title: Microelectrode recording-determined subthalamic nucleus length not predictive of stimulation-induced side effects.
abstract: OBJECTIVE
  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 (medial-lateral 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 (anterior-posterior 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.
authors.affiliation: Department of Neurological Surgery, Columbia University College of Physicians and Surgeons, New York, New York, USA.
authors.forename: Shearwood
authors.initials: S
authors.lastname: McClelland
authors.forename: Brian
authors.initials: B
authors.lastname: Kim
authors.forename: Linda M
authors.initials: LM
authors.lastname: Winfield
authors.forename: Blair
authors.initials: B
authors.lastname: Ford
authors.forename: Tresha A
authors.initials: TA
authors.lastname: Edwards
authors.forename: Seth L
authors.initials: SL
authors.lastname: Pullman
authors.forename: Qiping
authors.initials: Q
authors.lastname: Yu
authors.forename: Guy M
authors.initials: GM
authors.lastname: McKhann
authors.forename: Robert R
authors.initials: RR
authors.lastname: Goodman
mesh_terms: D016009:Chi-Square Distribution; D046690:Deep Brain Stimulation / Q000009:adverse effects / Q000295:instrumentation* / Q000379:methods*; D004567:Electrodes, Implanted; D006801:Humans; D008839:Microelectrodes; D010292:Paresthesia / Q000209:etiology; D011237:Predictive Value of Tests; D012189:Retrospective Studies; D020531:Subthalamic Nucleus / Q000502:physiology