Unilateral pallidothalamic tractotomy at Forel's field H1 for cervical dystonia

Neurosurgical ablation of Forel's field H1 for cervical dystonia, which is currently abandoned, was formerly used in the 1960s-1970s. Regardless of the lack of neuroimaging modalities and objective evaluation scales, the reported efficacy was significant. Although recent studies have reappraised the ablation of the pallidothalamic tract at Forel's field H1 for Parkinson's disease, the efficacy for cervical dystonia has not been investigated well.

Data of 35 patients with cervical dystonia who underwent unilateral pallidothalamic tractotomy at Forel's field H1 were retrospectively analyzed. The Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS) scores, the neck score of the Burke-Fahn-Marsden Dystonia Rating Scale (BFMDRS), and adverse events were evaluated preoperatively and at the last available follow-up period.

The mean clinical follow-up period was 13.9 ± 6.5 months. The mean TWSTRS total scores were 34.3 ± 14.0 preoperatively and 18.4 ± 16.5 at the last available follow-up period (46.4% improvement, p < 0.0001). The BFMDRS neck score also improved significantly from 6.2 ± 2.9 preoperatively to 2.8 ± 2.8 at the last available follow-up period (55.0% improvement on the neck score, p < 0.0001). Reduced hand dexterity in seven patients, hypophonia in five patients, dysarthria in four patients, and executive dysfunction in one patient were confirmed as adverse events at the last available follow-up evaluation. One patient had postoperative hemorrhage.

The current study confirmed significant improvement in TWSTRS total scores and BFMDRS neck scores at the 13.9-month follow-up after unilateral pallidothalamic tractotomy. The pallidothalamic tract in Forel's field H1 is expected to be an alternative treatment target for cervical dystonia.