Introduction: Nucleus ventralis intermedius (Vim) deep brain stimulation (DBS) is an effective therapy for the treatment of refractory essential tremor (ET). As many as 9% of patients may fail therapy despite positive initial results.[1] In cases where good placement has been confirmed, evidence suggests that anterior adjacent lead placement can improve symptoms [2,3] We describe our cumulative surgical experience.
Methods: A total of 6 patients were reviewed retrospectively. These patients had a second DBS array placed after programming failed to recapture initial tremor control. Additional leads were implanted with the with the intent of steering the field anteriorly to recapture tremor control in the motor thalamus, targeting a location 4-6mm anteromedial from the original VIM lead. Clinical, anatomic and intraoperative data were post-processed with respect to a probabilistic atlas.[4]
Results: A total of 9 leads were implanted in 6 patients (3 bilateral, 3 unilateral). Original leads plotted into the atlas overlaps with the normalized efficacy map predicting good initial tremor capture relative to the cumulative ET population. Time to secondary implant was 2.68±1.38 years with the exception of one outlier at 11 years. New leads were placed on average 4-6mm anteromedially, and programmed to allow for driving of the current between the two leads. Rescue of tremor control was demonstrated in all patients based on clinical evaluation, but programming voltage changes varied widely. A descriptive electric field diagram was also modeled.
Conclusions: Rescue lead therapy shows clinical benefit for tremor control in Vim refractory ET patients. There is debate regarding why this occurs- electrical tolerance vs physiologic ‘escape’ from capture by a single array lead. However, our results suggest that failed control with previously successful single array implants can be rescued by a second anterior array implant. Further investigation is ongoing and will allow us to further understand this therapeutic option.
Patient Care: Rescue lead therapy allows for patients with ET refractory to standard VIM DBS to have a positive results from stimulation.
Learning Objectives: By the conclusion of this session, participants should be able to:
1) Understand the hypothesis behind rescue lead placement
2) Understand the surgical procedure and targeting for the rescue lead
3) Be introduced to the field modeling concept for rescue lead placement.
References: 1. Papavassiliou E, Rau G, Heath S, Abosch A, Barbaro NM, Larson PS, et al.: Thalamic deep brain stimulation for essential tremor: relation of lead location to outcome. Neurosurgery 2004 May;54:1120–29; discussion 1129–30.
2. Yu H, Hedera P, Fang J, Davis TL, Konrad PE: Confined stimulation using dual thalamic deep brain stimulation leads rescues refractory essential tremor: report of three cases. Stereotact Funct Neurosurg 2009 Jul 29;87:309–313.
3. Oyama G, Foote KD, Hwynn N, Jacobson CE 4th, Malaty IA, Rodriguez RL, et al.: Rescue leads: a salvage technique for selected patients with a suboptimal response to standard DBS therapy. Parkinsonism Relat Disord 2011 Jul;17:451–455.
4. D’Haese P-F, Pallavaram S, Li R, Remple MS, Kao C, Neimat JS, et al.: CranialVault and its CRAVE tools: a clinical computer assistance system for deep brain stimulation (DBS) therapy. Med Image Anal 2012 Apr;16:744–753.