Deep brain stimulation of the subthalamic nucleus in Parkinson’s disease: eVects of variation in stimulation parameters

Objective—To investigate the relation between the variation of the parameters of stimulation and the clinical eVectiveness in parkinsonian patients treated with deep brain stimulation of the subthalamic nucleus (STN), to provide information on the electrical parameter setting and the mechanism of action of deep brain stimulation. Methods—Ten patients with Parkinson’s disease bilaterally implanted in the STN were studied. For every patient the intensity of the stimulus necessary to obtain the disappearance of contralateral wrist rigidity (required clinical eVect, RCE) and the side eVect threshold in 20 diVerent conditions of stimulation, coupling four pulse width values (60, 120, 210, 450 μs) with five rate values (10, 50, 90, 130, 170 Hz) were determined. All the patients were tested after a 12 hour withdrawal of antiparkinsonian drugs, and the clinical evaluation was double blind. Results—In all the patients it was impossible to obtain the RCE using 10 and 50 Hz stimulus rates. For all the other stimulus rate values, the intensity-pulse width curves (IPWCs) for the RCE and for the side eVect threshold showed a hyperbolic trend. For every pulse width value, increasing the rate from 90 to 130 and to 170 Hz progressively decreased the intensity of the stimulus necessary to reach the RCE, but the diVerences were not significant. Within the same rate value, the progressive reduction of the stimulus intensity necessary to obtain the RCE, obtained with the lengthening of the pulse width was significant (p<0.05) only comparing 60 with 210 μs and 60 with 450 μs. Conclusions—The findings give some useful indications for the electrical parameter setting in deep brain stimulation of the STN, and some information about the mechanism of action of deep brain stimulation. (J Neurol Neurosurg Psychiatry 2001;71:215–219)