Editing Deep brain stimulation (section)

====Speech and swallowing====
Almost 40% of patients develop speech impairment after DBS to the STN, with only 10% improving after reprogramming.<ref>{{cite journal |last1=Swinnen |first1=BEKS |last2=Lotfalla |first2=V |title=Programming Algorithm for the Management of Speech Impairment in Subthalamic Nucleus Deep Brain Stimulation for Parkinson's Disease. |journal=Neuromodulation |date=April 2024 |volume=27 |issue=3 |pages=528–537 |doi=10.1016/j.neurom.2023.05.002 |pmid=37452799|doi-access=free }}</ref> DBS to the GPi improves speech, in contrast to the STN, thalamus or zona incerta.<ref>{{cite journal |last1=Baudouin |first1=R |last2=Lechien |first2=JR |title=Deep Brain Stimulation Impact on Voice and Speech Quality in Parkinson's Disease: A Systematic Review. |journal=Otolaryngology–Head and Neck Surgery |date=March 2023 |volume=168 |issue=3 |pages=307–318 |doi=10.1177/01945998221120189 |pmid=36040825}}</ref> Up to 33% of patients can develop problems with speech after bilateral DBS to the STN, both by formal metrics<ref name="Swallowing Mvmt Disorders 2017">{{cite journal |last1=Alomar |first1=S |last2=King |first2=NK |last3=Tam |first3=J |last4=Bari |first4=AA |last5=Hamani |first5=C |last6=Lozano |first6=AM |title=Speech and language adverse effects after thalamotomy and deep brain stimulation in patients with movement disorders: A meta-analysis. |journal=Movement Disorders |date=January 2017 |volume=32 |issue=1 |pages=53–63 |doi=10.1002/mds.26924 |pmid=28124434}}</ref> and as subjectively reported by individuals and their families.<ref name="Swallowing ENT review 2023">{{cite journal |last1=Baudouin |first1=R |last2=Lechien |first2=JR |last3=Carpentier |first3=L |last4=Gurruchaga |first4=JM |last5=Lisan |first5=Q |last6=Hans |first6=S |title=Deep Brain Stimulation Impact on Voice and Speech Quality in Parkinson's Disease: A Systematic Review. |journal=Otolaryngology–Head and Neck Surgery |date=March 2023 |volume=168 |issue=3 |pages=307–318 |doi=10.1177/01945998221120189 |pmid=36040825}}</ref> This is less than that seen after thalamotomy (40%). The numbers are significantly lower for unilateral treatment, at 10-15%, but the symptomatic improvement with this is also one-sided, making it more appropriate for individuals with asymmetric disease.<ref name="Swallowing Mvmt Disorders 2017"/>

Speech impairment occurs in up to 20% of patients with DBS to the VIM of the thalamus. Focused ultrasound, by comparison, causes speech impairment in 15% of patients when done unilaterally and 40% when bilateral.<ref>{{cite journal |last1=Alomar |first1=S |last2=King |first2=NK  |title=Speech and language adverse effects after thalamotomy and deep brain stimulation in patients with movement disorders: A meta-analysis. |journal=Movement Disorders  |date=January 2017 |volume=32 |issue=1 |pages=53–63 |doi=10.1002/mds.26924 |pmid=28124434}}</ref>

Swallowing function after DBS can be impacted, analysis showing that it is either stable or improved after DBS to the GPi and has more variable effect after DBS to the STN, possibly worsening in on medication states, but stable or improved in off states.<ref>{{cite journal |last1=Yu |first1=H |last2=Takahashi |first2=K |last3=Bloom |first3=L |last4=Quaynor |first4=SD |last5=Xie |first5=T |title=Effect of Deep Brain Stimulation on Swallowing Function: A Systematic Review. |journal=Frontiers in Neurology |date=2020 |volume=11 |page=547 |doi=10.3389/fneur.2020.00547 |doi-access=free |pmid=32765388|pmc=7380112 }}</ref>

Speech disorders are more common after STN surgery, though dysphagia is more common after DBS to the GPi, an important finding because [[aspiration pneumonia]] is the most common cause of death in Parkinson's. The two nuclei have differing effects on the pedunculopontine nucleus, which in turn affects swallowing through the [[solitary nucleus]]. The GPi inhibits the PPN, while the STN excites it.<ref name ="Persistent 2018"/>