Virador, Gabriel

ABSTRACT Introduction/Aims There are no established biomarkers of upper motor neuron degeneration to aid in the diagnosis of motor neuron disease (MND). This study examines the diagnostic value of the motor band sign as a marker of upper motor neuron degeneration and its relationship to clinical findings in MND. Methods Records of consecutive patients who underwent 7T magnetic resonance imaging (MRI) between October 2021 and April 2025 for evaluation of MND or other neurologic indications were retrospectively reviewed. Clinical variables and plasma neurofilament light chain (pNfL) levels were recorded. An upper motor neuron score (Mayo UMNS) was derived from reflex scores. Blinded MRI review assessed the degree of susceptibility‐weighted imaging (SWI) hypointensity in the hand, foot, and bulbar motor cortex regions. Results An MBS was observed in 100 of 117 (85.5%) MND patients and in 16 (15.5%) patients with non‐MND diagnoses, corresponding to a sensitivity of 85.5% (78.0%–90.7%) and 84.5% (76.2%–90.2%) specificity. The MBS in 78 MND patients (70.9%) preferentially involved the middle and deep cortical layers, giving a trilaminar appearance, while only one non‐MND patient had this finding. Mayo UMNS ( β = 0.89, p < 0.001), pNfL ( β = 0.63, p = 0.033), and age at evaluation ( β = 0.68, p = 0.027) were independently associated with the summed SWI score. Discussion The 7T MRI MBS is a sensitive and specific marker for MND that complements established clinical evaluation. Using 7T, a trilaminar appearance of the motor cortex, reflecting known histopathological changes, can be visualized and may be specific to MND.