Shearwood McClelland III M.D.1, Brian Kim B.S.1, Linda M. Winfield R.N., M.P.H.2, Blair Ford M.D.2, Yunling E. Du Ph.D.3, Seth L. Pullman M.D.2, Qiping Yu Ph.D.2, Guy M. McKhann II M.D.1, Robert R. Goodman M.D., Ph.D.1
Departments of 1Neurological Surgery and 2Neurology, Columbia University, College of Physicians and Surgeons, New York, NY
3Center for Biostatistics and Epidemiology, Columbia University Mailman School of Public Health, New York, New York
Deep brain stimulation (DBS) of the subthalamic nucleus (STN) has become a popular treatment for patients with medically refractory Parkinson's disease (PD). Many surgeons feel that microelectrode recording (MER) during DBS electrode implantation is needed to optimize placement, while stimulation-induced side-effects (paresthesias, dystonic contractions, dyskinesias, eye motor signs) postoperatively may be an indicator of proximity to various boundaries of the STN. This study was performed to evaluate the relation between MER STN mapping and postoperative stimulation-induced side-effects.
82 electrodes (75 patients) implanted 3/1999-3/2003 were retrospectively examined for: a) Length of STN on the initial MER track and b) the number of, and threshold for, postoperative stimulation-induced side-effects. Electrodes were typically tested with increasing stimulation amplitude (6 volt maximum) with a monopolar array.
The 82 electrodes were associated with 97 stimulation-induced side-effects. Average time between surgery and testing stimulation-induced side-effects was 3.9 months. Statistical analysis revealed no significant difference in the number of stimulation-induced side-effects (or the mean threshold for paresthesias, the most common side-effect) between electrodes associated with STN length less than (n = 13) vs. greater than/equal to (n = 69) 4.5 mm. For every electrode, the target adjustment based on MER results was within 2 mm of the image-planned target (usually 1 mm anterior). There was no systematic difference in adjustments made for the electrodes associated with the shorter versus the longer STN lengths.
These results suggest that a shorter MER-determined STN length does not reliably predict proximity of the DBS electrode to various boundaries of the STN.