Deep brain stimulation in progressive supranuclear palsy: a dead-end story? A narrative review

Progressive supranuclear palsy (PSP) is a rare, debilitating neurodegenerative disorder that significantly impairs both motor and cognitive functions. Current pharmacological treatments offer only transient symptomatic relief, driving interest in the past in alternative therapeutic strategies such as deep brain stimulation. Deep brain stimulation (DBS), known for its success in treating motor symptoms of Parkinson's disease, has been explored as a possible symptomatic treatment for PSP, considering the pedunculopontine nucleus (PPN), involved in motor control and postural stability, as a promising target for deep brain stimulation in PSP. However, its complex anatomy and the clinical variability of PSP complicate the prediction and generalization of the effectiveness of DBS. The present review examines the existing studies in the literature about DBS in PSP patients. Some studies highlighted modest benefits in motor symptoms, while others reported variable outcomes and inherent risks of the procedure. Generally, patients with a parkinsonism predominant phenotype have shown some subjective or clinical improvements in gait and balance when subjected to low-frequency stimulation. While DBS of the PPN holds promise for ameliorating gait and balance of PSP, current evidence does not yet establish clear criteria for ideal candidates, nor does it provide overwhelmingly supportive results in favor of PPN-DBS in PSP patients. Without any further systematic study is not possible to define accurate candidate selection parameters and understand long-term outcomes and safety profiles.