Concepts and methods in chronic thalamic stimulation for treatment of tremor: Technique and application

OBJECTIVE: To rationalize the technique and reduce the costs associated wit h chronic deep brain stimulation of the thalamus for treatment of refractor y tremor. METHODS: The efficacy and safety of a modification in surgical techniques w as prospectively assessed in 94 patients with tremor. Bilateral electrodes were implanted in 29 patients, and 65 patients received unilateral implants . Forty-five patients had Parkinson's disease tremor, 42 patients had essen tial tremor, and 7 patients had kinetic tremors of different causes. In all instances, intraoperative stimulations to analyze the thresholds of intrin sic and extrinsic responses were performed directly with the implanted lead s. The electrodes were repositioned until satisfactory results were achieve d. The pulse generators were implanted directly after the first step in the same operative session. Patients were not subjected to interoperative test stimulation trials. RESULTS: Postoperative improvement of tremor at a mean follow-up of 11.9 mo nths was rated as excellent in 47 patients (50%), marked in 37 patients (39 %), moderate in 8 patients (9%), and minor in 2 patients (2%). There was no persistent morbidity related to surgery. In patients with Parkinson's dise ase, the symptomatic improvement of tremor was rated as excellent in 51% of patients, marked in 36%, moderate in 11%, and minor in 2%. In patients wit h essential tremor, symptomatic outcome was classified as excellent in 57% of patients, marked in 36%, moderate in 5%, and minor in 2%. Six of the sev en patients with kinetic tremor achieved marked symptomatic improvement, an d one patient experienced moderate improvement. Forty patients experienced stimulation-related side effects. Side effects were mild in general, and th ey were reversible with a change in electrical parameters. They occurred mo re frequently in patients who had bilateral stimulation. CONCLUSION: Excellent to marked improvement of tremor is achieved in the ma jority of patients with physiological target determination via implanted le ads in thalamic deep brain stimulation. Interoperative test stimulation tri als are unnecessary. Modifications in technique may help to reduce the cost s of the related hospital stay.