She grew up in the San Francisco Bay area. At school, she was involved with the theatre group and acted in drama and musicals. She went to college and received a degree in accounting. Then she worked as an electrician for two years, and also as a veterinary technician. In her early 20's Shanna and her husband embraced the swinging scene, and she also owned a pet boa constrictor which would later feature with her in the film Deviations. She replied to a wanted ad for porn performers in a San Francisco newspaper. McCullough made her porn debut in May 1983 in a scene with the actor Mike Horner for Deviations. She had her first sexual experience with another woman in a scene with Hyapatia Lee.
According to her IAFD profile, as of 2023, Shanna is still actively performing. https://www.iafd.com/person.rme/id=44fb4e1e-5c73-45b4-aec6-38c5a613833c
