Professor Spence has focused on Stroke Prevention throughout his career. After training in Neurology, then Internal Medicine in London, Canada, he did a fellowship in Clinical Pharmacology at the Cardiovascular Research Institute, University of California San Francisco. He is probably the only Neurologist who has run a hypertension clinic for 20 years. He pioneered measurement of carotid plaque burden for risk stratification and genetic research, and "Treating Arteries instead of treating Risk Factors". His expertise includes individualized therapy for resistant hypertension, , B vitamins to lower homocysteine for stroke prevention and transcranial Doppler for risk stratification in asymptomatic stenosis and patent foramen ovale.