The prevalence and role of the motor band sign (MBS) remain unclear in motor neuron disease. We report the frequency of MBS in amyotrophic lateral sclerosis (ALS) and primary lateral sclerosis (PLS), its correlation with clinical upper motor neuron (UMN) signs, and prognostic value in ALS.

We conducted a retrospective study of ALS, PLS, and controls with retrievable MRI between 2010 and 2018. We compared the frequencies of MBS across the three groups, and studied correlation between susceptibility-weighted MRI measurements in primary motor cortices and contralateral UMN features. Clinical outcomes were compared between ALS with and without MBS.

Thirteen ALS, 5 PLS, and 10 controls were included (median age 60 years, IQR 54–66 years; 14/28 males). MBS was present in 9/13 (69.2%, 95% CI 38.9–89.6%) and 4/5 (80.0%, 95% CI 29.9–99.0%) of ALS and PLS, respectively, and none in controls. 2/13 (15.4%, 95% CI 2.7–46.3%) ALS and 3/5 (60.0%, 95% CI 17.0–92.7%) PLS had MBS in the absence of corticospinal T2/FLAIR hyperintensity sign. Susceptibility measurements in left motor cortices had a significantly positive correlation with contralateral UMN signs in ALS (τ b = 0.628, p = 0.03). Similar but nonsignificant trends was observed for right motor cortices in ALS (τ b = 0.516, p = 0.07). There were no significant differences in mRS at last follow-up, mortality, or time from symptom onset to last follow-up between ALS patients with and without MBS.

We provide limited evidence that MBS and susceptibility quantification measurements in motor cortices may serve as surrogate markers of UMN involvement in motor neuron disease.