Lesion Network Mapping for Parkinsonism and Tremor relief

In two articles published this month, Juho Joutsa and Michael D Fox have applied their lesion network mapping approach to symptoms that are highly relevant to the field of DBS.

The technique, which has been introduced by Aaron D Boes and Michael D Fox (Brain, 2015) uses a normative functional connectome off a large healthy cohort to create connectivity maps seeding from a lesion that caused a specific symptom. These maps are then thresholded and used to find a “common denominator”, i.e. a region to which all of the lesions are connected.

So far, the technique has been successfully applied to freezing of gait (Alfonso Fasano, AoN 2017), hemichorea/hemiballismus (Simon Laganiere, Neurology 2016), delusions/capgrass syndrome (Ryan Darby, Brain 2016), criminal behavior (Ryan Darby, PNAS 2017) and coma (David Fischer, Neurology 2016).

With the two most recent articles, Juho Joutsa has shown that the technique may add relevant new insight to the field of deep brain stimulation.

In the first article (AoN), Joutsa et al. showed that focal lesions that led to tremor relief were all functionally connected to the VIM of the thalamus. Not only does this show the potential of using brain lesions to define a DBS target, but it also gives a functional target in normative (MNI) space using functional MRI. Needless to say, in this example, the target (VIM) was already established. However, one could picture using this technique to find new treatment targets based on brain lesions that lead to different symptoms.

In the second article (Brain), Joutsa et al. showed that lesions that led to Parkinsonism were all functionally connected to a common brain network that involved multiple basal ganglia structures. In further analysis, the most specific and sensitive region that was highlighted was a part of the claustrum. At first glance, this finding may be surprising given the claustrum has not much been linked to Parkinsonism in the past. However, alpha-synuclein deposition was found in the claustrum in PD (Article Clinical correlates of pathology in the claustrum in Parkins…) and just recently, the group of Angelo Quartarone found decreased connectivity between the Claustrum and areas mainly involved in visuomotor and attentional systems in PD (Article Claustral structural connectivity and cognitive impairment i…).

Together with these studies, the article by Joutsa et al. may encourage for more research of the claustrum in Parkinsonism.