Good long-term efficacy of pallidal stimulation in cervical dystonia: a prospective, observer-blinded study

Deep brain stimulation of the internal globus pallidus (GPi-DBS) is established as an effective treatment of primary generalised dystonia in controlled studies. In cervical dystonia (CD), only one previous study has reported observer-blinded outcome assessment of long-term GPi-DBS, with 1-year follow-up.

In this prospective, single-centre study, eight patients with CD (7 women:1 man, 4 focal:4 segmental) treated with bilateral GPi-DBS for median (range) 30 (12-48) months, were evaluated by the Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS; Severity, Disability and Pain scores), the Short-Form Health Survey-36 (SF-36), and the Becks Depression Index in an open design. In addition, a blinded rater assessed the TWSTRS Severity score from videos obtained preoperatively and at the last follow-up.

In the blinded evaluation, median (range) TWSTRS Severity score improved from 25 (19-30) to 8 (4-23) (P = 0.028), thus a 70% (23-82) score reduction. In the open evaluation, median Severity score improvement at the last follow-up was 73%, representing a significant further improvement from 50% at 6 months. The Disability and Pain scores improved by median 91% and 92%, respectively, and the SF-36 subdomain scores improved significantly. A reversible right hemiparesis and aphasia occured in one patient 4 days postoperatively, because of reversible oedema around the left electrode. No other serious adverse effects and no permanent morbidity were observed.

This single-blinded study shows good long-term efficacy of GPi-DBS in CD patients and supports using this treatment in those who have insufficient response to medical treatment.