Globus pallidus internus (GPi) deep brain stimulation (DBS) was used to treat a stiff-person syndrome (SPS) patient. Prior to implantation, microelectrode recordings measured firing frequencies and patterns (burst index). Contralateral and ipsilateral hemispheres relative to myoclonic jerks on the left side of the body were compared. Analysis revealed significantly lower firing frequencies and significantly higher and more variable burst index in the right contralateral GPi compared to the left ipsilateral GPi.