Motor Band Sign in Motor Neuron Diseases Using Magnetic Resonance Imaging: A Systematic Review

Abstract

Motor neuron diseases (MNDs) like amyotrophic lateral sclerosis (ALS) are progressive neurodegenerative disorders affecting upper and lower motor neurons (UMN and LMN). Magnetic resonance imaging (MRI) often reveals a “motor band sign” (MBS) of hypointensity along the precentral gyri in ALS, considered a radiologic hallmark. This review comprehensively summarizes the literature on MBS in ALS and related MNDs using multiple MRI techniques. A systematic search was conducted in the PubMed and Scopus databases to identify relevant studies on MBS in MNDs published until August 2023. Twelve studies were included. Most patients had UMN involvement at the onset. MBS was correlated with UMN impairment severity. Susceptibility-weighted imaging (SWI) detected MBS in the majority of MND patients. The use of SWI could be particularly useful in detecting MBS, and it should be considered as part of the routine clinical MRI protocols. Recent studies suggest that hypointensity and atrophy of the primary motor cortex (M1) and nearby regions can be used as MRI markers of UMN impairment in MNDs. Other MRI techniques like T2-weighted (T2-w), T2 ${}^{\ast }$ -w, and fluid-attenuated inversion recovery (FLAIR) also showed characteristic changes. Furthermore, quantitative susceptibility mapping (QSM) is an advanced MRI technique that allows sensitive quantification of iron deposition and has shown promise for accurately detecting MBS in MNDs. The findings suggest that MR neuroimaging techniques can provide valuable insights into the pathophysiology of MND and can be used to detect biomarkers such as MBS. The review demonstrates that advanced MRI techniques can detect cortical and white matter changes reflecting upper motor neuron degeneration in MNDs like ALS. To find out how sensitive and suggestive the MBS is in MNDs and neurodegenerative movement disorders and how well it works as a prognostic indicator, we will need to do more research that combines comprehensive prospective and longitudinal research.