Table 4.
Statistical Power Analyses for DBS in Dystonia Associated with TOR1A Mutations
| Source | Empirical observations | Expected improvement | ||||||
|---|---|---|---|---|---|---|---|---|
| Cases (N) | FM AVG | FM SD | Observed % Change | 40% | 50% | 60% | 70% | |
| Coubes, 2004 (Coubes et al. 2004) | 14 | 62.6 | 26.7 | 72 | 18 | 11 | 8 | 6 |
| Vidailhet, 2005 (Vidailhet et al. 2005) | 7 | 55.1 | 21.9 | 53 | 15 | 10 | 7 | 5 |
| Starr, 2006 (Starr et al. 2006) | 6 | 59.2 | 20.3 | 59 | 12 | 7 | 5 | 4 |
| Alterman, 2007 (Alterman et al. 2007) | 12 | 38.0 | 21.7 | 76 | 33 | 20 | 14 | 10 |
| Bruggemann, 2015 (Bruggemann et al. 2015) | 9 | 43.8 | 30.7 | 60 | 48 | 31 | 21 | 16 |
This table was based on published reports where relatively large numbers of cases with proven TOR1A mutations were presented with adequate information to calculate average pre-operative Fahn-Marsden Dystonia Rating Scale scores (FM AVG), standard deviations of these scores (FM SD) and average reductions in these scores following DBS (Observed % Change). The differences in the numbers of cases estimated to reach the expected degree of improvement are related to differences in the average starting severity and variance of the population reported.