Answer B. Amyotrophic lateral sclerosisWith his difficulty swallowing, the patient's tongue atrophy represents a bulbar symptom, and is most consistent with a diagnosis of amyotrophic lateral sclerosis (ALS). The patient also had clinical and neurophysiological evidence of upper-motor-neuron and lower-motor-neuron involvement, which supported the diagnosis. ALS is associated with dysarthria, hypophonia, dysphagia, and sialorrhea in addition to relentlessly progressive disability.