Effects of pedunculopontine nucleus deep brain stimulation on gait disorders in Parkinson's Disease: A meta-analysis of the literature

Objectives: The pedunculopontine nucleus (PPN) is considered a promising target to alleviate gait disorders. We aimed to evaluate the effects of PPN stimulation on motor symptoms and gait disorders in patients with Parkinson's disease (PD) to help assess the potential role of PPN-DBS treatment in gait disorders. Methods: Studies were searched for low-frequency PPN stimulation to treat gait disorders and freezing of gait (FOG) in the PubMed, Embase, Cochrane Library, Web of Science, and ClinicalKey up to April 2020. Outcomes of Unified Parkinson's Disease Rating Scale (UPDRS) part III, subitems 27- 30; UPDRS subitems 13 and 14; the Freezing of Gait Questionnaire (FOGQ), and the Gait and Falls Questionnaire (GFQ) were extracted and evaluated during PPN On-stimulation compared to preoperation or Off-stimulation in both Off- and On-medication states. Results: There was a significant improvement in subitems 27 - 30 with PPN On-stimulation versus Off-stimulation in Off-medication and On-medication states, but no improvement in UPDRS part III. The occurrence of FOG and falls also declined between PPN On-stimulation and presurgery, with a significant improvement in subitem 13 and subitem 14 in Off-medication and On-medication states, GFQ, and FQGQ. Heterogeneity in stimulation frequency, follow-up, electrode location, and unilateral or bilateral stimulation existed among the included studies. Conclusions: In some conditions and in some selective PD patients, low-frequency PPN-DBS has beneficial effects on FOG and falls but no wider benefits on rigidity, resting tremor, or bradykinesia.