Editing Deep brain stimulation (section)

=====Long term comparisons=====
[[File:Rate of adverse events after dbs.jpg|thumb|Persistent adverse effects after DBS can include decline in speech, gait, loss of cognitive function and depression, though problems with cognition mitigate after the first year.<ref name = "Persistent 2018"/>]]
In the longer term and with trials comparing targets head to head, STN and GPi were found to be equal for activities of daily living in the off state and for motor function in both the on and off state. GPi had less dyskinesia and improved activities of daily living in the on state for advanced Parkinson's disease. There was no significant difference between the STN and GPi for motor scores during the on medication phase.<ref name="Zhang 2021">{{cite journal |last1=Zhang |first1=J |last2=Li |first2=J |last3=Chen |first3=F |last4=Liu |first4=X |last5=Jiang |first5=C |last6=Hu |first6=X |last7=Ma |first7=L |last8=Xu |first8=Z |title=STN versus GPi deep brain stimulation for dyskinesia improvement in advanced Parkinson's disease: A meta-analysis of randomized controlled trials. |journal=Clinical Neurology and Neurosurgery |date=February 2021 |volume=201 |page=106450 |doi=10.1016/j.clineuro.2020.106450 |pmid=33421741}}</ref> The GPi reduces dyskinesia through a medication independent mechanism and has less neuropsychiatric effects (ie. depression, apathy, and suicide).<ref name="Lancet Neurol 2014"/> The long term duration of therapeutic benefit has not been clearly established, though reports suggest that individuals may have sustained clinical improvement for at least 10 years.<ref name="DBS review NJEM 2012"/>

There is usually a greater improvement in akinesia targeting the STN as compared to the pallidus, while there may be a wearing off of the initially excellent antiakinetic effect with pallidal stimulation after 5 years.<ref name="Lancet Neurol 2014"/> Conversely, deep brain stimulation of the GPi has consistently shown superior and sustained reduction in dyskinesia.<ref name = "JAMA Neurol 2018">{{cite journal |last1=Ramirez-Zamora |first1=A |last2=Ostrem |first2=JL |title=Globus Pallidus Interna or Subthalamic Nucleus Deep Brain Stimulation for Parkinson Disease: A Review. |journal=JAMA Neurology |date=1 March 2018 |volume=75 |issue=3 |pages=367–372 |doi=10.1001/jamaneurol.2017.4321 |pmid=29356826}}</ref> Although overall gait has been reported to improve consistently after DBS, postural instability, which can affect gait, is less likely to respond. A greater number of falls occur after surgery with DBS of the STN as compared to the GPi.<ref name = "JAMA Neurol 2018"/>

GPi programming requires less-intensive monitoring of medication and stimulation adjustments in most patients. The STN has multiple motor, cognitive, and limbic pathways that are not completely anatomically segregated. In contrast, the larger size of the GPi motor region reduces the likelihood of the current spreading into adjacent functional areas or to the internal capsule, causing less neuropsychological side effects,<ref name = "JAMA Neurol 2018"/> long term comorbidities<ref>{{cite journal |last1=Sako |first1=W |last2=Miyazaki |first2=Y |last3=Izumi |first3=Y |last4=Kaji |first4=R |title=Which target is best for patients with Parkinson's disease? A meta-analysis of pallidal and subthalamic stimulation. |journal=Journal of Neurology, Neurosurgery, and Psychiatry |date=September 2014 |volume=85 |issue=9 |pages=982–6 |doi=10.1136/jnnp-2013-306090 |pmid=24444854}}</ref> and global cognitive decline.<ref>{{cite journal |last1=Rački |first1=V |last2=Hero |first2=M |title=Cognitive Impact of Deep Brain Stimulation in Parkinson's Disease Patients: A Systematic Review. |journal=Frontiers in Human Neuroscience |date=2022 |volume=16 |page=867055 |doi=10.3389/fnhum.2022.867055 |doi-access=free |pmid=35634211|pmc=9135964 }}</ref> This could be due to the GPi being separate from the limbic component of the STN, the greater dopamine reduction allowed with STN stimulation, or that the  vast preponderance of studies in the literature are about the STN, causing an inadvertent [[publication bias]].<ref name="Lancet Neurol 2014"/><ref name="E-medicine 2024"/>

For individuals with unsatisfactory outcomes after DBS in Parkinson's, lead revision resulted in 30% improvement when leads were repositioned from the GPi to the STN, and no improvement when repositioned from the GPi to the STN. The cases in which improvement occurred were when there was clear evidence of lead mispositioning.<ref>{{cite journal |last1=Ten Brinke |first1=TR |last2=Odekerken |first2=VJJ |last3=van Laar |first3=T |last4=van Dijk |first4=JMC |last5=Dijk |first5=JM |last6=van den Munckhof |first6=P |last7=Schuurman |first7=PR |last8=de Bie |first8=RMA |title=Substituting the Target After Unsatisfactory Outcome of Deep Brain Stimulation in Advanced Parkinson's Disease: Cases From the NSTAPS Trial and Systematic Review of the Literature. |journal=Neuromodulation: Journal of the International Neuromodulation Society |date=August 2018 |volume=21 |issue=6 |pages=527–531 |doi=10.1111/ner.12732 |pmid=29164735|url=https://pure.rug.nl/ws/files/64715824/Substituting_the_Target_After_UnsatisfactoryOutcome_of_Deep_Brain_Stimulation_inAdvanced_Parkinson_s_Disease_Cases_From_theNSTAPS_Trial_and_Systematic_Review_of_theLiterature.pdf }}</ref>

A [[Bayesian statistics|Bayesian]] analysis comparing DBS with intestinal levodopa, subcutaneous apomorphine and best medical therapy found DBS and intestinal levodopa to be the superior treatments, though it did not distinguish specific nuclei as DBS targets. In the setting of this limitation, they found intestinal levodopa being the best at improving quality of life more and DBS being the best at reducing off time.<ref>{{cite journal |last1=Antonini |first1=A |title=Comparative Effectiveness of Device-Aided Therapies on Quality of Life and Off-Time in Advanced Parkinson's Disease: A Systematic Review and Bayesian Network Meta-analysis. |journal=CNS Drugs |date=December 2022 |volume=36 |issue=12 |pages=1269–1283 |doi=10.1007/s40263-022-00963-9 |pmid=36414908|pmc=9712309 }}</ref> A more specific Bayesian [[Monte Carlo method|Monte Carlo]] analysis comparing individual nuclei found bilateral STN, GPi and intrajejunal levodopa to be better than either subcutaneous apomorphine or best medical therapy. Amongst the three, STN had the greatest likelihood of improvement, though it was not statistically significant.<ref name = "AIIMS meta analysis 2022">{{cite journal |last1=Rajan |first1=R |last2=Garg |first2=K |last3=Srivastava |first3=AK |last4=Singh |first4=M |title=Device-Assisted and Neuromodulatory Therapies for Parkinson's Disease: A Network Meta-Analysis. |journal=Movement Disorders |date=September 2022 |volume=37 |issue=9 |pages=1785–1797 |doi=10.1002/mds.29160 |pmid=35866929}}</ref>