Microelectrode Recording-Determined Subthalamic Nucleus Length
Microelectrode Recording-Determined Subthalamic Nucleus Length
Object: Deep brain stimulation (DBS) of the subthalamic nucleus (STN) has become a popular treatment for patients with medically refractory Parkinson disease. Many surgeons believe that microelectrode recording (MER) during DBS electrode implantation is needed to optimize placement, whereas stimulation-induced side effects such as paresthesias, dystonic contractions, dyskinesias, and ocular motor signs that become apparent postoperatively may be an indicator of the proximity of the electrode to various boundaries of the STN. This study was performed to evaluate the relationship between mapping of the STN by using MER and postoperative stimulation-induced side effects.
Methods: Eighty-two electrodes implanted in 75 patients between March 1999 and March 2003 were retrospectively examined to evaluate the length of the STN defined by MER, and the number of and threshold for postoperative stimulation-induced side effects. Electrodes were typically tested with increasing stimulation amplitudes (maximum 6 V) by using a monopolar array.
The 82 electrodes were associated with 97 stimulation-induced side effects. The mean time between surgery and testing stimulation-induced side effects was 3.9 months. Statistical analysis (two-tailed t-test) revealed no significant difference in the number of stimulation-induced side effects (or the mean threshold for paresthesias, the most common side effect) for electrodes associated with an STN length less than 4.5 mm (13 electrodes) compared with those associated with an STN greater than or equal to 4.5 mm (69 electrodes, p = 0.616). For every electrode, the target adjustment based on MER results was within 2 mm of the image-planned target (usually 1 mm anterior). In the x axis (mediallateral orientation), there was no systematic difference in adjustments made for the electrodes associated with the shorter compared with the longer STN lengths. In the y axis (anteriorposterior orientation), there was a very small statistically significant difference in the mean adjustment (0.4 mm) between the two groups.
Conclusions: Analysis of these results suggests that a shorter MER-determined STN length alone does not reliably predict the incidence of stimulation-induced side effects.
Deep brain stimulation of the STN has become the most popular surgical modality for treating medically intractable PD and has largely replaced ablative stereotactic neurosurgical procedures. Deep brain stimulation of the STN provides consistent clinical benefit and can reduce dopamine replacement therapy requirements by 50 to 60%.
The DBS electrode tip is 1.27 mm in diameter and is thought to typically produce a current spread of less than 4 mm (the STN is approximately 5 mm in diameter). Consequently, electrode tip position relative to the center of the STN is presumed to determine the clinical efficacy of stimulation therapy. Because this efficacy is thought to be in part due to precise targeting, many surgeons believe that MER during DBS electrode implantation is needed to map the boundaries of the STN and optimize electrode placement.
Following electrode placement, stimulation-induced adverse side effects such as paresthesias, dystonic contractions, dyskinesias, and ocular motor signs may be an indicator of the electrode´s proximity to various boundaries of the STN. We performed this study to evaluate the relationship between MER mapping of the STN (that is, the length of the STN) and postoperative stimulation-induced adverse side effects.
Object: Deep brain stimulation (DBS) of the subthalamic nucleus (STN) has become a popular treatment for patients with medically refractory Parkinson disease. Many surgeons believe that microelectrode recording (MER) during DBS electrode implantation is needed to optimize placement, whereas stimulation-induced side effects such as paresthesias, dystonic contractions, dyskinesias, and ocular motor signs that become apparent postoperatively may be an indicator of the proximity of the electrode to various boundaries of the STN. This study was performed to evaluate the relationship between mapping of the STN by using MER and postoperative stimulation-induced side effects.
Methods: Eighty-two electrodes implanted in 75 patients between March 1999 and March 2003 were retrospectively examined to evaluate the length of the STN defined by MER, and the number of and threshold for postoperative stimulation-induced side effects. Electrodes were typically tested with increasing stimulation amplitudes (maximum 6 V) by using a monopolar array.
The 82 electrodes were associated with 97 stimulation-induced side effects. The mean time between surgery and testing stimulation-induced side effects was 3.9 months. Statistical analysis (two-tailed t-test) revealed no significant difference in the number of stimulation-induced side effects (or the mean threshold for paresthesias, the most common side effect) for electrodes associated with an STN length less than 4.5 mm (13 electrodes) compared with those associated with an STN greater than or equal to 4.5 mm (69 electrodes, p = 0.616). For every electrode, the target adjustment based on MER results was within 2 mm of the image-planned target (usually 1 mm anterior). In the x axis (mediallateral orientation), there was no systematic difference in adjustments made for the electrodes associated with the shorter compared with the longer STN lengths. In the y axis (anteriorposterior orientation), there was a very small statistically significant difference in the mean adjustment (0.4 mm) between the two groups.
Conclusions: Analysis of these results suggests that a shorter MER-determined STN length alone does not reliably predict the incidence of stimulation-induced side effects.
Deep brain stimulation of the STN has become the most popular surgical modality for treating medically intractable PD and has largely replaced ablative stereotactic neurosurgical procedures. Deep brain stimulation of the STN provides consistent clinical benefit and can reduce dopamine replacement therapy requirements by 50 to 60%.
The DBS electrode tip is 1.27 mm in diameter and is thought to typically produce a current spread of less than 4 mm (the STN is approximately 5 mm in diameter). Consequently, electrode tip position relative to the center of the STN is presumed to determine the clinical efficacy of stimulation therapy. Because this efficacy is thought to be in part due to precise targeting, many surgeons believe that MER during DBS electrode implantation is needed to map the boundaries of the STN and optimize electrode placement.
Following electrode placement, stimulation-induced adverse side effects such as paresthesias, dystonic contractions, dyskinesias, and ocular motor signs may be an indicator of the electrode´s proximity to various boundaries of the STN. We performed this study to evaluate the relationship between MER mapping of the STN (that is, the length of the STN) and postoperative stimulation-induced adverse side effects.
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