Abstract
The field of Forel (FF) is a subthalamic area through which the pallidothalamic tracts originating from the globus pallidus internus (GPi) traverse. The FF was used as a stereotactic surgical target (ablation and stimulation) to treat cervical dystonia in the 1960s and 1970s. Although recent studies have reappraised the ablation and stimulation of the pallidothalamic tract at FF for Parkinson’s disease, the efficacy of deep brain stimulation of FF (FF-DBS) for dystonia has not been well investigated. To confirm the efficacy and stimulation-induced adverse effects of FF-DBS, three consecutive patients with medically refractory dystonia who underwent FF-DBS were analyzed (tongue protrusion dystonia, cranio-cervico-axial dystonia, and hemidystonia). Compared to the Burke-Fahn-Marsden Dystonia Rating Scale-Movement Scale scores before surgery (23.3 ± 12.7), improvements were observed at 1 week (8.3 ± 5.9), 3 months (5.3 ± 5.9), and 6 months (4.7 ± 4.7, p = 0.0282) after surgery. Two patients had stimulation-induced complications, including bradykinesia and postural instability, all well controlled by stimulation adjustments.
Highlights
Deep brain stimulation (DBS) of the globus pallidus internus (GPi) is the most widely used surgical treatment for medically refractory dystonia, and its effects have been validated (Kupsch et al, 2006; Volkmann et al, 2014)
The pallidothalamic tract, including the ansa lenticularis and lenticular fasciculus, both originating from the globus pallidus internus (GPi), merge and become thalamic fasciculus at the field of Forel (FF) and reach thalamic subnuclei (Neudorfer and Maarouf, 2018)
The FF was used as a stereotactic surgical target to treat cervical dystonia in the 1960s and 1970s (Loher et al, 2004)
Summary
Deep brain stimulation (DBS) of the globus pallidus internus (GPi) is the most widely used surgical treatment for medically refractory dystonia, and its effects have been validated (Kupsch et al, 2006; Volkmann et al, 2014). Stimulation that spreads to surrounding structures or of the GPi itself can cause visual and motor complications and Parkinsonism, including bradykinesia, postural instability, and gait disturbance (Berman et al, 2009; Zauber et al, 2009; Schrader et al, 2011; Huebl et al, 2015; Rusz et al, 2018; Koeglsperger et al, 2019). One patient had tongue protrusion dystonia, another had left hemidystonia with right-hand tremor, and the last had tardive cranio-cervicotruncal dystonia. Based on our experience showing that patients with dystonia receiving ablation of pallidothalamic tracts at FF showed significant improvement of dystonia, we selected the FF as an alternative surgical target of DBS. The absence of bradykinesia, gait disorder, and postural instability was confirmed in all patients
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