping resolved sensory side effects while maintaining seizure reduction. 

During a scheduled clinic visit, contact-by-contact stimulation testing was performed. Test pulses were delivered at 2.5 µC and 3.0 µC per phase, with all other contacts on the alternate lead set to 0 to avoid confounds. Each condition was held long enough to allow patient report. Safety parameters (pulse width, burst duration, charge density) remained within recommended ranges. The patient was blinded to active contact to minimize expectation bias.

A 31-year-old man with drug-resistant focal epilepsy underwent RNS implantation with depth leads in the left amygdala and the right hippocampus. During follow-up visits, he reported brief, recurrent “vibrations” of the left upper forehead. Episodes did not correlate with electrographic seizures or detector-triggered events. Reduction in charge per phase, decreasing frequency, and revising bipolar montage did not resolve symptoms. RNS stimulation mapping was performed to identify potential problematic electrode contacts. 

Provocation testing reproduced the forehead vibration exclusively with stimulation of left amygdala Contact 1 at both 2.5 and 3.0 µC per phase. All other contacts were well-tolerated at both charge levels without adverse effects. Subsequent deactivation of Left amygdala Contact 1 resolved symptoms. Clinically, the patient maintained 75-89% reduction in seizure frequency compared with preimplant baseline. 

Outpatient RNS stimulation mapping can localize stimulation-induced adverse effects to a single contact and enable rapid, contact-specific adjustments without sacrificing seizure control. Incorporating structured mapping into routine follow-ups may streamline management of side effects as various parameters are titrated in the clinic setting.