EFFECTS OF THALAMIC DEEP BRAIN-STIMULATION BASED ON TREMOR TYPE AND DIAGNOSIS

It has been suggested that deep brain stimulation (DBS) is less effect ive in alleviating proximal than distal postural arm tremor and tremor reduction is said to be less in essential tremor (ET) than in Parkins on's disease (PD). We analyzed blinded rater's tremor scores and subje cts' disability ratings at 3-month follow-up to examine the effects of DBS based on tremor type (rest, kinetic, distal postural, proximal po stural) and diagnosis (ET, PD). An independent examiner provided tremo r scores using randomized videotaped footage of 19 ET and 10 PD subjec ts at baseline and at follow-up with DBS ''on.'' Subjects provided sel f-ratings of disability at baseline and at follow-up. Comparisons of b aseline and follow-up tremor scores and disability ratings were made u sing the Mann-Whitney U and Wilcoxon rank sum W test; correlation anal yses were performed using Spearman rank order correlation test. There were significant and essentially equal improvements in tremor scores f or rest, kinetic, distal postural, and proximal postural tremor at fol low-up. Only one subject had no improvement in tremor. Tremor improved significantly and to the same extent in ET and PD subjects in each po sition except ''at rest,'' which was most improved in PD (p = 0.0003). ET and PD subjects did not differ in the extent of disability improve ment. Improved disability correlated only with improved postural tremo r scores: proximal postural and distal postural (r = 0.41, p = 0.03; r = 0.47, p = 0.01). DBS is effective in alleviating tremor and disabil ity in both ET and PD. Resting, kinetic, distal postural, and proximal postural tremor can be reduced to an equal degree. However, DBS produ ces the greatest improvement in disability in association with improve d postural tremor in both ET and PD.