Teaching NeuroImages: The Motor Band Sign in Amyotrophic Lateral Sclerosis.

A 71-year-old woman presented with several months of progressive lower extremity weakness, followed by bulbar weakness. On examination, she had diffuse muscle atrophy, fasciculations, weakness, and hyperreflexia. A diagnosis of clinically definite ALS was made using the El Escorial criteria. At the time of presentation and imaging, she had both severe upper and lower motor neuron involvement. Her ALSFRS-R score was 15, indicating advanced disease. Her brain MRI showed increased signal on susceptibility-weighted imaging, consistent with superficial siderosis along the central sulcus (figure). This finding has been named the “motor band sign”.1 The intracellular iron may be from microglial phagocytosis of degenerated neurons in the motor strip.2 Careful scrutiny of susceptibility-weighted imaging should be performed when considering motor neuron disease, as this can be helpful in making the diagnosis.