Superolateral Medial Forebrain Bundle Damage Associated with MS Fatigue

A study observed a correlation between microstructural changes to the left superolateral medial forebrain bundle (slMFB) and the comorbid development of fatigue and depression in multiple sclerosis (MS).

“Lower reward responsiveness has been associated with fatigue in MS. However, association of MS‐related fatigue with damage to the mesocorticolimbic reward pathway (slMFB) has not been assessed,” the researchers explained.

Patients were stratified into groups based on fatigue status: sustained fatigue (SF), defined as latest two Modified Fatigue Impact Scale (MFIS) ≥38 (n=26); reversible fatigue (RF), defined as latest MFIS <38 and at least one previous MFIS ≥38 (n=25); never fatigued, defined as ≥5 consecutive MFIS <38 (n=42); and healthy controls (n=6). Comparisons were made in diffusion MRI-derived measures of fractional anisotropy (FA), axial (AD), mean (MD), and radial diffusivity (RD) of the slMFB. The Center for Epidemiologic Studies‐Depression Scale (CES‐D) was used to evaluate depression; patients with CES‐D ≥16 were considered depressed.

Patients in the SF group who were depressed had significantly higher MD and RD compared with patients in the SF group who were not depressed, as well as patients in the RF group regardless of depression status. The SF group with depression also had significantly lower FA in their left sIMFB compared with the non-depressed SF group, as well as the RF patients who were depressed. SF patients who were depressed had significantly higher left sIMFB MD and AD compared with healthy controls.