====== Chronic high-frequency deep brain stimulation ======

Patients with [[Parkinson's disease]] can develop axial symptoms, including [[speech]], [[gait]], and [[balance]] difficulties. Chronic [[high-frequency deep brain stimulation]] (>100 Hz) can contribute to these impairments while [[low-frequency stimulation]] (<100 Hz) may improve symptoms but only in some individuals. Factors predicting which patients benefit from low-frequency stimulation in the long term remain unclear. A study aimed to confirm that [[low-frequency stimulation]] improves axial symptoms and to go further to also explore which factors predict the durability of its effects. Vijiaratnam et al. recruited [[patient]]s who developed axial motor [[symptom]]s while using [[high-frequency stimulation]] and objectively assessed the short-term impact of [[low-frequency stimulation]] on axial symptoms, other aspects of [[motor]] function and [[quality of life]]. A retrospective chart review was then conducted on a larger cohort to identify which patient characteristics were associated with not only the need to trial low-frequency stimulation but also those which predicted its sustained use. Among 20 prospective patients, low-frequency stimulation objectively improved mean motor and axial symptom severity and [[quality of life]] in the short term. Among a retrospective cohort of 168 patients, those with less severe [[tremor]] and those in whom axial symptoms had emerged sooner after [[subthalamic nucleus deep brain stimulation]] were more likely to be switched to and remain on long-term low-frequency stimulation. These data suggest that low-frequency stimulation results in objective mean improvements in overall motor function and axial symptoms among a group of patients, while individual patient characteristics can predict sustained long-term benefits. Longer follow-up in the context of a larger, controlled, double-blinded study would be required to provide definitive evidence of the role of [[low-frequency deep brain stimulation]]
((Vijiaratnam N, Girges C, Wirth T, Grover T, Preda F, Tripoliti E, Foley J, Scelzo E, Macerollo A, Akram H, Hyam J, Zrinzo L, Limousin P, Foltynie T. Long-term success of low-frequency subthalamic nucleus stimulation for Parkinson's disease depends on tremor severity and symptom duration. Brain Commun. 2021 Jul 28;3(3):fcab165. doi: 10.1093/braincomms/fcab165. PMID: 34396114; PMCID: PMC8361419.)).