Objective: The  target during STN DBS  for Parkinson’s disease is the dorsolateral STN which plays a major role in motor functions in contrast to the venteromedial STN which has   limbic functions. Our aim was to increase this targeting accuracy

Background: Identification of dorsolateral STN can be  done via pre-operative high resolution imaging and via MER based software algorithms like HaGuide algorithm. However these methods have technical and logistic limitations. To improve dorsolateral STN targeting , we aimed to develop a novel test which can be used intra-operatively

Method: This test is based on following STN MER data findings -Firing frequency of dorsolateral STN neurons increases during the reaching phase of reach to grasp movement and this increase correlates positively with velocity of movement.¹  Increase in firing frequency of STN neurons was seen more commonly with shoulder movement  as compared to elbow , wrist or hand movement with percentage of neurons showing increase being 43%, 31%, 13% and 13% respectively.²Also joint rotation was the movement which led to biggest increase in firing frequency of STN neurons.² Test details- Patient’s were made to completely extend arm with an elbow angle of 180 degrees and  axillary angle of 45 degrees.Then they were asked to make a rapid grab/lunge at  the  lock which was dangled over them so that shoulder rotation took place during the movement and axillary angle at time of  rapid grab/lunge was around 120-130 degrees.Pre-op rehearsals were done to familiarize the patient with the maneuver.Fig 1.

Results: 16 STN’s were sampled and 11 STN’s demonstrated visible increase in firing frequency with this maneuver [68.75%] -Table 1. Out of  5 STN’s which did not show visible increase in firing frequency , 4 were STN’s whose DBS was done second

Conclusion: Our test showed 68.75% accuracy for correct identification of dorsolateral STN during DBS. This allows more accurate lead placement and better  results. Since in our centre, both leads were being implanted on same day ,likely  reasons for lower pickup rate of this maneuver with second STN lead were- patients getting tired and fatigued and not executing the maneuver correctly during second STN lead implantation , pneumocephalus and anesthesia effects. More studies using this test will clarify  better.

References: 1.Pötter-Nerger M, Reese R, Steigerwald F, Heiden JA, Herzog J, Moll CKE, Hamel W, Ramirez-Pasos U, Falk D, Mehdorn M, Gerloff C, Deuschl G, Volkmann J. Movement-Related Activity of Human Subthalamic Neurons during a Reach-to-Grasp Task. Front Hum Neurosci. 2017 Sep 7;11:436. doi: 10.3389/fnhum.2017.00436. PMID: 28936169; PMCID: PMC5594073.
2.Delong MR, Georgopoulos AP, Crutcher MD, Mitchell SJ, Richardson RT, Alexander GE. Functional organization of the basal ganglia: contributions of single-cell recording studies. Ciba Found Symp. 1984;107:64-82. doi: 10.1002/9780470720882.ch5. PMID: 6389041.

« Back to 2023 International Congress

MDS Abstracts - https://www.mdsabstracts.org/abstract/grab-the-lock-test-a-novel-clinical-test-for-identification-of-dorsolateral-subthalamic-nucleus-stn-during-deep-brain-stimulation-dbs/