Introduction: The subatantia nigra has recently gained traction as a target for deep brain stimulation (DBS) in clinical trials for Parkinsonian gait improvement as well as gene therapy delivery and cell therapy strategies in Parkinson’s Disease (PD). The potential electrophysiologic variability of the substantia nigra due to its inherent heterogeneity and its potential alteration in PD progression have made mapping throughout the nucleus more difficult and less defined than other basal ganglia nuclei. We report our experience in PD study participants with peripheral nerve grafts targeting the substantia nigra using visual based targeting both with and without microelectrode recording (MER).
Methods: Thirty participants were included in our study with a total of 47 different peripheral nerve graft implantations into the substantia nigra. Each participant underwent a pre-operative 3T MRI which was imported into Brainlab for definition of the substantia nigra structure, target determination using SWI and T2 sequences, and trajectory planning using T1 with contrast and T2 sequences. Participants underwent nerve graft implantation at the time of DBS lead implantation using of a CRW headframe. Intraoperative MER was used to aid in confirming 18 of the 47 targets intraoperatively.
Results: Post-operative MRI review and trajectory mapping after 47 peripheral nerve graft implantations within the substantia nigra demonstrated no occurrences of graft material or delivery cannula tract termination outside of the substantia nigra. Accuracy was not significantly impacted by the use of MER. Side effect profiles with graft implantation were not significantly different from DBS alone. Early data shows promising improvements in UPDRS part III scores but is still being collected.
Conclusions: Visual based targeting is a safe and accurate method for the purpose of intranigral targeting for therapeutic trial delivery in PD. MER can be used to identify the nigral-STN border, but may not provide additional benefit in all intranigral targeting applications.
Patient Care: Our research demonstrates and promotes the feasibility and safety in targeting the substantia nigra for cell graft delivery and demonstrates the accuracy of visual based targeting of basal ganglia and midbrain structures for the purpose of treating Parkinson’s disease and other movement disorders.
Learning Objectives: By the conclusion of this session, participants should be able to:
1) Recognize the substantia nigra as a potential surgical target for cell therapy in Parkinson's Disease
2) Discuss the utility of microelectrode recording in targeting the substantia nigra
3) Accurately identify the borders of and structures adjacent to the stubstantia nigra for the purpose of visual based targeting using MRI and neuronavigation software.