Deep brain stimulation for cervical dystonia.

I read with interest the recent case report by Chang and colleagues on unilateral deep brain stimulation (DBS) of the globus palli-dus internus (GPi) in a patient with delayed-onset posttraumatic cervical dystonia. 1 I congratulate the authors reporting another patient with cervical dystonia responding to GPi DBS. The unique feature in their case is that unilateral stimulation only was used. They report on a 23 year old man who developed cervical dystonia with head turning to the left three years after he sustained a severe closed head injury. Magnetic resonance (MR) studies five days after the injury demonstrated focal lesions of the left palli-dum, but also of the right thalamus. Six years later only the left pallidal lesion could be appreciated by MR studies. The authors chose to implant a quadripolar DBS electrode in the left GPi for chronic stimulation. They further report that during chronic stimulation the patient's cervical dystonia improved, and that he could turn his head to the midline easier than preoperatively. The improvement was not assessed by standard rating scales for cervical dystonia, and it is said that the dystonia was stable three months after electrode implantation. The authors conclude that the cervical dystonia in their patient was secondary to the GPi lesion, and that unilateral DBS of the GPi contralateral to the dystonic sternocleidomastoid muscle is the treatment option of choice. I wonder whether the thalamic lesion shown in the early MR scans could also have been relevant in the development of this patient's dystonia. It has been demonstrated previously that post-traumatic cervical dystonia may be associated with subthalamic and upper brainstem lesions. 2 Interestingly, Chang and colleagues conclusions on the side to be choosen for unilateral DBS are at odds with another recent case report. Escamilla-Sevilla and colleagues observed improvement of segmen-tal cervical and truncal dystonia in a 24 year old man with idiopathic dystonia during unilateral stimulation of the GPi ipsilateral to the dystonic sternocleidomastoid muscle. 3 In that case no notable change of cervical dystonia was observed with bilateral stimulation for six months. When it then was decided to switch to unilateral stimulation of the right GPi there was progressive improvement over the next three months. Unfortunately, chronic stimulation of the left GPi was not performed in that case. These authors concluded that stimulation should be started on the side ipsilateral to the dystonic sternocleidomastoid muscle. The discrepancy between these two reports …