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. Rick Savage made his acting debut in a scene with her in 1983 in the Bob Vosse production, Nasty Lady. After starting to work in porn, she also performed as a dancer in nightclubs. During a break from the business she also worked as a stripper and went back to school to study zoology, with the aim of working in the animal health care field. In 1999 wired.com reported that Shanna was operating a website giving members 24 hour access to multiple webcams installed in her home. As of March 2009, the website appears to have ceased operating. In March 2008, she ran the Los Angeles Marathon.Dave Cummings has said Shanna was one of the actresses he most enjoyed working with. As of 2010, now 50, she has yet to completely retire from the adult business, making her a 27-year veteran performer.