Thalamocortical networks involved in Pusher Syndrome

Abstract

Indirect quantification of functional and structural disconnection increases the knowledge derived from focal brain lesions by inferring subsequent brain network damage from the respective lesion. We applied both measures to a sample of 124 stroke patients to investigate brain disconnection in pusher syndrome - a disorder characterized by a disturbed perception of one's own upright body posture. Our results suggest a hub-like function of the posterior and lateral portions of the thalamus in the perception of ones own postural upright and identified dysfunction in a thalamo-cortical network as one likely cause of pusher syndrome. Lesion network-symptom-mapping investigating functional disconnection indicated cortical diaschisis in cerebellar, frontal, parietal, occipital, and temporal areas in patients with thalamic lesions suffering from pusher syndrome, but there was no evidence for functional diaschisis in cortical stroke and no evidence for the convergence of thalamic and cortical lesions onto a common functional network. Structural disconnectivity mapping identified several thalamo-cortical disconnections. Many of the thalamic and cortical regions disconnected by lesions that lead to pusher behavior correspond to previously reported lesion sites associated with pusher syndrome. Thus, while the presence of both, isolated thalamic and cortical lesions in context with pusher behavior has been reported previously and led to the conclusion that the correct estimation of one's own postural upright might depend on a thalamo-cortical network, our analyses offer the first evidence for a direct thalamo-cortical (or cortico-thalamic) interconnection and, more importantly, shed light on the location of the respective thalamo-cortical disconnections.

The need for hemispheric separation in pairwise structural disconnection studies

“…In a recent article of our group, we conducted both a joint analysis of unilateral left and right hemispheric patients as well as individual analyses separated by hemisphere on real data of stroke patients suffering from 'pusher syndrome' (Rosenzopf et al, 2023). We observed that the results obtained from the respective analyses indeed were in accordance with the here described pattern.…”

“…We observed that the results obtained from the respective analyses indeed were in accordance with the here described pattern. Indeed, we obtained a smaller amount of significant results when analyzing both hemispheres together; all additional disconnections that appeared in the separate analyses were ipsilesional intra-hemispheric disconnections (Rosenzopf et al, 2023).…”

“…Recent literature addressing target behaviors in patients suffering from brain injury primarily analyzed structural disconnections in a joint analysis, i.e., a single analysis based on patients with unilateral left and with unilateral right hemispheric lesions (e.g., Errante et al, 2022;Kuceyeski et al, 2016;Moore et al, 2022;Pan et al, 2022;Smaczny et al, 2023;Urbanski et al, 2016), and only a minority in individual analyses separated by hemisphere (e.g., Rosenzopf et al, 2023). The question thus arises whether joint or separate analyses, or both equally, are valid to study pairwise structural disconnections in humans.…”

The need for hemispheric separation in pairwise structural disconnection studies

“…In a recent article of our group, we conducted both a joint analysis of unilateral left and right hemispheric patients as well as individual analyses separated by hemisphere on real data of stroke patients suffering from “pusher syndrome” (Rosenzopf et al, 2023). We observed that the results obtained from the respective analyses were in accordance with the here described pattern.…”

“…Recent literature addressing target behaviors in patients suffering from brain injury primarily analyzed structural disconnections in a joint analysis, that is, a single analysis based on patients with unilateral left and with unilateral right hemispheric lesions (e.g., Errante et al, 2022; Kuceyeski et al, 2016; Moore et al, 2022; Pan et al, 2022; Smaczny et al, 2023; Urbanski et al, 2016), and only a minority in individual analyses separated by hemisphere (e.g., Rosenzopf et al, 2023). The question thus arises whether joint or separate analyses, or both equally, are valid to study pairwise structural disconnections in humans.…”