Zona incerta stimulation [Neurosurgery Wiki]

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====== Zona incerta stimulation ======

{{ ::zonaincertastimulation.jpg?500|}}

Surgical targets for [[Tourette's syndrome]] have included the frontal lobes, the cingulate gyrus, the anterior limb of the internal capsule ([[ALIC]]), the [[limbic system]], and the subthalamic [[zona incerta]].
((Temel Y, Visser-Vandewalle V. Surgery in Tourette syndrome. Mov Disord. 2004; 19:3–14))
Current targets of interest for DBS include: [[GPi]], [[STN]], ALIC, and [[thalamus]]. Early results have been promising.
((Martinez-Fernandez R, Zrinzo L, Aviles-Olmos I, et al. Deep brain stimulation for Gilles de la Tourette syndrome: a case series targeting subre- gions of the globus pallidus internus. Mov Disord. 2011; 26:1922–1930)).

Posterior [[subthalamic deep brain stimulation]] (DBS) targeting the [[zona incerta]] (ZI) is an emerging treatment for [[tremor]] syndromes, including [[Parkinson's disease]] (PD) and [[essential tremor]] (ET). 

Evidence from [[animal]] studies has indicated that the ZI may play a role in [[saccadic eye movement]]s via pathways between the ZI and [[superior colliculus]] ([[incerto collicular pathways]]).
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[[Optics]] can be used for [[guidance]] in [[deep brain stimulation]] (DBS) surgery. The aim of  Zsigmond and Wårdell was to use [[laser Doppler flowmetry]] (LDF) to investigate the intraoperative optical trajectory along the [[ventral intermediate nucleus]] ([[VIM]]) and [[zona incerta]] ([[Zi]]) regions in patients with [[essential tremor]] during [[asleep]] DBS surgery, and whether the Zi region could be identified.

A forward-looking LDF guide was used for the creation of the trajectory for the DBS lead, and the microcirculation and tissue greyness, i.e., total light intensity (TLI) was measured along 13 trajectories. TLI trajectories and the number of high-perfusion spots were investigated at 0.5-mm resolution in the last 25 mm from the targets.

All implantations were done without complications and with significant improvement of tremor (p < 0.01). Out of 798 measurements, 12 tissue spots showed high blood flow. The blood flow was significantly higher in VIM than in Zi (p < 0.001). The normalized mean TLI curve showed a significant (p < 0.001) lower TLI in the VIM region than in the Zi region.

Zi DBS performed asleep appears to be safe and effective. LDF monitoring provides direct in vivo measurement of the [[microvascular]] [[blood flow]] in front of the probe, which can help reduce the risk of hemorrhage. LDF can differentiate between the [[grey matter]] in the [[thalamus]] and the transmission border entering the posterior [[subthalamic]] area where the tissue consists of more [[white matter tract]]s
(( Zsigmond P, Wårdell K. Optical Measurements during Asleep Deep Brain
Stimulation Surgery along Vim-Zi Trajectories. Stereotact Funct Neurosurg. 2020
Feb 20:1-7. doi: 10.1159/000505708. [Epub ahead of print] PubMed PMID: 32079023.
)).
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Sixteen patients (12 with PD and 4 with ET) underwent DBS using the MRI-directed implantable guide tube technique. Active electrode positions were confirmed at the caudal ZI. Eye movements were tested using direct current electrooculography (EOG) in the medicated state pre- and postoperatively on a horizontal predictive task subtending 30°. Postoperative assessments consisted of stimulation-off, constituting a microlesion (ML) condition, and high-frequency stimulation (HFS; frequency = 130 Hz) up to 3 V.

With PSA HFS, the first saccade amplitude was significantly reduced by 10.4% (95% CI 8.68%-12.2%) and 12.6% (95% CI 10.0%-15.9%) in the PD and ET groups, respectively. With HFS, peak velocity was reduced by 14.7% (95% CI 11.7%-17.6%) in the PD group and 27.7% (95% CI 23.7%-31.7%) in the ET group. HFS led to PD patients performing 21% (95% CI 16%-26%) and ET patients 31% (95% CI 19%-38%) more saccadic steps to reach the target.

PSA DBS in patients with PD and ET leads to hypometric, slowed saccades with an increase in the number of steps taken to reach the target. These effects contrast with the saccadometric findings observed with subthalamic nucleus DBS. Given the location of the active contacts, incerto-collicular pathways are likely responsible. Whether the acute finding of saccadic impairment persists with chronic PSA stimulation is unknown
((Bangash OK, Dissanayake AS, Knight S, Murray J, Thorburn M, Thani N, Bala A,
Stell R, Lind CRP. Modulation of saccades in humans by electrical stimulation of 
the posterior subthalamic area. J Neurosurg. 2019 Mar 15:1-9. doi:
10.3171/2018.12.JNS18502. [Epub ahead of print] PubMed PMID: 30875687.
)).

===== References =====