[show abstract][hide abstract] ABSTRACT: BACKGROUND: Deep brain stimulation (DBS) is an effective therapy for advanced movement disorders, but its optimal use is still controversial. One factor that could play a role in the proper delivery of therapeutic stimulation by current DBS devices is the variability of the impedance at the interface between the electrode surface and surrounding tissue. OBJECTIVE: To analyze variability and trends in the impedance of chronically-implanted DBS electrodes in subjects with movement disorders. METHODS: We reviewed impedance values from medical records of DBS patients at an academic tertiary-care movement disorders center. The standard deviation of data recorded within individual subjects and single contacts were used as measures of longitudinal impedance variability. A generalized linear mixed model (GLMM) determined if a number of effects had significant influences on impedance. RESULTS: We analyzed 2863 impedance measurements from 94 subjects. Median variability, for subjects with follow-up from 6 months to 5 years (n = 77), was 194 Ω for individual subjects and 141 Ω for individual contacts, with a range spanning from 18 to over 600 Ω. The GLMM, incorporating all subjects (n = 94), identified time, electrical activity, implanted target, contact position on the electrode and side of implantation as significant predictors of impedance. Age and disease duration at surgery, gender or ethnicity were not significant predictors. CONCLUSIONS: Our analysis suggests that a significant amount of impedance variability can be expected in chronically implanted DBS electrodes and indicates a number of factors with possible predictive value. Further studies are needed to link impedance characteristics to clinical outcomes.
[show abstract][hide abstract] ABSTRACT: Deep brain stimulation (DBS) is a recent treatment modality. Few studies have examined referral practices for DBS.
To review referral patterns to a large movement disorders center to investigate the current level of knowledge surrounding DBS candidacy.
Tertiary care medical center.
Reviewed were 197 medical records of patients referred for DBS between December 1, 2005, and November 30, 2009.
Standardized criteria for DBS patient selection were used to categorize referred DBS candidates as the following: good candidates, possible future candidates, poor candidates because of neurological contraindications, or poor candidates because of medical contraindications. Yearly percentages were computed. Referral sources were categorized as movement disorder specialists vs non-movement disorder physicians and self-referred.
In total, 165 referrals (83.8%) had ailments for which DBS was indicated, and 100 referrals (50.8%) were good candidates (62 with idiopathic Parkinson disease, 35 with dystonia, and 3 with essential tremor). Referrals by movement disorder specialists vs other sources differed significantly in their percentages of good candidates (66.7% vs 40.4%, P = .002) and possible future candidates (14.7% vs 32.7%, P = .02) but not poor candidates (18.7% vs 25.0%, P = .60). Over the observed period of referrals, the yearly percentages significantly decreased for good candidates and increased for possible future candidates and poor candidates.
Compared with findings in prior studies, the quality of DBS referrals has improved. The increase in referral of possible future candidates and poor candidates may reflect greater confidence in the procedure.
Archives of neurology 08/2011; 68(8):1027-32. · 6.31 Impact Factor