Associations Between Temporomandibular Disorders and Brain Imaging-Derived Phenotypes

Area of Science:

• Neuroscience
• Genetics
• Medical Science

Background:

• Temporomandibular disorders (TMD) are prevalent conditions impacting quality of life, with unclear underlying mechanisms.
• Observational studies suggest brain abnormalities in TMD patients, but lack causal inference.
• Magnetic resonance imaging (MRI) studies have indicated potential links between TMD and brain structure.

Purpose of the Study:

• To investigate the causal relationships between temporomandibular disorders (TMD) and brain imaging-derived phenotypes (IDPs).
• To employ Mendelian randomization (MR) to establish genetic evidence for bidirectional associations between TMD and brain changes.
• To explore potential neurobiological mechanisms contributing to TMD development.

Main Methods:

• Utilized genome-wide association study (GWAS) summary statistics for TMD and brain IDPs.
• Performed bidirectional 2-sample Mendelian randomization (MR) analyses using selected instrumental variables.
• Employed inverse-variance weighted analysis as the primary method and applied false discovery rate (FDR) correction for P-values.

Main Results:

• Identified eleven brain imaging-derived phenotypes (IDPs) with significant causal associations with TMD (P-FDR < .05).
• Forward MR revealed causal effects of left caudal middle frontal gyrus thickness and right superior frontal gyrus volume on TMD.
• Reverse MR indicated TMD causally affects 9 IDPs, including left medial orbitofrontal cortex thickness and left magnocellular nucleus volume.

Conclusions:

• This study provides robust genetic evidence for bidirectional causal associations between TMD and brain IDPs.
• Findings illuminate potential neurobiological pathways involved in TMD.
• The research contributes to understanding the complex relationship between TMD and brain structure.