Deep Brain Stimulation for Generalized Dystonia and Spasmodic Torticollis: An Examination of the Rate and Extent of Improvement

Dystonia seems distinct from other tremulous disorders such as Parkinson’s disease in that improvement after deep brain stimulation frequently appears in a delayed and progressive manner. The rate of this improvement and the point at which no further progress can be expected are presently unknown. Knowledge of these parameters is important in the provision of accurate and relevant prognostic information to these patients, as well as to their carers and physicians. We studied 12 consecutive patients with generalized dystonia (n = 6) and spasmodic torticollis (n = 6) who underwent bilateral globus pallidus internus (GPi) deep brain stimulation (DBS). Patients were followed for a minimum of 2 years after surgery. Both groups experienced a statistically significant improvement in their dystonia rating scores after surgery. At 2 years follow-up, the spasmodic torticollis group exhibited a 59% improvement in their total Toronto Western Spasmodic Torticollis rating scale (TWSTRS), and the generalized dystonia group attained a 46% improvement in their overall Burke, Fahn, and Marsden dystonia rating scale (BFMDRS) evaluation. Ninety-five percent of the final improvement was attained by 6.4 months in the generalized dystonia group and by 6.6 months in those with spasmodic torticollis. There was no significant improvement after 1 year after surgery. These findings further support to GPi DBS as an effective treatment for generalized dystonia and spasmodic torticollis and furnish important data as to the expected rate of improvement and the point at which no further gains can be reasonably anticipated.