Objective: To describe 5 patients with ET who underwent replacement of VIM DBS with leads targeting both VIM and the posterior subthalamic area (PSA) due to loss of sufficient tremor control.
Background: DBS can provide up to 65.4% improvement in tremor though there may be a loss of benefit in up to 73% of individuals at a mean interval of 18months[1-3]. The PSA has been targeted in subthalamotomies for tremor control previously and has emerged as a potential target for DBS. Stimulation of the PSA may provide equivalent, and possibly, superior tremor control compared to the VIM[5, 6].
Method: Retrospective analysis of 5 patients with ET who underwent revision of VIM DBS due to loss of sufficient benefit. All patients had been implanted with quadrupolar leads spanning 10.5mm (Medtronic model3387). Following complete explant of the DBS system, an MRI was obtained and the VIM and PSA were targeted in a single trajectory. Patients then underwent surgical placement of octopolar leads with a 15mm span (Boston Scienitific modelDB-2201-45DC), the longer span allowing for electrodes to be placed in both targets. Charts were reviewed for relevant outcomes.
Results: All patients had symptomatic tremor for over 10years. Mean age at first DBS surgery was 63.1years (53 – 68) and 70.8years (66 – 79) at revision. Two patients had greater improvement with VIM and PSA stimulation than with either alone and remained on simultaneous stimulation at most recent evaluation. One patient had equivalent improvement in tremor scores with all locations. One had greater improvement with PSA alone. In these latter two patients, benefit was limited due to tremor habituation. One patient did not demonstrate reduction in tremor scores likely related to ceiling effect; however, he was able to perform ADLs better with PSA and simultaneous stimulation.
Conclusion: We report 5 patients with longstanding ET with loss of stimulation efficacy approximately 7 years after VIM DBS who underwent revision of DBS systems as salvage therapy targeting both VIM and PSA. Four patients benefited from PSA stimulation, two of whom had greater benefit with simultaneous stimulation. These cases demonstrate that salvage therapy targeting both VIM and PSA may be of benefit in severe functionally limiting tremor, refractory to VIM stimulation. However, further controlled studies are warranted to better characterize the benefit of various stimulation parameters.
References: 1. Flora, E.D., et al., Deep brain stimulation for essential tremor: a systematic review. Mov Disord, 2010. 25(11): p. 1550-9. 2. Shih, L.C., et al., Loss of benefit in VIM thalamic deep brain stimulation (DBS) for essential tremor (ET): how prevalent is it? Parkinsonism Relat Disord, 2013. 19(7): p. 676-9. 3. Schuurman, P.R., et al., Long-term follow-up of thalamic stimulation versus thalamotomy for tremor suppression. Mov Disord, 2008. 23(8): p. 1146-53. 4. Blacker, H.M., et al., Hypotonia accompanying the neurosurgical relief of essential tremor. J Nerv Ment Dis, 1968. 147(1): p. 49-55. 5. Hamel, W., et al., Deep brain stimulation in the subthalamic area is more effective than nucleus ventralis intermedius stimulation for bilateral intention tremor. Acta Neurochir (Wien), 2007. 149(8): p. 749-58; discussion 758. 6. Blomstedt, P., et al., Deep brain stimulation of the subthalamic nucleus versus the zona incerta in the treatment of essential tremor. Acta Neurochir (Wien), 2011. 153(12): p. 2329-35.
To cite this abstract in AMA style:S. Aslam, F. Ponce, H. Shill, J. Chan, S. Barbu, M. Lambert, G. Moguel-Cobos. Deep brain stimulation revision from VIM to VIM and PSA severe long-standing refractory ET: case series [abstract]. Mov Disord. 2020; 35 (suppl 1). https://www.mdsabstracts.org/abstract/deep-brain-stimulation-revision-from-vim-to-vim-and-psa-severe-long-standing-refractory-et-case-series/. Accessed December 7, 2023.
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