Expanding the Motor Band Sign in Motor Neuron Disease Using 7T MRI: Visualization of Cortical Layer-Dependent Iron
Jaimin S Shah1, Björn Oskarsson1, Xiangzhi Zhou2
1Department of Neurology, Mayo Clinic, Jacksonville, Florida, USA.
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.
Insights
The 7T MRI motor band sign (MBS) is a sensitive and specific biomarker for diagnosing motor neuron disease (MND). This imaging marker, particularly its trilaminar appearance, aids in identifying upper motor neuron degeneration.
Area of Science:
- Neurology
- Radiology
- Biomarkers
Background:
- Established biomarkers for upper motor neuron degeneration in motor neuron disease (MND) are lacking.
- The motor band sign (MBS) is being investigated as a potential imaging biomarker.
Purpose of the Study:
- To evaluate the diagnostic value of the 7T MRI MBS in identifying upper motor neuron degeneration in MND.
- To explore the relationship between the MBS and clinical findings in MND patients.
Main Methods:
- Retrospective review of 7T MRI scans from patients evaluated for MND or other neurological conditions.
- Assessment of MBS presence and characteristics (trilaminar appearance) on susceptibility-weighted imaging (SWI).
- Correlation of MBS findings with clinical variables, including Mayo Upper Motor Neuron Score (UMNS) and plasma neurofilament light chain (pNfL) levels.
Main Results:
- The MBS was detected in 85.5% of MND patients and 15.5% of non-MND controls, indicating high sensitivity and specificity.
- A trilaminar MBS appearance, reflecting middle and deep cortical layer involvement, was observed in 70.9% of MND patients, with only one non-MND patient showing this finding.
- Mayo UMNS, pNfL levels, and age were independently associated with the summed SWI score.
Conclusions:
- The 7T MRI MBS is a sensitive and specific imaging marker for MND, complementing clinical assessments.
- The visualization of a trilaminar MBS appearance using 7T MRI may be specific to MND and reflects known histopathological changes.
