Authorities believe a medical emergency while driving may have lead to the death  of a 48-year-old Milwaukee man in Menomonee Falls this morning.   The Menomonee Falls Police were called to the scene of the accident at N 124th Street and Appleton Avenue around 5:50 AM and found the man unconscious behind the wheel.    Police and Menomonee Falls Fire Department  personnel provided first aid on the scene and then transported the driver to a local hospital where he died.  The Menomonee Falls Police are continuing to investigate the accident.