He was born and raised in Cairo, Illinois, a small town at the confluence of the Ohio and Mississippi rivers. Asa was educated at Westminster College in Fulton, Missouri. He received his medical degree from Northwestern University and completed a medical internship at Parkland Memorial Hospital in Dallas, Texas. Following his internship, Asa enlisted in the air force and served for 2½ years during the Vietnam War. After his military service, Asa resumed his medical training and completed a neurology residency at Yale University. Asa then pursued postgraduate training at the Mayo Clinic, where he completed an electroencephalography fellowship under the direction of Donald Klass, MD, and an EMG fellowship under the direction of Edward Lambert, MD. He then moved to Cleveland, Ohio, in 1973. There, he established the EMG laboratory at the Cleveland Clinic, where he worked until his death.