The motor band sign in ALS: presentations and frequencies in a consecutive series of ALS patients.

The primary role of magnetic resonance imaging (MRI) in routine diagnostic work-up of motor neuron disease patients is currently still largely limited to exclusion of relevant non-degenerative pathologies. We here present an illustrative case of a 63-year-old woman with early stage Frontotemporal-Dementia-Amyotrophic-Lateral-Sclerosis (FTD-ALS) spectrum disorder showing a striking hypointense signal of the cortical band along the precentral gyrus, termed "motor band sign" (MBS). Based on this finding, we analysed the frequency of the MBS in clinical routine MRIs in a large consecutive series of ALS patients (MRIs available from 157 patients). MBS was present in 5% patients of the total series, but in 78% of patients where susceptibility-weighted images (SWI) were available. These findings suggest that the MBS is a recurrent finding in ALS, which can be identified even on clinical routine 3 T-MRI, and as part of more complex motor neuron syndromes, such as FTD-ALS. Moreover, they indicate that SWI sequences should be considered as part of the clinical routine MRI protocol in the diagnostic work-up of ALS patients.