AnalyzeDirect

Parkinson’s disease is a progressive disorder of the nervous system caused by the loss of dopamine-producing brain cells. Gait disturbance and balance impairment are some of the most incapacitating symptoms of this condition.

Several clinical studies have shown that electrical stimulation of the pedunculopontine tegmental nucleus (PPTg), an area of the brain involved in many functions including voluntary limb movement and locomotion, may be a successful strategy for alleviating gait and postural difficulties.

In order to improve deep brain stimulation in this region and limit possible side effects, scientists from the University of Minnesota recently further investigated the mechanisms that rule this promising technique. The group developed a novel subject-specific computational model tailored for the PPTg area, which allowed them to better calibrate the parameters that define successful outcome, such as axon diameter, tissue conductivity, and stimulation lead location.

Two nonhuman primates were implanted with a deep brain stimulation lead in the PPTg region. Leveraging information from susceptibility-weighted imaging (SWI) scans, Analyze software was used to reconstruct the 3D structure of the PPTg area aligning the SWI volume in anterior commissure to posterior commissure space.

Variability of model predictions when changing axon diameter, tissue conductivity, and lead location was evaluated and then compared to behavioral and functional imaging measures, enhancing the predictive power of the model. Results showed that changes in these parameters reflected in differences in percentage of activated axons.

For the first time, the team was able to show that the inclusion of conductivity is critical for models of deep brain stimulation. The subject-specific computational model developed in this study provides an accurate tool for the prediction of those mechanisms triggered by electrical stimulation and the identification of active neural pathways that cause freezing of gait. Moreover, these results may help further the understanding and management of this debilitating symptom of Parkinson’s disease.

Tags: Brain Studies, Parkinson's Disease