Effects of DBS in dorsal vs. ventral STN

What is it about?

Deep brain stimulation (DBS) of the subthalamic nucleus (STN) has become an important part of modern Parkinson disease (PD) treatment. Here, we studied the effects of STN DBS in a novel way in 74 people with PD. Some results fit previous assumptions: contact location significantly affected motor response (rigidity, tremor at rest, and body hypokinesia), with stimulation of dorsal STN or zona incerta improving these functions most, and DBS improved anxiety more in ventral STN than in dorsal STN. However, other results did not fit with prior assumptions: stimulation to either site improved movement without worsening cognition, and DBS to ventral STN improved rigidity more than DBS to dorsal STN. We conclude that although motor function is best represented in dorsal STN, as the anatomical connections suggest, functional segregation of motor and nonmotor pathways in STN is quite limited.

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Why is it important?

Which parts of the STN are wired preferentially to which other parts of the brain has been known for some time. This is important information, but does not necessarily predict which part of the STN should be stimulated to affect which brain function. The latter is what patients and doctors are most interested in, and that is what this work addresses. This work is also valuable because our methods were very rigorous. We selected locations near the upper (dorsal) or lower (ventral) border of the STN, based on brain imaging, without awareness of the prior clinical effects at either location. We examined the short-term effects of DBS at each of these two locations, compared to how the person was doing with the stimulator off (here, short-term or acute refers to effects observed about 40 to 90 minutes after changing the DBS stimulation). Stimulation was applied to the more affected side of the brain. Those assessing the volunteers did not know whether DBS was being applied to the dorsal STN, ventral STN, or neither. The electrical settings were standard across subjects.

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