Dr. Brennan graduated summa cum laude from Michigan State University and is a member of Phi Kappa Phi Honor Society. He graduated from Wayne State Medical School in 1984. Internship in Internal Medicine followed at William Beaumont Hospital — Royal Oak where he also completed his residency in his specialty, Physical Medicine Rehabilitation and was Chief Resident.

Dr. Brennan is Board Certified in Physical Medicine and Rehabilitation and in Electrodiagnostic Medicine.  Memberships in professional societies by Dr. Brennan include: Fellow-American Academy of Physical Medicine and Rehabilitation, Michigan Academy of Physical Medicine and Rehabilitation, American Congress of Rehabilitation Medicine, Fellow-American Academy of Electrodiagnostic Medicine,  American College of Sports Medicine, American Running and Fitness Association, American Medical Association, Michigan State Medical Society, and Oakland and Macomb Medical Societies.