Quantitative and qualitative outcome measures after thalamic deep brain stimulation to treat disabling tremors

OBJECTIVE: We studied outcome measures after unilateral and bilateral thala mic stimulation to treat disabling tremor resulting from essential tremor a nd Parkinson's disease. The surgical technique, qualitative and quantitativ e tremor assessments, stimulation parameters, locations of active electrode s, complications, and side effects ave described and analyzed. METHODS: Forty-one patients with essential tremor or Parkinson's disease un derwent implantation of 56 thalamic stimulators. Preoperative qualitative a nd quantitative tremor measurements were compared with those obtained after unilateral and bilateral surgery, with activated and deactivated stimulato rs. Stimulation parameters and stimulation-related side effects were record ed, and outcome measures were statistically analyzed. RESULTS: Qualitative measurements demonstrated significant improvement of c ontralateral upper-limb (P < 0.001), lower-limb (P < 0.04), and midline (P < 0.001) tremors after unilateral surgery. Ipsilateral arm tremor also impr oved (P < 0.01). No differences were observed with the Purdue pegboard task . Quantitative accelerometer measurements were correlated with qualitative assessments and confirmed improvements in contralateral resting (P < 0.001) and postural (P < 0.01) tremors and ipsilateral postural tremor (P < 0.05) . Activities of daily living improved after unilateral surgery (P < 0.001) and additionally after bilateral surgery (P < 0.05). Adjustments of the pul se generator were required more frequently for tremor control than for amel ioration of side effects. Bilateral thalamic stimulation caused move dysart hria and dysequilibrium than did unilateral stimulation. Stimulation-relate d side effects were reversible for all patients. Stimulation parameters did not change significantly with time. A significantly lower voltage and grea ter pulse width were used for patients with bilateral implants. CONCLUSION: Unilateral thalamic stimulation and bilateral thalamic stimulat ion are safe and effective procedures that produce qualitative and quantita tive improvements in resting, postural, and kinetic tremor. Thalamic stimul ation-related side effects ave mild and reversible.