Objective: To 1) evaluate the presence of Parkinsonian symptoms in patients with cervical dystonia treated with bilateral deep brain stimulation (DBS) of the globus pallidus internus (GPi) and 2) compare them with patients with cervical dystonia on nonsurgical treatments.

Background: GPi-DBS is an established treatment option in patients with medically refractory dystonia. Few studies have reported appearance of distinct Parkinsonian signs with chronic GPi stimulation in these patients, such as gait disturbances or micrographia. However, there is no study evaluating post-GPi-DBS Parkinsonian signs with a universal assessment tool, nor have any of the studies included a control group of dystonia patients on conventional treatments.

Methods: Twenty-four cervical dystonia patients treated with bilateral GPi-DBS (14 females; mean age 63.8±7.8y; 2 in combination with minor facial, and 1 in combination with minor trunk involvement) and 22 age, gender, handedness and disease duration matched unoperated patients with cervical dystonia (17 females; mean age 60.2±10.2), were recruited. All patients underwent a standardized neurological examination including the BFMDRS for evaluation of dystonic symptoms and the MDS-UPDRS part III for assessing presence and severity of Parkinsonian signs.

Results: There was a significant improvement of dystonia in the DBS group pre vs. post operation (BFMDRS 12.0±2.4 vs. 6.8±1.1, p=.038). BFMDRS of unoperated patients was 5.4±1.9. GPi-DBS patients had higher MDS-UPDRS-III scores compared to the non-surgical patients (15.9±6.7 vs. 6.4±5.1, p<.001). Patients on stimulation had higher subscores in all bradykinesia items compared to unoperated dystonia patients (all Bonferroni corrected, p<.001). In addition, the limb rigidity score was higher in operated patients, p=.046. However, there was no difference between groups in the subscores for the speech, the overall tremor subscore, the ability to rise from a chair, gait, freezing of gait, or postural stability.

Conclusions: GPi-DBS dystonia patients had significantly higher MDS-UPDRS scores than unoperated patients. This was mostly due to higher scores on bradykinesia items, whereas gait, speech or postural stability subscores were not significantly different between groups. Further studies are needed to elucidate the mechanisms of this GPi-DBS-induced Parkinsonian symptoms in dystonia patients.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/parkinsonian-symptoms-in-patients-with-cervical-dystonia-treated-with-bilateral-pallidal-deep-brain-stimulation-a-controlled-study/