Electrode Location Does Not Predict Contralateral Limb Motor Function Improvement in Subthalamic Stimulation for Parkinson's Disease

 

Shearwood McClelland III A.B.¹, Blair Ford M.D., F.R.C.P.C.², Patrick B. Senatus M.D., Ph.D.¹, Steven J. Frucht M.D.², Linda M. Winfield R.N., M.P.H.², Yunling E. Du Ph.D.³, Seth L. Pullman M.D., F.R.C.P.C.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

 

 

Introduction: 

Deep brain stimulation (DBS) of the subthalamic nucleus (STN) is an effective treatment for patients with medically refractory Parkinson's disease (PD).  The degree to which DBS electrode tip anatomic location determines the improvement of contralateral limb movement function has not been defined.  This retrospective study was performed to address this issue.

 

Methods: 

42 DBS electrode tips in 21 bilaterally implanted patients were localized on postoperative magnetic resonance imaging (MRI).  The postoperative and preoperative planning MRIs were merged with the Stealth stereotactic planning workstation to determine the DBS tip coordinates.  Stimulation settings were postoperatively optimized for maximal clinical effect.  Patients were videotaped one year postoperatively and assessed by a movement disorder neurologist blinded to electrode tip locations.  The nine limb-related components of the Unified PD Rating Scale (UPDRS) Part III [Rest tremor (hand, foot), Action tremor, Rigidity (upper, lower extremity), Finger tapping, Hand gripping, Hand pronation/supination, Leg agility] were tabulated to obtain a limb score [(off-stimulation, off-medications) minus (on-stimulation, off-medications)].  The electrode tip locations associated with the 15 least and 15 greatest limb response scores were compared to postoperative limb function.

 

Results:

Statistical analysis (two-tailed t-test) revealed no significant difference in electrode tip location between the two groups with regard to three-dimensional distance (P=.759), lateral-medial (X) axis distance (P=.983), anterior-posterior (Y) axis distance (P=.949) or superior-inferior (Z) axis distance (P=.894) from the intended anatomical target.  The range of difference in tip location (X-axis = 2.5 mm lateral to 5.1 mm medial; Y-axis = 4.1 mm posterior to 2 mm anterior) and limb scores (-2.5 to +22.5) was extensive. 

 

Conclusions:

Within the range of electrode tip locations (relative to the intended target) in this study, the postoperative MRI-determined electrode position does not predict the improvement of contralateral limb motor parkinsonism.  Other factors may have a greater bearing on the limb responsiveness of these patients.