Neuropsychological outcome of bilateral pallidal stimulation in dystonia

Objective: To evaluate the effects of deep brain stimulation (DBS) of the globus pallidus internus (GPi) in dystonia on cognition, mood, functional ability and quality of life.

Background: GPi-DBS is a promising neurosurgical treatment for patients with different types of dystonia, but little is known about its neuropsychological effects. In Parkinson's disease (PD) GPi-DBS seems to be safe regarding cognition, however, some studies report post-operative impairments of executive functions and memory.

Patients and Methods: 15 Patients suffering from primary and secondary dystonia were assessed preoperatively and 3–12 months after bilateral implantation of GPi electrodes while on stimulation. The following tests were used: Cognitive screening: Mattis Dementia Rating Scale (Mattis); Learning and Memory: Rey Auditory Verbal Learning Test (RAVLT), Digit Span (WMS-R); Phasic and tonic Alertness: simple and precued visual reaction task (TAP); Executive functions: Phonemic and Category Word Fluency, Trail Making Test (TMT), Stroop Test; Mood: Beck Depression Inventory (BDI), Montgomery and Asberg Depression Rating Scale (MADRS); Anxiety: Beck Anxiety Inventory (BAI); Hedonism: Snaith-Hamilton-Pleasure-Scale (SHAPS); Psychiatric Screening: Brief Psychiatric Rating Scale (BPRS), Bech-Rafaelsen Mania Rating Scale (BRMAS); Quality of life: modified PDQ 39; Motor function: Burke–Fahn-Marsden-Dystonia Rating Scale and Disability score.

Results: GPi-DBS significantly improved motor scores of the Burke-Fahn-Marsden-Dystonia Rating Scale by approximately 65%. Furthermore, ameliorations were found postoperatively for quality of life and mood and trends for improved overall neuropsychiatric state and hedonism. No changes were found in anxiety. No significant effect of stimulation was observed on any of the cognitive tests: Mattis, RAVLT, Digit Span, simple and precued visual reaction task, Phonemic and Category Word Fluency, TMT, Stroop.

Conclusion: The present study confirms the efficiency of GPi-DBS for the treatment of dystonia resulting in significant improvement of motor functions and quality of life. Extending current knowledge, our data provide evidence that GPi-DBS might improve mood as well as hedonism and can be considered a safe neurosurgical treatment of dystonia with regard to cognitive functions.