The rubral wing and its connectome

Imaging developments optimizing stereotactic surgery for tremor have yielded white matter attenuating sequences (FGATIR/FLAWS) showing a targetable hypointensity in the subthalamic region (rubral wing, RW). RW has been reported to coincide with yet to be defined portions of the dentato-rubro-thalamic tract (DRT). Its discernibility on the single subject level might be hampered by low signal-to-noise ratio (SNR), potentially compromising with surgical outcomes. We here set out to investigate RW as a target structure for tremor surgery by further characterizing it volumetrically and with tractography.

We performed manual delineations of RW on FLAWS sequences (n = 77, 3 raters) and warped results into MNI 152. We performed tractographic analyses of DRT (human connectome project body, n = 1000), using the red nuclei and RW as waypoints. Further, we investigated fiber tightness peaks of crossed (DRTx) and uncrossed DRT portions (DRTu) along their z-axis.

Identification of RW was possible in all subjects. DICE coefficient for volumetric comparison was rather low with 0.54. Euclidean distance of the RW centers of gravity (COG) was <2 mm. RW defines DRTx and optimally routes fibers to the precentral gyrus (PCG). A tightness peak for fibers descending from PCG (DRTx only) was found to coincide with RW.

RW potentially represents a valid candidate target for tremor surgery and is part of the post-crossing portion of the DRTx. COG of RW can be determined with good accuracy, but full volumetric appreciation is difficult on the single subject level (SNR), potentially necessitating additional imaging for surgical targeting.