Ascension Medical Group Saint Thomas Brentwood. Primary Care/Clinic; Specialty Care; Address. 791 Old Hickory Blvd Brentwood, TN 37027. Phone. 629-888-5125 Hours. ... For patients of Ascension Saint Thomas Hickman Hospital, Ascension Saint Thomas Midtown Hospital, Ascension Saint Thomas Rutherford Hospital, and Ascension Saint Thomas West ....