A 69-year-old man who was initially diagnosed with essential tremor presented with dysphagia and dysarthria following bilateral deep brain stimulation (DBS) of the ventral intermediate nucleus of the thalamus. He later developed parkinsonian features. Evaluation included needle electromyography, which revealed small biphasic spikes firing regularly at 200 Hz (the same as DBS frequency; Figure). Spikes disappeared after contralateral DBS was turned off.
Sadeghian H, Chitnis S, Elliott JL. Deep Brain Stimulation Artifact in Needle Electromyography. Arch Neurol. 2010;67(8):1030. doi:10.1001/archneurol.2010.183