A team of researchers from Washington University School of Medicine in St Louis (MO, USA) have determined that the positioning of functional brain networks vary on an individual basis. They suggest that electrode placement during deep brain stimulation (DBS) needs to be personalized to the patient.
DBS can often vary in effectiveness, with some patients receiving symptomatic relief and others experiencing adverse side effects. The authors of this paper, which has been published in Neuron, hope that in the future, their work will help neurosurgeons optimize the placement of DBS electrodes in patients with Parkinson’s disease, Tourette’s syndrome and obsessive-compulsive disorder.
The research group analyzed the brain activity of 10 individuals who had participated in an MRI brain scan program. Scans were performed either when the participants were at rest or while performing tasks. From the data, the group were able to create individual 3D maps of different functional networks in the basal ganglia and thalamus, including those relating to vision, motion and goal-directed behavior.
Zones where the different networks integrated were identified. The location of the motor integration zone was determined to be in the same place in each individual. This region was correlated with the brain region targeted during DBS for essential tremor.
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“The sites we target for DBS were discovered serendipitously,” explained Scott Norris (Washington University School of Medicine). “Someone had a stroke or an injury in a specific part of the brain, and suddenly their tremor, for example, got better, and so neurologists concluded that targeting that area might treat tremor.”
However, the locations of other functional networks and their integration zones varied from person to person. For example, different individuals had a range of functional networks in the region generally targeted by DBS for the treatment of Parkinson’s disease.
“Historically, our understanding of DBS has been based on averaging data across many people,” commented Norris. “This study suggests that a particular patient may do better if the wire is placed in relation to their personal functional brain map rather than in context of the population average.”
Looking forward, the research group hope to further understand where different functional networks are located and how they interact, in addition to how they react to DBS.
“Now, we can make a map and give it to neurosurgeons and potentially improve treatment for these devastating conditions. We still have to prove the hypothesis that DBS outcomes are linked to functional networks, and translation will take time, but this really could make a difference in people’s lives,” concluded Nico Dosenbach (Washington University School of Medicine).
Sources: Greene DJ, Marek S, Gordon EM et al. Integrative and network-specific connectivity of the basal ganglia and thalamus defined in individuals. Neuron doi:10.1016/j.neuron.2019.11.012 (2019); https://medicine.wustl.edu/news/new-clues-to-why-deep-brain-stimulation-doesnt-always-help-patients/