Objective: To ascertain the structural connectivity of the executive network in progressive supranuclear palsy (PSP) using probabilistic tractography.

Background: Cognitive deficits are highly prevalent in PSP, and executive dysfunction has been suggested to be the primary cognitive impairment followed by milder deficits in memory, construction and naming. Neuroimaging studies in PSP have demonstrated distinct patterns of frontal atrophy, hence, it is plausible to expect abnormalities in connectivity of the executive network.

Method: This study included 41 subjects, of which 29 were patients with PSP and 12 healthy controls. PSP was diagnosed as per the NINDS-SPSP criteria. MRI scans were acquired in a 3T scanner and diffusion-weighted images were acquired at 32 diffusion gradient directions with a b value of 1000s/mm2. Diffusion data was pre-processed using FSL 5.0.9 and nodes were defined using the Desikan atlas from Freesurfer. Probabilistic tractography was implemented to track fibers from each node to every other node using the FSL toolbox. Edge-wise analysis was performed using the network-based statistic toolbox, global and nodal network measures were ascertained using the brain connectivity toolbox. Age and gender of subjects were used as regressors for analysis. An executive network composed of the frontal pole, middle frontal (rostral and caudal), anterior cingulate (rostral and caudal), medial orbitofrontal, pars orbitalis, pars triangularis, and pars opercularis was considered. Significant measures which included these above regions were further evaluated.

Results: No significant abnormalities were observed at global or nodal levels. However, 28 abnormal edges including nodes from the above defined executive network were identified. A significantly high number of these abnormal connections (75%) were found to involve the right rostral and caudal middle frontal gyrus. These nodes were part of edges comprised of the pars opercularis, orbitalis and temporalis, and other regions such as the insula, superior temporal and frontal, inferior parietal and lateral occipital.

Conclusion: Aberrant structural connectivity of edges involved in the executive network was observed in patients with PSP, and the right middle frontal gyrus significantly contributed to this abnormality. These finding further contribute to the neuroanatomical basis for executive dysfunction in PSP.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/aberrant-structural-connectivity-of-the-executive-network-in-progressive-supranuclear-palsy/